<?php

namespace App\Services;

use App\Models\Question;
use DateTimeInterface;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\File;
use Illuminate\Support\Facades\Schema;
use Illuminate\Support\Str;
use Throwable;

/**
 * 从 JSON 批量导入 questions，并生成可在 MySQL 客户端执行的 INSERT…ON DUPLICATE KEY UPDATE 脚本。
 */
class QuestionBulkImportService
{
    /** @var array<int, string>|null */
    private ?array $questionsColumns = null;

    /**
     * @return array<int, array<string, mixed>>
     */
    public function loadRowsFromFile(string $path): array
    {
        if (! is_readable($path)) {
            throw new \InvalidArgumentException('文件不可读：'.$path);
        }

        $raw = file_get_contents($path);
        if ($raw === false || trim($raw) === '') {
            throw new \InvalidArgumentException('文件为空：'.$path);
        }

        $trimmed = ltrim($raw);
        if ($trimmed === '') {
            return [];
        }

        if ($trimmed[0] === '[') {
            $decoded = json_decode($raw, true);
            if (! is_array($decoded)) {
                throw new \InvalidArgumentException('JSON 解析失败（应为对象数组）：'.json_last_error_msg());
            }

            return array_values(array_filter($decoded, static fn ($row) => is_array($row)));
        }

        // NDJSON：每行一个 JSON 对象
        $lines = preg_split('/\r\n|\n|\r/', $raw) ?: [];
        $rows = [];
        foreach ($lines as $line) {
            $line = trim($line);
            if ($line === '' || str_starts_with($line, '#')) {
                continue;
            }
            $one = json_decode($line, true);
            if (! is_array($one)) {
                throw new \InvalidArgumentException('NDJSON 解析失败：'.$line);
            }
            $rows[] = $one;
        }

        return $rows;
    }

    /**
     * @param  array<string, mixed>  $row
     * @return array<string, mixed>
     */
    public function normalizeImportRow(array $row, int $lineIndex): array
    {
        $stem = (string) ($row['stem'] ?? $row['content'] ?? '');
        $kp = isset($row['kp_code']) ? (string) $row['kp_code'] : '';

        $code = isset($row['question_code']) ? trim((string) $row['question_code']) : '';
        if ($code === '') {
            $code = 'QI'.strtoupper(Str::random(12));
        }

        $options = $row['options'] ?? null;
        if (is_string($options) && trim($options) !== '') {
            $decoded = json_decode($options, true);
            $options = is_array($decoded) ? $decoded : null;
        }

        $meta = $row['meta'] ?? null;
        if (is_string($meta) && trim($meta) !== '') {
            $decoded = json_decode($meta, true);
            $meta = is_array($decoded) ? $decoded : null;
        }

        $out = [
            'question_code' => $code,
            'kp_code' => $kp !== '' ? $kp : null,
            'stem' => $stem,
            'options' => is_array($options) ? $options : null,
            'answer' => isset($row['answer']) ? (string) $row['answer'] : null,
            'solution' => isset($row['solution']) ? (string) $row['solution'] : null,
            'difficulty' => isset($row['difficulty']) ? (float) $row['difficulty'] : null,
            'question_type' => isset($row['question_type']) ? (string) $row['question_type'] : (isset($row['type']) ? (string) $row['type'] : null),
            'source' => isset($row['source']) ? (string) $row['source'] : 'json_bulk_import',
            'tags' => isset($row['tags']) ? (string) $row['tags'] : null,
            'meta' => is_array($meta) ? $meta : null,
            'textbook_id' => isset($row['textbook_id']) ? (int) $row['textbook_id'] : null,
            'source_file_id' => isset($row['source_file_id']) ? (int) $row['source_file_id'] : null,
            'source_paper_id' => isset($row['source_paper_id']) ? (int) $row['source_paper_id'] : null,
            'paper_part_id' => isset($row['paper_part_id']) ? (int) $row['paper_part_id'] : null,
            'kp_id' => isset($row['kp_id']) ? (string) $row['kp_id'] : null,
            'kp_name' => isset($row['kp_name']) ? (string) $row['kp_name'] : null,
            'kp_reference' => isset($row['kp_reference']) ? (string) $row['kp_reference'] : null,
            'grade' => isset($row['grade']) ? (int) $row['grade'] : null,
            'audit_status' => isset($row['audit_status']) ? (int) $row['audit_status'] : null,
            'audit_reason' => isset($row['audit_reason']) ? (string) $row['audit_reason'] : null,
            'title_1' => isset($row['title_1']) ? (string) $row['title_1'] : null,
            'title_2' => isset($row['title_2']) ? (string) $row['title_2'] : null,
            'title_3' => isset($row['title_3']) ? (string) $row['title_3'] : null,
            'create_by' => isset($row['create_by']) ? (string) $row['create_by'] : null,
            'textbook_catalog_nodes_id' => isset($row['textbook_catalog_nodes_id']) ? (int) $row['textbook_catalog_nodes_id'] : null,
            'question_category' => isset($row['question_category']) ? (int) $row['question_category'] : null,
            'step_num' => isset($row['step_num']) ? (int) $row['step_num'] : null,
            'solution_temp' => isset($row['solution_temp']) ? (string) $row['solution_temp'] : null,
            'solution_temp2' => isset($row['solution_temp2']) ? (string) $row['solution_temp2'] : null,
        ];

        if (isset($row['id'])) {
            $out['_import_id'] = (int) $row['id'];
        }

        $out['_line'] = $lineIndex;

        return $out;
    }

    /**
     * @param  array<int, array<string, mixed>>  $rows  normalizeImportRow 的输出
     * @return array{created: int, updated: int, skipped: int, errors: array<int, string>}
     */
    public function importToDatabase(array $rows, bool $dryRun = false): array
    {
        $created = 0;
        $updated = 0;
        $skipped = 0;
        $errors = [];

        if (! Schema::hasTable('questions')) {
            return ['created' => 0, 'updated' => 0, 'skipped' => 0, 'errors' => ['questions 表不存在']];
        }

        foreach ($rows as $row) {
            $line = (int) ($row['_line'] ?? 0);
            try {
                $stem = (string) ($row['stem'] ?? '');
                $kp = (string) ($row['kp_code'] ?? '');
                if ($stem === '' || $kp === '') {
                    $skipped++;
                    $errors[] = "第 {$line} 行：题干或 kp_code 为空，已跳过";

                    continue;
                }

                $code = (string) ($row['question_code'] ?? '');
                $payload = $this->filterToTableColumns($row);
                unset($payload['_line'], $payload['_import_id']);

                if ($dryRun) {
                    $exists = Question::query()->where('question_code', $code)->exists();
                    $exists ? $updated++ : $created++;

                    continue;
                }

                $existing = Question::query()->where('question_code', $code)->first();
                $question = Question::query()->firstOrNew(['question_code' => $code]);
                $question->forceFill($payload);
                $question->save();

                if ($existing) {
                    $updated++;
                } else {
                    $created++;
                }
            } catch (Throwable $e) {
                $skipped++;
                $errors[] = "第 {$line} 行：".$e->getMessage();
            }
        }

        return compact('created', 'updated', 'skipped', 'errors');
    }

    /**
     * @param  array<int, array<string, mixed>>  $rows
     */
    public function renderMysqlScript(array $rows, bool $includeId = false): string
    {
        $lines = [];
        $lines[] = '-- 由 math_cms QuestionBulkImportService 生成';
        $lines[] = '-- 在目标库执行前请确认 `questions` 表结构一致，并已备份。';
        $lines[] = '-- 冲突键：`question_code`（UNIQUE），使用 ON DUPLICATE KEY UPDATE 合并更新。';
        $lines[] = 'SET NAMES utf8mb4;';
        $lines[] = '';

        $cols = $this->questionsColumnList();
        foreach ($rows as $row) {
            $stem = (string) ($row['stem'] ?? '');
            if ($stem === '') {
                continue;
            }

            $filtered = $this->filterToTableColumns($row);
            if ($includeId && isset($row['_import_id'])) {
                $filtered['id'] = (int) $row['_import_id'];
            }

            $sql = $this->buildSingleUpsertSql($filtered, $cols, $includeId);

            if ($sql !== '') {
                $lines[] = $sql;
                $lines[] = '';
            }
        }

        return rtrim(implode("\n", $lines))."\n";
    }

    /**
     * @param  array<int>  $ids
     */
    public function exportIdsToMysqlScript(array $ids, bool $includeId = false): string
    {
        if ($ids === []) {
            return "-- 无 id\n";
        }

        $questions = Question::query()->whereIn('id', $ids)->orderBy('id')->get();
        $rows = [];
        foreach ($questions as $q) {
            $arr = $q->toArray();
            $arr['_line'] = 0;
            $rows[] = $this->normalizeImportRow($arr, 0);
        }

        return $this->renderMysqlScript($rows, $includeId);
    }

    /**
     * @param  array<string, mixed>  $row
     * @param  array<int, string>  $tableColumns
     */
    private function buildSingleUpsertSql(array $row, array $tableColumns, bool $includeId): string
    {
        $assign = [];
        foreach ($row as $key => $value) {
            if (str_starts_with($key, '_')) {
                continue;
            }
            if (! in_array($key, $tableColumns, true)) {
                continue;
            }
            if ($key === 'id' && ! $includeId) {
                continue;
            }
            $assign[$key] = $value;
        }

        if (! isset($assign['question_code']) || $assign['question_code'] === '') {
            return '';
        }

        $assign = array_filter($assign, static fn ($v) => $v !== null);

        $now = date('Y-m-d H:i:s');
        if (! array_key_exists('created_at', $assign)) {
            $assign['created_at'] = $now;
        }
        if (! array_key_exists('updated_at', $assign)) {
            $assign['updated_at'] = $now;
        }

        $columns = array_keys($assign);
        $values = [];
        foreach ($columns as $col) {
            $values[] = $this->quoteSqlValue($assign[$col], $col);
        }

        $colList = implode('`, `', $columns);
        $valList = implode(', ', $values);

        $updates = [];
        foreach ($columns as $col) {
            if ($col === 'question_code' || $col === 'id' || $col === 'created_at') {
                continue;
            }
            $updates[] = '`'.$col.'` = VALUES(`'.$col.'`)';
        }

        if ($updates === []) {
            $updates[] = '`updated_at` = VALUES(`updated_at`)';
        }

        return 'INSERT INTO `questions` (`'.$colList.'`) VALUES ('.$valList.') ON DUPLICATE KEY UPDATE '.implode(', ', $updates).';';
    }

    /**
     * @param  mixed  $value
     */
    private function quoteSqlValue($value, string $column): string
    {
        if ($value === null) {
            return 'NULL';
        }

        if ($value instanceof DateTimeInterface) {
            return $this->pdoQuote($value->format('Y-m-d H:i:s'));
        }

        $jsonCols = ['options', 'meta'];
        if (in_array($column, $jsonCols, true)) {
            if (is_array($value)) {
                $value = json_encode($value, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
            }

            return $this->pdoQuote((string) $value);
        }

        if (is_bool($value)) {
            return $value ? '1' : '0';
        }

        if (is_int($value) || is_float($value)) {
            return (string) $value;
        }

        return $this->pdoQuote((string) $value);
    }

    private function pdoQuote(string $value): string
    {
        $pdo = DB::connection()->getPdo();

        return $pdo->quote($value);
    }

    /**
     * @param  array<string, mixed>  $row
     * @return array<string, mixed>
     */
    private function filterToTableColumns(array $row): array
    {
        $cols = array_flip($this->questionsColumnList());
        $out = [];
        foreach ($row as $k => $v) {
            if ($k === '_line' || $k === '_import_id') {
                continue;
            }
            if (! isset($cols[$k])) {
                continue;
            }
            if ($k === 'id') {
                continue;
            }
            $out[$k] = $v;
        }

        return $out;
    }

    /**
     * @return array<int, string>
     */
    private function questionsColumnList(): array
    {
        if ($this->questionsColumns !== null) {
            return $this->questionsColumns;
        }

        if (! Schema::hasTable('questions')) {
            $this->questionsColumns = [];

            return $this->questionsColumns;
        }

        $this->questionsColumns = Schema::getColumnListing('questions');

        return $this->questionsColumns;
    }

    /**
     * 从本地可读文件路径执行：解析 JSON → 写 SQL → 可选写入 questions。
     *
     * @return array{ok: bool, sql_path?: string, message?: string, stats?: array{created: int, updated: int, skipped: int, errors: array<int, string>}, error?: string}
     */
    public function runImportPipeline(
        string $absolutePath,
        bool $dryRun,
        bool $sqlOnly,
        bool $withId
    ): array {
        try {
            $rawRows = $this->loadRowsFromFile($absolutePath);
        } catch (\Throwable $e) {
            return ['ok' => false, 'error' => $e->getMessage()];
        }

        $rows = [];
        foreach ($rawRows as $i => $raw) {
            if (! is_array($raw)) {
                continue;
            }
            $rows[] = $this->normalizeImportRow($raw, $i + 1);
        }

        if ($rows === []) {
            return ['ok' => false, 'error' => '未解析到题目'];
        }

        $outPath = storage_path('app/exports/questions_import_'.date('YmdHis').'.sql');
        File::ensureDirectoryExists(dirname($outPath));
        File::put($outPath, $this->renderMysqlScript($rows, $withId));

        if ($sqlOnly) {
            return [
                'ok' => true,
                'sql_path' => $outPath,
                'message' => '已生成 SQL（未写本地库）。',
            ];
        }

        $stats = $this->importToDatabase($rows, $dryRun);
        $message = sprintf(
            '新建 %d，更新 %d，跳过 %d。SQL：%s',
            $stats['created'],
            $stats['updated'],
            $stats['skipped'],
            $outPath
        );

        return [
            'ok' => true,
            'sql_path' => $outPath,
            'message' => $message,
            'stats' => $stats,
        ];
    }
}