const express = require('express');
const router = express.Router();
const { getDb, ensureUserDefaultCategories } = require('../db/database');
const { standardizeError } = require('../middleware/errorFormatter');
const { fromCents } = require('../utils/money');
const {
  createSubscriptionFromRecommendation,
  declineRecommendation,
  decorateSubscription,
  getSubscriptionRecommendations,
  getSubscriptionSummary,
  getSubscriptions,
  monthlyEquivalent,
  recordSubscriptionFeedback,
  searchSubscriptionTransactions,
} = require('../services/subscriptionService');
const { addMerchantRule, applyMerchantRules } = require('../services/billMerchantRuleService');

router.get('/', (req, res) => {
  const db = getDb();
  ensureUserDefaultCategories(req.user.id);
  const subscriptions = getSubscriptions(db, req.user.id);
  res.json({
    summary: getSubscriptionSummary(subscriptions),
    subscriptions,
  });
});

router.get('/recommendations', (req, res) => {
  const db = getDb();
  res.json({
    recommendations: getSubscriptionRecommendations(db, req.user.id),
  });
});

router.get('/transaction-matches', (req, res) => {
  try {
    res.json({
      transactions: searchSubscriptionTransactions(getDb(), req.user.id, req.query),
    });
  } catch (err) {
    res.status(500).json(standardizeError(err.message || 'Failed to search subscription transactions', 'SUBSCRIPTION_SEARCH_ERROR'));
  }
});

router.post('/recommendations/decline', (req, res) => {
  const { decline_key } = req.body || {};
  if (!decline_key || typeof decline_key !== 'string' || decline_key.length > 200) {
    return res.status(400).json(standardizeError('decline_key is required', 'VALIDATION_ERROR', 'decline_key'));
  }
  try {
    const db = getDb();
    declineRecommendation(db, req.user.id, decline_key);
    recordSubscriptionFeedback(db, req.user.id, {
      action: 'decline',
      catalog_id: req.body?.catalog_id,
      merchant: req.body?.merchant,
      confidence: req.body?.confidence,
      metadata: { decline_key },
    });
    res.json({ ok: true });
  } catch (err) {
    res.status(500).json(standardizeError(err.message || 'Failed to decline recommendation', 'DECLINE_ERROR'));
  }
});

// POST /api/subscriptions/recommendations/match-bill
// Link an existing bill to all transactions in a recommendation (no new bill created).
router.post('/recommendations/match-bill', (req, res) => {
  const billId = parseInt(req.body?.bill_id, 10);
  const rawIds = Array.isArray(req.body?.transaction_ids) ? req.body.transaction_ids : [];
  const txIds  = rawIds.map(id => parseInt(id, 10)).filter(n => Number.isInteger(n) && n > 0).slice(0, 50);

  if (!Number.isInteger(billId) || billId < 1) {
    return res.status(400).json(standardizeError('bill_id is required', 'VALIDATION_ERROR', 'bill_id'));
  }
  if (txIds.length === 0) {
    return res.status(400).json(standardizeError('transaction_ids must be a non-empty array', 'VALIDATION_ERROR', 'transaction_ids'));
  }

  const db = getDb();
  const bill = db.prepare('SELECT id, name, catalog_id FROM bills WHERE id = ? AND user_id = ? AND deleted_at IS NULL').get(billId, req.user.id);
  if (!bill) return res.status(404).json(standardizeError('Bill not found', 'NOT_FOUND', 'bill_id'));
  const catalogId = parseInt(req.body?.catalog_id, 10);
  const catalogEntry = Number.isInteger(catalogId) && catalogId > 0
    ? db.prepare('SELECT id FROM subscription_catalog WHERE id = ?').get(catalogId)
    : null;

  const placeholders = txIds.map(() => '?').join(',');
  const txRows = db.prepare(`
    SELECT id, amount, posted_date, transacted_at
    FROM transactions
    WHERE user_id = ? AND id IN (${placeholders}) AND ignored = 0 AND match_status != 'matched'
  `).all(req.user.id, ...txIds);

  const updateTx = db.prepare(`
    UPDATE transactions
    SET matched_bill_id = ?, match_status = 'matched', updated_at = CURRENT_TIMESTAMP
    WHERE id = ? AND user_id = ? AND ignored = 0 AND match_status != 'matched'
  `);
  const insertPayment = db.prepare(`
    INSERT OR IGNORE INTO payments (bill_id, amount, paid_date, payment_source, transaction_id)
    VALUES (?, ?, ?, 'auto_match', ?)
  `);
  let matchedCount = 0;
  db.transaction(() => {
    for (const tx of txRows) {
      const paidDate = tx.posted_date || (tx.transacted_at ? String(tx.transacted_at).slice(0, 10) : null);
      const amount   = Math.round(Math.abs(tx.amount)); // tx.amount and payments.amount are both cents
      matchedCount  += updateTx.run(billId, tx.id, req.user.id).changes;
      if (paidDate) insertPayment.run(billId, amount, paidDate, tx.id);
    }
  })();

  // Store merchant rule for ongoing auto-matching on future syncs
  const merchant = typeof req.body?.merchant === 'string' ? req.body.merchant.trim() : '';
  if (merchant) addMerchantRule(db, req.user.id, billId, merchant);
  if (catalogEntry && !bill.catalog_id) {
    try {
      db.prepare('UPDATE bills SET catalog_id = ?, updated_at = datetime(\'now\') WHERE id = ? AND user_id = ?')
        .run(catalogEntry.id, billId, req.user.id);
    } catch { /* pre-v0.96 */ }
  }
  recordSubscriptionFeedback(db, req.user.id, {
    action: 'link_existing_bill',
    catalog_id: catalogEntry?.id,
    bill_id: billId,
    merchant,
    confidence: req.body?.confidence,
    metadata: { transaction_ids: txIds },
  });

  // Apply rules immediately to catch any unmatched transactions beyond the explicit list
  const { matched: autoMatched } = applyMerchantRules(db, req.user.id);

  res.json({ ok: true, matched_count: matchedCount + autoMatched, bill_name: bill.name });
});

router.post('/recommendations/create', (req, res) => {
  const db = getDb();
  ensureUserDefaultCategories(req.user.id);
  if (req.body?.category_id) {
    const categoryId = parseInt(req.body.category_id, 10);
    const category = Number.isInteger(categoryId)
      ? db.prepare('SELECT id FROM categories WHERE id = ? AND user_id = ? AND deleted_at IS NULL').get(categoryId, req.user.id)
      : null;
    if (!category) {
      return res.status(400).json(standardizeError('category_id is invalid for this user', 'VALIDATION_ERROR', 'category_id'));
    }
  }
  try {
    const created = createSubscriptionFromRecommendation(db, req.user.id, req.body || {});
    // Store merchant rule so future SimpleFIN transactions auto-match this bill
    if (req.body?.merchant) addMerchantRule(db, req.user.id, created.id, req.body.merchant);
    recordSubscriptionFeedback(db, req.user.id, {
      action: 'accept_track_new',
      catalog_id: req.body?.catalog_match?.id,
      bill_id: created.id,
      merchant: req.body?.merchant,
      confidence: req.body?.confidence,
      metadata: { transaction_ids: req.body?.transaction_ids || [] },
    });
    res.status(201).json(created);
  } catch (err) {
    res.status(err.status || 400).json(standardizeError(err.message || 'Could not create subscription', err.status ? 'VALIDATION_ERROR' : 'SUBSCRIPTION_CREATE_ERROR', err.field || null));
  }
});

// ── Catalog browser ───────────────────────────────────────────────────────────

router.get('/catalog', (req, res) => {
  const db = getDb();
  try {
    const catalogEntries = db.prepare(`
      SELECT id, rank, name, category, subcategory, subscription_type,
             website, starting_monthly_usd, starting_annual_usd
      FROM subscription_catalog
      ORDER BY rank ASC
    `).all();

    if (!catalogEntries.length) return res.json({ catalog: [] });

    // User's subscription bills that are linked to a catalog entry
    const matchedBills = db.prepare(`
      SELECT b.id, b.name, b.expected_amount, b.active, b.catalog_id,
             b.cycle_type, b.billing_cycle
      FROM bills b
      WHERE b.user_id = ?
        AND b.is_subscription = 1
        AND b.deleted_at IS NULL
        AND b.catalog_id IS NOT NULL
    `).all(req.user.id);

    const billByCatalogId = new Map(matchedBills.map(b => [b.catalog_id, b]));

    // User's custom descriptors
    let userDescriptors = [];
    try {
      userDescriptors = db.prepare(
        'SELECT id, catalog_id, descriptor FROM user_catalog_descriptors WHERE user_id = ?'
      ).all(req.user.id);
    } catch { /* pre-v0.96 */ }

    const userDescsByCatalogId = new Map();
    for (const d of userDescriptors) {
      if (!userDescsByCatalogId.has(d.catalog_id)) userDescsByCatalogId.set(d.catalog_id, []);
      userDescsByCatalogId.get(d.catalog_id).push({ id: d.id, descriptor: d.descriptor });
    }

    const catalog = catalogEntries.map(entry => {
      const bill = billByCatalogId.get(entry.id) ?? null;
      return {
        ...entry,
        matched_bill: bill ? {
          id: bill.id,
          name: bill.name,
          expected_amount: fromCents(bill.expected_amount),
          active: !!bill.active,
          monthly_equivalent: monthlyEquivalent(fromCents(bill.expected_amount), bill.cycle_type, bill.billing_cycle),
        } : null,
        user_descriptors: userDescsByCatalogId.get(entry.id) ?? [],
      };
    });

    res.json({ catalog });
  } catch (err) {
    res.status(500).json(standardizeError(err.message || 'Failed to load catalog', 'CATALOG_ERROR'));
  }
});

// Update which catalog entry a bill is linked to (or unlink with null)
router.put('/:id/catalog-link', (req, res) => {
  const db = getDb();
  const billId = parseInt(req.params.id, 10);
  if (!Number.isInteger(billId) || billId < 1) {
    return res.status(400).json(standardizeError('Invalid bill ID', 'VALIDATION_ERROR'));
  }

  const bill = db.prepare(
    'SELECT id, name, catalog_id FROM bills WHERE id = ? AND user_id = ? AND deleted_at IS NULL'
  ).get(billId, req.user.id);
  if (!bill) return res.status(404).json(standardizeError('Bill not found', 'NOT_FOUND'));

  const rawCatalogId = req.body?.catalog_id;

  if (rawCatalogId === null || rawCatalogId === undefined) {
    db.prepare("UPDATE bills SET catalog_id = NULL, updated_at = datetime('now') WHERE id = ? AND user_id = ?")
      .run(billId, req.user.id);
    recordSubscriptionFeedback(db, req.user.id, {
      action: 'catalog_unlink',
      catalog_id: bill.catalog_id,
      bill_id: billId,
      merchant: bill.name,
    });
    return res.json({ ok: true, catalog_id: null });
  }

  const catalogId = parseInt(rawCatalogId, 10);
  if (!Number.isInteger(catalogId) || catalogId < 1) {
    return res.status(400).json(standardizeError('catalog_id must be a positive integer or null', 'VALIDATION_ERROR', 'catalog_id'));
  }
  const catalogEntry = db.prepare('SELECT id FROM subscription_catalog WHERE id = ?').get(catalogId);
  if (!catalogEntry) return res.status(404).json(standardizeError('Catalog entry not found', 'NOT_FOUND', 'catalog_id'));

  db.prepare("UPDATE bills SET catalog_id = ?, updated_at = datetime('now') WHERE id = ? AND user_id = ?")
    .run(catalogId, billId, req.user.id);
  recordSubscriptionFeedback(db, req.user.id, {
    action: 'catalog_relink',
    catalog_id: catalogId,
    bill_id: billId,
    merchant: bill.name,
    metadata: { previous_catalog_id: bill.catalog_id || null },
  });
  res.json({ ok: true, catalog_id: catalogId });
});

// Add a custom bank descriptor for a catalog entry (per-user)
router.post('/catalog/:catalogId/descriptors', (req, res) => {
  const db = getDb();
  const catalogId = parseInt(req.params.catalogId, 10);
  if (!Number.isInteger(catalogId) || catalogId < 1) {
    return res.status(400).json(standardizeError('Invalid catalog ID', 'VALIDATION_ERROR'));
  }

  const catalogEntry = db.prepare('SELECT id FROM subscription_catalog WHERE id = ?').get(catalogId);
  if (!catalogEntry) return res.status(404).json(standardizeError('Catalog entry not found', 'NOT_FOUND'));

  const descriptor = String(req.body?.descriptor ?? '').trim();
  if (!descriptor) {
    return res.status(400).json(standardizeError('descriptor is required', 'VALIDATION_ERROR', 'descriptor'));
  }
  if (descriptor.length > 100) {
    return res.status(400).json(standardizeError('descriptor must be 100 characters or less', 'VALIDATION_ERROR', 'descriptor'));
  }

  try {
    // Check for case-insensitive duplicate
    const exists = db.prepare(
      'SELECT id FROM user_catalog_descriptors WHERE user_id = ? AND catalog_id = ? AND LOWER(descriptor) = LOWER(?)'
    ).get(req.user.id, catalogId, descriptor);
    if (exists) {
      return res.status(409).json(standardizeError('Descriptor already exists for this service', 'DUPLICATE_ERROR', 'descriptor'));
    }

    const result = db.prepare(
      'INSERT INTO user_catalog_descriptors (user_id, catalog_id, descriptor) VALUES (?, ?, ?)'
    ).run(req.user.id, catalogId, descriptor);
    recordSubscriptionFeedback(db, req.user.id, {
      action: 'add_descriptor',
      catalog_id: catalogId,
      merchant: descriptor,
      descriptor,
    });

    res.status(201).json({ id: result.lastInsertRowid, descriptor, catalog_id: catalogId });
  } catch (err) {
    res.status(500).json(standardizeError(err.message || 'Failed to add descriptor', 'DESCRIPTOR_ADD_ERROR'));
  }
});

// Delete a user-added catalog descriptor
router.delete('/catalog/descriptors/:id', (req, res) => {
  const db = getDb();
  const descriptorId = parseInt(req.params.id, 10);
  if (!Number.isInteger(descriptorId) || descriptorId < 1) {
    return res.status(400).json(standardizeError('Invalid descriptor ID', 'VALIDATION_ERROR'));
  }

  try {
    const existing = db.prepare(
      'SELECT catalog_id, descriptor FROM user_catalog_descriptors WHERE id = ? AND user_id = ?'
    ).get(descriptorId, req.user.id);
    const result = db.prepare(
      'DELETE FROM user_catalog_descriptors WHERE id = ? AND user_id = ?'
    ).run(descriptorId, req.user.id);
    if (result.changes === 0) {
      return res.status(404).json(standardizeError('Descriptor not found', 'NOT_FOUND'));
    }
    if (existing) {
      recordSubscriptionFeedback(db, req.user.id, {
        action: 'delete_descriptor',
        catalog_id: existing.catalog_id,
        merchant: existing.descriptor,
        descriptor: existing.descriptor,
      });
    }
    res.json({ ok: true });
  } catch (err) {
    res.status(500).json(standardizeError(err.message || 'Failed to delete descriptor', 'DESCRIPTOR_DELETE_ERROR'));
  }
});

router.patch('/:id', (req, res) => {
  const db = getDb();
  const billId = parseInt(req.params.id, 10);
  if (!Number.isInteger(billId)) {
    return res.status(400).json(standardizeError('bill_id must be an integer', 'VALIDATION_ERROR', 'bill_id'));
  }

  const existing = db.prepare('SELECT * FROM bills WHERE id = ? AND user_id = ? AND deleted_at IS NULL').get(billId, req.user.id);
  if (!existing) return res.status(404).json(standardizeError('Bill not found', 'NOT_FOUND', 'bill_id'));

  const allowedTypes = new Set(['streaming', 'software', 'cloud', 'music', 'news', 'fitness', 'gaming', 'utilities', 'insurance', 'other']);
  const next = {
    is_subscription: req.body.is_subscription !== undefined ? (req.body.is_subscription ? 1 : 0) : existing.is_subscription,
    subscription_type: req.body.subscription_type !== undefined
      ? (allowedTypes.has(req.body.subscription_type) ? req.body.subscription_type : 'other')
      : existing.subscription_type,
    reminder_days_before: req.body.reminder_days_before !== undefined
      ? Number(req.body.reminder_days_before)
      : existing.reminder_days_before,
    active: req.body.active !== undefined ? (req.body.active ? 1 : 0) : existing.active,
  };

  if (!Number.isInteger(next.reminder_days_before) || next.reminder_days_before < 0 || next.reminder_days_before > 30) {
    return res.status(400).json(standardizeError('reminder_days_before must be between 0 and 30', 'VALIDATION_ERROR', 'reminder_days_before'));
  }

  db.prepare(`
    UPDATE bills
    SET is_subscription = ?,
        subscription_type = ?,
        reminder_days_before = ?,
        active = ?,
        updated_at = datetime('now')
    WHERE id = ? AND user_id = ?
  `).run(next.is_subscription, next.subscription_type, next.reminder_days_before, next.active, billId, req.user.id);

  const updated = db.prepare(`
    SELECT b.*, c.name AS category_name
    FROM bills b
    LEFT JOIN categories c ON c.id = b.category_id AND c.user_id = b.user_id AND c.deleted_at IS NULL
    WHERE b.id = ? AND b.user_id = ?
  `).get(billId, req.user.id);

  res.json(decorateSubscription(updated));
});

module.exports = router;