import { appendFileSync } from "node:fs";

import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

function appendResultEntry(
  type: "assistant" | "final" | "toolResult",
  message: unknown
): void {
  const outputFile = process.env.PI_SUBAGENT_OUTPUT_FILE;
  if (!outputFile) {
    throw new Error(
      "PI_SUBAGENT_OUTPUT_FILE is required for Herdr child result capture."
    );
  }

  appendFileSync(
    outputFile,
    `${JSON.stringify({
      isSidechain: true,
      agentId: process.env.PI_SUBAGENT_ID,
      type,
      message,
      timestamp: new Date().toISOString(),
      cwd: process.cwd(),
    })}\n`,
    "utf-8"
  );
}

export default function (pi: ExtensionAPI): void {
  let lastAssistantMessage: unknown;
  let finalWritten = false;

  pi.on("message_end", (event) => {
    if (finalWritten) {
      return;
    }

    if (event.message.role === "assistant") {
      lastAssistantMessage = event.message;
      appendResultEntry("assistant", event.message);
    }
  });

  pi.on("agent_end", (event, ctx) => {
    if (finalWritten) {
      return;
    }

    const finalAssistantMessage = [...event.messages]
      .reverse()
      .find((message) => message.role === "assistant");
    appendResultEntry(
      "final",
      finalAssistantMessage ?? lastAssistantMessage ?? null
    );
    finalWritten = true;
    (
      ctx as
        | { ui?: { notify?: (message: string, level: "warning") => void } }
        | undefined
    )?.ui?.notify?.(
      "Herdr child pane is now manual and untracked by the parent.",
      "warning"
    );
  });

  pi.on("tool_execution_end", (event) => {
    if (finalWritten) {
      return;
    }

    appendResultEntry("toolResult", {
      role: "toolResult",
      toolCallId: event.toolCallId,
      toolName: event.toolName,
      content: event.result,
      isError: event.isError,
      timestamp: Date.now(),
    });
  });
}