/**
 * Structured JSON logger with a hard redaction pass.
 *
 * Two separate concerns:
 *  - secrets (tokens, keys, Authorization headers) are ALWAYS redacted;
 *  - PII (customer e-mail, name, message bodies) is redacted unless LOG_PII=true,
 *    which should only ever be enabled temporarily while debugging.
 */

export type LogLevel = 'debug' | 'info' | 'warn' | 'error';

const LEVELS: Record<LogLevel, number> = { debug: 10, info: 20, warn: 30, error: 40 };

const SECRET_KEY_PATTERN =
  /(token|secret|password|passwd|api[_-]?key|authorization|consumer_key|consumer_secret|cookie|credential|private[_-]?key)/i;

const PII_KEY_PATTERN = /(email|phone|content|question|answer|text|address|first_name|last_name)/i;

const EMAIL_PATTERN = /[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}/g;
const BEARER_PATTERN = /Bearer\s+[A-Za-z0-9._\-+/=]+/gi;
const WOO_KEY_PATTERN = /\b(ck|cs)_[A-Za-z0-9]{8,}\b/g;
const QUERY_SECRET_PATTERN = /([?&](?:consumer_key|consumer_secret|token|api_key)=)[^&\s]+/gi;

export interface LoggerOptions {
  level: LogLevel;
  logPii: boolean;
}

let options: LoggerOptions = { level: 'info', logPii: false };

export function configureLogger(next: Partial<LoggerOptions>): void {
  options = { ...options, ...next };
}

/** Redact secret-looking substrings inside a free-form string. */
export function redactString(input: string, logPii = options.logPii): string {
  let out = input
    .replace(BEARER_PATTERN, 'Bearer [REDACTED]')
    .replace(WOO_KEY_PATTERN, '[REDACTED_WOO_KEY]')
    .replace(QUERY_SECRET_PATTERN, '$1[REDACTED]');
  if (!logPii) {
    out = out.replace(EMAIL_PATTERN, '[REDACTED_EMAIL]');
  }
  return out;
}

/** Mask an e-mail for audit records: `jan.kowalski@example.com` -> `j***@example.com`. */
export function maskEmail(email: string): string {
  const at = email.indexOf('@');
  if (at <= 0) return '[REDACTED]';
  const local = email.slice(0, at);
  const domain = email.slice(at + 1);
  return `${local[0]}***@${domain}`;
}

/**
 * Deep-redact an arbitrary value for logging. Secret keys become `[REDACTED]`
 * unconditionally; PII keys are masked unless PII logging is switched on.
 */
export function redact(value: unknown, logPii = options.logPii, depth = 0): unknown {
  if (depth > 8) return '[TRUNCATED_DEPTH]';
  if (value === null || value === undefined) return value;
  if (typeof value === 'string') {
    const s = redactString(value, logPii);
    return s.length > 2000 ? `${s.slice(0, 2000)}…[TRUNCATED]` : s;
  }
  if (typeof value === 'number' || typeof value === 'boolean') return value;
  if (Array.isArray(value)) {
    return value.slice(0, 50).map((v) => redact(v, logPii, depth + 1));
  }
  if (value instanceof Error) {
    return { name: value.name, message: redactString(value.message, logPii) };
  }
  if (typeof value === 'object') {
    const out: Record<string, unknown> = {};
    for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
      if (SECRET_KEY_PATTERN.test(k)) {
        out[k] = '[REDACTED]';
      } else if (!logPii && PII_KEY_PATTERN.test(k)) {
        out[k] = typeof v === 'string' && v.includes('@') ? maskEmail(v) : '[REDACTED_PII]';
      } else {
        out[k] = redact(v, logPii, depth + 1);
      }
    }
    return out;
  }
  return '[UNSERIALIZABLE]';
}

function emit(level: LogLevel, msg: string, ctx?: Record<string, unknown>): void {
  if (LEVELS[level] < LEVELS[options.level]) return;
  const line = {
    ts: new Date().toISOString(),
    level,
    msg: redactString(msg),
    ...(ctx ? { ctx: redact(ctx) } : {}),
  };
  const serialized = JSON.stringify(line);
  if (level === 'error' || level === 'warn') process.stderr.write(`${serialized}\n`);
  else process.stdout.write(`${serialized}\n`);
}

export const logger = {
  debug: (msg: string, ctx?: Record<string, unknown>) => emit('debug', msg, ctx),
  info: (msg: string, ctx?: Record<string, unknown>) => emit('info', msg, ctx),
  warn: (msg: string, ctx?: Record<string, unknown>) => emit('warn', msg, ctx),
  error: (msg: string, ctx?: Record<string, unknown>) => emit('error', msg, ctx),
};