// Pure subset/combination generators used by the optimizer.
// All callable through `ctx` so this file stays free of class state.
// `ctx` must provide:
//   - groupCurves: { groupFlow, groupPower } (from ../groupOps/groupCurves)
//   - logger (warn/debug)
//   - readChildMeasurement(machine, type, variant, position, canonicalUnit)
//   - POSITIONS, unitPolicy.canonical.flow

const EXCLUDED_STATES = new Set(['off', 'coolingdown', 'stopping', 'emergencystop']);

// Reduce demand by the flow that manually-driven operational machines
// are already delivering. Returns the adjusted Qd (may be < 0).
function checkSpecialCases(machines, Qd, ctx) {
    const { logger, readChildMeasurement, POSITIONS, unitPolicy } = ctx;
    const canonicalFlow = unitPolicy?.canonical?.flow;

    Object.values(machines).forEach(machine => {
        const state = machine.state?.getCurrentState?.();
        const mode = machine.currentMode;

        if (state !== 'operational') return;
        if (mode !== 'virtualControl' && mode !== 'fysicalControl') return;

        const measuredFlow = readChildMeasurement
            ? readChildMeasurement(machine, 'flow', 'measured', POSITIONS.DOWNSTREAM, canonicalFlow)
            : undefined;
        const predictedFlow = readChildMeasurement
            ? readChildMeasurement(machine, 'flow', 'predicted', POSITIONS.DOWNSTREAM, canonicalFlow)
            : undefined;

        let flow = 0;
        if (Number.isFinite(measuredFlow) && measuredFlow !== 0) {
            flow = measuredFlow;
        } else if (Number.isFinite(predictedFlow) && predictedFlow !== 0) {
            flow = predictedFlow;
        } else {
            // Unrecoverable: a machine is producing flow we can't quantify.
            // Caller decides whether to abort the dispatch tick.
            logger?.error?.(
                "Dont perform calculation at all seeing that there is a machine working but we dont know the flow its producing"
            );
            return;
        }

        Qd = Qd - flow;
    });
    return Qd;
}

// Generate all non-empty machine subsets that can deliver Qd within powerCap.
// Inputs that can't possibly contribute (off / coolingdown / mode-locked) are
// excluded before the power set is built, so 2^N stays small in practice.
function validPumpCombinations(machines, Qd, ctx, powerCap = Infinity) {
    const { groupCurves } = ctx;
    const groupFlow = groupCurves?.groupFlow;
    const groupPower = groupCurves?.groupPower;

    Qd = checkSpecialCases(machines, Qd, ctx);

    let subsets = [[]];
    Object.keys(machines).forEach(machineId => {
        const machine = machines[machineId];
        const state = machine.state?.getCurrentState?.();
        const validActionForMode =
            typeof machine.isValidActionForMode === 'function'
                ? machine.isValidActionForMode('execsequence', 'auto')
                : true;

        if (EXCLUDED_STATES.has(state) || !validActionForMode) return;

        const newSubsets = subsets.map(set => [...set, machineId]);
        subsets = subsets.concat(newSubsets);
    });

    return subsets.filter(subset => {
        if (subset.length === 0) return false;

        const { maxFlow, minFlow, maxPower } = subset.reduce(
            (acc, machineId) => {
                const machine = machines[machineId];
                const f = groupFlow(machine);
                const p = groupPower(machine);
                return {
                    maxFlow: acc.maxFlow + f.currentFxyYMax,
                    minFlow: acc.minFlow + f.currentFxyYMin,
                    maxPower: acc.maxPower + p.currentFxyYMax,
                };
            },
            { maxFlow: 0, minFlow: 0, maxPower: 0 },
        );

        return maxFlow >= Qd && minFlow <= Qd && maxPower <= powerCap;
    });
}

module.exports = { validPumpCombinations, checkSpecialCases, EXCLUDED_STATES };