/**
 * ═══════════════════════════════════════════════════════════════════════════
 * AAMOS Ledger — Input Validation Module
 * ═══════════════════════════════════════════════════════════════════════════
 *
 * Använder Joi för robust schema-validering av alla inkommande requests.
 */

import Joi from 'joi';

// ── Reusable validators ─────────────────────────────────────────────────────

const UUID_PATTERN = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;

export const schemas = {

  // ── Account schemas ───────────────────────────────────────────────────────
  createAccount: Joi.object({
    account_number: Joi.string().max(20).required()
      .pattern(/^\d+$/)
      .messages({ 'string.pattern.base': 'account_number måste vara numeriskt' }),
    name: Joi.string().min(1).max(200).required(),
    account_type: Joi.string().valid('asset', 'liability', 'equity', 'revenue', 'expense').required(),
    normal_balance: Joi.string().valid('debit', 'credit').required(),
    coa_standard: Joi.string().valid('BAS', 'IFRS', 'USGAAP', 'custom').default('BAS'),
    parent_account: Joi.string().max(20).allow(null),
    vat_code: Joi.string().max(20).allow(null),
    metadata: Joi.object().default({}),
  }),

  listAccounts: Joi.object({
    standard: Joi.string().valid('BAS', 'IFRS', 'USGAAP', 'custom').default('BAS'),
  }),

  // ── Journal entry schemas ─────────────────────────────────────────────────
  createJournalEntry: Joi.object({
    entry_date: Joi.date().iso().required()
      .messages({ 'date.format': 'entry_date måste vara ISO-8601 (YYYY-MM-DD)' }),
    description: Joi.string().min(1).max(1000).required(),
    reference: Joi.string().max(200).allow(null, ''),
    source_type: Joi.string().valid('manual', 'import_sie', 'import_csv', 'bank', 'system', 'agent').default('manual'),
    source_id: Joi.string().max(200).allow(null, ''),
    period: Joi.string().pattern(/^\d{4}-\d{2}$/).allow(null)
      .messages({ 'string.pattern.base': 'period måste vara YYYY-MM' }),
    fiscal_year: Joi.number().integer().min(2000).max(2100).allow(null),
    metadata: Joi.object().default({}),
    lines: Joi.array().items(
      Joi.object({
        account_number: Joi.string().max(20).required(),
        account_name: Joi.string().max(200).allow(null, ''),
        debit: Joi.number().positive().allow(null),
        credit: Joi.number().positive().allow(null),
        currency: Joi.string().length(3).uppercase().default('SEK'),
        amount_base: Joi.number().positive().allow(null),
        vat_code: Joi.string().max(20).allow(null, ''),
        vat_amount: Joi.number().min(0).allow(null),
        cost_center: Joi.string().max(50).allow(null, ''),
        project_code: Joi.string().max(50).allow(null, ''),
        description: Joi.string().max(500).allow(null, ''),
        metadata: Joi.object().default({}),
      }).custom((value, helpers) => {
        // Antingen debit ELLER credit, inte båda/ingen
        const hasDebit = value.debit != null;
        const hasCredit = value.credit != null;
        if (hasDebit === hasCredit) {
          return helpers.error('journal.line.debit_credit');
        }
        return value;
      }, 'debit_credit_check')
      .messages({ 'journal.line.debit_credit': 'Varje journalrad måste ha antingen debit ELLER credit' })
    ).min(2).required()
      .messages({ 'array.min': 'Minst 2 journalrader krävs för dubbel bokföring' }),
  }).custom((value, helpers) => {
    // Beräkna och validera att debet = kredit
    const totalDebit = value.lines.reduce((s, l) => s + (l.debit || 0), 0);
    const totalCredit = value.lines.reduce((s, l) => s + (l.credit || 0), 0);
    if (Math.abs(totalDebit - totalCredit) > 0.01) {
      return helpers.error('journal.balance', { totalDebit, totalCredit });
    }
    return value;
  }, 'balance_check')
  .messages({
    'journal.balance': 'Dubbelbokföring bruten: debet {{#totalDebit}} ≠ kredit {{#totalCredit}}',
  }),

  listJournalEntries: Joi.object({
    period: Joi.string().pattern(/^\d{4}-\d{2}$/).allow(null, ''),
    fiscal_year: Joi.number().integer().min(2000).max(2100).allow(null, ''),
    status: Joi.string().valid('draft', 'posted', 'voided').allow(null, ''),
    limit: Joi.number().integer().min(1).max(1000).default(50),
    offset: Joi.number().integer().min(0).default(0),
  }),

  postJournalEntry: Joi.object({
    id: Joi.string().pattern(UUID_PATTERN).required()
      .messages({ 'string.pattern.base': 'id måste vara ett giltigt UUID' }),
  }),

  // ── Trial balance schemas ─────────────────────────────────────────────────
  trialBalance: Joi.object({
    period: Joi.string().pattern(/^\d{4}-\d{2}$/).allow(null, ''),
    fiscal_year: Joi.number().integer().min(2000).max(2100).required(),
  }),

  // ── Period schemas ────────────────────────────────────────────────────────
  listPeriods: Joi.object({
    fiscal_year: Joi.number().integer().min(2000).max(2100).allow(null, ''),
  }),

  closePeriod: Joi.object({
    period: Joi.string().pattern(/^\d{4}-\d{2}$/).required()
      .messages({ 'string.pattern.base': 'period måste vara YYYY-MM' }),
    fiscal_year: Joi.number().integer().min(2000).max(2100).allow(null),
  }),
};

// ── Custom error messages ───────────────────────────────────────────────────
export const validationMessages = {
  'journal.line.debit_credit': 'Varje journalrad måste ha antingen debit ELLER credit',
  'journal.balance': 'Dubbelbokföring bruten: debet {{#totalDebit}} ≠ kredit {{#totalCredit}}',
};

// ── Middleware factory ──────────────────────────────────────────────────────
export function validate(schema) {
  return (req, res, next) => {
    // Samla data från body, query, och params
    const data = {
      ...req.body,
      ...req.query,
      ...req.params,
    };

    const { error, value } = schema.validate(data, {
      abortEarly: false,
      stripUnknown: true,
      allowUnknown: true,
    });

    if (error) {
      const details = error.details.map(d => ({
        field: d.path.join('.'),
        message: d.message,
      }));
      return res.status(400).json({
        ok: false,
        error: 'Valideringsfel',
        details,
      });
    }

    // Spara validerad data tillbaka till request
    req.validated = value;
    next();
  };
}

// ── Sanitizer helpers ───────────────────────────────────────────────────────
export function sanitizeString(str, maxLength = 1000) {
  if (typeof str !== 'string') return str;
  return str
    .replace(/[<>]/g, '')
    .trim()
    .slice(0, maxLength);
}

export function sanitizeMetadata(obj) {
  if (typeof obj !== 'object' || obj === null) return {};
  // Ta bort potentiellt farliga nycklar
  const dangerousKeys = ['__proto__', 'constructor', 'prototype'];
  const cleaned = {};
  for (const [key, value] of Object.entries(obj)) {
    if (dangerousKeys.includes(key)) continue;
    if (typeof value === 'string') {
      cleaned[key] = sanitizeString(value, 5000);
    } else if (typeof value === 'object' && value !== null) {
      cleaned[key] = sanitizeMetadata(value);
    } else {
      cleaned[key] = value;
    }
  }
  return cleaned;
}

export default { schemas, validate, sanitizeString, sanitizeMetadata };