export type ValidationResult = {
  valid: boolean;
  errors: string[];
  warnings: string[];
};

export class ContentValidationError extends Error {
  constructor(
    message: string,
    public readonly validation: ValidationResult,
  ) {
    super(message);
    this.name = 'ContentValidationError';
  }
}

const PLACEHOLDER_PATTERNS = [
  { pattern: /\[.*?\]/i, message: 'Bracket placeholder detected' },
  { pattern: /\{\{.*?\}\}/, message: 'Mustache placeholder detected' },
  { pattern: /\[Your .*?\]/i, message: 'Template placeholder detected' },
  { pattern: /\[Director .*?\]/i, message: 'Template placeholder detected' },
  { pattern: /\[Company .*?\]/i, message: 'Template placeholder detected' },
  { pattern: /INSERT .* HERE/i, message: 'Template placeholder detected' },
  { pattern: /\bTODO\b/, message: 'TODO placeholder detected' },
  { pattern: /lorem ipsum/i, message: 'Lorem ipsum placeholder detected' },
];

const TIER1_SPAM = [
  'act now',
  '100% free',
  'risk-free',
  'free money',
  'click here',
  'limited time',
  'winner',
  'viagra',
  'casino',
  'lottery',
  'guarantee',
];

const TIER2_SPAM = [
  'urgent',
  'limited',
  'offer',
  'discount',
  'sale',
  'promotion',
  'buy now',
];

const URL_PATTERN = /https?:\/\//i;

function wordCount(text: string): number {
  return text.trim().split(/\s+/).filter(Boolean).length;
}

export type ValidateOptions = {
  isReply?: boolean;
  failOnWarnings?: boolean;
};

export function validateEmailContent(
  subject: string,
  body: string,
  options: ValidateOptions = {},
): ValidationResult {
  const errors: string[] = [];
  const warnings: string[] = [];
  const combined = `${subject}\n${body}`;

  for (const { pattern, message } of PLACEHOLDER_PATTERNS) {
    if (pattern.test(combined)) {
      errors.push(message);
    }
  }

  if (URL_PATTERN.test(combined)) {
    errors.push('URLs are not allowed in warmup content');
  }

  if (subject.length > 60) {
    errors.push('Subject exceeds 60 characters');
  }

  const minWords = options.isReply ? 20 : 40;
  const maxWords = options.isReply ? 120 : 200;
  const words = wordCount(body);
  if (words < minWords || words > maxWords) {
    errors.push(`Body word count ${words} outside allowed range ${minWords}-${maxWords}`);
  }

  const lower = combined.toLowerCase();
  for (const phrase of TIER1_SPAM) {
    if (lower.includes(phrase)) {
      errors.push(`Spam trigger phrase: "${phrase}"`);
    }
  }
  for (const phrase of TIER2_SPAM) {
    if (lower.includes(phrase)) {
      warnings.push(`Soft spam phrase: "${phrase}"`);
    }
  }

  const valid = errors.length === 0 && (!options.failOnWarnings || warnings.length === 0);

  return { valid, errors, warnings };
}