import { createHash } from 'node:crypto';
import { mkdir, readFile, stat, writeFile } from 'node:fs/promises';
import { isAbsolute, parse, resolve } from 'node:path';
import { Injectable, InternalServerErrorException, NotFoundException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { DataSource } from 'typeorm';
import { buildInspectionReportWord } from './inspection-report-word-builder';

const WORD_MIME = 'application/vnd.openxmlformats-officedocument.wordprocessingml.document';

interface WordRow {
  id: string;
  code: string;
  title: string;
  generatedAt: Date;
  frozenSha256: string;
  frozenSnapshot: Record<string, unknown>;
  wordStatus: 'PENDING' | 'READY' | 'FAILED';
  wordOriginalName: string | null;
  wordStoredName: string | null;
  wordMimeType: string | null;
  wordSizeBytes: number | null;
  wordSha256: string | null;
  generatedBy: string;
}

@Injectable()
export class InspectionReportWordService {
  private readonly root: string;

  constructor(private readonly dataSource: DataSource, config: ConfigService) {
    const configured = config.get<string>('INSPECTION_REPORT_WORD_ROOT') ?? '/app/storage/asset-media/inspection-reports-word';
    if (!isAbsolute(configured)) throw new Error('INSPECTION_REPORT_WORD_ROOT must be an absolute path');
    this.root = resolve(configured);
    if (this.root === parse(this.root).root) throw new Error('INSPECTION_REPORT_WORD_ROOT cannot be the filesystem root');
  }

  async ensure(reportId: string): Promise<void> {
    const row = await this.load(reportId);
    if (row.wordStatus === 'READY' && row.wordStoredName) {
      try { await this.content(row.id); await this.ensureInitialRevision(row); return; } catch {}
    }
    try {
      const built = buildInspectionReportWord({
        code: row.code,
        title: row.title,
        generatedAt: new Date(row.generatedAt),
        frozenSha256: row.frozenSha256,
        frozenSnapshot: row.frozenSnapshot,
      });
      await mkdir(this.root, { recursive: true, mode: 0o700 });
      const storedName = `${row.id}.docx`;
      const originalName = `${row.code}.docx`;
      const filePath = resolve(this.root, storedName);
      await writeFile(filePath, built.buffer, { mode: 0o600 });
      await this.dataSource.query(`
        UPDATE inspection_reports
        SET word_status = 'READY',
            word_original_name = $2,
            word_stored_name = $3,
            word_mime_type = $4,
            word_size_bytes = $5,
            word_sha256 = $6,
            word_generated_at = CURRENT_TIMESTAMP,
            word_error = NULL,
            updated_at = CURRENT_TIMESTAMP
        WHERE id = $1
      `, [row.id, originalName, storedName, WORD_MIME, built.buffer.length, built.sha256]);
      await this.ensureInitialRevision(await this.load(row.id));
    } catch (error) {
      const message = error instanceof Error ? error.message.slice(0, 500) : 'Error desconocido';
      await this.dataSource.query(`
        UPDATE inspection_reports
        SET word_status = 'FAILED', word_error = $2, updated_at = CURRENT_TIMESTAMP
        WHERE id = $1
      `, [row.id, message]).catch(() => undefined);
    }
  }

  async content(reportId: string): Promise<{ filePath: string; originalName: string; mimeType: string }> {
    const row = await this.load(reportId);
    if (row.wordStatus !== 'READY' || !row.wordStoredName || !row.wordOriginalName || !row.wordSha256 || !row.wordSizeBytes) {
      throw new NotFoundException({ code: 'INSPECTION_REPORT_WORD_NOT_READY', message: 'El archivo Word del informe todavía no está disponible' });
    }
    const filePath = resolve(this.root, row.wordStoredName);
    if (!filePath.startsWith(`${this.root}/`)) throw this.storageError();
    const fileStat = await stat(filePath).catch(() => null);
    if (!fileStat?.isFile() || fileStat.size !== row.wordSizeBytes) throw this.storageError();
    const buffer = await readFile(filePath);
    const sha256 = createHash('sha256').update(buffer).digest('hex');
    if (sha256 !== row.wordSha256) throw this.storageError();
    return { filePath, originalName: row.wordOriginalName, mimeType: row.wordMimeType ?? WORD_MIME };
  }


  private async ensureInitialRevision(row: WordRow): Promise<void> {
    if (row.wordStatus !== 'READY' || !row.wordOriginalName || !row.wordStoredName || !row.wordMimeType || !row.wordSizeBytes || !row.wordSha256) return;
    await this.dataSource.query(`
      INSERT INTO inspection_report_revisions (
        report_id, revision_number, source, original_name, stored_name, mime_type,
        size_bytes, sha256, change_summary, created_by, created_at
      ) VALUES ($1,1,'AUTO',$2,$3,$4,$5,$6,'Versión automática inicial',$7,COALESCE((SELECT word_generated_at FROM inspection_reports WHERE id=$1),CURRENT_TIMESTAMP))
      ON CONFLICT (report_id, revision_number) DO NOTHING
    `, [row.id, row.wordOriginalName, row.wordStoredName, row.wordMimeType, row.wordSizeBytes, row.wordSha256, row.generatedBy]);
    await this.dataSource.query(`
      UPDATE inspection_reports
      SET current_revision_number = GREATEST(current_revision_number, 1), updated_at = CURRENT_TIMESTAMP
      WHERE id = $1
    `, [row.id]);
  }

  private async load(reportId: string): Promise<WordRow> {
    const [row] = await this.dataSource.query(`
      SELECT id, code, title, generated_at AS "generatedAt", frozen_sha256 AS "frozenSha256",
             frozen_snapshot AS "frozenSnapshot", word_status AS "wordStatus",
             word_original_name AS "wordOriginalName", word_stored_name AS "wordStoredName",
             word_mime_type AS "wordMimeType", word_size_bytes::integer AS "wordSizeBytes",
             word_sha256 AS "wordSha256", generated_by AS "generatedBy"
      FROM inspection_reports WHERE id = $1
    `, [reportId]) as WordRow[];
    if (!row) throw new NotFoundException({ code: 'INSPECTION_REPORT_NOT_FOUND', message: 'Informe de inspección no encontrado' });
    return row;
  }

  private storageError(): InternalServerErrorException {
    return new InternalServerErrorException({ code: 'INSPECTION_REPORT_WORD_STORAGE_ERROR', message: 'El archivo Word del informe no está disponible o no supera la validación de integridad' });
  }
}