/**
 * Update CLI command handler.
 *
 * Handles `omp update` to check for and install updates.
 * Uses bun if available, otherwise downloads binary from GitHub releases.
 */
import * as fs from "node:fs";
import * as path from "node:path";
import { pipeline } from "node:stream/promises";
import { $which, APP_NAME, isEnoent, VERSION } from "@oh-my-pi/pi-utils";
import { $ } from "bun";
import chalk from "chalk";
import { theme } from "../modes/theme/theme";

const REPO = "can1357/oh-my-pi";
const PACKAGE = "@oh-my-pi/pi-coding-agent";

interface ReleaseInfo {
	tag: string;
	version: string;
}

/** Result from running the installed binary and parsing its reported version. */
export interface InstalledVersionVerification {
	ok: boolean;
	actual?: string;
	path?: string;
}

/** Paths and verifier used while replacing a downloaded binary update. */
export interface BinaryReplacementOptions {
	targetPath: string;
	tempPath: string;
	backupPath: string;
	expectedVersion: string;
	verifyInstalledVersion: (expectedVersion: string) => Promise<InstalledVersionVerification>;
}

/**
 * Parse update subcommand arguments.
 * Returns undefined if not an update command.
 */
export function parseUpdateArgs(args: string[]): { force: boolean; check: boolean } | undefined {
	if (args.length === 0 || args[0] !== "update") {
		return undefined;
	}

	return {
		force: args.includes("--force") || args.includes("-f"),
		check: args.includes("--check") || args.includes("-c"),
	};
}

async function getBunGlobalBinDir(): Promise<string | undefined> {
	if (!$which("bun")) return undefined;
	try {
		const result = await $`bun pm bin -g`.quiet().nothrow();
		if (result.exitCode !== 0) return undefined;
		const output = result.text().trim();
		return output.length > 0 ? output : undefined;
	} catch {
		return undefined;
	}
}

function normalizePathForComparison(filePath: string): string {
	const normalized = path.normalize(filePath);
	if (process.platform === "win32") return normalized.toLowerCase();
	return normalized;
}

function tryRealpath(p: string): string | undefined {
	try {
		return fs.realpathSync.native(p);
	} catch {
		return undefined;
	}
}

function isPathInDirectoryLexical(filePath: string, directoryPath: string): boolean {
	const normalizedPath = normalizePathForComparison(path.resolve(filePath));
	const normalizedDirectory = normalizePathForComparison(path.resolve(directoryPath));
	const relativePath = path.relative(normalizedDirectory, normalizedPath);
	return relativePath === "" || (!relativePath.startsWith("..") && !path.isAbsolute(relativePath));
}

function isPathInDirectory(filePath: string, directoryPath: string): boolean {
	if (isPathInDirectoryLexical(filePath, directoryPath)) return true;
	// Layer realpath resolution on top of the lexical guard. On Windows, ~/.bun
	// is a junction when Bun is installed via Scoop, so `bun pm bin -g` and the
	// PATH-resolved omp path can refer to the same directory through different
	// strings. path.resolve does not traverse junctions/symlinks; realpath does.
	// Resolve the file's parent directory to tolerate the file itself not yet
	// existing (e.g. a fresh install path) while still catching link-traversed
	// equality once the directory exists.
	const fileDir = tryRealpath(path.dirname(path.resolve(filePath)));
	const dirReal = tryRealpath(path.resolve(directoryPath));
	if (!fileDir || !dirReal) return false;
	const resolvedFile = path.join(fileDir, path.basename(filePath));
	return isPathInDirectoryLexical(resolvedFile, dirReal);
}

type UpdateTarget = { method: "bun" } | { method: "binary"; path: string };

function resolveUpdateMethod(ompPath: string, bunBinDir: string | undefined): "bun" | "binary" {
	if (!bunBinDir) return "binary";
	return isPathInDirectory(ompPath, bunBinDir) ? "bun" : "binary";
}

export function resolveUpdateMethodForTest(ompPath: string, bunBinDir: string | undefined): "bun" | "binary" {
	return resolveUpdateMethod(ompPath, bunBinDir);
}
async function resolveUpdateTarget(): Promise<UpdateTarget> {
	const bunBinDir = await getBunGlobalBinDir();
	const ompPath = resolveOmpPath();

	if (ompPath) {
		const method = resolveUpdateMethod(ompPath, bunBinDir);
		if (method === "bun") return { method };
		return { method, path: ompPath };
	}

	if (bunBinDir) return { method: "bun" };

	throw new Error(`Could not resolve ${APP_NAME} binary path in PATH`);
}

/**
 * Get the latest release info from the npm registry.
 * Uses npm instead of GitHub API to avoid unauthenticated rate limiting.
 */
async function getLatestRelease(): Promise<ReleaseInfo> {
	const response = await fetch(`https://registry.npmjs.org/${PACKAGE}/latest`);
	if (!response.ok) {
		throw new Error(`Failed to fetch release info: ${response.statusText}`);
	}

	const data = (await response.json()) as { version: string };
	const version = data.version;
	const tag = `v${version}`;

	return {
		tag,
		version,
	};
}

/**
 * Compare semver versions. Returns:
 * - negative if a < b
 * - 0 if a == b
 * - positive if a > b
 */
function compareVersions(a: string, b: string): number {
	const pa = a.split(".").map(Number);
	const pb = b.split(".").map(Number);

	for (let i = 0; i < Math.max(pa.length, pb.length); i++) {
		const na = pa[i] || 0;
		const nb = pb[i] || 0;
		if (na !== nb) return na - nb;
	}
	return 0;
}

/**
 * Get the appropriate binary name for this platform.
 */
function getBinaryName(): string {
	const platform = process.platform;
	const arch = process.arch;

	let os: string;
	switch (platform) {
		case "linux":
			os = "linux";
			break;
		case "darwin":
			os = "darwin";
			break;
		case "win32":
			os = "windows";
			break;
		default:
			throw new Error(`Unsupported platform: ${platform}`);
	}

	let archName: string;
	switch (arch) {
		case "x64":
			archName = "x64";
			break;
		case "arm64":
			archName = "arm64";
			break;
		default:
			throw new Error(`Unsupported architecture: ${arch}`);
	}

	if (os === "windows") {
		return `${APP_NAME}-${os}-${archName}.exe`;
	}
	return `${APP_NAME}-${os}-${archName}`;
}

/**
 * Resolve the path that `omp` maps to in the user's PATH.
 */
function resolveOmpPath(): string | undefined {
	return $which(APP_NAME) ?? undefined;
}

/**
 * Run the resolved omp binary and check if it reports the expected version.
 */
async function verifyInstalledVersion(expectedVersion: string): Promise<InstalledVersionVerification> {
	const ompPath = resolveOmpPath();
	if (!ompPath) return { ok: false };
	try {
		const result = await $`${ompPath} --version`.quiet().nothrow();
		if (result.exitCode !== 0) return { ok: false, path: ompPath };
		const output = result.text().trim();
		// Output format: "omp/X.Y.Z"
		const match = output.match(/\/(\d+\.\d+\.\d+)/);
		const actual = match?.[1];
		return { ok: actual === expectedVersion, actual, path: ompPath };
	} catch {
		return { ok: false, path: ompPath };
	}
}

function printVerifiedVersion(expectedVersion: string): void {
	console.log(chalk.green(`\n${theme.status.success} Updated to ${expectedVersion}`));
}

function formatVerificationFailure(result: InstalledVersionVerification, expectedVersion: string): string {
	if (result.actual) {
		return `${APP_NAME} at ${result.path} still reports ${result.actual} (expected ${expectedVersion})`;
	}
	return `could not verify updated version${result.path ? ` at ${result.path}` : ""}`;
}

/**
 * Print post-update verification result.
 */
async function printVerification(expectedVersion: string): Promise<void> {
	const result = await verifyInstalledVersion(expectedVersion);
	if (result.ok) {
		printVerifiedVersion(expectedVersion);
		return;
	}
	console.log(chalk.yellow(`\nWarning: ${formatVerificationFailure(result, expectedVersion)}`));
	console.log(chalk.yellow(`You may need to reinstall: curl -fsSL https://omp.sh/install | sh`));
}

async function unlinkIfExists(filePath: string): Promise<void> {
	try {
		await fs.promises.unlink(filePath);
	} catch (err) {
		if (!isEnoent(err)) throw err;
	}
}

/**
 * Atomically replace the installed binary and roll back if version verification fails.
 */
export async function replaceBinaryForUpdate(options: BinaryReplacementOptions): Promise<InstalledVersionVerification> {
	let backupReady = false;
	try {
		await unlinkIfExists(options.backupPath);
		await fs.promises.rename(options.targetPath, options.backupPath);
		backupReady = true;
		await fs.promises.rename(options.tempPath, options.targetPath);

		const verification = await options.verifyInstalledVersion(options.expectedVersion);
		if (!verification.ok) {
			throw new Error(
				`${formatVerificationFailure(verification, options.expectedVersion)}; restored previous ${APP_NAME} binary`,
			);
		}

		backupReady = false;
		await unlinkIfExists(options.backupPath);
		return verification;
	} catch (err) {
		if (backupReady) {
			await unlinkIfExists(options.targetPath);
			await fs.promises.rename(options.backupPath, options.targetPath);
		}
		await unlinkIfExists(options.tempPath);
		throw err;
	}
}

/**
 * Update via bun package manager.
 */
async function updateViaBun(expectedVersion: string): Promise<void> {
	console.log(chalk.dim("Updating via bun..."));
	const result = await $`bun install -g ${PACKAGE}@${expectedVersion}`.nothrow();
	if (result.exitCode !== 0) {
		throw new Error(`bun install failed with exit code ${result.exitCode}`);
	}

	await printVerification(expectedVersion);
}

/**
 * Download a release binary to a target path, replacing an existing file.
 */
async function updateViaBinaryAt(targetPath: string, expectedVersion: string): Promise<void> {
	const binaryName = getBinaryName();
	const tag = `v${expectedVersion}`;
	const url = `https://github.com/${REPO}/releases/download/${tag}/${binaryName}`;

	const tempPath = `${targetPath}.new`;
	const backupPath = `${targetPath}.bak`;
	console.log(chalk.dim(`Downloading ${binaryName}…`));

	const response = await fetch(url, { redirect: "follow" });
	if (!response.ok || !response.body) {
		throw new Error(`Download failed: ${response.statusText}`);
	}
	const fileStream = fs.createWriteStream(tempPath, { mode: 0o755 });
	await pipeline(response.body, fileStream);

	console.log(chalk.dim("Installing update..."));
	await replaceBinaryForUpdate({
		targetPath,
		tempPath,
		backupPath,
		expectedVersion,
		verifyInstalledVersion,
	});
	printVerifiedVersion(expectedVersion);
	console.log(chalk.dim(`Restart ${APP_NAME} to use the new version`));
}

/**
 * Run the update command.
 */
export async function runUpdateCommand(opts: { force: boolean; check: boolean }): Promise<void> {
	console.log(chalk.dim(`Current version: ${VERSION}`));

	// Check for updates
	let release: ReleaseInfo;
	try {
		release = await getLatestRelease();
	} catch (err) {
		console.error(chalk.red(`Failed to check for updates: ${err}`));
		process.exit(1);
	}

	const comparison = compareVersions(release.version, VERSION);

	if (comparison <= 0 && !opts.force) {
		console.log(chalk.green(`${theme.status.success} Already up to date`));
		return;
	}

	if (comparison > 0) {
		console.log(chalk.cyan(`New version available: ${release.version}`));
	} else {
		console.log(chalk.yellow(`Forcing reinstall of ${release.version}`));
	}

	if (opts.check) {
		// Just check, don't install
		return;
	}

	// Choose update method based on the prioritized omp binary in PATH
	try {
		const target = await resolveUpdateTarget();
		if (target.method === "bun") {
			await updateViaBun(release.version);
		} else {
			await updateViaBinaryAt(target.path, release.version);
		}
	} catch (err) {
		console.error(chalk.red(`Update failed: ${err}`));
		process.exit(1);
	}
}

/**
 * Print update command help.
 */
export function printUpdateHelp(): void {
	console.log(`${chalk.bold(`${APP_NAME} update`)} - Check for and install updates

${chalk.bold("Usage:")}
  ${APP_NAME} update [options]

${chalk.bold("Options:")}
  -c, --check   Check for updates without installing
  -f, --force   Force reinstall even if up to date

${chalk.bold("Examples:")}
  ${APP_NAME} update           Update to latest version
  ${APP_NAME} update --check   Check if updates are available
  ${APP_NAME} update --force   Force reinstall
`);
}