<?php

namespace App\Http\Controllers\Api;

use App\Http\Controllers\Controller;
use App\Models\Expense;
use App\Models\Category;
use App\Models\CategoryRule;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;

class InvoiceImportController extends Controller
{
    /**
     * 1. API 主入口：執行發票/帳本 CSV 上傳匯入
     * POST /api/expenses/import
     */
    public function store(Request $request)
    {
        $request->validate([
            'file' => 'required|file',
        ]);

        $file = $request->file('file');
        
        $content = file_get_contents($file->getPathname());
        $encoding = mb_detect_encoding($content, ['UTF-8', 'BIG-5', 'UTF-16LE', 'CP950'], true);
        
        if ($encoding && $encoding !== 'UTF-8') {
            $content = mb_convert_encoding($content, 'UTF-8', $encoding);
        }
        $content = preg_replace('/^\xEF\xBB\xBF/', '', $content);

        $rules = CategoryRule::with('category')
            ->where('user_id', auth()->id())
            ->get();

        // 智慧判定財政部官方載具格式
        if (str_contains($content, '表頭=M') || str_contains($content, 'M|')) {
            [$imported, $updated] = $this->importPipeInvoice($content, $rules);
            $formatName = '財政部官方載具發票';
        } else {
            $handle = fopen('php://memory', 'r+');
            fwrite($handle, $content);
            rewind($handle);
            
            $firstRow = fgetcsv($handle);
            $format = $this->detectFormat($firstRow);
            rewind($handle);
            
            if ($format === 'andromoney') {
                [$imported, $updated] = $this->importAndroMoney($handle);
                $formatName = 'AndroMoney 帳本';
            } else {
                [$imported, $updated] = $this->importOldCommaInvoice($handle, $rules);
                $formatName = '傳統扁平發票 CSV';
            }
            fclose($handle);
        }

        return response()->json([
            'success'  => true,
            'imported' => $imported,
            'updated'  => $updated,
            'message'  => "【{$formatName}】匯入完成！成功新增 {$imported} 筆紀錄，自動跳過重複/負值金額共 {$updated} 筆。"
        ]);
    }

    /**
     * 2. 財政部官網 Pipe 格式解析
     */
    private function importPipeInvoice(string $content, $rules): array
    {
        $imported = 0;
        $updated  = 0;

        $lines = preg_split('/\r\n|\r|\n/', $content);
        $invoices = [];

        foreach ($lines as $line) {
            if (empty($line) || str_contains($line, '表頭=')) continue;
            
            $parts = explode('|', $line);
            $type = $parts[0] ?? '';

            if ($type === 'M') {
                $invNum = trim($parts[6] ?? '');
                if (!$invNum) continue;
                
                $invoices[$invNum] = [
                    'date'   => trim($parts[3] ?? ''),
                    'seller' => trim($parts[5] ?? ''),
                    'amount' => (float)trim($parts[7] ?? 0),
                    'items'  => []
                ];
            } elseif ($type === 'D') {
                $invNum = trim($parts[1] ?? '');
                $itemName = trim($parts[3] ?? '');
                if ($invNum && isset($invoices[$invNum]) && $itemName) {
                    $invoices[$invNum]['items'][] = $itemName;
                }
            }
        }

        DB::transaction(function () use ($invoices, $rules, &$imported, &$updated) {
            foreach ($invoices as $invoiceNumber => $info) {
                if ($info['amount'] < 0) {
                    $updated++;
                    continue;
                }

                $exists = Expense::where('user_id', auth()->id())
                    ->where('invoice_number', $invoiceNumber)
                    ->exists();

                if ($exists) {
                    $updated++;
                    continue;
                }

                $d = $info['date'];
                $formattedDate = (strlen($d) === 8) ? substr($d, 0, 4) . '-' . substr($d, 4, 2) . '-' . substr($d, 6, 2) : now()->toDateString();
                
                $itemName = implode(', ', $info['items']);
                if (mb_strlen($itemName) > 255) {
                    $itemName = mb_substr($itemName, 0, 252) . '...';
                }

                $categoryId = $this->guessCategory($info['seller'], $rules);

                $expense = Expense::updateOrCreate(
                    [
                        'user_id'        => auth()->id(),
                        'invoice_number' => $invoiceNumber,
                    ],
                    [
                        'amount'         => $info['amount'],
                        'date'           => $formattedDate,
                        'seller_name'    => $info['seller'],
                        'item_name'      => $itemName ?: $info['seller'],
                        'note'           => $info['seller'],
                        'category_id'    => $categoryId,
                    ]
                );

                if ($expense->wasRecentlyCreated) {
                    $imported++;
                } else {
                    $updated++;
                }
            }
        });

        return [$imported, $updated];
    }

    /**
     * 3. 舊版扁平逗號 CSV 匯入
     */
    private function importOldCommaInvoice($handle, $rules): array
    {
        $imported = 0; $updated = 0;

        while (($row = fgetcsv($handle)) !== false) {
            if (count($row) < 8) continue;

            $invoiceNumber = trim($row[2] ?? '');
            $date          = trim($row[1] ?? '');
            $amount        = trim($row[3] ?? '0');
            $sellerName    = trim($row[7] ?? '');
            $itemName      = trim($row[13] ?? '');

            if (empty($invoiceNumber)) continue;
            if ((float)$amount < 0) { $updated++; continue; }

            $formattedDate = null;
            if (strlen($date) === 8) {
                $formattedDate = substr($date, 0, 4) . '-' . substr($date, 4, 2) . '-' . substr($date, 6, 2);
            }

            $exists = Expense::where('user_id', auth()->id())->where('invoice_number', $invoiceNumber)->exists();
            if ($exists) { $updated++; continue; }

            $categoryId = $this->guessCategory($sellerName, $rules);

            // 🟢 校正：移除所有舊外鍵欄位，對齊 Migration
            $expense = Expense::updateOrCreate(
                [
                    'user_id'        => auth()->id(), 
                    'invoice_number' => $invoiceNumber
                ],
                [
                    'amount'         => (float)$amount, 
                    'date'           => $formattedDate ?: now()->toDateString(),
                    'seller_name'    => $sellerName, 
                    'item_name'      => $itemName, 
                    'note'           => $sellerName, 
                    'category_id'    => $categoryId,
                ]
            );
            if ($expense->wasRecentlyCreated) { $imported++; } else { $updated++; }
        }
        return [$imported, $updated];
    }

    /**
     * 4. AndroMoney 格式匯入
     */
    private function importAndroMoney($handle): array
    {
        $imported = 0; $updated = 0;
        fgetcsv($handle);

        while (($row = fgetcsv($handle)) !== false) {
            $row = array_map(fn($val) => mb_convert_encoding($val, 'UTF-8', 'Big5'), $row);
            if (count($row) < 6) continue;

            $amount      = trim($row[2]  ?? '0');
            $catName     = trim($row[3]  ?? '');
            $subCatName  = trim($row[4]  ?? '');
            $date        = trim($row[5]  ?? '');
            $note        = trim($row[8]  ?? '');
            $sellerName  = trim($row[13] ?? '');

            if (preg_match('/^[0-9a-f]{20,}$/i', $note)) { $note = ''; }
            if (empty($amount) || empty($date) || (float)$amount == 0) continue;

            $formattedDate = null;
            if (strlen($date) === 8 && is_numeric($date)) {
                $formattedDate = substr($date, 0, 4) . '-' . substr($date, 4, 2) . '-' . substr($date, 6, 2);
            }
            if (!$formattedDate) { $updated++; continue; }

            $categoryId = !empty($catName) ? $this->findOrCreateCategory($catName) : null;
            $subcategoryId = (!empty($subCatName) && $categoryId) ? $this->findOrCreateCategory($subCatName, $categoryId) : null;
            
            // 🟢 校正：AndroMoney 沒有發票號碼，所以單純用使用者、日期、金額與備註作防重判斷
            $exists = Expense::where('user_id', auth()->id())
                ->where('date', $formattedDate)
                ->where('amount', abs((float)$amount))
                ->where('note', $note ?: $sellerName)
                ->exists();

            if ($exists) {
                $updated++;
                continue;
            }

            Expense::create([
                'user_id'        => auth()->id(),
                'amount'         => abs((float)$amount), 
                'date'           => $formattedDate,
                'category_id'    => $categoryId, 
                'subcategory_id' => $subcategoryId,
                'note'           => $note ?: $sellerName, 
                'seller_name'    => $sellerName,
            ]);
            
            $imported++;
        }
        return [$imported, $updated];
    }

    private function detectFormat(array $firstRow): string
    {
        if (isset($firstRow[1]) && str_contains($firstRow[1], 'AndroMoney')) { return 'andromoney'; }
        return 'invoice';
    }

    private function findOrCreateCategory(string $name, ?int $parentId = null): int
    {
        $category = Category::firstOrCreate(
            ['user_id' => auth()->id(), 'name' => $name, 'parent_id' => $parentId],
            ['color' => $this->randomColor()]
        );
        return $category->id;
    }

    private function randomColor(): string
    {
        $colors = ['#EF4444', '#F59E0B', '#10B981', '#3B82F6', '#8B5CF6', '#EC4899', '#14B8A6', '#F97316'];
        return $colors[array_rand($colors)];
    }

    private function guessCategory($sellerName, $rules)
    {
        foreach ($rules as $rule) {
            if (str_contains($sellerName, $rule->keyword)) { return $rule->category_id; }
        }
        return null;
    }
}