<?php

namespace Modules\IndustrialEngineering\Services;

use Illuminate\Support\Facades\DB;
use Modules\IndustrialEngineering\Models\Bom;
use Modules\IndustrialEngineering\Models\CostScenario;
use Modules\IndustrialEngineering\Models\CostScenarioLine;
use Modules\IndustrialEngineering\Models\ItemMaster;
use Modules\IndustrialEngineering\Models\LineRevision;
use Modules\IndustrialEngineering\Models\RoutingOperation;

class CostingService
{
    public function __construct(
        protected BomService $bomService
    ) {
    }

    /**
     * Build a cost scenario from a BOM with optional per-line alternate selections.
     *
     * @param  array<int, int|null>  $alternateSelections  bom_line_id => alternate_item_id
     */
    public function buildScenario(
        int $businessId,
        Bom $bom,
        string $scenarioCode,
        string $name,
        array $alternateSelections = [],
        string $scenarioType = 'what_if'
    ): CostScenario {
        return DB::transaction(function () use ($businessId, $bom, $scenarioCode, $name, $alternateSelections, $scenarioType) {
            $scenario = CostScenario::create([
                'business_id' => $businessId,
                'line_revision_id' => $bom->line_revision_id,
                'bom_id' => $bom->id,
                'scenario_code' => $scenarioCode,
                'name' => $name,
                'scenario_type' => $scenarioType,
                'status' => 'draft',
                'created_by' => auth()->id(),
            ]);

            $flat = $this->bomService->explode($bom);
            $materialTotal = 0;

            foreach ($flat as $row) {
                $bomLineId = $row['bom_line_id'];
                $selectedAlternateId = $alternateSelections[$bomLineId] ?? null;
                $unitCost = $row['unit_cost'];
                $itemId = $row['item_master_id'];

                if ($selectedAlternateId) {
                    $altItem = ItemMaster::find($selectedAlternateId);
                    if ($altItem) {
                        $unitCost = (float) $altItem->standard_cost;
                        $itemId = $altItem->id;
                    }
                }

                $extended = $row['quantity'] * $unitCost;
                $materialTotal += $extended;

                CostScenarioLine::create([
                    'cost_scenario_id' => $scenario->id,
                    'bom_line_id' => $bomLineId,
                    'item_master_id' => $itemId,
                    'selected_alternate_item_id' => $selectedAlternateId,
                    'quantity' => $row['quantity'],
                    'unit_cost' => $unitCost,
                    'extended_cost' => $extended,
                    'lead_time_days' => $row['lead_time_days'],
                ]);
            }

            $routingCosts = $this->calculateRoutingCosts($bom->line_revision_id);
            $overhead = $materialTotal * 0.1;

            $scenario->update([
                'total_material_cost' => $materialTotal,
                'total_labor_cost' => $routingCosts['labor'],
                'total_machine_cost' => $routingCosts['machine'],
                'total_overhead_cost' => $overhead,
                'total_cost' => $materialTotal + $routingCosts['labor'] + $routingCosts['machine'] + $overhead,
            ]);

            return $scenario->fresh(['lines.itemMaster', 'lines.selectedAlternateItem']);
        });
    }

    protected function calculateRoutingCosts(?int $lineRevisionId): array
    {
        if (! $lineRevisionId) {
            return ['labor' => 0, 'machine' => 0];
        }

        $operations = RoutingOperation::with('workCenter')
            ->where('line_revision_id', $lineRevisionId)
            ->get();

        $labor = 0;
        $machine = 0;

        foreach ($operations as $op) {
            $wc = $op->workCenter;
            if (! $wc) {
                continue;
            }
            $hours = (float) $op->setup_time_hours + (float) $op->run_time_hours;
            $labor += $hours * (float) $wc->labor_rate_per_hour;
            $machine += $hours * (float) $wc->machine_rate_per_hour;
        }

        return ['labor' => $labor, 'machine' => $machine];
    }

    /**
     * Compare multiple scenarios side by side.
     */
    public function compareScenarios(array $scenarioIds): array
    {
        $scenarios = CostScenario::with('lines.itemMaster')
            ->whereIn('id', $scenarioIds)
            ->get();

        return $scenarios->map(fn (CostScenario $s) => [
            'id' => $s->id,
            'scenario_code' => $s->scenario_code,
            'name' => $s->name,
            'total_material_cost' => (float) $s->total_material_cost,
            'total_labor_cost' => (float) $s->total_labor_cost,
            'total_machine_cost' => (float) $s->total_machine_cost,
            'total_overhead_cost' => (float) $s->total_overhead_cost,
            'total_cost' => (float) $s->total_cost,
            'line_count' => $s->lines->count(),
        ])->values()->all();
    }

    /**
     * What-if: replace one component and recalculate.
     */
    public function whatIfReplaceComponent(
        CostScenario $baseScenario,
        int $bomLineId,
        int $alternateItemId,
        string $newScenarioCode
    ): CostScenario {
        $selections = [];
        foreach ($baseScenario->lines as $line) {
            if ($line->bom_line_id) {
                $selections[$line->bom_line_id] = $line->selected_alternate_item_id;
            }
        }
        $selections[$bomLineId] = $alternateItemId;

        $bom = $baseScenario->bom;
        if (! $bom) {
            throw new \RuntimeException('Base scenario has no linked BOM.');
        }

        return $this->buildScenario(
            $baseScenario->business_id,
            $bom,
            $newScenarioCode,
            $baseScenario->name.' (What-if)',
            $selections,
            'what_if'
        );
    }
}