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

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

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

  async ensure(actId: string): Promise<void> {
    const [row] = await this.dataSource.query(`
      SELECT
        act.id,
        act.code,
        act.closure_sha256 AS "closureSha256",
        closure.final_snapshot AS "finalSnapshot",
        artifact.status,
        artifact.stored_name AS "storedName"
      FROM inspection_acts act
      JOIN inspection_act_closures closure ON closure.act_id=act.id
      LEFT JOIN inspection_act_pdf_artifacts artifact ON artifact.act_id=act.id
      WHERE act.id=$1 AND act.status='SEALED'
    `, [actId]) as Array<{
      id: string;
      code: string;
      closureSha256: string;
      finalSnapshot: Record<string, unknown>;
      status: string | null;
      storedName: string | null;
    }>;
    if (!row) {
      throw new NotFoundException({
        code: 'INSPECTION_ACT_NOT_SEALED',
        message: 'El PDF sólo puede generarse desde un Acta SELLADA',
      });
    }
    if (row.status === 'READY' && row.storedName) {
      try {
        await this.content(actId);
        return;
      } catch {}
    }
    await this.dataSource.query(`
      INSERT INTO inspection_act_pdf_artifacts(act_id,status)
      VALUES($1,'PENDING')
      ON CONFLICT (act_id) DO UPDATE SET
        status='PENDING',error=NULL,updated_at=CURRENT_TIMESTAMP
    `, [actId]);
    try {
      const snapshot = { ...row.finalSnapshot, finalSha256: row.closureSha256 };
      const built = buildInspectionActPdf(snapshot);
      await mkdir(this.root, { recursive: true, mode: 0o700 });
      const storedName = `${actId}.pdf`;
      const originalName = `${row.code}.pdf`;
      const filePath = resolve(this.root, storedName);
      await writeFile(filePath, built.buffer, { mode: 0o600 });
      await this.dataSource.query(`
        UPDATE inspection_act_pdf_artifacts
        SET status='READY',original_name=$2,stored_name=$3,mime_type='application/pdf',
            size_bytes=$4,sha256=$5,generated_at=CURRENT_TIMESTAMP,error=NULL,
            updated_at=CURRENT_TIMESTAMP
        WHERE act_id=$1
      `, [actId, originalName, storedName, built.buffer.length, built.sha256]);
    } catch (error) {
      const message = error instanceof Error ? error.message.slice(0, 500) : 'Error desconocido';
      await this.dataSource.query(`
        UPDATE inspection_act_pdf_artifacts
        SET status='FAILED',error=$2,updated_at=CURRENT_TIMESTAMP
        WHERE act_id=$1
      `, [actId, message]).catch(() => undefined);
    }
  }

  async content(actId: string): Promise<{ buffer: Buffer; originalName: string; mimeType: string }> {
    const [row] = await this.dataSource.query(`
      SELECT original_name AS "originalName",stored_name AS "storedName",
             mime_type AS "mimeType",size_bytes::integer AS "sizeBytes",sha256
      FROM inspection_act_pdf_artifacts
      WHERE act_id=$1 AND status='READY'
    `, [actId]) as Array<{
      originalName: string;
      storedName: string;
      mimeType: string;
      sizeBytes: number;
      sha256: string;
    }>;
    if (!row) {
      throw new NotFoundException({
        code: 'INSPECTION_ACT_PDF_NOT_READY',
        message: 'El PDF del Acta todavía no está disponible',
      });
    }
    const filePath = resolve(this.root, row.storedName);
    if (!filePath.startsWith(`${this.root}/`)) throw this.storageError();
    const fileStat = await stat(filePath).catch(() => null);
    if (!fileStat?.isFile() || fileStat.size !== row.sizeBytes) throw this.storageError();
    const buffer = await readFile(filePath);
    if (createHash('sha256').update(buffer).digest('hex') !== row.sha256) throw this.storageError();
    return { buffer, originalName: row.originalName, mimeType: row.mimeType };
  }

  private storageError(): InternalServerErrorException {
    return new InternalServerErrorException({
      code: 'INSPECTION_ACT_PDF_STORAGE_ERROR',
      message: 'El PDF del Acta no está disponible o no supera la validación de integridad',
    });
  }
}