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

import type { QQMediaSttConfig } from "./types";

export class SttError extends Error {
	constructor(
		readonly code: string,
		message: string,
	) {
		super(message);
	}
}

export interface SttInput {
	path: string;
	filename: string;
	mimeType: string;
}

/** Transcribe audio through an OpenAI-compatible /audio/transcriptions endpoint. */
export async function transcribeOpenAI(
	input: SttInput,
	config: QQMediaSttConfig,
	outerSignal: AbortSignal,
): Promise<string> {
	const key = process.env[config.apiKeyEnv];
	if (!key) throw new SttError("stt_key_missing", `未设置 STT 密钥环境变量 ${config.apiKeyEnv}`);
	if (!config.baseUrl) throw new SttError("stt_not_configured", "STT baseUrl 未配置");

	const controller = new AbortController();
	const onAbort = () => controller.abort(outerSignal.reason);
	outerSignal.addEventListener("abort", onAbort, { once: true });
	const timer = setTimeout(() => controller.abort(new Error("stt timeout")), config.timeoutMs);
	try {
		const bytes = await readFile(input.path);
		const form = new FormData();
		form.append("model", config.model);
		form.append("file", new Blob([bytes], { type: input.mimeType }), input.filename);
		let response: Response;
		try {
			response = await fetch(`${config.baseUrl.replace(/\/+$/, "")}/audio/transcriptions`, {
				method: "POST",
				headers: { Authorization: `Bearer ${key}` },
				body: form,
				signal: controller.signal,
			});
		} catch (err) {
			if (outerSignal.aborted) throw new SttError("aborted", "语音处理已取消");
			if (controller.signal.aborted) throw new SttError("stt_timeout", "语音转写超时");
			throw new SttError("stt_failed", `语音转写请求失败：${safeError(err)}`);
		}
		if (!response.ok) {
			await response.body?.cancel().catch(() => undefined);
			throw new SttError("stt_http_error", `语音转写服务返回 HTTP ${response.status}`);
		}
		let body: unknown;
		try {
			body = await response.json();
		} catch {
			throw new SttError("stt_invalid_response", "语音转写服务返回了无效 JSON");
		}
		const text = (body as { text?: unknown })?.text;
		if (typeof text !== "string" || !text.trim()) throw new SttError("stt_empty", "语音转写没有返回文本");
		return text.trim();
	} finally {
		clearTimeout(timer);
		outerSignal.removeEventListener("abort", onAbort);
	}
}

function safeError(err: unknown): string {
	const message = err instanceof Error ? err.message : String(err);
	return message.replace(/https?:\/\/\S+/g, "[URL]").slice(0, 200);
}