import type { CustomField } from './custom-field.ts';

export interface ValidationResult {
  valid: boolean;
  error?: string;
}

/**
 * Dispatch to the correct type-specific validator based on field.field_type.
 */
export function validateCustomFieldValue(
  field: CustomField,
  value: string,
): ValidationResult {
  if (!value) return { valid: true };

  const config = (field.validation_config ?? {}) as Record<string, unknown>;

  // Backward-compatible pattern check (field-level pattern, not validation_config)
  if (field.pattern) {
    try {
      const regex = new RegExp(field.pattern);
      if (!regex.test(value)) {
        return { valid: false, error: 'Value does not match the required pattern' };
      }
    } catch {
      // Invalid regex — skip
    }
  }

  switch (field.field_type) {
    case 'Number':
      return validateNumberValue(value, config);
    case 'Date':
      return validateDateValue(value, config);
    case 'DateTime':
      return validateDateTimeValue(value, config);
    case 'SelectOne':
    case 'SelectMultiple':
      return validateSelectValue(value, field, config);
    case 'Text':
    case 'Textarea':
      return validateTextValue(value, config);
    default:
      return { valid: true };
  }
}

function validateNumberValue(
  value: string,
  config: Record<string, unknown>,
): ValidationResult {
  const num = Number(value);
  if (isNaN(num)) {
    return { valid: false, error: 'Value must be a number' };
  }
  if (config.min !== undefined && num < Number(config.min)) {
    return { valid: false, error: `Value must be at least ${config.min}` };
  }
  if (config.max !== undefined && num > Number(config.max)) {
    return { valid: false, error: `Value must be at most ${config.max}` };
  }
  return { valid: true };
}

function validateDateValue(
  value: string,
  config: Record<string, unknown>,
): ValidationResult {
  // Accept YYYY-MM-DD format
  if (!/^\d{4}-\d{2}-\d{2}$/.test(value)) {
    return { valid: false, error: 'Value must be a date in YYYY-MM-DD format' };
  }
  const parsed = new Date(value);
  if (isNaN(parsed.getTime())) {
    return { valid: false, error: 'Invalid date' };
  }
  if (config.min_date) {
    const minDate = new Date(String(config.min_date));
    if (!isNaN(minDate.getTime()) && parsed < minDate) {
      return { valid: false, error: `Date must be on or after ${config.min_date}` };
    }
  }
  if (config.max_date) {
    const maxDate = new Date(String(config.max_date));
    if (!isNaN(maxDate.getTime()) && parsed > maxDate) {
      return { valid: false, error: `Date must be on or before ${config.max_date}` };
    }
  }
  return { valid: true };
}

function validateDateTimeValue(
  value: string,
  config: Record<string, unknown>,
): ValidationResult {
  const parsed = new Date(value);
  if (isNaN(parsed.getTime())) {
    return { valid: false, error: 'Value must be a valid ISO 8601 datetime' };
  }
  if (config.min_date) {
    const minDate = new Date(String(config.min_date));
    if (!isNaN(minDate.getTime()) && parsed < minDate) {
      return { valid: false, error: `Datetime must be on or after ${config.min_date}` };
    }
  }
  if (config.max_date) {
    const maxDate = new Date(String(config.max_date));
    if (!isNaN(maxDate.getTime()) && parsed > maxDate) {
      return { valid: false, error: `Datetime must be on or before ${config.max_date}` };
    }
  }
  return { valid: true };
}

function validateSelectValue(
  value: string,
  field: CustomField,
  config: Record<string, unknown>,
): ValidationResult {
  const allowed: string[] = [];

  // Check validation_config.options first, then fall back to field.values
  if (Array.isArray(config.options)) {
    allowed.push(...config.options.map(String));
  } else if (Array.isArray(field.values)) {
    allowed.push(...field.values.map(String));
  }

  if (allowed.length > 0 && !allowed.includes(value)) {
    return { valid: false, error: `Value is not an allowed option. Allowed: ${allowed.join(', ')}` };
  }
  return { valid: true };
}

function validateTextValue(
  value: string,
  config: Record<string, unknown>,
): ValidationResult {
  if (config.min_length !== undefined && value.length < Number(config.min_length)) {
    return { valid: false, error: `Value must be at least ${config.min_length} characters` };
  }
  if (config.max_length !== undefined && value.length > Number(config.max_length)) {
    return { valid: false, error: `Value must be at most ${config.max_length} characters` };
  }
  if (config.pattern && typeof config.pattern === 'string') {
    try {
      const regex = new RegExp(config.pattern);
      if (!regex.test(value)) {
        return { valid: false, error: 'Value does not match the required pattern' };
      }
    } catch {
      // Invalid regex — skip validation
    }
  }
  return { valid: true };
}