/**
 * Voice settings from the environment. Model ids live here and nowhere else
 * (spec 7.1): a change of model is a change of this list and of VOICE_MODEL.
 */
export const VOICE_MODELS = [
  'claude-sonnet-5-5',
  'claude-haiku-5-5',
  'claude-opus-5-5',
] as const;
export type VoiceModel = (typeof VOICE_MODELS)[number];

export const DEFAULT_VOICE_MODEL: VoiceModel = 'claude-sonnet-5-5';

/**
 * Models with a server-side fallback when their safety check declines
 * (`fallbacks: "default"`). Haiku has none: a declined request stays
 * declined there.
 */
export const VOICE_SERVER_FALLBACK_MODELS: readonly string[] = [
  'claude-sonnet-5-5',
  'claude-opus-5-5',
];

/** VOICE_SERVER_FALLBACK: "default" uses the fallback above, "off" never. */
export const SERVER_FALLBACK_MODES = ['off', 'default'] as const;
export type ServerFallbackMode = (typeof SERVER_FALLBACK_MODES)[number];

export const WHISPER_MODELS = ['small', 'medium'] as const;
export type WhisperModel = (typeof WHISPER_MODELS)[number];

const DEFAULT_DAILY_EXTRACTIONS = 60;
const MIN_DAILY_EXTRACTIONS = 1;
const MAX_DAILY_EXTRACTIONS = 10000;

export interface VoiceConfig {
  model: VoiceModel;
  /** Operation-wide limit of Claude calls per UTC day. */
  dailyExtractions: number;
  /** Switch that shows or hides audio recording in the app (ConfigMap). */
  recordingEnabled: boolean;
  whisperModel: WhisperModel;
  /** Whether a declined request may be re-run server-side on another model. */
  serverFallback: ServerFallbackMode;
}

function trimmed(value: string | undefined): string | null {
  const text = value?.trim();
  return text ? text : null;
}

function oneOf<T extends string>(
  name: string,
  raw: string | undefined,
  allowed: readonly T[],
  fallback: T,
): T {
  const value = trimmed(raw);
  if (value === null) {
    return fallback;
  }
  const match = allowed.find((each) => each === value);
  if (match === undefined) {
    throw new Error(`${name} must be one of ${allowed.join(', ')}`);
  }
  return match;
}

function dailyExtractions(raw: string | undefined): number {
  const value = trimmed(raw);
  if (value === null) {
    return DEFAULT_DAILY_EXTRACTIONS;
  }
  const number = /^\d+$/.test(value) ? Number(value) : NaN;
  if (
    !Number.isInteger(number) ||
    number < MIN_DAILY_EXTRACTIONS ||
    number > MAX_DAILY_EXTRACTIONS
  ) {
    throw new Error(
      `VOICE_DAILY_EXTRACTIONS must be a whole number from ${MIN_DAILY_EXTRACTIONS} to ${MAX_DAILY_EXTRACTIONS}`,
    );
  }
  return number;
}

function recordingEnabled(raw: string | undefined): boolean {
  const value = trimmed(raw)?.toLowerCase() ?? null;
  if (value === null || value === 'false') {
    return false;
  }
  if (value === 'true') {
    return true;
  }
  throw new Error('VOICE_RECORDING_ENABLED must be "true" or "false"');
}

/** Invalid values fail with the variable name (never a secret): startup refuses them. */
export function voiceConfig(env: NodeJS.ProcessEnv = process.env): VoiceConfig {
  return {
    model: oneOf(
      'VOICE_MODEL',
      env.VOICE_MODEL,
      VOICE_MODELS,
      DEFAULT_VOICE_MODEL,
    ),
    dailyExtractions: dailyExtractions(env.VOICE_DAILY_EXTRACTIONS),
    recordingEnabled: recordingEnabled(env.VOICE_RECORDING_ENABLED),
    whisperModel: oneOf(
      'WHISPER_MODEL',
      env.WHISPER_MODEL,
      WHISPER_MODELS,
      'small',
    ),
    serverFallback: oneOf(
      'VOICE_SERVER_FALLBACK',
      env.VOICE_SERVER_FALLBACK,
      SERVER_FALLBACK_MODES,
      'default',
    ),
  };
}