muse2/

asset.rs

//! Assets are instances of a process which are owned and invested in by agents.
use crate::agent::AgentID;
use crate::commodity::{CommodityID, CommodityType};
use crate::finance::annual_capital_cost;
use crate::process::{
    ActivityLimits, FlowDirection, Process, ProcessFlow, ProcessID, ProcessParameter,
};
use crate::region::RegionID;
use crate::simulation::CommodityPrices;
use crate::time_slice::{TimeSliceID, TimeSliceSelection};
use crate::units::{
    Activity, ActivityPerCapacity, Capacity, Dimensionless, FlowPerActivity, MoneyPerActivity,
    MoneyPerCapacity, MoneyPerFlow, Year,
};
use anyhow::{Context, Result, ensure};
use indexmap::IndexMap;
use log::debug;
use serde::{Deserialize, Serialize};
use std::cell::Cell;
use std::cmp::Ordering;
use std::hash::{Hash, Hasher};
use std::iter;
use std::ops::{Deref, RangeInclusive};
use std::rc::Rc;

mod capacity;
pub use capacity::AssetCapacity;
mod pool;
pub use pool::AssetPool;

/// A unique identifier for an asset
#[derive(
    Clone,
    Copy,
    Debug,
    derive_more::Display,
    Eq,
    Hash,
    Ord,
    PartialEq,
    PartialOrd,
    Deserialize,
    Serialize,
)]
pub struct AssetID(u32);

/// A unique identifier for an asset group
#[derive(
    Clone,
    Copy,
    Debug,
    derive_more::Display,
    Eq,
    Hash,
    Ord,
    PartialEq,
    PartialOrd,
    Deserialize,
    Serialize,
)]
pub struct AssetGroupID(u32);

/// The state of an asset
///
/// New assets are created as either `Future` or `Candidate` assets. `Future` assets (which are
/// specified in the input data) have a fixed capacity and capital costs already accounted for,
/// whereas `Candidate` assets capital costs are not yet accounted for, and their capacity is
/// determined by the investment algorithm.
///
/// `Future` and `Candidate` assets can be converted to `Commissioned` assets by calling
/// the `commission` method (or via pool operations that commission future/selected assets).
///
/// `Commissioned` assets can be decommissioned by calling `decommission`.
#[derive(Clone, Debug, PartialEq, strum::Display)]
pub enum AssetState {
    /// The asset has been commissioned
    Commissioned {
        /// The ID of the asset
        id: AssetID,
        /// The ID of the agent that owns the asset
        agent_id: AgentID,
        /// Year in which the asset was mothballed. None, if it is not mothballed
        mothballed_year: Option<u32>,
        /// Parent asset, if any.
        ///
        /// All divided assets have a parent, which tracks the total capacity across the children.
        parent: Option<AssetRef>,
    },
    /// The asset has been decommissioned
    Decommissioned {
        /// The ID of the asset
        id: AssetID,
        /// The ID of the agent that owned the asset
        agent_id: AgentID,
        /// The year the asset was decommissioned
        decommission_year: u32,
    },
    /// The asset is planned for commissioning in the future
    Future {
        /// The ID of the agent that will own the asset
        agent_id: AgentID,
    },
    /// The asset has been selected for investment, but not yet confirmed
    Selected {
        /// The ID of the agent that would own the asset
        agent_id: AgentID,
    },
    /// The asset is a parent of other assets.
    ///
    /// Parents are used for grouping (commissioned) divided assets, which can be used as an
    /// optimisation.
    Parent {
        /// The ID of the agent which owns this asset's children
        agent_id: AgentID,
        /// ID of the asset group
        group_id: AssetGroupID,
    },
    /// The asset is a candidate for investment but has not yet been selected by an agent
    Candidate,
}

/// An asset controlled by an agent.
#[derive(Clone, PartialEq)]
pub struct Asset {
    /// The status of the asset
    state: AssetState,
    /// The [`Process`] that this asset corresponds to
    process: Rc<Process>,
    /// Activity limits for this asset
    activity_limits: Rc<ActivityLimits>,
    /// The commodity flows for this asset
    flows: Rc<IndexMap<CommodityID, ProcessFlow>>,
    /// The [`ProcessParameter`] corresponding to the asset's region and commission year
    process_parameter: Rc<ProcessParameter>,
    /// The region in which the asset is located
    region_id: RegionID,
    /// Capacity of asset (for candidates this is a hypothetical capacity which may be altered)
    capacity: Cell<AssetCapacity>,
    /// The year the asset was/will be commissioned
    commission_year: u32,
    /// The maximum year that the asset could be decommissioned
    max_decommission_year: u32,
}

impl Asset {
    /// Create a new candidate asset
    pub fn new_candidate(
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
    ) -> Result<Self> {
        let unit_size = process.unit_size;
        Self::new_with_state(
            AssetState::Candidate,
            process,
            region_id,
            AssetCapacity::from_capacity(capacity, unit_size),
            commission_year,
            None,
        )
    }

    /// Create a new candidate for use in dispatch runs
    ///
    /// These candidates will have a single continuous capacity specified by the model parameter
    /// `candidate_asset_capacity`, regardless of whether the underlying process is divisible or
    /// not.
    pub fn new_candidate_for_dispatch(
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
    ) -> Result<Self> {
        Self::new_with_state(
            AssetState::Candidate,
            process,
            region_id,
            AssetCapacity::Continuous(capacity),
            commission_year,
            None,
        )
    }

    /// Create a new candidate asset from a commissioned asset
    pub fn new_candidate_from_commissioned(asset: &Asset) -> Self {
        assert!(asset.is_commissioned(), "Asset must be commissioned");

        Self {
            state: AssetState::Candidate,
            ..asset.clone()
        }
    }

    /// Create a new future asset
    pub fn new_future_with_max_decommission(
        agent_id: AgentID,
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
        max_decommission_year: Option<u32>,
    ) -> Result<Self> {
        check_capacity_valid_for_asset(capacity)?;
        let unit_size = process.unit_size;
        Self::new_with_state(
            AssetState::Future { agent_id },
            process,
            region_id,
            AssetCapacity::from_capacity(capacity, unit_size),
            commission_year,
            max_decommission_year,
        )
    }

    /// Create a new future asset
    pub fn new_future(
        agent_id: AgentID,
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
    ) -> Result<Self> {
        Self::new_future_with_max_decommission(
            agent_id,
            process,
            region_id,
            capacity,
            commission_year,
            None,
        )
    }

    /// Create a new selected asset
    ///
    /// This is only used for testing. In the real program, Selected assets can only be created from
    /// Candidate assets by calling `select_candidate_for_investment`.
    #[cfg(test)]
    fn new_selected(
        agent_id: AgentID,
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
    ) -> Result<Self> {
        let unit_size = process.unit_size;
        Self::new_with_state(
            AssetState::Selected { agent_id },
            process,
            region_id,
            AssetCapacity::from_capacity(capacity, unit_size),
            commission_year,
            None,
        )
    }

    /// Create a new commissioned asset
    ///
    /// This is only used for testing. WARNING: These assets always have an ID of zero, so can
    /// create hash collisions. Use with care.
    #[cfg(test)]
    pub fn new_commissioned(
        agent_id: AgentID,
        process: Rc<Process>,
        region_id: RegionID,
        capacity: Capacity,
        commission_year: u32,
    ) -> Result<Self> {
        let unit_size = process.unit_size;
        Self::new_with_state(
            AssetState::Commissioned {
                id: AssetID(0),
                agent_id,
                mothballed_year: None,
                parent: None,
            },
            process,
            region_id,
            AssetCapacity::from_capacity(capacity, unit_size),
            commission_year,
            None,
        )
    }

    /// Private helper to create an asset with the given state
    fn new_with_state(
        state: AssetState,
        process: Rc<Process>,
        region_id: RegionID,
        capacity: AssetCapacity,
        commission_year: u32,
        max_decommission_year: Option<u32>,
    ) -> Result<Self> {
        check_region_year_valid_for_process(&process, &region_id, commission_year)?;
        ensure!(
            capacity.total_capacity() >= Capacity(0.0),
            "Capacity must be non-negative"
        );

        // There should be activity limits, commodity flows and process parameters for all
        // **milestone** years, but it is possible to have assets that are commissioned before the
        // simulation start from assets.csv. We check for the presence of the params lazily to
        // prevent users having to supply them for all the possible valid years before the time
        // horizon.
        let key = (region_id.clone(), commission_year);
        let activity_limits = process
            .activity_limits
            .get(&key)
            .with_context(|| {
                format!(
                    "No process availabilities supplied for process {} in region {} in year {}. \
                    You should update process_availabilities.csv.",
                    &process.id, region_id, commission_year
                )
            })?
            .clone();
        let flows = process
            .flows
            .get(&key)
            .with_context(|| {
                format!(
                    "No commodity flows supplied for process {} in region {} in year {}. \
                    You should update process_flows.csv.",
                    &process.id, region_id, commission_year
                )
            })?
            .clone();
        let process_parameter = process
            .parameters
            .get(&key)
            .with_context(|| {
                format!(
                    "No process parameters supplied for process {} in region {} in year {}. \
                    You should update process_parameters.csv.",
                    &process.id, region_id, commission_year
                )
            })?
            .clone();

        let max_decommission_year =
            max_decommission_year.unwrap_or(commission_year + process_parameter.lifetime);
        ensure!(
            max_decommission_year >= commission_year,
            "Max decommission year must be after/same as commission year"
        );

        Ok(Self {
            state,
            process,
            activity_limits,
            flows,
            process_parameter,
            region_id,
            capacity: Cell::new(capacity),
            commission_year,
            max_decommission_year,
        })
    }

    /// Get the state of this asset
    pub fn state(&self) -> &AssetState {
        &self.state
    }

    /// The process parameter for this asset
    pub fn process_parameter(&self) -> &ProcessParameter {
        &self.process_parameter
    }

    /// The last year in which this asset should be decommissioned
    pub fn max_decommission_year(&self) -> u32 {
        self.max_decommission_year
    }

    /// Get the activity limits per unit of capacity for this asset in a particular time slice
    pub fn get_activity_per_capacity_limits(
        &self,
        time_slice: &TimeSliceID,
    ) -> RangeInclusive<ActivityPerCapacity> {
        let limits = &self.activity_limits.get_limit_for_time_slice(time_slice);
        let cap2act = self.process.capacity_to_activity;
        (cap2act * *limits.start())..=(cap2act * *limits.end())
    }

    /// Get the activity limits for this asset for a given time slice selection
    pub fn get_activity_limits_for_selection(
        &self,
        time_slice_selection: &TimeSliceSelection,
    ) -> RangeInclusive<Activity> {
        let activity_per_capacity_limits = self.activity_limits.get_limit(time_slice_selection);
        let cap2act = self.process.capacity_to_activity;
        let max_activity = self.total_capacity() * cap2act;
        let lb = max_activity * *activity_per_capacity_limits.start();
        let ub = max_activity * *activity_per_capacity_limits.end();
        lb..=ub
    }

    /// Iterate over activity limits for this asset
    pub fn iter_activity_limits(
        &self,
    ) -> impl Iterator<Item = (TimeSliceSelection, RangeInclusive<Activity>)> + '_ {
        let max_act = self.max_activity();
        self.activity_limits
            .iter_limits()
            .map(move |(ts_sel, limit)| {
                (
                    ts_sel,
                    (max_act * *limit.start())..=(max_act * *limit.end()),
                )
            })
    }

    /// Iterate over activity per capacity limits for this asset
    pub fn iter_activity_per_capacity_limits(
        &self,
    ) -> impl Iterator<Item = (TimeSliceSelection, RangeInclusive<ActivityPerCapacity>)> + '_ {
        let cap2act = self.process.capacity_to_activity;
        self.activity_limits
            .iter_limits()
            .map(move |(ts_sel, limit)| {
                (
                    ts_sel,
                    (cap2act * *limit.start())..=(cap2act * *limit.end()),
                )
            })
    }

    /// Gets the total SED/SVD output per unit of activity for this asset
    ///
    /// Note: Since we are summing coefficients from different commodities, this ONLY makes sense
    /// if these commodities have the same units (e.g., all in PJ). Users are currently not made to
    /// give units for commodities, so we cannot possibly enforce this. Something to potentially
    /// address in future.
    pub fn get_total_output_per_activity(&self) -> FlowPerActivity {
        self.iter_output_flows().map(|flow| flow.coeff).sum()
    }

    /// Get the operating cost for this asset in a given year and time slice
    pub fn get_operating_cost(&self, year: u32, time_slice: &TimeSliceID) -> MoneyPerActivity {
        // The cost for all commodity flows (including levies/incentives)
        let flows_cost = self
            .iter_flows()
            .map(|flow| flow.get_total_cost_per_activity(&self.region_id, year, time_slice))
            .sum();

        self.process_parameter.variable_operating_cost + flows_cost
    }

    /// Get the total revenue from all flows for this asset.
    ///
    /// If a price is missing, it is assumed to be zero.
    pub fn get_revenue_from_flows(
        &self,
        prices: &CommodityPrices,
        time_slice: &TimeSliceID,
    ) -> MoneyPerActivity {
        self.get_revenue_from_flows_with_filter(prices, time_slice, |_| true)
    }

    /// Get the total revenue from all flows excluding the primary output.
    ///
    /// If a price is missing, it is assumed to be zero.
    pub fn get_revenue_from_flows_excluding_primary(
        &self,
        prices: &CommodityPrices,
        time_slice: &TimeSliceID,
    ) -> MoneyPerActivity {
        let excluded_commodity = self.primary_output().map(|flow| &flow.commodity.id);

        self.get_revenue_from_flows_with_filter(prices, time_slice, |flow| {
            excluded_commodity.is_none_or(|commodity_id| commodity_id != &flow.commodity.id)
        })
    }

    /// Get the total cost of purchasing input commodities per unit of activity for this asset.
    ///
    /// If a price is missing, there is assumed to be no cost.
    pub fn get_input_cost_from_prices(
        &self,
        prices: &CommodityPrices,
        time_slice: &TimeSliceID,
    ) -> MoneyPerActivity {
        // Revenues of input flows are negative costs, so we negate the result
        -self.get_revenue_from_flows_with_filter(prices, time_slice, |x| {
            x.direction() == FlowDirection::Input
        })
    }

    /// Get the total revenue from a subset of flows.
    ///
    /// Takes a function as an argument to filter the flows. If a price is missing, it is assumed to
    /// be zero.
    fn get_revenue_from_flows_with_filter<F>(
        &self,
        prices: &CommodityPrices,
        time_slice: &TimeSliceID,
        mut filter_for_flows: F,
    ) -> MoneyPerActivity
    where
        F: FnMut(&ProcessFlow) -> bool,
    {
        self.iter_flows()
            .filter(|flow| filter_for_flows(flow))
            .map(|flow| {
                flow.coeff
                    * prices
                        .get(&flow.commodity.id, &self.region_id, time_slice)
                        .unwrap_or(MoneyPerFlow(0.0))
            })
            .sum()
    }

    /// Get the generic activity cost per unit of activity for this asset.
    ///
    /// These are all activity-related costs that are not associated with specific SED/SVD outputs.
    /// Includes levies, flow costs, costs of inputs and variable operating costs
    fn get_generic_activity_cost(
        &self,
        prices: &CommodityPrices,
        year: u32,
        time_slice: &TimeSliceID,
    ) -> MoneyPerActivity {
        // The cost of purchasing input commodities
        let cost_of_inputs = self.get_input_cost_from_prices(prices, time_slice);

        // Flow costs/levies for all flows except SED/SVD outputs
        let excludes_sed_svd_output = |flow: &&ProcessFlow| {
            !(flow.direction() == FlowDirection::Output
                && matches!(
                    flow.commodity.kind,
                    CommodityType::SupplyEqualsDemand | CommodityType::ServiceDemand
                ))
        };
        let flow_costs = self
            .iter_flows()
            .filter(excludes_sed_svd_output)
            .map(|flow| flow.get_total_cost_per_activity(&self.region_id, year, time_slice))
            .sum();

        cost_of_inputs + flow_costs + self.process_parameter.variable_operating_cost
    }

    /// Iterate over marginal costs for a filtered set of SED/SVD output commodities for this asset
    ///
    /// For each SED/SVD output commodity, the marginal cost is calculated as the sum of:
    /// - Generic activity costs (variable operating costs, cost of purchasing inputs, plus all
    ///   levies and flow costs not associated with specific SED/SVD outputs), which are
    ///   shared equally over all SED/SVD outputs
    /// - Production levies and flow costs for the specific SED/SVD output commodity
    pub fn iter_marginal_costs_with_filter<'a>(
        &'a self,
        prices: &'a CommodityPrices,
        year: u32,
        time_slice: &'a TimeSliceID,
        filter: impl Fn(&CommodityID) -> bool + 'a,
    ) -> Box<dyn Iterator<Item = (CommodityID, MoneyPerFlow)> + 'a> {
        // Iterator over SED/SVD output flows matching the filter
        let mut output_flows_iter = self
            .iter_output_flows()
            .filter(move |flow| filter(&flow.commodity.id))
            .peekable();

        // If there are no output flows after filtering, return an empty iterator
        if output_flows_iter.peek().is_none() {
            return Box::new(std::iter::empty::<(CommodityID, MoneyPerFlow)>());
        }

        // Calculate generic activity costs.
        // This is all activity costs not associated with specific SED/SVD outputs, which will get
        // shared equally over all SED/SVD outputs. Includes levies, flow costs, costs of inputs and
        // variable operating costs
        let generic_activity_cost = self.get_generic_activity_cost(prices, year, time_slice);

        // Share generic activity costs equally over all SED/SVD outputs
        // We sum the output coefficients of all SED/SVD commodities to get total output, then
        // divide costs by this total output to get the generic cost per unit of output.
        // Note: only works if all SED/SVD outputs have the same units - not currently checked!
        let total_output_per_activity = self.get_total_output_per_activity();
        assert!(total_output_per_activity > FlowPerActivity::EPSILON); // input checks should guarantee this
        let generic_cost_per_flow = generic_activity_cost / total_output_per_activity;

        // Iterate over SED/SVD output flows
        Box::new(output_flows_iter.map(move |flow| {
            // Get the costs for this specific commodity flow
            let commodity_specific_costs_per_flow =
                flow.get_total_cost_per_flow(&self.region_id, year, time_slice);

            // Add these to the generic costs to get total cost for this commodity
            let marginal_cost = generic_cost_per_flow + commodity_specific_costs_per_flow;
            (flow.commodity.id.clone(), marginal_cost)
        }))
    }

    /// Iterate over marginal costs for all SED/SVD output commodities for this asset
    ///
    /// See `iter_marginal_costs_with_filter` for details.
    pub fn iter_marginal_costs<'a>(
        &'a self,
        prices: &'a CommodityPrices,
        year: u32,
        time_slice: &'a TimeSliceID,
    ) -> Box<dyn Iterator<Item = (CommodityID, MoneyPerFlow)> + 'a> {
        self.iter_marginal_costs_with_filter(prices, year, time_slice, move |_| true)
    }

    /// Get the annual capital cost per unit of capacity for this asset
    pub fn get_annual_capital_cost_per_capacity(&self) -> MoneyPerCapacity {
        let capital_cost = self.process_parameter.capital_cost;
        let lifetime = self.process_parameter.lifetime;
        let discount_rate = self.process_parameter.discount_rate;
        annual_capital_cost(capital_cost, lifetime, discount_rate)
    }

    /// Get the annual fixed costs (AFC) per unit of activity for this asset
    ///
    /// Total capital costs and fixed opex are shared equally over the year in accordance with the
    /// annual activity.
    pub fn get_annual_fixed_costs_per_activity(
        &self,
        annual_activity: Activity,
    ) -> MoneyPerActivity {
        let annual_capital_cost_per_capacity = self.get_annual_capital_cost_per_capacity();
        let annual_fixed_opex = self.process_parameter.fixed_operating_cost * Year(1.0);
        let total_annual_fixed_costs =
            (annual_capital_cost_per_capacity + annual_fixed_opex) * self.total_capacity();
        assert!(
            annual_activity > Activity::EPSILON,
            "Cannot calculate annual fixed costs per activity for an asset with zero annual activity"
        );
        total_annual_fixed_costs / annual_activity
    }

    /// Get the annual fixed costs (AFC) per unit of output flow for this asset
    ///
    /// Total capital costs and fixed opex are shared equally across all output flows in accordance
    /// with the annual activity and total output per unit of activity.
    pub fn get_annual_fixed_costs_per_flow(&self, annual_activity: Activity) -> MoneyPerFlow {
        let annual_fixed_costs_per_activity =
            self.get_annual_fixed_costs_per_activity(annual_activity);
        let total_output_per_activity = self.get_total_output_per_activity();
        assert!(total_output_per_activity > FlowPerActivity::EPSILON); // input checks should guarantee this
        annual_fixed_costs_per_activity / total_output_per_activity
    }

    /// Maximum activity for this asset
    pub fn max_activity(&self) -> Activity {
        self.total_capacity() * self.process.capacity_to_activity
    }

    /// Get a specific process flow
    pub fn get_flow(&self, commodity_id: &CommodityID) -> Option<&ProcessFlow> {
        self.flows.get(commodity_id)
    }

    /// Iterate over the asset's flows
    pub fn iter_flows(&self) -> impl Iterator<Item = &ProcessFlow> {
        self.flows.values()
    }

    /// Iterate over the asset's output SED/SVD flows
    pub fn iter_output_flows(&self) -> impl Iterator<Item = &ProcessFlow> {
        self.flows.values().filter(|flow| {
            flow.direction() == FlowDirection::Output
                && matches!(
                    flow.commodity.kind,
                    CommodityType::SupplyEqualsDemand | CommodityType::ServiceDemand
                )
        })
    }

    /// Get the primary output flow (if any) for this asset
    pub fn primary_output(&self) -> Option<&ProcessFlow> {
        self.process
            .primary_output
            .as_ref()
            .map(|commodity_id| &self.flows[commodity_id])
    }

    /// Whether this asset has been commissioned
    pub fn is_commissioned(&self) -> bool {
        matches!(&self.state, AssetState::Commissioned { .. })
    }

    /// Get the commission year for this asset
    pub fn commission_year(&self) -> u32 {
        self.commission_year
    }

    /// Get the decommission year for this asset
    pub fn decommission_year(&self) -> Option<u32> {
        match &self.state {
            AssetState::Decommissioned {
                decommission_year, ..
            } => Some(*decommission_year),
            _ => None,
        }
    }

    /// Get the region ID for this asset
    pub fn region_id(&self) -> &RegionID {
        &self.region_id
    }

    /// Get the process for this asset
    pub fn process(&self) -> &Process {
        &self.process
    }

    /// Get the process ID for this asset
    pub fn process_id(&self) -> &ProcessID {
        &self.process.id
    }

    /// Get the ID for this asset
    pub fn id(&self) -> Option<AssetID> {
        match &self.state {
            AssetState::Commissioned { id, .. } | AssetState::Decommissioned { id, .. } => {
                Some(*id)
            }
            _ => None,
        }
    }

    /// Get the parent asset of this asset, if any
    pub fn parent(&self) -> Option<&AssetRef> {
        match &self.state {
            AssetState::Commissioned { parent, .. } => parent.as_ref(),
            _ => None,
        }
    }

    /// Whether this asset is a parent of divided assets
    pub fn is_parent(&self) -> bool {
        matches!(self.state, AssetState::Parent { .. })
    }

    /// Get the number of children this asset has.
    ///
    /// If this asset is not a parent, then `None` is returned.
    pub fn num_children(&self) -> Option<u32> {
        match &self.state {
            AssetState::Parent { .. } => Some(self.capacity().n_units().unwrap()),
            _ => None,
        }
    }

    /// Get the group ID for this asset, if any
    pub fn group_id(&self) -> Option<AssetGroupID> {
        match &self.state {
            AssetState::Commissioned { parent, .. } => {
                // Get group ID from parent
                parent
                    .as_ref()
                    // Safe because parents always have state `Parent`
                    .map(|parent| parent.group_id().unwrap())
            }
            AssetState::Parent { group_id, .. } => Some(*group_id),
            _ => None,
        }
    }

    /// Get the agent ID for this asset, if any
    pub fn agent_id(&self) -> Option<&AgentID> {
        match &self.state {
            AssetState::Commissioned { agent_id, .. }
            | AssetState::Decommissioned { agent_id, .. }
            | AssetState::Future { agent_id }
            | AssetState::Selected { agent_id }
            | AssetState::Parent { agent_id, .. } => Some(agent_id),
            AssetState::Candidate => None,
        }
    }

    /// Get the capacity for this asset
    pub fn capacity(&self) -> AssetCapacity {
        self.capacity.get()
    }

    /// Get the total capacity for this asset
    pub fn total_capacity(&self) -> Capacity {
        self.capacity().total_capacity()
    }

    /// Set the capacity for this asset (only for Candidate or Selected assets)
    pub fn set_capacity(&mut self, capacity: AssetCapacity) {
        assert!(
            matches!(
                self.state,
                AssetState::Candidate | AssetState::Selected { .. }
            ),
            "set_capacity can only be called on Candidate or Selected assets"
        );
        assert!(
            capacity.total_capacity() >= Capacity(0.0),
            "Capacity must be >= 0"
        );
        self.capacity().assert_same_type(capacity);

        // As `capacity` is a `Cell`, we don't actually need a `mut` ref to `self`, but allowing for
        // changing the capacity of immutable refs would be potentially dangerous
        self.capacity.set(capacity);
    }

    /// Increase the capacity for this asset (only for Candidate assets)
    pub fn increase_capacity(&mut self, capacity: AssetCapacity) {
        assert!(
            self.state == AssetState::Candidate,
            "increase_capacity can only be called on Candidate assets"
        );
        assert!(
            capacity.total_capacity() > Capacity(0.0),
            "Capacity increase must be positive"
        );

        // As `capacity` is a `Cell`, we don't actually need a `mut` ref to `self`, but allowing for
        // changing the capacity of immutable refs would be potentially dangerous
        self.capacity.update(|c| c + capacity);
    }

    /// Decrease the unit count (number of units) of this asset by one.
    ///
    /// Note that this method uses interior mutability so that we can operate on an immutable ref to
    /// `self`. Accordingly, calling this method will result in a change in the capacity for all
    /// `Rc` copies of the asset, which is potentially dangerous. This method is therefore private
    /// and should **only** be used for the case where we want to decrease the unit count for parent
    /// assets.
    fn decrement_unit_count(&self) {
        let AssetCapacity::Discrete(n_units, unit_size) = self.capacity() else {
            panic!("Cannot decrement unit count of non-divisible asset");
        };
        assert!(n_units > 0, "Unit count has dropped below zero");

        self.capacity
            .set(AssetCapacity::Discrete(n_units - 1, unit_size));
    }

    /// Decommission this asset
    fn decommission(&mut self, decommission_year: u32, reason: &str) {
        let (id, agent_id, parent) = match &self.state {
            AssetState::Commissioned {
                id,
                agent_id,
                parent,
                ..
            } => (*id, agent_id.clone(), parent),
            _ => panic!("Cannot decommission an asset that hasn't been commissioned"),
        };
        debug!(
            "Decommissioning '{}' asset (ID: {}) for agent '{}' (reason: {})",
            self.process_id(),
            id,
            agent_id,
            reason
        );

        // If this is a child asset, we need to decrease the parent's capacity appropriately
        if let Some(parent) = parent {
            parent.decrement_unit_count();
        }

        self.state = AssetState::Decommissioned {
            id,
            agent_id,
            decommission_year: decommission_year.min(self.max_decommission_year()),
        };
    }

    /// Commission the asset.
    ///
    /// Only assets with an [`AssetState`] of `Future` or `Selected` can be commissioned. If the
    /// asset's state is something else, this function will panic.
    ///
    /// # Arguments
    ///
    /// * `id` - The ID to give the newly commissioned asset
    /// * `reason` - The reason for commissioning (included in log)
    /// * `parent` - The parent asset, if this is a child asset
    fn commission(&mut self, id: AssetID, parent: Option<AssetRef>, reason: &str) {
        let agent_id = match &self.state {
            AssetState::Future { agent_id } | AssetState::Selected { agent_id } => agent_id,
            state => panic!("Assets with state {state} cannot be commissioned"),
        };
        debug!(
            "Commissioning '{}' asset (ID: {}, capacity: {}) for agent '{}' (reason: {})",
            self.process_id(),
            id,
            self.total_capacity(),
            agent_id,
            reason
        );
        self.state = AssetState::Commissioned {
            id,
            agent_id: agent_id.clone(),
            mothballed_year: None,
            parent,
        };
    }

    /// Select a Candidate asset for investment, converting it to a Selected state
    pub fn select_candidate_for_investment(&mut self, agent_id: AgentID) {
        assert!(
            self.state == AssetState::Candidate,
            "select_candidate_for_investment can only be called on Candidate assets"
        );
        check_capacity_valid_for_asset(self.total_capacity()).unwrap();
        self.state = AssetState::Selected { agent_id };
    }

    /// Set the year this asset was mothballed
    pub fn mothball(&mut self, year: u32) {
        let (id, agent_id, parent) = match &self.state {
            AssetState::Commissioned {
                id,
                agent_id,
                parent,
                ..
            } => (*id, agent_id.clone(), parent.clone()),
            _ => panic!("Cannot mothball an asset that hasn't been commissioned"),
        };
        self.state = AssetState::Commissioned {
            id,
            agent_id,
            mothballed_year: Some(year),
            parent,
        };
    }

    /// Remove the mothballed year - presumably because the asset has been used
    pub fn unmothball(&mut self) {
        let (id, agent_id, parent) = match &self.state {
            AssetState::Commissioned {
                id,
                agent_id,
                parent,
                ..
            } => (*id, agent_id.clone(), parent.clone()),
            _ => panic!("Cannot unmothball an asset that hasn't been commissioned"),
        };
        self.state = AssetState::Commissioned {
            id,
            agent_id,
            mothballed_year: None,
            parent,
        };
    }

    /// Get the mothballed year for the asset
    pub fn get_mothballed_year(&self) -> Option<u32> {
        let AssetState::Commissioned {
            mothballed_year, ..
        } = &self.state
        else {
            panic!("Cannot get mothballed year for an asset that hasn't been commissioned")
        };
        *mothballed_year
    }

    /// Get the unit size for this asset's capacity (if any)
    pub fn unit_size(&self) -> Option<Capacity> {
        match self.capacity() {
            AssetCapacity::Discrete(_, size) => Some(size),
            AssetCapacity::Continuous(_) => None,
        }
    }

    /// For non-commissioned assets, get the maximum capacity permitted to be installed based on the
    /// investment constraints for the asset's process.
    ///
    /// The limit is taken from the process's investment constraints for the asset's region and
    /// commission year, and the portion of the commodity demand being considered.
    ///
    /// For divisible assets, the returned capacity will be rounded down to the nearest multiple of
    /// the asset's unit size.
    pub fn max_installable_capacity(
        &self,
        commodity_portion: Dimensionless,
    ) -> Option<AssetCapacity> {
        assert!(
            !self.is_commissioned(),
            "max_installable_capacity can only be called on uncommissioned assets"
        );
        assert!(
            commodity_portion >= Dimensionless(0.0) && commodity_portion <= Dimensionless(1.0),
            "commodity_portion must be between 0 and 1 inclusive"
        );

        self.process
            .investment_constraints
            .get(&(self.region_id.clone(), self.commission_year))
            .and_then(|c| c.get_addition_limit().map(|l| l * commodity_portion))
            .map(|limit| AssetCapacity::from_capacity_floor(limit, self.unit_size()))
    }
}

#[allow(clippy::missing_fields_in_debug)]
impl std::fmt::Debug for Asset {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Asset")
            .field("state", &self.state)
            .field("process_id", &self.process_id())
            .field("region_id", &self.region_id)
            .field("capacity", &self.total_capacity())
            .field("commission_year", &self.commission_year)
            .finish()
    }
}

/// Whether the process operates in the specified region and year
pub fn check_region_year_valid_for_process(
    process: &Process,
    region_id: &RegionID,
    year: u32,
) -> Result<()> {
    ensure!(
        process.regions.contains(region_id),
        "Process {} does not operate in region {}",
        process.id,
        region_id
    );
    ensure!(
        process.active_for_year(year),
        "Process {} does not operate in the year {}",
        process.id,
        year
    );
    Ok(())
}

/// Whether the specified value is a valid capacity for an asset
pub fn check_capacity_valid_for_asset(capacity: Capacity) -> Result<()> {
    ensure!(
        capacity.is_finite() && capacity > Capacity(0.0),
        "Capacity must be a finite, positive number"
    );
    Ok(())
}

/// A wrapper around [`Asset`] for storing references in maps.
///
/// If the asset has been commissioned, then comparison and hashing is done based on the asset ID,
/// otherwise a combination of other parameters is used.
///
/// [`Ord`] is implemented for [`AssetRef`], but it will panic for non-commissioned assets.
#[derive(Clone, Debug)]
pub struct AssetRef(Rc<Asset>);

impl AssetRef {
    /// Make a mutable reference to the underlying [`Asset`]
    pub fn make_mut(&mut self) -> &mut Asset {
        Rc::make_mut(&mut self.0)
    }

    /// Apply a function to each of this asset's children, consuming the asset in the process.
    ///
    /// If this asset is divisible, the first argument to `f` will be this asset after it has been
    /// converted to a parent and the second will be each child.
    ///
    /// If this asset is non-divisible (i.e. does not have a discrete capacity), then `f` will be
    /// called with the first argument set to `None` and the second will be `self`.
    ///
    /// When the asset has a discrete capacity, each of the children will be made up of a single
    /// unit of the original asset's unit size.
    ///
    /// Panics if this asset's state is not `Future` or `Selected`.
    fn into_for_each_child<F>(mut self, next_group_id: &mut u32, mut f: F)
    where
        F: FnMut(Option<&AssetRef>, AssetRef),
    {
        assert!(
            matches!(
                self.state,
                AssetState::Future { .. } | AssetState::Selected { .. }
            ),
            "Assets with state {} cannot be divided. Only Future or Selected assets can be divided",
            self.state
        );

        let AssetCapacity::Discrete(n_units, unit_size) = self.capacity() else {
            // Asset is non-divisible
            f(None, self);
            return;
        };

        // Create a child of size `unit_size`
        let child = AssetRef::from(Asset {
            capacity: Cell::new(AssetCapacity::Discrete(1, unit_size)),
            ..Asset::clone(&self)
        });

        // Turn this asset into a parent
        let agent_id = self.agent_id().unwrap().clone();
        self.make_mut().state = AssetState::Parent {
            agent_id,
            group_id: AssetGroupID(*next_group_id),
        };
        *next_group_id += 1;

        // Run `f` over each child
        for child in iter::repeat_n(child, n_units as usize) {
            f(Some(&self), child);
        }
    }
}

impl From<Rc<Asset>> for AssetRef {
    fn from(value: Rc<Asset>) -> Self {
        Self(value)
    }
}

impl From<Asset> for AssetRef {
    fn from(value: Asset) -> Self {
        Self::from(Rc::new(value))
    }
}

impl From<AssetRef> for Rc<Asset> {
    fn from(value: AssetRef) -> Self {
        value.0
    }
}

impl Deref for AssetRef {
    type Target = Asset;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl PartialEq for AssetRef {
    fn eq(&self, other: &Self) -> bool {
        // For assets to be considered equal, they must have the same process, region, commission
        // year and state
        Rc::ptr_eq(&self.0.process, &other.0.process)
            && self.0.region_id == other.0.region_id
            && self.0.commission_year == other.0.commission_year
            && self.0.state == other.0.state
    }
}

impl Eq for AssetRef {}

impl Hash for AssetRef {
    /// Hash an asset according to its state:
    /// - Commissioned assets are hashed based on their ID alone
    /// - Selected assets are hashed based on `process_id`, `region_id`, `commission_year` and
    ///   `agent_id`
    /// - Candidate assets are hashed based on `process_id`, `region_id` and `commission_year`
    /// - Parent assets are hashed based on `agent_id` and `group_id`
    /// - Future and Decommissioned assets cannot currently be hashed
    fn hash<H: Hasher>(&self, state: &mut H) {
        match &self.0.state {
            AssetState::Commissioned { id, .. } => {
                // Hashed based on their ID alone, since this is sufficient to uniquely identify the
                // asset
                id.hash(state);
            }
            AssetState::Candidate | AssetState::Selected { .. } | AssetState::Parent { .. } => {
                self.0.process.id.hash(state);
                self.0.region_id.hash(state);
                self.0.commission_year.hash(state);
                self.0.agent_id().hash(state);
                self.0.group_id().hash(state);
            }
            state => {
                // We don't need to hash other types of asset
                panic!("Cannot hash {state} assets");
            }
        }
    }
}

impl PartialOrd for AssetRef {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for AssetRef {
    fn cmp(&self, other: &Self) -> Ordering {
        self.id().unwrap().cmp(&other.id().unwrap())
    }
}

/// Additional methods for iterating over assets
pub trait AssetIterator<'a>: Iterator<Item = &'a AssetRef> + Sized
where
    Self: 'a,
{
    /// Filter assets by the agent that owns them
    fn filter_agent(self, agent_id: &'a AgentID) -> impl Iterator<Item = &'a AssetRef> + 'a {
        self.filter(move |asset| asset.agent_id() == Some(agent_id))
    }

    /// Iterate over assets that have the given commodity as a primary output
    fn filter_primary_producers_of(
        self,
        commodity_id: &'a CommodityID,
    ) -> impl Iterator<Item = &'a AssetRef> + 'a {
        self.filter(move |asset| {
            asset
                .primary_output()
                .is_some_and(|flow| &flow.commodity.id == commodity_id)
        })
    }

    /// Filter the assets by region
    fn filter_region(self, region_id: &'a RegionID) -> impl Iterator<Item = &'a AssetRef> + 'a {
        self.filter(move |asset| asset.region_id == *region_id)
    }

    /// Iterate over process flows affecting the given commodity
    fn flows_for_commodity(
        self,
        commodity_id: &'a CommodityID,
    ) -> impl Iterator<Item = (&'a AssetRef, &'a ProcessFlow)> + 'a {
        self.filter_map(|asset| Some((asset, asset.get_flow(commodity_id)?)))
    }
}

impl<'a, I> AssetIterator<'a> for I where I: Iterator<Item = &'a AssetRef> + Sized + 'a {}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::commodity::Commodity;
    use crate::fixture::{
        assert_error, assert_patched_runs_ok_simple, assert_validate_fails_with_simple, asset,
        asset_divisible, process, process_activity_limits_map, process_flows_map, region_id,
        svd_commodity, time_slice, time_slice_info,
    };
    use crate::patch::FilePatch;
    use crate::process::{FlowType, Process, ProcessFlow};
    use crate::region::RegionID;
    use crate::time_slice::{TimeSliceID, TimeSliceInfo};
    use crate::units::{
        ActivityPerCapacity, Capacity, Dimensionless, FlowPerActivity, MoneyPerActivity,
        MoneyPerFlow,
    };
    use float_cmp::assert_approx_eq;
    use indexmap::indexmap;
    use rstest::{fixture, rstest};
    use std::rc::Rc;

    #[rstest]
    fn get_input_cost_from_prices_works(
        region_id: RegionID,
        svd_commodity: Commodity,
        mut process: Process,
        time_slice: TimeSliceID,
    ) {
        // Update the process flows using the existing commodity fixture
        let commodity_rc = Rc::new(svd_commodity);
        let process_flow = ProcessFlow {
            commodity: Rc::clone(&commodity_rc),
            coeff: FlowPerActivity(-2.0), // Input
            kind: FlowType::Fixed,
            cost: MoneyPerFlow(0.0),
        };
        let process_flows = indexmap! { commodity_rc.id.clone() => process_flow.clone() };
        let process_flows_map = process_flows_map(process.regions.clone(), Rc::new(process_flows));
        process.flows = process_flows_map;

        // Create asset
        let asset =
            Asset::new_candidate(Rc::new(process), region_id.clone(), Capacity(1.0), 2020).unwrap();

        // Set input prices
        let mut input_prices = CommodityPrices::default();
        input_prices.insert(&commodity_rc.id, &region_id, &time_slice, MoneyPerFlow(3.0));

        // Call function
        let cost = asset.get_input_cost_from_prices(&input_prices, &time_slice);
        // Should be -coeff * price = -(-2.0) * 3.0 = 6.0
        assert_approx_eq!(MoneyPerActivity, cost, MoneyPerActivity(6.0));
    }

    #[rstest]
    #[case(Capacity(0.01))]
    #[case(Capacity(0.5))]
    #[case(Capacity(1.0))]
    #[case(Capacity(100.0))]
    fn asset_new_valid(process: Process, #[case] capacity: Capacity) {
        let agent_id = AgentID("agent1".into());
        let region_id = RegionID("GBR".into());
        let asset = Asset::new_future(agent_id, process.into(), region_id, capacity, 2015).unwrap();
        assert!(asset.id().is_none());
    }

    #[rstest]
    #[case(Capacity(0.0))]
    #[case(Capacity(-0.01))]
    #[case(Capacity(-1.0))]
    #[case(Capacity(f64::NAN))]
    #[case(Capacity(f64::INFINITY))]
    #[case(Capacity(f64::NEG_INFINITY))]
    fn asset_new_invalid_capacity(process: Process, #[case] capacity: Capacity) {
        let agent_id = AgentID("agent1".into());
        let region_id = RegionID("GBR".into());
        assert_error!(
            Asset::new_future(agent_id, process.into(), region_id, capacity, 2015),
            "Capacity must be a finite, positive number"
        );
    }

    #[rstest]
    fn asset_new_invalid_commission_year(process: Process) {
        let agent_id = AgentID("agent1".into());
        let region_id = RegionID("GBR".into());
        assert_error!(
            Asset::new_future(agent_id, process.into(), region_id, Capacity(1.0), 2007),
            "Process process1 does not operate in the year 2007"
        );
    }

    #[rstest]
    fn asset_new_invalid_region(process: Process) {
        let agent_id = AgentID("agent1".into());
        let region_id = RegionID("FRA".into());
        assert_error!(
            Asset::new_future(agent_id, process.into(), region_id, Capacity(1.0), 2015),
            "Process process1 does not operate in region FRA"
        );
    }

    #[fixture]
    fn process_with_activity_limits(
        mut process: Process,
        time_slice_info: TimeSliceInfo,
        time_slice: TimeSliceID,
    ) -> Process {
        // Add activity limits to the process
        let mut activity_limits = ActivityLimits::new_with_full_availability(&time_slice_info);
        activity_limits.add_time_slice_limit(time_slice, Dimensionless(0.1)..=Dimensionless(0.5));
        process.activity_limits =
            process_activity_limits_map(process.regions.clone(), activity_limits);

        // Update cap2act
        process.capacity_to_activity = ActivityPerCapacity(2.0);
        process
    }

    #[fixture]
    fn asset_with_activity_limits(process_with_activity_limits: Process) -> Asset {
        Asset::new_future(
            "agent1".into(),
            Rc::new(process_with_activity_limits),
            "GBR".into(),
            Capacity(2.0),
            2010,
        )
        .unwrap()
    }

    #[rstest]
    fn asset_get_activity_per_capacity_limits(
        asset_with_activity_limits: Asset,
        time_slice: TimeSliceID,
    ) {
        // With cap2act of 2, and activity limits of 0.1..=0.5, should get 0.2..=1.0
        assert_eq!(
            asset_with_activity_limits.get_activity_per_capacity_limits(&time_slice),
            ActivityPerCapacity(0.2)..=ActivityPerCapacity(1.0)
        );
    }

    #[rstest]
    #[case::exact_multiple(Capacity(12.0), Capacity(4.0), 3)] // 12 / 4 = 3
    #[case::rounded_up(Capacity(11.0), Capacity(4.0), 3)] // 11 / 4 = 2.75 -> 3
    #[case::unit_size_equals_capacity(Capacity(4.0), Capacity(4.0), 1)] // 4 / 4 = 1
    #[case::unit_size_greater_than_capacity(Capacity(3.0), Capacity(4.0), 1)] // 3 / 4 = 0.75 -> 1
    fn into_for_each_child_divisible(
        mut process: Process,
        #[case] capacity: Capacity,
        #[case] unit_size: Capacity,
        #[case] n_expected_children: usize,
    ) {
        process.unit_size = Some(unit_size);
        let asset = AssetRef::from(
            Asset::new_future(
                "agent1".into(),
                Rc::new(process),
                "GBR".into(),
                capacity,
                2010,
            )
            .unwrap(),
        );

        let mut count = 0;
        let mut total_child_capacity = Capacity(0.0);
        asset.clone().into_for_each_child(&mut 0, |parent, child| {
            assert!(parent.is_some_and(|parent| matches!(parent.state, AssetState::Parent { .. })));

            // Check each child has capacity equal to unit_size
            assert_eq!(
                child.total_capacity(),
                unit_size,
                "Child capacity should equal unit_size"
            );

            total_child_capacity += child.total_capacity();
            count += 1;
        });
        assert_eq!(count, n_expected_children, "Unexpected number of children");

        // Check total capacity is >= parent capacity
        assert!(
            total_child_capacity >= asset.total_capacity(),
            "Total capacity should be >= parent capacity"
        );
    }

    #[rstest]
    fn into_for_each_child_nondivisible(asset: Asset) {
        assert!(
            asset.process.unit_size.is_none(),
            "Asset should be non-divisible"
        );

        let asset = AssetRef::from(asset);
        let mut count = 0;
        asset.clone().into_for_each_child(&mut 0, |parent, child| {
            assert!(parent.is_none());
            assert_eq!(child, asset);
            count += 1;
        });
        assert_eq!(count, 1);
    }

    #[rstest]
    fn asset_commission(process: Process) {
        // Test successful commissioning of Future asset
        let process_rc = Rc::new(process);
        let mut asset1 = Asset::new_future(
            "agent1".into(),
            Rc::clone(&process_rc),
            "GBR".into(),
            Capacity(1.0),
            2020,
        )
        .unwrap();
        asset1.commission(AssetID(1), None, "");
        assert!(asset1.is_commissioned());
        assert_eq!(asset1.id(), Some(AssetID(1)));

        // Test successful commissioning of Selected asset
        let mut asset2 = Asset::new_selected(
            "agent1".into(),
            Rc::clone(&process_rc),
            "GBR".into(),
            Capacity(1.0),
            2020,
        )
        .unwrap();
        asset2.commission(AssetID(2), None, "");
        assert!(asset2.is_commissioned());
        assert_eq!(asset2.id(), Some(AssetID(2)));
    }

    #[rstest]
    #[case::commission_during_process_lifetime(2024, 2024)]
    #[case::decommission_after_process_lifetime_ends(2026, 2025)]
    fn asset_decommission(
        #[case] requested_decommission_year: u32,
        #[case] expected_decommission_year: u32,
        process: Process,
    ) {
        // Test successful commissioning of Future asset
        let process_rc = Rc::new(process);
        let mut asset = Asset::new_future(
            "agent1".into(),
            Rc::clone(&process_rc),
            "GBR".into(),
            Capacity(1.0),
            2020,
        )
        .unwrap();
        asset.commission(AssetID(1), None, "");
        assert!(asset.is_commissioned());
        assert_eq!(asset.id(), Some(AssetID(1)));

        // Test successful decommissioning
        asset.decommission(requested_decommission_year, "");
        assert!(!asset.is_commissioned());
        assert_eq!(asset.decommission_year(), Some(expected_decommission_year));
    }

    #[rstest]
    #[case::decommission_after_predefined_max_year(2026, 2025, Some(2025))]
    #[case::decommission_before_predefined_max_year(2024, 2024, Some(2025))]
    #[case::decommission_during_process_lifetime_end_no_max_year(2024, 2024, None)]
    #[case::decommission_after_process_lifetime_end_no_max_year(2026, 2025, None)]
    fn asset_decommission_with_max_decommission_year_predefined(
        #[case] requested_decommission_year: u32,
        #[case] expected_decommission_year: u32,
        #[case] max_decommission_year: Option<u32>,
        process: Process,
    ) {
        // Test successful commissioning of Future asset
        let process_rc = Rc::new(process);
        let mut asset = Asset::new_future_with_max_decommission(
            "agent1".into(),
            Rc::clone(&process_rc),
            "GBR".into(),
            Capacity(1.0),
            2020,
            max_decommission_year,
        )
        .unwrap();
        asset.commission(AssetID(1), None, "");
        assert!(asset.is_commissioned());
        assert_eq!(asset.id(), Some(AssetID(1)));

        // Test successful decommissioning
        asset.decommission(requested_decommission_year, "");
        assert!(!asset.is_commissioned());
        assert_eq!(asset.decommission_year(), Some(expected_decommission_year));
    }

    #[rstest]
    fn asset_decommission_divisible(asset_divisible: Asset) {
        let asset = AssetRef::from(asset_divisible);
        let original_capacity = asset.capacity();

        // Commission children
        let mut children = Vec::new();
        let mut next_id = 0;
        asset.into_for_each_child(&mut 0, |parent, mut child| {
            child
                .make_mut()
                .commission(AssetID(next_id), parent.cloned(), "");
            next_id += 1;
            children.push(child);
        });

        let parent = children[0].parent().unwrap().clone();
        assert_eq!(parent.capacity(), original_capacity);
        children[0].make_mut().decommission(2020, "");

        let AssetCapacity::Discrete(original_units, original_unit_size) = original_capacity else {
            panic!("Capacity type should be discrete");
        };
        assert_eq!(
            parent.capacity(),
            AssetCapacity::Discrete(original_units - 1, original_unit_size)
        );
    }

    #[rstest]
    #[should_panic(expected = "Assets with state Candidate cannot be commissioned")]
    fn commission_wrong_states(process: Process) {
        let mut asset =
            Asset::new_candidate(process.into(), "GBR".into(), Capacity(1.0), 2020).unwrap();
        asset.commission(AssetID(1), None, "");
    }

    #[rstest]
    #[should_panic(expected = "Cannot decommission an asset that hasn't been commissioned")]
    fn decommission_wrong_state(process: Process) {
        let mut asset =
            Asset::new_candidate(process.into(), "GBR".into(), Capacity(1.0), 2020).unwrap();
        asset.decommission(2025, "");
    }

    #[test]
    fn commission_year_before_time_horizon() {
        let processes_patch = FilePatch::new("processes.csv")
            .with_deletion("GASDRV,Dry gas extraction,all,GASPRD,2020,2040,1.0,")
            .with_addition("GASDRV,Dry gas extraction,all,GASPRD,1980,2040,1.0,");

        // Check we can run model with asset commissioned before time horizon (simple starts in
        // 2020)
        let patches = vec![
            processes_patch.clone(),
            FilePatch::new("assets.csv").with_addition("GASDRV,GBR,A0_GEX,4002.26,1980"),
        ];
        assert_patched_runs_ok_simple!(patches);

        // This should fail if it is not one of the years supported by the process, though
        let patches = vec![
            processes_patch,
            FilePatch::new("assets.csv").with_addition("GASDRV,GBR,A0_GEX,4002.26,1970"),
        ];
        assert_validate_fails_with_simple!(
            patches,
            "Agent A0_GEX has asset with commission year 1970, not within process GASDRV commission years: 1980..=2040"
        );
    }

    #[test]
    fn commission_year_after_time_horizon() {
        let processes_patch = FilePatch::new("processes.csv")
            .with_deletion("GASDRV,Dry gas extraction,all,GASPRD,2020,2040,1.0,")
            .with_addition("GASDRV,Dry gas extraction,all,GASPRD,2020,2050,1.0,");

        // Check we can run model with asset commissioned after time horizon (simple ends in 2040)
        let patches = vec![
            processes_patch.clone(),
            FilePatch::new("assets.csv").with_addition("GASDRV,GBR,A0_GEX,4002.26,2050"),
        ];
        assert_patched_runs_ok_simple!(patches);

        // This should fail if it is not one of the years supported by the process, though
        let patches = vec![
            processes_patch,
            FilePatch::new("assets.csv").with_addition("GASDRV,GBR,A0_GEX,4002.26,2060"),
        ];
        assert_validate_fails_with_simple!(
            patches,
            "Agent A0_GEX has asset with commission year 2060, not within process GASDRV commission years: 2020..=2050"
        );
    }

    #[rstest]
    fn max_installable_capacity(mut process: Process, region_id: RegionID) {
        // Set an addition limit of 3 for (region, year 2015)
        process.investment_constraints.insert(
            (region_id.clone(), 2015),
            Rc::new(crate::process::ProcessInvestmentConstraint {
                addition_limit: Some(Capacity(3.0)),
            }),
        );
        let process_rc = Rc::new(process);

        // Create a candidate asset with commission year 2015
        let asset =
            Asset::new_candidate(process_rc.clone(), region_id.clone(), Capacity(1.0), 2015)
                .unwrap();

        // commodity_portion = 0.5 -> limit = 3 * 0.5 = 1.5
        let result = asset.max_installable_capacity(Dimensionless(0.5));
        assert_eq!(result, Some(AssetCapacity::Continuous(Capacity(1.5))));
    }
}