/**
 * @fileoverview Runtime debug configuration.
 *
 * Reads process environment at call time of {@link loadDebugConfig} so tests can
 * mutate `process.env` between cases. Production servers typically load once at boot.
 *
 * @module debug/config
 */

/**
 * @typedef {Object} DebugConfig
 * @property {boolean} enabled - True when any debug output should be produced.
 * @property {Set<string>|null} namespaces - Allowed namespaces; `null` means all.
 * @property {'debug'|'info'|'warn'|'error'} level - Minimum severity to emit.
 * @property {string|null} filePath - Optional secondary log file path.
 */

const LEVEL_ORDER = { debug: 10, info: 20, warn: 30, error: 40 };

/**
 * Parse `DEBUG_VERAE` into an enabled flag and optional namespace allow-list.
 *
 * @param {string|undefined} raw - Raw env value (e.g. `"1"`, `"*"`, `"auth,nats"`).
 * @returns {{ enabled: boolean, namespaces: Set<string>|null }}
 *
 * @example
 * parseDebugVeraeEnv('auth,jobs'); // { enabled: true, namespaces: Set{'auth','jobs'} }
 * parseDebugVeraeEnv(undefined);   // { enabled: false, namespaces: null }
 */
export function parseDebugVeraeEnv(raw) {
  if (raw === undefined || raw === null) {
    return { enabled: false, namespaces: null };
  }

  const trimmed = String(raw).trim();
  if (!trimmed || trimmed === '0' || trimmed.toLowerCase() === 'false' || trimmed.toLowerCase() === 'off') {
    return { enabled: false, namespaces: null };
  }

  if (trimmed === '1' || trimmed === '*' || trimmed.toLowerCase() === 'true' || trimmed.toLowerCase() === 'all') {
    return { enabled: true, namespaces: null };
  }

  const parts = trimmed
    .split(',')
    .map((p) => p.trim().toLowerCase())
    .filter(Boolean);

  if (parts.length === 0) {
    return { enabled: false, namespaces: null };
  }

  return { enabled: true, namespaces: new Set(parts) };
}

/**
 * Normalize a level string to a known level.
 *
 * @param {string|undefined} raw - Env level value.
 * @param {'debug'|'info'|'warn'|'error'} [fallback='debug'] - Default level.
 * @returns {'debug'|'info'|'warn'|'error'}
 */
export function parseLevel(raw, fallback = 'debug') {
  const value = String(raw ?? fallback).toLowerCase();
  if (value in LEVEL_ORDER) return /** @type {'debug'|'info'|'warn'|'error'} */ (value);
  return fallback;
}

/**
 * Load full debug configuration from `process.env`.
 *
 * Environment variables:
 * - `DEBUG_VERAE` — enable + namespaces (see {@link parseDebugVeraeEnv})
 * - `DEBUG_VERAE_LEVEL` — minimum level
 * - `DEBUG_VERAE_FILE` — optional log file path
 *
 * @param {NodeJS.ProcessEnv} [env=process.env] - Environment map (injectable for tests).
 * @returns {DebugConfig}
 */
export function loadDebugConfig(env = process.env) {
  const { enabled, namespaces } = parseDebugVeraeEnv(env.DEBUG_VERAE);
  return {
    enabled,
    namespaces,
    level: parseLevel(env.DEBUG_VERAE_LEVEL, 'debug'),
    filePath: env.DEBUG_VERAE_FILE ? String(env.DEBUG_VERAE_FILE) : null,
  };
}

/**
 * Whether a message at `messageLevel` in `namespace` should be emitted.
 *
 * @param {DebugConfig} config - Active config.
 * @param {string} namespace - Logger namespace (e.g. `auth`).
 * @param {'debug'|'info'|'warn'|'error'} messageLevel - Message severity.
 * @returns {boolean}
 */
export function shouldLog(config, namespace, messageLevel) {
  if (!config.enabled) return false;
  if (config.namespaces && !config.namespaces.has(String(namespace).toLowerCase())) {
    return false;
  }
  return LEVEL_ORDER[messageLevel] >= LEVEL_ORDER[config.level];
}

export { LEVEL_ORDER };