import crypto from 'crypto';
import { pool } from '../db/pool';
import { maskAccountNumber } from '../utils';
import type { StatementFile, ImportStatementResponse } from '@family-budget/shared';

const TRANSFER_PHRASES = [
  'перевод между своими счетами',
  'перевод средств на счет',
  'внутри втб',
];

function computeFingerprint(
  accountNumber: string,
  tx: { operationAt: string; amountSigned: number; commission: number; description: string },
): string {
  const raw = [
    accountNumber,
    tx.operationAt,
    String(tx.amountSigned),
    String(tx.commission),
    tx.description.trim(),
  ].join('|');
  const hash = crypto.createHash('sha256').update(raw, 'utf-8').digest('hex');
  return `sha256:${hash}`;
}

function determineDirection(amountSigned: number, description: string): string {
  const lower = description.toLowerCase();
  for (const phrase of TRANSFER_PHRASES) {
    if (lower.includes(phrase)) return 'transfer';
  }
  return amountSigned > 0 ? 'income' : 'expense';
}

interface ValidationError {
  status: number;
  error: string;
  message: string;
}

const ISO_WITH_OFFSET = /\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}([+-]\d{2}:\d{2}|Z)/;

function validateStructure(body: unknown): ValidationError | null {
  const b = body as Record<string, unknown>;
  if (!b || typeof b !== 'object') {
    return { status: 400, error: 'BAD_REQUEST', message: 'Body must be a JSON object' };
  }

  if (b.schemaVersion !== '1.0') {
    return { status: 400, error: 'BAD_REQUEST', message: "schemaVersion must be '1.0'" };
  }
  if (typeof b.bank !== 'string' || !b.bank) {
    return { status: 400, error: 'BAD_REQUEST', message: 'bank is required and must be a non-empty string' };
  }

  const st = b.statement as Record<string, unknown> | undefined;
  if (!st || typeof st !== 'object') {
    return { status: 400, error: 'BAD_REQUEST', message: 'statement is required' };
  }
  for (const f of ['accountNumber', 'currency'] as const) {
    if (typeof st[f] !== 'string' || !(st[f] as string)) {
      return { status: 400, error: 'BAD_REQUEST', message: `statement.${f} is required and must be a non-empty string` };
    }
  }
  for (const f of ['openingBalance', 'closingBalance'] as const) {
    if (typeof st[f] !== 'number' || !Number.isInteger(st[f])) {
      return { status: 400, error: 'BAD_REQUEST', message: `statement.${f} must be an integer` };
    }
  }
  if (typeof st.exportedAt !== 'string' || !ISO_WITH_OFFSET.test(st.exportedAt as string)) {
    return { status: 400, error: 'BAD_REQUEST', message: 'statement.exportedAt must be ISO 8601 with offset' };
  }

  const txs = b.transactions;
  if (!Array.isArray(txs) || txs.length === 0) {
    return { status: 400, error: 'BAD_REQUEST', message: 'transactions must be a non-empty array' };
  }

  for (let i = 0; i < txs.length; i++) {
    const t = txs[i];
    if (!t || typeof t !== 'object') {
      return { status: 400, error: 'BAD_REQUEST', message: `transactions[${i}] must be an object` };
    }
    if (typeof t.operationAt !== 'string' || !ISO_WITH_OFFSET.test(t.operationAt)) {
      return { status: 400, error: 'BAD_REQUEST', message: `transactions[${i}].operationAt must be ISO 8601 with offset` };
    }
    if (typeof t.amountSigned !== 'number' || !Number.isInteger(t.amountSigned) || t.amountSigned === 0) {
      return { status: 400, error: 'BAD_REQUEST', message: `transactions[${i}].amountSigned must be a non-zero integer` };
    }
    if (typeof t.commission !== 'number' || !Number.isInteger(t.commission) || t.commission < 0) {
      return { status: 400, error: 'BAD_REQUEST', message: `transactions[${i}].commission must be a non-negative integer` };
    }
    if (typeof t.description !== 'string' || !t.description) {
      return { status: 400, error: 'BAD_REQUEST', message: `transactions[${i}].description must be a non-empty string` };
    }
  }

  return null;
}

function validateSemantics(data: StatementFile): ValidationError | null {
  if (data.statement.currency !== 'RUB') {
    return { status: 422, error: 'VALIDATION_ERROR', message: `Unsupported currency: ${data.statement.currency}` };
  }

  for (let i = 0; i < data.transactions.length; i++) {
    if (isNaN(Date.parse(data.transactions[i].operationAt))) {
      return { status: 422, error: 'VALIDATION_ERROR', message: `Invalid date at transaction index ${i}` };
    }
  }

  const fps = new Set<string>();
  for (let i = 0; i < data.transactions.length; i++) {
    const fp = computeFingerprint(data.statement.accountNumber, data.transactions[i]);
    if (fps.has(fp)) {
      return { status: 422, error: 'VALIDATION_ERROR', message: `Duplicate fingerprint found within file at transaction index ${i}` };
    }
    fps.add(fp);
  }

  return null;
}

export async function importStatement(
  body: unknown,
): Promise<ImportStatementResponse | ValidationError> {
  const structErr = validateStructure(body);
  if (structErr) return structErr;

  const data = body as StatementFile;
  const semErr = validateSemantics(data);
  if (semErr) return semErr;

  const client = await pool.connect();
  try {
    await client.query('BEGIN');

    // Find or create account
    let accountId: number;
    let isNewAccount = false;

    const accResult = await client.query(
      'SELECT id FROM accounts WHERE bank = $1 AND account_number = $2',
      [data.bank, data.statement.accountNumber],
    );

    if (accResult.rows.length > 0) {
      accountId = Number(accResult.rows[0].id);
    } else {
      const ins = await client.query(
        'INSERT INTO accounts (bank, account_number, currency) VALUES ($1, $2, $3) RETURNING id',
        [data.bank, data.statement.accountNumber, data.statement.currency],
      );
      accountId = Number(ins.rows[0].id);
      isNewAccount = true;
    }

    // Create import record (counts updated after loop)
    const accountNumberMasked = maskAccountNumber(data.statement.accountNumber);
    const importResult = await client.query(
      `INSERT INTO imports (account_id, bank, account_number_masked, imported_count, duplicates_skipped, total_in_file)
       VALUES ($1, $2, $3, 0, 0, $4)
       RETURNING id`,
      [accountId, data.bank, accountNumberMasked, data.transactions.length],
    );
    const importId = Number(importResult.rows[0].id);

    // Insert transactions
    const insertedIds: number[] = [];

    for (const tx of data.transactions) {
      const fp = computeFingerprint(data.statement.accountNumber, tx);
      const dir = determineDirection(tx.amountSigned, tx.description);

      const result = await client.query(
        `INSERT INTO transactions
           (account_id, operation_at, amount_signed, commission, description, direction, fingerprint, category_id, is_category_confirmed, import_id)
         VALUES ($1, $2, $3, $4, $5, $6, $7, NULL, FALSE, $8)
         ON CONFLICT (account_id, fingerprint) DO NOTHING
         RETURNING id`,
        [accountId, tx.operationAt, tx.amountSigned, tx.commission, tx.description, dir, fp, importId],
      );

      if (result.rows.length > 0) {
        insertedIds.push(Number(result.rows[0].id));
      }
    }

    // Update import record with actual counts
    const duplicatesSkipped = data.transactions.length - insertedIds.length;
    await client.query(
      `UPDATE imports SET imported_count = $1, duplicates_skipped = $2 WHERE id = $3`,
      [insertedIds.length, duplicatesSkipped, importId],
    );

    // Auto-categorize newly inserted transactions
    if (insertedIds.length > 0) {
      await client.query(
        `UPDATE transactions t
         SET category_id = sub.category_id,
             is_category_confirmed = NOT sub.requires_confirmation,
             updated_at = NOW()
         FROM (
           SELECT DISTINCT ON (t2.id)
             t2.id AS tx_id,
             cr.category_id,
             cr.requires_confirmation
           FROM transactions t2
           JOIN category_rules cr
             ON cr.is_active = TRUE
             AND (
               (cr.match_type = 'contains'     AND t2.description ILIKE '%' || cr.pattern || '%')
               OR (cr.match_type = 'starts_with' AND t2.description ILIKE cr.pattern || '%')
             )
           WHERE t2.id = ANY($1::bigint[])
           ORDER BY t2.id, cr.priority DESC, cr.id ASC
         ) sub
         WHERE t.id = sub.tx_id`,
        [insertedIds],
      );
    }

    await client.query('COMMIT');

    return {
      accountId,
      isNewAccount,
      accountNumberMasked,
      imported: insertedIds.length,
      duplicatesSkipped: data.transactions.length - insertedIds.length,
      totalInFile: data.transactions.length,
    };
  } catch (err) {
    await client.query('ROLLBACK');
    throw err;
  } finally {
    client.release();
  }
}

export function isValidationError(r: unknown): r is ValidationError {
  return (
    typeof r === 'object' &&
    r !== null &&
    'status' in r &&
    'error' in r &&
    'message' in r
  );
}