/**
 * 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";
/**
 * Official npm registry origin.
 *
 * Pinned across both the version check and the bun install step so the two
 * agree on which catalog they are talking to. A user's bun may be pointed at
 * an unofficial mirror (corporate proxy, Taobao, etc.) that lags the upstream
 * registry by minutes-to-hours, in which case `getLatestRelease` would resolve
 * a version the mirror has not yet replicated and the install would fail with
 * `No version matching "X" found for specifier "<pkg>" (but package exists)`.
 * See #1686.
 */
const NPM_REGISTRY = "https://registry.npmjs.org/";

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(`${NPM_REGISTRY}${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;
}

interface BunInstallCachePruneResult {
	scannedPackages: number;
	removedEntries: number;
}

interface BunCachePackageGroup {
	actualDirs: Map<string, string[]>;
	markerDir?: string;
	markerEntries: Map<string, string[]>;
}

function stripBunCacheVersionSuffix(name: string): string {
	const suffixIndex = name.indexOf("@@@");
	return suffixIndex === -1 ? name : name.slice(0, suffixIndex);
}

function compareSemverIdentifier(a: string, b: string): number {
	const aNumber = /^\d+$/.test(a);
	const bNumber = /^\d+$/.test(b);
	if (aNumber && bNumber) return Number(a) - Number(b);
	if (aNumber) return -1;
	if (bNumber) return 1;
	return a.localeCompare(b);
}

function compareSemverLikeVersions(a: string, b: string): number {
	const [aCoreWithPrerelease] = a.split("+", 1);
	const [bCoreWithPrerelease] = b.split("+", 1);
	const [aCore, aPrerelease] = aCoreWithPrerelease.split("-", 2);
	const [bCore, bPrerelease] = bCoreWithPrerelease.split("-", 2);
	const aParts = aCore.split(".");
	const bParts = bCore.split(".");
	for (let i = 0; i < Math.max(aParts.length, bParts.length); i++) {
		const diff = Number(aParts[i] ?? 0) - Number(bParts[i] ?? 0);
		if (diff !== 0 && Number.isFinite(diff)) return diff;
	}
	if (!aPrerelease && !bPrerelease) return 0;
	if (!aPrerelease) return 1;
	if (!bPrerelease) return -1;
	const aPrereleaseParts = aPrerelease.split(".");
	const bPrereleaseParts = bPrerelease.split(".");
	for (let i = 0; i < Math.max(aPrereleaseParts.length, bPrereleaseParts.length); i++) {
		const aPart = aPrereleaseParts[i];
		const bPart = bPrereleaseParts[i];
		if (aPart === undefined) return -1;
		if (bPart === undefined) return 1;
		const diff = compareSemverIdentifier(aPart, bPart);
		if (diff !== 0) return diff;
	}
	return 0;
}

async function readdirIfExists(dir: string): Promise<fs.Dirent[]> {
	try {
		return await fs.promises.readdir(dir, { withFileTypes: true });
	} catch (err) {
		if (isEnoent(err)) return [];
		throw err;
	}
}

function getBunCacheGroup(groups: Map<string, BunCachePackageGroup>, packageName: string): BunCachePackageGroup {
	let group = groups.get(packageName);
	if (!group) {
		group = { actualDirs: new Map(), markerEntries: new Map() };
		groups.set(packageName, group);
	}
	return group;
}

function addVersionPath(entries: Map<string, string[]>, version: string, entryPath: string): void {
	const paths = entries.get(version);
	if (paths) {
		paths.push(entryPath);
		return;
	}
	entries.set(version, [entryPath]);
}

async function addBunCacheActualDir(
	groups: Map<string, BunCachePackageGroup>,
	dirPath: string,
	packageNames: Set<string> | undefined,
): Promise<void> {
	try {
		const manifest = (await Bun.file(path.join(dirPath, "package.json")).json()) as Partial<
			Record<"name" | "version", unknown>
		>;
		if (typeof manifest.name !== "string" || typeof manifest.version !== "string") return;
		if (packageNames && !packageNames.has(manifest.name)) return;
		const group = getBunCacheGroup(groups, manifest.name);
		addVersionPath(group.actualDirs, manifest.version, dirPath);
	} catch (err) {
		if (isEnoent(err)) return;
		throw err;
	}
}

async function addBunCacheMarkerDir(
	groups: Map<string, BunCachePackageGroup>,
	packageName: string,
	markerDir: string,
	packageNames: Set<string> | undefined,
): Promise<void> {
	if (packageNames && !packageNames.has(packageName)) return;
	const markerEntries = await readdirIfExists(markerDir);
	const group = getBunCacheGroup(groups, packageName);
	group.markerDir = markerDir;
	for (const entry of markerEntries) {
		const cacheVersion = stripBunCacheVersionSuffix(entry.name);
		addVersionPath(group.markerEntries, cacheVersion, path.join(markerDir, entry.name));
	}
}

async function collectBunCacheGroups(
	cacheDir: string,
	packageNames: Set<string> | undefined,
): Promise<Map<string, BunCachePackageGroup>> {
	const groups = new Map<string, BunCachePackageGroup>();
	for (const entry of await readdirIfExists(cacheDir)) {
		if (!entry.isDirectory()) continue;
		const entryPath = path.join(cacheDir, entry.name);
		if (entry.name.startsWith("@")) {
			for (const scopedEntry of await readdirIfExists(entryPath)) {
				if (!scopedEntry.isDirectory()) continue;
				const scopedEntryPath = path.join(entryPath, scopedEntry.name);
				const versionSeparator = scopedEntry.name.lastIndexOf("@");
				if (versionSeparator === -1) {
					await addBunCacheMarkerDir(groups, `${entry.name}/${scopedEntry.name}`, scopedEntryPath, packageNames);
				} else {
					await addBunCacheActualDir(groups, scopedEntryPath, packageNames);
				}
			}
			continue;
		}
		const versionSeparator = entry.name.lastIndexOf("@");
		if (versionSeparator === -1) {
			await addBunCacheMarkerDir(groups, entry.name, entryPath, packageNames);
		} else {
			await addBunCacheActualDir(groups, entryPath, packageNames);
		}
	}
	return groups;
}

async function removeCacheEntries(paths: string[]): Promise<number> {
	for (const entryPath of paths) {
		await fs.promises.rm(entryPath, { recursive: true, force: true });
	}
	return paths.length;
}

/**
 * Prune Bun's package cache so each package keeps only its newest cached version.
 *
 * Bun stores package cache entries as both a package marker directory
 * (`react/19.2.6@@@1`) and a materialized package directory
 * (`react@19.2.6@@@1`). Global `omp` updates can leave one full copy per
 * release. The marker and materialized entries are removed together so the
 * cache stays internally consistent.
 */
export async function pruneBunInstallCache(
	cacheDir: string,
	packageNames?: Set<string>,
): Promise<BunInstallCachePruneResult> {
	const groups = await collectBunCacheGroups(cacheDir, packageNames);
	let scannedPackages = 0;
	let removedEntries = 0;
	for (const group of groups.values()) {
		if (group.actualDirs.size === 0) continue;
		scannedPackages++;
		let latestVersion: string | undefined;
		for (const version of group.actualDirs.keys()) {
			if (!latestVersion || compareSemverLikeVersions(version, latestVersion) > 0) latestVersion = version;
		}
		if (!latestVersion) continue;
		for (const [version, paths] of group.actualDirs) {
			if (version !== latestVersion) removedEntries += await removeCacheEntries(paths);
		}
		for (const [version, paths] of group.markerEntries) {
			if (version !== latestVersion) removedEntries += await removeCacheEntries(paths);
		}
	}
	return { scannedPackages, removedEntries };
}

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

export function resolveBunGlobalNodeModulesDirFromLocations(
	globalBinDir: string | undefined,
	cacheDir: string | undefined,
): string | undefined {
	if (globalBinDir && globalBinDir.length > 0) {
		return path.join(path.dirname(globalBinDir), "install", "global", "node_modules");
	}
	if (cacheDir && cacheDir.length > 0) {
		return path.join(path.dirname(cacheDir), "global", "node_modules");
	}
	return undefined;
}

async function resolveBunGlobalNodeModulesDir(cacheDir: string): Promise<string | undefined> {
	try {
		const result = await $`bun pm bin -g`.quiet().nothrow();
		const globalBinDir = result.exitCode === 0 ? result.text().trim() : undefined;
		return resolveBunGlobalNodeModulesDirFromLocations(globalBinDir, cacheDir);
	} catch {
		return resolveBunGlobalNodeModulesDirFromLocations(undefined, cacheDir);
	}
}

async function collectInstalledPackageNames(nodeModulesDir: string): Promise<Set<string>> {
	const packageNames = new Set<string>();
	for (const entry of await readdirIfExists(nodeModulesDir)) {
		if (!entry.isDirectory() || entry.name === ".bin") continue;
		if (entry.name.startsWith("@")) {
			for (const scopedEntry of await readdirIfExists(path.join(nodeModulesDir, entry.name))) {
				if (scopedEntry.isDirectory()) packageNames.add(`${entry.name}/${scopedEntry.name}`);
			}
			continue;
		}
		packageNames.add(entry.name);
	}
	return packageNames;
}

async function pruneBunCacheAfterGlobalInstall(): Promise<BunInstallCachePruneResult | undefined> {
	const cacheDir = await resolveBunInstallCacheDir();
	if (!cacheDir) return undefined;
	const globalNodeModulesDir = await resolveBunGlobalNodeModulesDir(cacheDir);
	const packageNames = globalNodeModulesDir
		? await collectInstalledPackageNames(globalNodeModulesDir)
		: new Set<string>();
	if (packageNames.size === 0 && !path.basename(cacheDir).toLowerCase().includes("omp")) return undefined;
	return await pruneBunInstallCache(cacheDir, packageNames.size === 0 ? undefined : packageNames);
}

/**
 * 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;
	}
}

/**
 * Build the bun argv used to globally install a specific omp version.
 *
 * The version is selected by hitting {@link NPM_REGISTRY} directly in
 * {@link getLatestRelease}, so the install MUST observe the same catalog:
 *
 * - `--registry=${NPM_REGISTRY}` pins the install to the official registry
 *   regardless of the user's bunfig/`.npmrc`. A mirror (corporate proxy,
 *   Taobao, …) that hasn't yet replicated the release would otherwise reject
 *   a version the upstream registry already advertises.
 * - `--no-cache` tells bun to ignore its on-disk manifest snapshot so it
 *   re-fetches metadata from that registry on every invocation.
 *
 * Together these two flags make `omp update` produce exactly the registry
 * lookup the version check just performed. See #1686.
 */
export function buildBunInstallArgs(expectedVersion: string): string[] {
	return ["install", "-g", "--no-cache", `--registry=${NPM_REGISTRY}`, `${PACKAGE}@${expectedVersion}`];
}

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

	await printVerification(expectedVersion);
	try {
		const pruneResult = await pruneBunCacheAfterGlobalInstall();
		if (pruneResult && pruneResult.removedEntries > 0) {
			console.log(chalk.dim(`Pruned ${pruneResult.removedEntries} stale Bun cache entries`));
		}
	} catch (err) {
		console.log(chalk.yellow(`Warning: could not prune stale Bun cache entries: ${err}`));
	}
}

/**
 * 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
`);
}