import { execFile } from "node:child_process";
import * as fs from "node:fs";
import * as os from "node:os";
import * as path from "node:path";
import { promisify } from "node:util";

const run = promisify(execFile);

export interface Worktree {
	isolated: boolean;
	cwd: string;
	reason?: string;
	dir?: string;
}

/**
 * Create a throwaway git worktree for an isolated agent (opts.isolation:
 * 'worktree'). Falls back to non-isolated (runs in baseCwd) when the dir isn't a
 * git repo or git is unavailable — exactly like CC, where isolation is a
 * best-effort optimization, never a hard requirement.
 */
export async function createWorktree(baseCwd: string, name: string): Promise<Worktree> {
	const slug = name.replace(/[^a-zA-Z0-9_-]+/g, "-").slice(0, 60);
	try {
		await run("git", ["rev-parse", "--is-inside-work-tree"], { cwd: baseCwd });
	} catch {
		return { isolated: false, cwd: baseCwd, reason: "not a git repository" };
	}
	const dir = path.join(os.tmpdir(), "cc-wf-worktrees", slug);
	try {
		fs.mkdirSync(path.dirname(dir), { recursive: true });
		await run("git", ["worktree", "add", "--detach", "-f", dir, "HEAD"], { cwd: baseCwd });
		return { isolated: true, cwd: dir, dir };
	} catch (err) {
		return { isolated: false, cwd: baseCwd, reason: (err as Error).message };
	}
}

/** Remove a worktree. Auto-prunes; best-effort (never throws). */
export async function removeWorktree(wt: Worktree, baseCwd: string): Promise<void> {
	if (!wt.isolated || !wt.dir) return;
	try {
		await run("git", ["worktree", "remove", "--force", wt.dir], { cwd: baseCwd });
	} catch {
		try {
			fs.rmSync(wt.dir, { recursive: true, force: true });
			await run("git", ["worktree", "prune"], { cwd: baseCwd }).catch(() => {});
		} catch {
			// best-effort
		}
	}
}