#!/usr/bin/env bun
/**
 * PreToolUse Hook: Auto-sync claude-code-knowledge documentation when skill loads
 *
 * This hook combines all documentation fetching and syncing logic in one place.
 * It runs transparently before the Skill tool executes, checking if docs need
 * updating and fetching from docs.anthropic.com if necessary.
 *
 * Features:
 * - Smart caching (3-hour threshold)
 * - Automatic sitemap discovery
 * - Retry logic with exponential backoff
 * - Silent failures (never blocks skill loading)
 * - Complete manifest tracking
 */

import { createHash } from 'node:crypto';
import { existsSync } from 'node:fs';
import { mkdir, readFile, writeFile } from 'node:fs/promises';
import { dirname, join } from 'node:path';
import type { PreToolUseHookInput } from '@anthropic-ai/claude-agent-sdk';
import { XMLParser } from 'fast-xml-parser';

// ============================================================================
// Constants
// ============================================================================

const SITEMAP_URLS = [
	'https://docs.anthropic.com/sitemap.xml',
	'https://docs.claude.com/sitemap.xml',
];

const MANIFEST_FILE = 'docs_manifest.json';

const HEADERS = {
	'User-Agent': 'Claude-Code-Knowledge-Skill/1.0',
	'Cache-Control': 'no-cache, no-store, must-revalidate',
	Pragma: 'no-cache',
	Expires: '0',
};

const MAX_RETRIES = 3;
const RETRY_DELAY = 2000; // ms
const MAX_RETRY_DELAY = 30000; // ms
const MAX_CONCURRENT_FETCHES = 10; // parallel fetch limit

// ============================================================================
// Types
// ============================================================================

interface ManifestFile {
	original_url?: string;
	original_md_url?: string;
	original_raw_url?: string;
	hash: string;
	last_updated: string;
	source?: string;
}

interface Manifest {
	files: Record<string, ManifestFile>;
	last_updated?: string;
	source?: string;
	skill?: string;
	fetch_metadata?: {
		last_fetch_completed: string;
		fetch_duration_seconds: number;
		total_pages_discovered: number;
		pages_fetched_successfully: number;
		pages_failed: number;
		failed_pages: string[];
		sitemap_url: string;
		base_url: string;
		total_files: number;
	};
}

interface SitemapUrlEntry {
	loc?: string;
	[key: string]: unknown;
}

interface FetchResult {
	success: boolean;
	filename?: string;
	pagePath?: string;
	manifestEntry?: ManifestFile;
}

// ============================================================================
// Path Resolution
// ============================================================================

const SCRIPT_DIR = dirname(new URL(import.meta.url).pathname);
const PLUGIN_ROOT = join(SCRIPT_DIR, '..');
const DOCS_DIR = join(PLUGIN_ROOT, 'skills/claude-code-knowledge/docs');
const MANIFEST_PATH = join(DOCS_DIR, MANIFEST_FILE);

// ============================================================================
// Hook Input Handling
// ============================================================================

async function readHookInput(): Promise<PreToolUseHookInput | null> {
	try {
		const input = await Bun.stdin.text();
		return JSON.parse(input);
	} catch {
		return null;
	}
}

function shouldSync(hookInput: PreToolUseHookInput | null): boolean {
	if (!hookInput) return false;
	if (hookInput.tool_name !== 'Skill') return false;

	const toolInput = hookInput.tool_input as Record<string, unknown>;
	const skillName = (toolInput.skill as string) || '';
	return (
		skillName === 'claude-code-knowledge' ||
		skillName === 'claude-code-knowledge:claude-code-knowledge'
	);
}

// ============================================================================
// Sync Need Detection
// ============================================================================

async function checkIfSyncNeeded(): Promise<boolean> {
	if (!existsSync(MANIFEST_PATH)) {
		return true; // First time, need to fetch
	}

	try {
		const manifestContent = await readFile(MANIFEST_PATH, 'utf-8');
		const manifest = JSON.parse(manifestContent);
		const lastUpdate = manifest.last_updated || 'unknown';

		if (lastUpdate === 'unknown') return true;

		const lastUpdateDate = new Date(lastUpdate.slice(0, 19));
		const currentDate = new Date();
		const hoursSinceUpdate = Math.floor(
			(currentDate.getTime() - lastUpdateDate.getTime()) / (1000 * 60 * 60)
		);

		return hoursSinceUpdate >= 3;
	} catch {
		return true; // Error reading manifest, re-fetch
	}
}

// ============================================================================
// Manifest Management
// ============================================================================

async function loadManifest(): Promise<Manifest> {
	if (existsSync(MANIFEST_PATH)) {
		try {
			const content = await readFile(MANIFEST_PATH, 'utf-8');
			const manifest = JSON.parse(content);
			if (!manifest.files) manifest.files = {};
			return manifest;
		} catch {
			// Ignore error, return empty manifest
		}
	}
	return { files: {}, last_updated: undefined };
}

async function saveManifest(manifest: Manifest): Promise<void> {
	manifest.last_updated = new Date().toISOString();
	manifest.source = 'https://docs.anthropic.com/en/docs/claude-code/';
	manifest.skill = 'claude-code-knowledge';
	await writeFile(MANIFEST_PATH, JSON.stringify(manifest, null, 2));
}

// ============================================================================
// Utility Functions
// ============================================================================

const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));

function urlToSafeFilename(urlPath: string): string {
	const prefixes = ['/en/docs/claude-code/', '/docs/claude-code/', '/claude-code/'];

	let path = urlPath;
	for (const prefix of prefixes) {
		if (urlPath.includes(prefix)) {
			path = urlPath.split(prefix).pop() || urlPath;
			break;
		}
	}

	if (path === urlPath && urlPath.includes('claude-code/')) {
		path = urlPath.split('claude-code/').pop() || urlPath;
	}

	if (!path.includes('/')) {
		return path.endsWith('.md') ? path : `${path}.md`;
	}

	let safeName = path.replace(/\//g, '__');
	if (!safeName.endsWith('.md')) {
		safeName += '.md';
	}

	return safeName;
}

function contentHasChanged(content: string, oldHash: string): boolean {
	const newHash = createHash('sha256').update(content, 'utf-8').digest('hex');
	return newHash !== oldHash;
}

// ============================================================================
// Sitemap and Page Discovery
// ============================================================================

async function discoverSitemapAndBaseUrl(): Promise<{ sitemapUrl: string; baseUrl: string }> {
	for (const sitemapUrl of SITEMAP_URLS) {
		try {
			const response = await fetch(sitemapUrl, { headers: HEADERS });

			if (response.status === 200) {
				const content = await response.text();
				const parser = new XMLParser();
				const result = parser.parse(content);

				let firstUrl: string | null = null;
				if (result.urlset?.url) {
					const urls = Array.isArray(result.urlset.url) ? result.urlset.url : [result.urlset.url];
					if (urls[0]?.loc) {
						firstUrl = urls[0].loc;
					}
				}

				if (firstUrl) {
					const url = new URL(firstUrl);
					const baseUrl = `${url.protocol}//${url.hostname}`;
					return { sitemapUrl, baseUrl };
				}
			}
		} catch {}
	}

	throw new Error('Could not find a valid sitemap');
}

function getFallbackPages(): string[] {
	return [
		'/en/docs/claude-code/overview',
		'/en/docs/claude-code/quickstart',
		'/en/docs/claude-code/setup',
		'/en/docs/claude-code/cli-reference',
		'/en/docs/claude-code/common-workflows',
		'/en/docs/claude-code/interactive-mode',
		'/en/docs/claude-code/settings',
		'/en/docs/claude-code/model-config',
		'/en/docs/claude-code/network-config',
		'/en/docs/claude-code/terminal-config',
		'/en/docs/claude-code/output-styles',
		'/en/docs/claude-code/statusline',
		'/en/docs/claude-code/hooks',
		'/en/docs/claude-code/hooks-guide',
		'/en/docs/claude-code/mcp',
		'/en/docs/claude-code/skills',
		'/en/docs/claude-code/slash-commands',
		'/en/docs/claude-code/plugins',
		'/en/docs/claude-code/plugins-reference',
		'/en/docs/claude-code/plugin-marketplaces',
		'/en/docs/claude-code/sub-agents',
		'/en/docs/claude-code/memory',
		'/en/docs/claude-code/checkpointing',
		'/en/docs/claude-code/analytics',
		'/en/docs/claude-code/monitoring-usage',
		'/en/docs/claude-code/costs',
		'/en/docs/claude-code/github-actions',
		'/en/docs/claude-code/gitlab-ci-cd',
		'/en/docs/claude-code/vs-code',
		'/en/docs/claude-code/jetbrains',
		'/en/docs/claude-code/devcontainer',
		'/en/docs/claude-code/claude-code-on-the-web',
		'/en/docs/claude-code/third-party-integrations',
		'/en/docs/claude-code/amazon-bedrock',
		'/en/docs/claude-code/google-vertex-ai',
		'/en/docs/claude-code/llm-gateway',
		'/en/docs/claude-code/iam',
		'/en/docs/claude-code/security',
		'/en/docs/claude-code/sandboxing',
		'/en/docs/claude-code/data-usage',
		'/en/docs/claude-code/legal-and-compliance',
		'/en/docs/claude-code/headless',
		'/en/docs/claude-code/troubleshooting',
		'/en/docs/claude-code/sdk/migration-guide',
	];
}

async function discoverClaudeCodePages(sitemapUrl: string): Promise<string[]> {
	try {
		const response = await fetch(sitemapUrl, { headers: HEADERS });
		if (!response.ok) throw new Error(`HTTP ${response.status}`);

		const content = await response.text();
		const parser = new XMLParser();
		const result = parser.parse(content);

		let urls: string[] = [];
		if (result.urlset?.url) {
			const urlEntries = Array.isArray(result.urlset.url) ? result.urlset.url : [result.urlset.url];
			urls = urlEntries
				.map((entry: SitemapUrlEntry) => entry.loc)
				.filter((loc: unknown): loc is string => typeof loc === 'string');
		}

		const claudeCodePages: string[] = [];
		const englishPatterns = ['/en/docs/claude-code/'];

		for (const url of urls) {
			if (englishPatterns.some((pattern) => url.includes(pattern))) {
				const urlObj = new URL(url);
				let path = urlObj.pathname;

				if (path.endsWith('.html')) {
					path = path.slice(0, -5);
				} else if (path.endsWith('/')) {
					path = path.slice(0, -1);
				}

				const skipPatterns = ['/tool-use/', '/examples/', '/legacy/', '/api/', '/reference/'];
				if (!skipPatterns.some((skip) => path.includes(skip))) {
					claudeCodePages.push(path);
				}
			}
		}

		const uniquePages = [...new Set(claudeCodePages)].sort();

		if (uniquePages.length === 0) {
			return getFallbackPages();
		}

		return uniquePages;
	} catch {
		return getFallbackPages();
	}
}

// ============================================================================
// Content Fetching
// ============================================================================

function validateMarkdownContent(content: string, _filename: string): void {
	if (!content || content.startsWith('<!DOCTYPE') || content.slice(0, 100).includes('<html')) {
		throw new Error('Received HTML instead of markdown');
	}

	if (content.trim().length < 50) {
		throw new Error(`Content too short (${content.length} bytes)`);
	}

	const lines = content.split('\n');
	const markdownIndicators = ['# ', '## ', '### ', '```', '- ', '* ', '1. ', '[', '**', '_', '> '];

	const indicatorCount = lines.slice(0, 50).reduce((count, line) => {
		return (
			count +
			markdownIndicators.filter(
				(indicator) => line.trim().startsWith(indicator) || line.includes(indicator)
			).length
		);
	}, 0);

	if (indicatorCount < 3) {
		throw new Error(`Content doesn't appear to be markdown (${indicatorCount} indicators found)`);
	}
}

async function fetchMarkdownContent(
	path: string,
	baseUrl: string
): Promise<{ filename: string; content: string }> {
	const markdownUrl = `${baseUrl}${path}.md`;
	const filename = urlToSafeFilename(path);

	for (let attempt = 0; attempt < MAX_RETRIES; attempt++) {
		try {
			const response = await fetch(markdownUrl, {
				headers: HEADERS,
				redirect: 'follow',
			});

			if (response.status === 429) {
				const retryAfter = Number.parseInt(response.headers.get('Retry-After') || '60', 10);
				await sleep(retryAfter * 1000);
				continue;
			}

			if (!response.ok) {
				throw new Error(`HTTP ${response.status}`);
			}

			const content = await response.text();
			validateMarkdownContent(content, filename);

			return { filename, content };
		} catch (e) {
			if (attempt < MAX_RETRIES - 1) {
				const delay = Math.min(RETRY_DELAY * 2 ** attempt, MAX_RETRY_DELAY);
				const jitteredDelay = delay * (0.5 + Math.random() * 0.5);
				await sleep(jitteredDelay);
			} else {
				throw new Error(`Failed to fetch ${filename} after ${MAX_RETRIES} attempts: ${e}`);
			}
		}
	}

	throw new Error(`Failed to fetch ${path}`);
}

async function fetchChangelog(): Promise<{ filename: string; content: string }> {
	const changelogUrl = 'https://raw.githubusercontent.com/anthropics/claude-code/main/CHANGELOG.md';
	const filename = 'changelog.md';

	for (let attempt = 0; attempt < MAX_RETRIES; attempt++) {
		try {
			const response = await fetch(changelogUrl, {
				headers: HEADERS,
				redirect: 'follow',
			});

			if (response.status === 429) {
				const retryAfter = Number.parseInt(response.headers.get('Retry-After') || '60', 10);
				await sleep(retryAfter * 1000);
				continue;
			}

			if (!response.ok) {
				throw new Error(`HTTP ${response.status}`);
			}

			const content = await response.text();

			const header = `# Claude Code Changelog

> **Source**: https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md
>
> This is the official Claude Code release changelog from the Claude Code repository.

---

`;
			const fullContent = header + content;

			if (fullContent.trim().length < 100) {
				throw new Error(`Changelog content too short (${fullContent.length} bytes)`);
			}

			return { filename, content: fullContent };
		} catch (e) {
			if (attempt < MAX_RETRIES - 1) {
				const delay = Math.min(RETRY_DELAY * 2 ** attempt, MAX_RETRY_DELAY);
				const jitteredDelay = delay * (0.5 + Math.random() * 0.5);
				await sleep(jitteredDelay);
			} else {
				throw new Error(`Failed to fetch changelog after ${MAX_RETRIES} attempts: ${e}`);
			}
		}
	}

	throw new Error('Failed to fetch changelog');
}

async function saveMarkdownFile(filename: string, content: string): Promise<string> {
	const filePath = join(DOCS_DIR, filename);
	await writeFile(filePath, content, 'utf-8');
	const contentHash = createHash('sha256').update(content, 'utf-8').digest('hex');
	return contentHash;
}

// ============================================================================
// Parallel Fetch Helpers
// ============================================================================

async function fetchAndSavePage(
	pagePath: string,
	baseUrl: string,
	manifest: Manifest
): Promise<FetchResult> {
	try {
		const { filename, content } = await fetchMarkdownContent(pagePath, baseUrl);

		const oldHash = manifest.files[filename]?.hash || '';
		const oldEntry = manifest.files[filename] || {};
		const filePath = join(DOCS_DIR, filename);
		const fileExists = existsSync(filePath);

		let contentHash: string;
		let lastUpdated: string;

		if (!fileExists || contentHasChanged(content, oldHash)) {
			contentHash = await saveMarkdownFile(filename, content);
			lastUpdated = new Date().toISOString();
		} else {
			contentHash = oldHash;
			lastUpdated = oldEntry.last_updated || new Date().toISOString();
		}

		return {
			success: true,
			filename,
			pagePath,
			manifestEntry: {
				original_url: `${baseUrl}${pagePath}`,
				original_md_url: `${baseUrl}${pagePath}.md`,
				hash: contentHash,
				last_updated: lastUpdated,
			},
		};
	} catch (e) {
		return { success: false, pagePath };
	}
}

async function fetchAndSaveChangelog(manifest: Manifest): Promise<FetchResult> {
	try {
		const { filename, content } = await fetchChangelog();

		const oldHash = manifest.files[filename]?.hash || '';
		const oldEntry = manifest.files[filename] || {};
		const filePath = join(DOCS_DIR, filename);
		const fileExists = existsSync(filePath);

		let contentHash: string;
		let lastUpdated: string;

		if (!fileExists || contentHasChanged(content, oldHash)) {
			contentHash = await saveMarkdownFile(filename, content);
			lastUpdated = new Date().toISOString();
		} else {
			contentHash = oldHash;
			lastUpdated = oldEntry.last_updated || new Date().toISOString();
		}

		return {
			success: true,
			filename,
			pagePath: 'changelog',
			manifestEntry: {
				original_url: 'https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md',
				original_raw_url:
					'https://raw.githubusercontent.com/anthropics/claude-code/main/CHANGELOG.md',
				hash: contentHash,
				last_updated: lastUpdated,
				source: 'claude-code-repository',
			},
		};
	} catch (e) {
		return { success: false, pagePath: 'changelog' };
	}
}

async function fetchAllPagesInParallel(
	documentationPages: string[],
	baseUrl: string,
	manifest: Manifest
): Promise<FetchResult[]> {
	// Create all fetch tasks (documentation pages + changelog)
	const pageTasks = documentationPages.map(
		(pagePath) => () => fetchAndSavePage(pagePath, baseUrl, manifest)
	);
	const allTasks = [...pageTasks, () => fetchAndSaveChangelog(manifest)];

	const results: FetchResult[] = [];

	// Process in batches to limit concurrency
	for (let i = 0; i < allTasks.length; i += MAX_CONCURRENT_FETCHES) {
		const batch = allTasks.slice(i, i + MAX_CONCURRENT_FETCHES);
		const batchResults = await Promise.allSettled(batch.map((task) => task()));

		for (const result of batchResults) {
			if (result.status === 'fulfilled') {
				results.push(result.value);
			} else {
				results.push({ success: false, pagePath: 'unknown' });
			}
		}

		// Small delay between batches to be respectful to the server
		if (i + MAX_CONCURRENT_FETCHES < allTasks.length) {
			await sleep(500);
		}
	}

	return results;
}

// ============================================================================
// Main Fetch Logic
// ============================================================================

async function runFetch(): Promise<void> {
	const startTime = Date.now();

	// Create docs directory if needed
	if (!existsSync(DOCS_DIR)) {
		await mkdir(DOCS_DIR, { recursive: true });
	}

	// Load existing manifest
	const manifest = await loadManifest();

	// Statistics
	let successful = 0;
	let failed = 0;
	const failedPages: string[] = [];
	const newManifest: Manifest = { files: {} };

	// Discover sitemap and base URL
	let sitemapUrl: string;
	let baseUrl: string;

	try {
		const result = await discoverSitemapAndBaseUrl();
		sitemapUrl = result.sitemapUrl;
		baseUrl = result.baseUrl;
	} catch (e) {
		throw new Error(`Failed to discover sitemap: ${e}`);
	}

	// Discover documentation pages
	const documentationPages = await discoverClaudeCodePages(sitemapUrl);

	if (documentationPages.length === 0) {
		throw new Error('No documentation pages discovered!');
	}

	// Fetch all pages in parallel (including changelog)
	const results = await fetchAllPagesInParallel(documentationPages, baseUrl, manifest);

	// Process results
	for (const result of results) {
		if (result.success && result.filename && result.manifestEntry) {
			newManifest.files[result.filename] = result.manifestEntry;
			successful++;
		} else {
			failed++;
			failedPages.push(result.pagePath || 'unknown');
		}
	}

	// Add metadata
	const duration = (Date.now() - startTime) / 1000;
	newManifest.fetch_metadata = {
		last_fetch_completed: new Date().toISOString(),
		fetch_duration_seconds: duration,
		total_pages_discovered: documentationPages.length,
		pages_fetched_successfully: successful,
		pages_failed: failed,
		failed_pages: failedPages,
		sitemap_url: sitemapUrl,
		base_url: baseUrl,
		total_files: successful,
	};

	// Save manifest
	await saveManifest(newManifest);

	// If no pages were fetched successfully, throw error
	if (successful === 0) {
		throw new Error('No pages were fetched successfully!');
	}
}

// ============================================================================
// Main Hook Logic
// ============================================================================

async function main() {
	// Read hook input
	const hookInput = await readHookInput();

	// Check if we should sync
	if (!shouldSync(hookInput)) {
		process.exit(0);
	}

	// Check if sync is needed
	const syncNeeded = await checkIfSyncNeeded();

	if (!syncNeeded) {
		process.exit(0);
	}

	// Run fetch (blocks, but with timeout handled by hook system)
	try {
		await runFetch();
	} catch {
		// Silent failure - don't block skill loading
	}

	// Always exit 0 (non-blocking, silent)
	process.exit(0);
}

// Run main function
main().catch(() => {
	// Silent failure - always exit 0
	process.exit(0);
});