/**
 * Ext-Toggle Extension
 *
 * Provides `/ext` to list and toggle pi extensions installed under
 * `~/.pi/agent/extensions/` (the global auto-discovery dir).
 *
 * Toggling works by renaming the file (or symlink) between `name.ts` and
 * `name.ts.off`. Pi discovers `*.ts` only, so a `.ts.off` file is invisible
 * at load time. `ctx.reload()` is invoked after a toggle so the change takes
 * effect without a restart.
 *
 * Subdirectory-style extensions (`name/index.ts`) are listed as read-only
 * in v1 — toggling a directory cleanly is more work than the renaming trick
 * is worth. If you need to disable one, move the directory aside manually.
 */

import * as fs from "node:fs";
import * as path from "node:path";
import * as os from "node:os";
import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";

const EXT_DIR = path.join(os.homedir(), ".pi", "agent", "extensions");

type Entry = {
  name: string;          // bare name without extension (e.g. "notify")
  fullPath: string;      // absolute path on disk
  enabled: boolean;      // .ts (true) or .ts.off (false)
  kind: "file" | "dir";  // flat .ts file or subdir/index.ts
  isSymlink: boolean;
  linkTarget?: string;   // resolved target if symlink
};

function listEntries(): Entry[] {
  if (!fs.existsSync(EXT_DIR)) return [];
  const out: Entry[] = [];
  for (const ent of fs.readdirSync(EXT_DIR, { withFileTypes: true })) {
    const full = path.join(EXT_DIR, ent.name);
    const isSymlink = ent.isSymbolicLink();
    let stat: fs.Stats | undefined;
    try {
      stat = fs.statSync(full);
    } catch {
      continue;
    }
    let linkTarget: string | undefined;
    if (isSymlink) {
      try {
        linkTarget = fs.readlinkSync(full);
      } catch {
        // ignore
      }
    }

    if (stat.isDirectory()) {
      // Subdir extension: pi expects index.ts inside.
      const indexPath = path.join(full, "index.ts");
      if (fs.existsSync(indexPath)) {
        out.push({
          name: ent.name,
          fullPath: full,
          enabled: true,
          kind: "dir",
          isSymlink,
          linkTarget,
        });
      }
      continue;
    }

    if (ent.name.endsWith(".ts")) {
      out.push({
        name: ent.name.slice(0, -3),
        fullPath: full,
        enabled: true,
        kind: "file",
        isSymlink,
        linkTarget,
      });
    } else if (ent.name.endsWith(".ts.off")) {
      out.push({
        name: ent.name.slice(0, -7),
        fullPath: full,
        enabled: false,
        kind: "file",
        isSymlink,
        linkTarget,
      });
    }
  }
  return out.sort((a, b) => a.name.localeCompare(b.name));
}

function formatRow(e: Entry): string {
  const dot = e.enabled ? "●" : "○";
  const kind = e.kind === "dir" ? " [dir]" : "";
  const link = e.isSymlink ? "  ↳ symlink" : "";
  return `${dot}  ${e.name}${kind}${link}`;
}

function toggleFile(e: Entry): { newPath: string; action: "enabled" | "disabled" } {
  if (e.kind !== "file") {
    throw new Error(`Cannot toggle directory-style extension "${e.name}" — move it aside manually.`);
  }
  const dir = path.dirname(e.fullPath);
  if (e.enabled) {
    const target = path.join(dir, `${e.name}.ts.off`);
    fs.renameSync(e.fullPath, target);
    return { newPath: target, action: "disabled" };
  } else {
    const target = path.join(dir, `${e.name}.ts`);
    fs.renameSync(e.fullPath, target);
    return { newPath: target, action: "enabled" };
  }
}

export default function extToggleExtension(pi: ExtensionAPI) {
  pi.registerCommand("ext", {
    description: "List and toggle pi extensions in ~/.pi/agent/extensions/",
    handler: async (_args, ctx) => {
      const entries = listEntries();
      if (entries.length === 0) {
        ctx.ui.notify(`No extensions found in ${EXT_DIR}`, "info");
        return;
      }

      const labels = entries.map(formatRow);
      const selected = await ctx.ui.select(
        `Extensions (${entries.filter((e) => e.enabled).length}/${entries.length} active)`,
        labels,
      );
      if (!selected) return;

      const idx = labels.indexOf(selected);
      if (idx < 0) return;
      const entry = entries[idx];

      if (entry.kind === "dir") {
        ctx.ui.notify(
          `"${entry.name}" is a directory-style extension. Move it aside manually if you need to disable it.`,
          "info",
        );
        return;
      }

      const verb = entry.enabled ? "Disable" : "Enable";
      const ok = await ctx.ui.confirm(
        `${verb} "${entry.name}"?`,
        `${entry.fullPath}\n\nWill be renamed to ${
          entry.enabled ? entry.name + ".ts.off" : entry.name + ".ts"
        } and pi will reload.`,
      );
      if (!ok) return;

      try {
        const { action } = toggleFile(entry);
        ctx.ui.notify(`${entry.name}: ${action}. Reloading…`, "info");
        await ctx.reload();
      } catch (err) {
        const msg = err instanceof Error ? err.message : String(err);
        ctx.ui.notify(`Toggle failed: ${msg}`, "error");
      }
    },
  });
}