pi /edit extension for editing Markdown plans

edit.ts

// Adds `/edit` to pi.
//
// Useful for plans: pi writes the Markdown, then you refine it in your editor.
//
// How it works:
// - remembers the last `.md` file written via the `write` tool
// - suggests `/edit` after writing a Markdown file
// - opens that file in `$EDITOR`
//
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
import { spawnSync } from "node:child_process";
import { resolve } from "node:path";

export default function (pi: ExtensionAPI) {
  let lastMarkdownFile: string | null = null;

  pi.on("tool_result", async (event, ctx) => {
    if (event.toolName !== "write") return;
    const path = event.input.path as string;
    if (!path?.endsWith(".md")) return;

    lastMarkdownFile = resolve(ctx.cwd, path);
    const editor = process.env.EDITOR || "nvim";
    ctx.ui.notify(`Use /edit to open the file in ${editor}`, "info");
  });

  pi.registerCommand("edit", {
    description: "Open a file in a text editor. No arg = last written .md file",
    handler: async (args, ctx) => {
      await ctx.waitForIdle();

      const editor = process.env.EDITOR || "nvim";
      const filePath = args.trim()
        ? resolve(ctx.cwd, args.trim())
        : lastMarkdownFile;

      if (!filePath) {
        ctx.ui.notify("No file specified and no recent .md file written", "error");
        return;
      }

      if (!ctx.hasUI) {
        ctx.ui.notify("/edit requires TUI mode", "error");
        return;
      }

      const exitCode = await ctx.ui.custom<number | null>((tui, _theme, _kb, done) => {
        tui.stop();
        process.stdout.write("\x1b[2J\x1b[H");
        const [cmd, ...editorArgs] = editor.split(/\s+/);
        const result = spawnSync(cmd!, [...editorArgs, filePath], {
          stdio: "inherit",
          env: process.env,
        });
        tui.start();
        tui.requestRender(true);
        done(result.status);
        return { render: () => [], invalidate: () => { } };
      });

      if (exitCode !== 0 && exitCode !== null) {
        ctx.ui.notify(`Editor exited with code ${exitCode}`, "info");
      }
    },
  });
}