import { readFile } from "node:fs/promises"
import { fileURLToPath } from "node:url"
import { Agent, type StreamFn } from "@earendil-works/pi-agent-core"
import {
  type AssistantMessage,
  createAssistantMessageEventStream,
  type Model,
} from "@earendil-works/pi-ai"
import { obj } from "@earendil-works/pi-schema"
import { Recorder } from "./recorder.js"
import { requestSummary } from "./request-summary.js"

const model: Model<"openai-responses"> = {
  id: "lesson-mock",
  name: "教学模拟模型",
  api: "openai-responses",
  provider: "openai",
  baseUrl: "https://example.invalid",
  reasoning: false,
  input: ["text"],
  contextWindow: 8192,
  maxTokens: 1024,
  cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
}

export async function runMock(failTool = false) {
  const recorder = new Recorder("lesson-run")
  const requests: ReturnType<typeof requestSummary>[] = []
  let calls = 0
  let toolExecutions = 0
  const streamFn: StreamFn = (_model, context) => {
    requests.push(requestSummary(context))
    const first = calls++ === 0
    const message: AssistantMessage = {
      role: "assistant",
      api: "openai-responses",
      provider: "openai",
      model: model.id,
      timestamp: Date.now(),
      stopReason: first ? "toolUse" : "stop",
      content: first
        ? [{ type: "toolCall", id: "inspect-1", name: "lesson_inspect", arguments: {} }]
        : [{ type: "text", text: failTool ? "检查失败，请核对文件" : "检查完成" }],
      usage: {
        input: 0,
        output: 0,
        cacheRead: 0,
        cacheWrite: 0,
        totalTokens: 0,
        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
      },
    }
    const stream = createAssistantMessageEventStream()
    stream.push({ type: "done", reason: first ? "toolUse" : "stop", message })
    stream.end()
    return stream
  }
  const agent = new Agent({
    streamFn,
    initialState: {
      model,
      tools: [
        {
          name: "lesson_inspect",
          label: "检查教学文件",
          description: "返回教学文件中的命名函数匹配",
          parameters: obj({}),
          async execute() {
            toolExecutions += 1
            if (failTool) {
              throw new Error("教学工具失败")
            }
            const source = await readFile(
              fileURLToPath(new URL("../fixtures/sample.ts", import.meta.url)),
              "utf8",
            )
            const names = [...source.matchAll(/\bfunction\s+([A-Za-z_$][\w$]*)\s*\(/g)].map(
              (match) => match[1],
            )
            return {
              content: [{ type: "text", text: JSON.stringify({ names }) }],
              details: { names },
            }
          },
        },
      ],
    },
  })
  const unsubscribe = agent.subscribe((event) => {
    recorder.accept(event)
  })
  try {
    await agent.prompt("检查教学文件")
    // 这是应用等待 prompt 返回的边界，不冒充 coding-agent 的 agent_settled。
    recorder.accept({ type: "lesson_run_end" })
    return {
      timeline: recorder.snapshot(),
      requests,
      toolExecutions,
      messages: agent.state.messages,
    }
  } finally {
    unsubscribe()
  }
}