<?php

namespace Modules\IndustrialEngineering\Services;

use Illuminate\Support\Collection;
use Modules\IndustrialEngineering\Models\Bom;
use Modules\IndustrialEngineering\Models\BomLine;

class BomService
{
    /**
     * Explode a multi-level BOM into a flat list with rolled-up quantities.
     */
    public function explode(Bom $bom, float $parentQty = 1.0, ?int $parentLineId = null): Collection
    {
        $lines = $bom->lines()
            ->with(['itemMaster', 'alternates.alternateItem', 'children'])
            ->when($parentLineId === null, fn ($q) => $q->whereNull('parent_line_id'))
            ->when($parentLineId !== null, fn ($q) => $q->where('parent_line_id', $parentLineId))
            ->orderBy('sort_order')
            ->get();

        $result = collect();

        foreach ($lines as $line) {
            $qty = (float) $line->quantity * $parentQty;
            $result->push([
                'bom_line_id' => $line->id,
                'parent_line_id' => $line->parent_line_id,
                'item_master_id' => $line->item_master_id,
                'item_code' => $line->itemMaster?->item_code,
                'item_name' => $line->itemMaster?->name,
                'position_code' => $line->position_code,
                'quantity' => $qty,
                'unit_cost' => (float) ($line->standard_cost ?: $line->itemMaster?->standard_cost ?? 0),
                'extended_cost' => $qty * (float) ($line->standard_cost ?: $line->itemMaster?->standard_cost ?? 0),
                'alternate_group' => $line->alternate_group,
                'alternates' => $line->alternates->map(fn ($alt) => [
                    'item_id' => $alt->alternate_item_id,
                    'item_code' => $alt->alternateItem?->item_code,
                    'item_name' => $alt->alternateItem?->name,
                    'priority' => $alt->priority,
                    'cost_delta' => (float) $alt->cost_delta,
                    'is_approved' => $alt->is_approved,
                ])->values(),
                'is_serviceable' => $line->is_serviceable,
                'lead_time_days' => $line->lead_time_days ?: $line->itemMaster?->lead_time_days ?? 0,
            ]);

            $children = $this->explode($bom, $qty, $line->id);
            $result = $result->merge($children);
        }

        return $result;
    }

    /**
     * Explode BOM to leaf components only (no double-counting assemblies).
     */
    public function explodeLeaves(Bom $bom, float $parentQty = 1.0, ?int $parentLineId = null): Collection
    {
        $lines = $bom->lines()
            ->with(['itemMaster', 'children'])
            ->when($parentLineId === null, fn ($q) => $q->whereNull('parent_line_id'))
            ->when($parentLineId !== null, fn ($q) => $q->where('parent_line_id', $parentLineId))
            ->orderBy('sort_order')
            ->get();

        $result = collect();

        foreach ($lines as $line) {
            $qty = (float) $line->quantity * $parentQty;
            if ($line->children()->exists()) {
                $result = $result->merge($this->explodeLeaves($bom, $qty, $line->id));
            } else {
                $result->push([
                    'bom_line_id' => $line->id,
                    'item_master_id' => $line->item_master_id,
                    'item_code' => $line->itemMaster?->item_code,
                    'item_name' => $line->itemMaster?->name,
                    'quantity' => $qty,
                    'unit_cost' => (float) ($line->standard_cost ?: $line->itemMaster?->standard_cost ?? 0),
                ]);
            }
        }

        return $result;
    }

    /**
     * Build hierarchical tree for UI display.
     */
    public function buildTree(Bom $bom): array
    {
        $bom->load(['rootLines.itemMaster', 'rootLines.alternates.alternateItem', 'rootLines.children']);

        return $bom->rootLines->map(fn (BomLine $line) => $this->lineToTreeNode($line))->values()->all();
    }

    protected function lineToTreeNode(BomLine $line): array
    {
        $line->loadMissing(['itemMaster', 'alternates.alternateItem', 'children.itemMaster']);

        return [
            'id' => $line->id,
            'item_code' => $line->itemMaster?->item_code,
            'item_name' => $line->itemMaster?->name,
            'position_code' => $line->position_code,
            'quantity' => (float) $line->quantity,
            'alternate_group' => $line->alternate_group,
            'alternates' => $line->alternates,
            'children' => $line->children->map(fn ($child) => $this->lineToTreeNode($child))->values()->all(),
        ];
    }

    /**
     * Create SBOM from MBOM by filtering serviceable lines.
     */
    public function deriveServiceBom(Bom $mbom, int $businessId, string $bomCode): Bom
    {
        $sbom = Bom::create([
            'business_id' => $businessId,
            'line_revision_id' => $mbom->line_revision_id,
            'item_master_id' => $mbom->item_master_id,
            'bom_type' => 'sbom',
            'bom_code' => $bomCode,
            'name' => $mbom->name.' (Service)',
            'revision_code' => $mbom->revision_code,
            'status' => 'draft',
        ]);

        $this->copyServiceableLines($mbom, $sbom, null, null);

        return $sbom->fresh(['lines']);
    }

    protected function copyServiceableLines(Bom $source, Bom $target, ?int $sourceParentId, ?int $targetParentId): void
    {
        $lines = BomLine::where('bom_id', $source->id)
            ->where('parent_line_id', $sourceParentId)
            ->where('is_serviceable', true)
            ->orderBy('sort_order')
            ->get();

        foreach ($lines as $line) {
            $newLine = $line->replicate(['bom_id', 'parent_line_id']);
            $newLine->bom_id = $target->id;
            $newLine->parent_line_id = $targetParentId;
            $newLine->save();

            foreach ($line->alternates as $alt) {
                $alt->replicate(['bom_line_id'])->fill(['bom_line_id' => $newLine->id])->save();
            }

            $this->copyServiceableLines($source, $target, $line->id, $newLine->id);
        }
    }

    public function snapshot(Bom $bom): array
    {
        return [
            'bom_id' => $bom->id,
            'bom_code' => $bom->bom_code,
            'bom_type' => $bom->bom_type,
            'revision_code' => $bom->revision_code,
            'tree' => $this->buildTree($bom),
            'flat' => $this->explode($bom)->values()->all(),
            'snapshot_at' => now()->toIso8601String(),
        ];
    }
}