import { writeFile } from "node:fs/promises";

export type VoiceParams = Record<string, unknown>;

/**
 * Common contract for every TTS provider. Subclasses override either
 * `getSpeech` (returning a fetch-like Response) or `getSpeechFile` (writing
 * directly to disk) — the default `getSpeechFile` pipes `getSpeech` to a file.
 */
export abstract class BaseEngine {
  /** Short ID used in env / commands (e.g. "azure"). */
  readonly shortName: string;
  /** Human-readable name shown in messages. */
  readonly longName: string;
  /** Output file extension without the dot (e.g. "mp3"). */
  readonly fileExtension: string;

  protected voices: Record<string, string | { name: string; lang: string }> = {};

  constructor(shortName: string, longName: string, fileExtension: string) {
    this.shortName = shortName;
    this.longName = longName;
    this.fileExtension = fileExtension;
  }

  /** Maps a user-friendly voice name to the provider's internal identifier. */
  getInternalVoiceName(str: string): string {
    const v = this.voices[str];
    if (v == null) return str;
    return typeof v === "string" ? v : v.name;
  }

  abstract getDefaultVoice(): string;

  validateVoice(voice: string): boolean {
    if (Object.keys(this.voices).length === 0) return true;
    return this.voices[voice] != null;
  }

  /** Default implementation: subclass should override either this or getSpeechFile. */
  async getSpeech(_text: string, _voice?: string, _params?: VoiceParams): Promise<Response> {
    throw new Error(`${this.shortName}: getSpeech not implemented`);
  }

  async getSpeechFile(
    text: string,
    filepath: string,
    voice: string = this.getDefaultVoice(),
    params: VoiceParams = {},
  ): Promise<string> {
    const data = await this.getSpeech(text, voice, params);
    const buf = Buffer.from(await data.arrayBuffer());
    await writeFile(filepath, buf);
    return filepath;
  }
}