<?php

namespace Modules\IndustrialEngineering\Services;

use App\Variation;
use Illuminate\Support\Collection;
use Modules\IndustrialEngineering\Models\Bom;
use Modules\IndustrialEngineering\Models\ItemMaster;

/**
 * Live BOM costing from ERP inventory, purchase prices, and supplier catalog.
 */
class LiveBomCostingService
{
    public function __construct(
        protected BomService $bomService,
        protected SourcingService $sourcingService,
        protected ErpItemLinkService $erpItemLink
    ) {
    }

    public function analyze(Bom $bom, float $plannedQty = 1.0, ?int $locationId = null): array
    {
        $flat = $this->bomService->explodeLeaves($bom, $plannedQty);
        $lines = [];
        $totals = [
            'standard_material' => 0,
            'live_material' => 0,
            'linked_items' => 0,
            'shortage_value' => 0,
        ];

        $aggregated = $flat->groupBy('item_master_id')->map(function ($group) {
            $first = $group->first();

            return [
                'bom_line_id' => $first['bom_line_id'],
                'item_master_id' => $first['item_master_id'],
                'item_code' => $first['item_code'],
                'item_name' => $first['item_name'],
                'quantity' => $group->sum('quantity'),
                'unit_cost' => $first['unit_cost'],
            ];
        })->values();

        $itemIds = $aggregated->pluck('item_master_id')->filter()->unique()->values()->all();
        $items = ItemMaster::query()
            ->whereIn('id', $itemIds)
            ->get()
            ->keyBy('id');

        $variationIds = $items->pluck('variation_id')->filter()->unique()->values()->all();
        $variations = Variation::query()
            ->whereIn('id', $variationIds)
            ->get()
            ->keyBy('id');

        $stockByItem = $this->preloadStock($bom->business_id, $itemIds, $locationId);

        foreach ($aggregated as $row) {
            $item = $items->get($row['item_master_id']);
            $live = $this->resolveLiveCost($item, $variations);
            $stock = $stockByItem[$row['item_master_id']] ?? ['available' => 0.0];
            $requiredQty = (float) $row['quantity'];
            $shortage = max(0, $requiredQty - $stock['available']);
            $standardExtended = $requiredQty * (float) $row['unit_cost'];
            $liveExtended = $requiredQty * $live['unit_cost'];
            $shortageExtended = $shortage * $live['unit_cost'];

            if ($item?->variation_id) {
                $totals['linked_items']++;
            }

            $totals['standard_material'] += $standardExtended;
            $totals['live_material'] += $liveExtended;
            $totals['shortage_value'] += $shortageExtended;

            $lines[] = [
                'bom_line_id' => $row['bom_line_id'],
                'item_master_id' => $row['item_master_id'],
                'item_code' => $row['item_code'],
                'item_name' => $row['item_name'],
                'item_type' => $item?->item_type,
                'required_qty' => $requiredQty,
                'stock_available' => $stock['available'],
                'shortage_qty' => $shortage,
                'standard_unit_cost' => (float) $row['unit_cost'],
                'live_unit_cost' => $live['unit_cost'],
                'cost_source' => $live['source'],
                'standard_extended' => $standardExtended,
                'live_extended' => $liveExtended,
                'shortage_extended' => $shortageExtended,
                'variation_id' => $item?->variation_id,
                'product_id' => $item?->variation_id ? ($variations->get($item->variation_id)?->product_id) : null,
                'erp_label' => $this->erpItemLink->erpLabel($item),
                'is_purchasable' => (bool) $item?->variation_id,
            ];
        }

        $leafLines = $this->filterLeafRequirements($lines);

        return [
            'planned_quantity' => $plannedQty,
            'line_count' => count($lines),
            'leaf_count' => count($leafLines),
            'totals' => $totals,
            'delta' => $totals['live_material'] - $totals['standard_material'],
            'lines' => $lines,
            'leaf_lines' => $leafLines,
            'shortages' => collect($leafLines)->where('shortage_qty', '>', 0)->values()->all(),
        ];
    }

    /**
     * Leaf purchasable lines only (for MRP / PO generation).
     */
    public function filterLeafRequirements(array $lines): array
    {
        return collect($lines)
            ->filter(fn ($l) => in_array($l['item_type'], ['part', 'consumable', 'tool'], true) || $l['is_purchasable'])
            ->values()
            ->all();
    }

    public function compareStandardVsLive(Bom $bom, float $plannedQty = 1.0, ?int $locationId = null): array
    {
        $analysis = $this->analyze($bom, $plannedQty, $locationId);

        return [
            'standard_total' => $analysis['totals']['standard_material'],
            'live_total' => $analysis['totals']['live_material'],
            'delta' => $analysis['delta'],
            'delta_percent' => $analysis['totals']['standard_material'] > 0
                ? round(($analysis['delta'] / $analysis['totals']['standard_material']) * 100, 2)
                : 0,
            'shortage_value' => $analysis['totals']['shortage_value'],
            'shortage_count' => count($analysis['shortages']),
        ];
    }

    /**
     * @param  array<int, int>  $itemIds
     * @return array<int, array{available: float}>
     */
    protected function preloadStock(int $businessId, array $itemIds, ?int $locationId): array
    {
        $stockByItem = array_fill_keys($itemIds, ['available' => 0.0]);

        foreach ($itemIds as $itemId) {
            $stock = $this->sourcingService->findStock($businessId, $itemId);
            if ($locationId) {
                $stock = $stock->where('location_id', $locationId);
            }
            $stockByItem[$itemId]['available'] = (float) $stock->sum('quantity');
        }

        return $stockByItem;
    }

    protected function resolveLiveCost(?ItemMaster $item, Collection $variations): array
    {
        if (! $item) {
            return ['unit_cost' => 0, 'source' => 'none'];
        }

        if ($item->variation_id) {
            $variation = $variations->get($item->variation_id);
            if ($variation && (float) $variation->dpp_inc_tax > 0) {
                return ['unit_cost' => (float) $variation->dpp_inc_tax, 'source' => 'erp_purchase_price'];
            }
        }

        $supplierCost = $this->sourcingService->resolveItemCost($item);

        return [
            'unit_cost' => $supplierCost,
            'source' => $supplierCost > 0 ? 'supplier_or_standard' : 'standard',
        ];
    }
}