import { execSync } from "node:child_process";
import { chmodSync, existsSync, mkdirSync, readFileSync, renameSync, writeFileSync } from "node:fs";
import path from "node:path";
import { postCheckoutHookScript, TFF_HOOK_MARKER } from "./post-checkout-template.js";

/**
 * Install post-checkout hook in the git repository at repoDir.
 * - If an existing non-tff hook exists, renames it to post-checkout.pre-tff
 * - If an existing tff hook exists, overwrites it
 * - Creates .git/hooks/ directory if needed
 */
export function installPostCheckoutHook(repoDir: string): void {
	// Resolve hook directory (handles worktrees via --git-common-dir)
	let gitCommonDir: string;
	try {
		gitCommonDir = execSync("git rev-parse --git-common-dir", {
			cwd: repoDir,
			encoding: "utf8",
		}).trim();
	} catch {
		return; // Not a git repo
	}

	// Resolve to absolute path
	if (!path.isAbsolute(gitCommonDir)) {
		gitCommonDir = path.resolve(repoDir, gitCommonDir);
	}

	const hooksDir = path.join(gitCommonDir, "hooks");
	mkdirSync(hooksDir, { recursive: true });

	const hookPath = path.join(hooksDir, "post-checkout");
	const preTffPath = path.join(hooksDir, "post-checkout.pre-tff");

	if (existsSync(hookPath)) {
		const existing = readFileSync(hookPath, "utf8");
		if (existing.includes(TFF_HOOK_MARKER)) {
			// Our hook — overwrite
		} else {
			// Third-party hook — rename to .pre-tff
			renameSync(hookPath, preTffPath);
		}
	}

	writeFileSync(hookPath, postCheckoutHookScript, { mode: 0o755 });
	chmodSync(hookPath, 0o755);
}