<?php

namespace Modules\IndustrialEngineering\Services;

use App\Variation;
use App\VariationLocationDetails;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Modules\IndustrialEngineering\Models\ItemMaster;
use Modules\IndustrialEngineering\Models\PartEquivalent;
use Modules\IndustrialEngineering\Models\ProcurementTask;
use Modules\IndustrialEngineering\Models\SupplierPartNumber;
use Modules\IndustrialEngineering\Models\SupplierSourcingCase;

class SourcingService
{
    /**
     * Search holding-wide stock for an item (current business + linked businesses via suppliers).
     */
    public function findStock(int $businessId, int $itemMasterId): Collection
    {
        $item = ItemMaster::findOrFail($itemMasterId);
        $results = collect();

        if ($item->variation_id) {
            $stock = VariationLocationDetails::join('business_locations as bl', 'variation_location_details.location_id', '=', 'bl.id')
                ->where('variation_location_details.variation_id', $item->variation_id)
                ->where('bl.business_id', $businessId)
                ->select(
                    'bl.business_id',
                    'bl.id as location_id',
                    'bl.name as location_name',
                    'variation_location_details.qty_available'
                )
                ->get();

            foreach ($stock as $row) {
                if ((float) $row->qty_available > 0) {
                    $results->push([
                        'source' => 'internal_stock',
                        'business_id' => $row->business_id,
                        'location_id' => $row->location_id,
                        'location_name' => $row->location_name,
                        'quantity' => (float) $row->qty_available,
                    ]);
                }
            }
        }

        $equivalents = PartEquivalent::where('primary_item_id', $itemMasterId)
            ->where('is_approved', true)
            ->with('equivalentItem')
            ->orderBy('priority')
            ->get();

        foreach ($equivalents as $equiv) {
            $alt = $equiv->equivalentItem;
            if ($alt?->variation_id) {
                $altStock = VariationLocationDetails::join('business_locations as bl', 'variation_location_details.location_id', '=', 'bl.id')
                    ->where('variation_location_details.variation_id', $alt->variation_id)
                    ->where('bl.business_id', $businessId)
                    ->where('variation_location_details.qty_available', '>', 0)
                    ->select('bl.name as location_name', 'variation_location_details.qty_available')
                    ->get();

                foreach ($altStock as $s) {
                    $results->push([
                        'source' => 'equivalent_stock',
                        'item_code' => $alt->item_code,
                        'item_name' => $alt->name,
                        'location_name' => $s->location_name,
                        'quantity' => (float) $s->qty_available,
                        'equivalence_type' => $equiv->equivalence_type,
                    ]);
                }
            }
        }

        return $results;
    }

    /**
     * Find approved suppliers for an item.
     */
    public function findSuppliers(int $itemMasterId): Collection
    {
        return SupplierPartNumber::with('supplier')
            ->where('item_master_id', $itemMasterId)
            ->where('is_approved', true)
            ->orderByDesc('is_preferred')
            ->get()
            ->map(fn ($spn) => [
                'supplier_id' => $spn->supplier_id,
                'supplier_name' => $spn->supplier?->name,
                'supplier_part_number' => $spn->supplier_part_number,
                'unit_price' => (float) $spn->unit_price,
                'lead_time_days' => $spn->lead_time_days,
                'is_preferred' => $spn->is_preferred,
            ]);
    }

    /**
     * Create sourcing case and procurement tasks when part not available.
     */
    public function createSourcingCase(
        int $businessId,
        int $itemMasterId,
        float $quantity,
        ?int $installedAssetId = null,
        ?string $neededBy = null,
        string $priority = 'medium'
    ): SupplierSourcingCase {
        return DB::transaction(function () use ($businessId, $itemMasterId, $quantity, $installedAssetId, $neededBy, $priority) {
            $caseNumber = 'SRC-'.now()->format('Ymd').'-'.str_pad((string) (SupplierSourcingCase::forBusiness($businessId)->count() + 1), 4, '0', STR_PAD_LEFT);

            $case = SupplierSourcingCase::create([
                'business_id' => $businessId,
                'case_number' => $caseNumber,
                'item_master_id' => $itemMasterId,
                'installed_asset_id' => $installedAssetId,
                'required_quantity' => $quantity,
                'needed_by' => $neededBy,
                'priority' => $priority,
                'status' => 'open',
                'assigned_to' => auth()->id(),
            ]);

            $stock = $this->findStock($businessId, $itemMasterId);
            if ($stock->isEmpty()) {
                ProcurementTask::create([
                    'business_id' => $businessId,
                    'sourcing_case_id' => $case->id,
                    'item_master_id' => $itemMasterId,
                    'task_type' => 'find_supplier',
                    'title' => 'Find supplier for '.$case->itemMaster?->name,
                    'status' => 'pending',
                    'assigned_to' => auth()->id(),
                    'due_date' => $neededBy,
                ]);
            } else {
                ProcurementTask::create([
                    'business_id' => $businessId,
                    'sourcing_case_id' => $case->id,
                    'item_master_id' => $itemMasterId,
                    'task_type' => 'internal_transfer',
                    'title' => 'Internal transfer for '.$case->itemMaster?->name,
                    'status' => 'pending',
                    'assigned_to' => auth()->id(),
                    'due_date' => $neededBy,
                ]);
            }

            return $case->fresh(['itemMaster', 'procurementTasks']);
        });
    }

    /**
     * Resolve item cost from variation purchase price or standard cost.
     */
    public function resolveItemCost(ItemMaster $item): float
    {
        if ((float) $item->standard_cost > 0) {
            return (float) $item->standard_cost;
        }

        if ($item->variation_id) {
            $variation = Variation::find($item->variation_id);

            return (float) ($variation?->dpp_inc_tax ?? 0);
        }

        $spn = SupplierPartNumber::where('item_master_id', $item->id)
            ->where('is_preferred', true)
            ->first();

        return (float) ($spn?->unit_price ?? 0);
    }
}