'use strict';

const express = require('express');
const { standardizeError } = require('../middleware/errorFormatter');
const router  = express.Router();
const {
  previewSpreadsheet,
  applyImportDecisions,
  getImportHistory,
} = require('../services/spreadsheetImportService');
const {
  previewUserDbImport,
  applyUserDbImport,
} = require('../services/userDbImportService');

function makeErrorId() {
  return `imp_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 8)}`;
}

function sendImportError(res, err, fallback, defaultCode) {
  if (err.status) {
    return res.status(err.status).json({
      error: fallback,
      message: err.message,
      code: err.code || defaultCode,
      details: Array.isArray(err.details) ? err.details : [],
    });
  }

  // Log error ID server-side only — never expose to clients
  const errorId = makeErrorId();
  console.error(`[import] ${fallback} (${errorId}):`, err.stack || err.message);
  return res.status(500).json({
    error: fallback,
    message: 'Unexpected import server error. Please try again or adjust the import decisions.',
    code: defaultCode,
  });
}

// ─── POST /api/import/spreadsheet/preview ─────────────────────────────────────
// Accepts an XLSX file as raw binary body.
// Send with Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
// or application/octet-stream. Optionally pass X-Filename header for audit logging.
// Returns a preview with proposed row mappings and bill matches; writes no data.

router.post(
  '/spreadsheet/preview',
  express.raw({
    type: [
      'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
      'application/octet-stream',
      'application/xlsx',
      'application/vnd.ms-excel',
    ],
    limit: '10mb',
  }),
  async (req, res) => {
    try {
      if (!Buffer.isBuffer(req.body) || req.body.length === 0) {
        return res.status(400).json({
          error: 'XLSX file is required. Send as raw binary with Content-Type application/octet-stream or the XLSX MIME type.',
        });
      }

      const rawFilename = req.headers['x-filename'];
      const originalFilename = rawFilename
        ? rawFilename.replace(/[^a-zA-Z0-9._\-\s]/g, '').trim().slice(0, 255)
        : null;

      const options = {
        sheet_name:        req.query.sheet             || null,
        parse_all_sheets:  req.query.parse_all_sheets === 'true',
        default_year:      req.query.year   ? parseInt(req.query.year,  10) : null,
        default_month:     req.query.month  ? parseInt(req.query.month, 10) : null,
        original_filename: originalFilename,
      };

      if (options.default_year && (options.default_year < 2000 || options.default_year > 2100)) {
        return res.status(400).json(standardizeError('year must be a 4-digit integer between 2000 and 2100', 'VALIDATION_ERROR', 'year'));
      }
      if (options.default_month && (options.default_month < 1 || options.default_month > 12)) {
        return res.status(400).json(standardizeError('month must be an integer between 1 and 12', 'VALIDATION_ERROR', 'month'));
      }

      const result = await previewSpreadsheet(req.user.id, req.body, options);
      res.json(result);
    } catch (err) {
      return sendImportError(res, err, 'Import preview failed', 'IMPORT_PREVIEW_ERROR');
    }
  },
);

// ─── POST /api/import/spreadsheet/apply ──────────────────────────────────────
// Applies confirmed import decisions from a previous preview session.
// Body: { import_session_id, decisions: [...], options: { overwrite: false } }
// Each decision must have: row_id, action, and action-specific fields.
// Only writes data for explicitly confirmed decisions; skips ambiguous rows.

router.post('/spreadsheet/apply', express.json({ limit: '2mb' }), async (req, res) => {
  try {
    const { import_session_id, decisions, options } = req.body || {};

    if (!import_session_id || typeof import_session_id !== 'string') {
      return res.status(400).json(standardizeError('import_session_id is required', 'VALIDATION_ERROR', 'import_session_id'));
    }
    if (!Array.isArray(decisions) || decisions.length === 0) {
      return res.status(400).json(standardizeError('decisions array is required and must not be empty', 'VALIDATION_ERROR', 'decisions'));
    }
    if (decisions.length > 5000) {
      return res.status(400).json(standardizeError('Too many decisions in a single apply request (max 5000)', 'VALIDATION_ERROR', 'decisions'));
    }

    const result = await applyImportDecisions(
      req.user.id,
      import_session_id,
      decisions,
      options || {},
    );
    res.json(result);
  } catch (err) {
    return sendImportError(res, err, 'Import apply failed', 'IMPORT_APPLY_ERROR');
  }
});

// ─── POST /api/import/user-db/preview ────────────────────────────────────────
// Accepts a SQLite user data export created by this app. This is not an admin
// full-database restore and writes no live bill/payment/category data.

router.post(
  '/user-db/preview',
  express.raw({
    type: [
      'application/octet-stream',
      'application/x-sqlite3',
      'application/vnd.sqlite3',
      'application/x-sqlite',
      'application/vnd.sqlite',
    ],
    limit: '50mb',
  }),
  async (req, res) => {
    try {
      const rawFilename = req.headers['x-filename'];
      const originalFilename = rawFilename
        ? rawFilename.replace(/[^a-zA-Z0-9._\-\s]/g, '').trim().slice(0, 255)
        : null;
      const result = await previewUserDbImport(req.user.id, req.body, { original_filename: originalFilename });
      res.json(result);
    } catch (err) {
      return sendImportError(res, err, 'User SQLite import preview failed', 'USER_DB_IMPORT_PREVIEW_ERROR');
    }
  },
);

// ─── POST /api/import/user-db/apply ──────────────────────────────────────────
// Applies a previously previewed user SQLite export session. User ownership is
// derived from req.user only; existing data is skipped by default.

router.post('/user-db/apply', express.json({ limit: '1mb' }), async (req, res) => {
  try {
    const { import_session_id, options } = req.body || {};
    if (!import_session_id || typeof import_session_id !== 'string') {
      return res.status(400).json(standardizeError('import_session_id is required', 'VALIDATION_ERROR', 'import_session_id'));
    }
    const result = await applyUserDbImport(req.user.id, import_session_id, options || {});
    res.json(result);
  } catch (err) {
    return sendImportError(res, err, 'User SQLite import apply failed', 'USER_DB_IMPORT_APPLY_ERROR');
  }
});

// ─── GET /api/import/history ──────────────────────────────────────────────────
// Returns the authenticated user's import history (last 100 imports).

router.get('/history', (req, res) => {
  try {
    const history = getImportHistory(req.user.id);
    res.json({ history });
  } catch (err) {
    console.error('[import] history error:', err.message);
    res.status(500).json({ error: 'Failed to load import history' });
  }
});

module.exports = router;