import { createWriteStream, mkdirSync, type WriteStream } from 'node:fs';
import { homedir } from 'node:os';
import { join } from 'node:path';
import { query } from '@anthropic-ai/claude-agent-sdk';
import { isModelError, pickFallbackModel } from './models.js';

/** 转录目录：<MAESTRO_DATA_DIR 或 ~/.maestro>/transcripts */
export function transcriptDir(): string {
  return join(process.env.MAESTRO_DATA_DIR ?? join(homedir(), '.maestro'), 'transcripts');
}

export interface CCOptions {
  prompt: string;
  cwd: string;
  model: string;
  runId: string;
  maxTurns: number;
  timeoutMs: number;
  allowedTools: string[];
  permissionMode?: 'acceptEdits' | 'default';
}

export interface CCResult {
  ok: boolean;
  finalText: string;           // SDK result 消息的文本（失败时为 ''）
  sessionId: string | null;
  transcriptRef: string;
  modelUsed: string;           // 实际使用的模型（发生回退时为回退模型）
  fellBack: boolean;
  error?: string;
}

interface AttemptResult {
  ok: boolean;
  finalText: string;
  sessionId: string | null;
  error?: string;
}

/** 单次 headless CC 会话：流式消息逐行写 transcript，不抛错（失败折叠进 error） */
async function attempt(opts: CCOptions, model: string, out: WriteStream): Promise<AttemptResult> {
  let sessionId: string | null = null;
  let finalText = '';
  let resultOk = false;
  let resultError: string | undefined;
  let sawResult = false;

  const abort = new AbortController();
  const killer = setTimeout(() => abort.abort(new Error('执行超时')), opts.timeoutMs);

  try {
    const q = query({
      prompt: opts.prompt,
      options: {
        cwd: opts.cwd,
        permissionMode: opts.permissionMode ?? 'default',
        maxTurns: opts.maxTurns,
        settingSources: ['project'],              // 读项目 CLAUDE.md / settings，不读用户全局
        abortController: abort,
        model,
        allowedTools: opts.allowedTools,
      },
    });

    for await (const message of q) {
      out.write(`${JSON.stringify(message)}\n`);
      const sid = (message as { session_id?: unknown }).session_id;
      if (typeof sid === 'string' && sid) sessionId = sid;
      if (message.type === 'result') {
        sawResult = true;
        if (message.subtype === 'success' && !message.is_error) {
          resultOk = true;
          const txt = (message as { result?: unknown }).result;
          if (typeof txt === 'string') finalText = txt;
        } else {
          const errs = 'errors' in message && Array.isArray(message.errors) ? message.errors.join('; ') : '';
          resultError = `Claude Code 结束于 ${message.subtype}${errs ? `：${errs}` : ''}`;
        }
      }
    }
    if (!sawResult && !resultError) resultError = '未收到 result 消息（会话异常结束）';
  } catch (e) {
    resultError = `Claude Code 执行异常：${(e as Error).message}`;
    resultOk = false;
  } finally {
    clearTimeout(killer);
  }

  if (!resultOk) return { ok: false, finalText: '', sessionId, error: resultError ?? '未知错误' };
  return { ok: true, finalText, sessionId };
}

/**
 * 跑一次 headless CC（runner / reviewer 公用）。
 * 模型可用性兜底：失败且错误信息像模型不可用（not_found/invalid/permission 等）时，
 * 自动用回退链取一个 ≠ 原模型的模型在同一 run 内重试一次；回退记入 transcript 与 finalText。
 */
export async function runClaude(opts: CCOptions): Promise<CCResult> {
  const dir = transcriptDir();
  mkdirSync(dir, { recursive: true });
  const transcriptRef = join(dir, `${opts.runId}.jsonl`);
  const out = createWriteStream(transcriptRef, { flags: 'a' });

  try {
    let r = await attempt(opts, opts.model, out);
    let modelUsed = opts.model;
    let fellBack = false;

    if (!r.ok && r.error && isModelError(r.error)) {
      const fb = pickFallbackModel(opts.model);
      if (fb) {
        out.write(`${JSON.stringify({ type: 'maestro.model_fallback', from: opts.model, to: fb, reason: r.error })}\n`);
        r = await attempt(opts, fb, out);
        modelUsed = fb;
        fellBack = true;
      }
    }

    const note = fellBack && r.ok ? `\n\n[模型回退] 原模型 ${opts.model} 不可用，实际使用 ${modelUsed}` : '';
    return {
      ok: r.ok,
      finalText: r.finalText + note,
      sessionId: r.sessionId,
      transcriptRef,
      modelUsed,
      fellBack,
      ...(r.error ? { error: fellBack ? `${r.error}（已回退至 ${modelUsed} 重试）` : r.error } : {}),
    };
  } finally {
    await new Promise<void>((resolve) => out.end(resolve));
  }
}