/**
 * Improved caching layer.
 * - mtime-aware file cache
 * - shared TTL helpers
 * - explicit invalidation by prefix / file
 * - integrates with stateRegistry hit/miss counters
 */

import crypto from "crypto";
import fs from "fs/promises";
import {
  incrementCacheHits,
  incrementCacheMisses,
  addCachedKey,
  removeCachedKey,
  isCacheValid,
} from "../stateRegistry";

function generateKey(...parts: string[]): string {
  return crypto.createHash("sha256").update(parts.join("|")).digest("hex");
}

// ─── RAG cache ───────────────────────────────────────────────────────────────
const ragCache = new Map<string, { result: any; timestamp: number }>();
const RAG_TTL_MS = 60 * 60 * 1000; // 1 hour

export async function cachedRagQuery(
  query: string,
  workspacePath: string,
  actualWork?: () => Promise<any>,
): Promise<any> {
  const key = generateKey("rag", query, workspacePath);

  if (isCacheValid(key) && ragCache.has(key)) {
    incrementCacheHits();
    return ragCache.get(key)!.result;
  }

  const result = actualWork
    ? await actualWork()
    : { chunks: [], query, note: "No RAG worker provided – cache miss placeholder" };

  ragCache.set(key, { result, timestamp: Date.now() });
  addCachedKey(key, RAG_TTL_MS);
  incrementCacheMisses();
  return result;
}

// ─── Web fetch cache ─────────────────────────────────────────────────────────
const webFetchCache = new Map<string, { content: string; timestamp: number }>();
const WEB_FETCH_TTL_MS = 30 * 60 * 1000; // 30 min

export async function cachedWebFetch(
  url: string,
): Promise<{ content: string; fromCache: boolean }> {
  const key = generateKey("web", url);

  if (isCacheValid(key) && webFetchCache.has(key)) {
    incrementCacheHits();
    return { content: webFetchCache.get(key)!.content, fromCache: true };
  }

  try {
    const response = await fetch(url, {
      headers: { "User-Agent": "BeledariansLMStudioTools/1.0" },
      signal: AbortSignal.timeout(30_000),
    });
    if (!response.ok) {
      throw new Error(`HTTP ${response.status} ${response.statusText}`);
    }
    const text = await response.text();
    webFetchCache.set(key, { content: text, timestamp: Date.now() });
    addCachedKey(key, WEB_FETCH_TTL_MS);
    incrementCacheMisses();
    return { content: text, fromCache: false };
  } catch (err) {
    incrementCacheMisses();
    throw err;
  }
}

// ─── File read cache (mtime-aware) ───────────────────────────────────────────
const fileReadCache = new Map<
  string,
  { content: string; mtimeMs: number; timestamp: number }
>();
const FILE_READ_TTL_MS = 60 * 60 * 1000; // 1 hour absolute max

export async function cachedFileRead(
  filePath: string,
): Promise<{ content: string; fromCache: boolean }> {
  const stat = await fs.stat(filePath);
  // Key includes mtime so a changed file is automatically a miss
  const key = generateKey("file", filePath, String(stat.mtimeMs));

  if (isCacheValid(key) && fileReadCache.has(key)) {
    const entry = fileReadCache.get(key)!;
    // Double-check mtime in case of clock skew / external change
    if (entry.mtimeMs === stat.mtimeMs) {
      incrementCacheHits();
      return { content: entry.content, fromCache: true };
    }
    // Stale – fall through
    fileReadCache.delete(key);
    removeCachedKey(key);
  }

  const content = await fs.readFile(filePath, "utf-8");
  fileReadCache.set(key, {
    content,
    mtimeMs: stat.mtimeMs,
    timestamp: Date.now(),
  });
  addCachedKey(key, FILE_READ_TTL_MS);
  incrementCacheMisses();
  return { content, fromCache: false };
}

/**
 * Invalidate every cache entry that touches a given file path.
 * Call this after any write / delete / rename.
 */
export function invalidateFileCache(filePath: string): void {
  const keysToDelete: string[] = [];
  for (const [key, entry] of fileReadCache.entries()) {
    // We can't reverse the hash, so we keep a parallel index if needed.
    // For now we clear the whole file cache on any write – still cheap.
    keysToDelete.push(key);
  }
  for (const key of keysToDelete) {
    fileReadCache.delete(key);
    removeCachedKey(key);
  }
  // Also clear RAG entries that might have indexed this file
  for (const key of ragCache.keys()) {
    if (key.includes("rag")) {
      // Conservative: leave RAG for now; caller can call clearAllCaches if needed
    }
  }
}

/**
 * Broader invalidation by prefix (e.g. "memory_search:", "kb_get_entries:").
 * Used by toolsProvider when memory or knowledge-base data changes.
 */
export function invalidateByPrefix(prefix: string, toolResultCache?: Map<string, any>): void {
  if (toolResultCache) {
    for (const key of toolResultCache.keys()) {
      if (key.startsWith(prefix)) {
        toolResultCache.delete(key);
      }
    }
  }
}

export function clearAllCaches(): {
  success: boolean;
  clearedKeys: number;
} {
  const count =
    ragCache.size + webFetchCache.size + fileReadCache.size;
  ragCache.clear();
  webFetchCache.clear();
  fileReadCache.clear();
  return { success: true, clearedKeys: count };
}

export function getCacheStats(): {
  ragSize: number;
  webFetchSize: number;
  fileReadSize: number;
} {
  return {
    ragSize: ragCache.size,
    webFetchSize: webFetchCache.size,
    fileReadSize: fileReadCache.size,
  };
}

/**
 * Improved caching layer.
 * - mtime-aware file cache
 * - shared TTL helpers
 * - explicit invalidation by prefix / file
 * - integrates with stateRegistry hit/miss counters
 */

import crypto from "crypto";
import fs from "fs/promises";
import {
  incrementCacheHits,
  incrementCacheMisses,
  addCachedKey,
  removeCachedKey,
  isCacheValid,
} from "../stateRegistry";

function generateKey(...parts: string[]): string {
  return crypto.createHash("sha256").update(parts.join("|")).digest("hex");
}

// ─── RAG cache ───────────────────────────────────────────────────────────────
const ragCache = new Map<string, { result: any; timestamp: number }>();
const RAG_TTL_MS = 60 * 60 * 1000; // 1 hour

export async function cachedRagQuery(
  query: string,
  workspacePath: string,
  actualWork?: () => Promise<any>,
): Promise<any> {
  const key = generateKey("rag", query, workspacePath);

  if (isCacheValid(key) && ragCache.has(key)) {
    incrementCacheHits();
    return ragCache.get(key)!.result;
  }

  const result = actualWork
    ? await actualWork()
    : { chunks: [], query, note: "No RAG worker provided – cache miss placeholder" };

  ragCache.set(key, { result, timestamp: Date.now() });
  addCachedKey(key, RAG_TTL_MS);
  incrementCacheMisses();
  return result;
}

// ─── Web fetch cache ─────────────────────────────────────────────────────────
const webFetchCache = new Map<string, { content: string; timestamp: number }>();
const WEB_FETCH_TTL_MS = 30 * 60 * 1000; // 30 min

export async function cachedWebFetch(
  url: string,
): Promise<{ content: string; fromCache: boolean }> {
  const key = generateKey("web", url);

  if (isCacheValid(key) && webFetchCache.has(key)) {
    incrementCacheHits();
    return { content: webFetchCache.get(key)!.content, fromCache: true };
  }

  try {
    const response = await fetch(url, {
      headers: { "User-Agent": "BeledariansLMStudioTools/1.0" },
      signal: AbortSignal.timeout(30_000),
    });
    if (!response.ok) {
      throw new Error(`HTTP ${response.status} ${response.statusText}`);
    }
    const text = await response.text();
    webFetchCache.set(key, { content: text, timestamp: Date.now() });
    addCachedKey(key, WEB_FETCH_TTL_MS);
    incrementCacheMisses();
    return { content: text, fromCache: false };
  } catch (err) {
    incrementCacheMisses();
    throw err;
  }
}

// ─── File read cache (mtime-aware) ───────────────────────────────────────────
const fileReadCache = new Map<
  string,
  { content: string; mtimeMs: number; timestamp: number }
>();
const FILE_READ_TTL_MS = 60 * 60 * 1000; // 1 hour absolute max

export async function cachedFileRead(
  filePath: string,
): Promise<{ content: string; fromCache: boolean }> {
  const stat = await fs.stat(filePath);
  // Key includes mtime so a changed file is automatically a miss
  const key = generateKey("file", filePath, String(stat.mtimeMs));

  if (isCacheValid(key) && fileReadCache.has(key)) {
    const entry = fileReadCache.get(key)!;
    // Double-check mtime in case of clock skew / external change
    if (entry.mtimeMs === stat.mtimeMs) {
      incrementCacheHits();
      return { content: entry.content, fromCache: true };
    }
    // Stale – fall through
    fileReadCache.delete(key);
    removeCachedKey(key);
  }

  const content = await fs.readFile(filePath, "utf-8");
  fileReadCache.set(key, {
    content,
    mtimeMs: stat.mtimeMs,
    timestamp: Date.now(),
  });
  addCachedKey(key, FILE_READ_TTL_MS);
  incrementCacheMisses();
  return { content, fromCache: false };
}

/**
 * Invalidate every cache entry that touches a given file path.
 * Call this after any write / delete / rename.
 */
export function invalidateFileCache(filePath: string): void {
  const keysToDelete: string[] = [];
  for (const [key, entry] of fileReadCache.entries()) {
    // We can't reverse the hash, so we keep a parallel index if needed.
    // For now we clear the whole file cache on any write – still cheap.
    keysToDelete.push(key);
  }
  for (const key of keysToDelete) {
    fileReadCache.delete(key);
    removeCachedKey(key);
  }
  // Also clear RAG entries that might have indexed this file
  for (const key of ragCache.keys()) {
    if (key.includes("rag")) {
      // Conservative: leave RAG for now; caller can call clearAllCaches if needed
    }
  }
}

/**
 * Broader invalidation by prefix (e.g. "memory_search:", "kb_get_entries:").
 * Used by toolsProvider when memory or knowledge-base data changes.
 */
export function invalidateByPrefix(prefix: string, toolResultCache?: Map<string, any>): void {
  if (toolResultCache) {
    for (const key of toolResultCache.keys()) {
      if (key.startsWith(prefix)) {
        toolResultCache.delete(key);
      }
    }
  }
}

export function clearAllCaches(): {
  success: boolean;
  clearedKeys: number;
} {
  const count =
    ragCache.size + webFetchCache.size + fileReadCache.size;
  ragCache.clear();
  webFetchCache.clear();
  fileReadCache.clear();
  return { success: true, clearedKeys: count };
}

export function getCacheStats(): {
  ragSize: number;
  webFetchSize: number;
  fileReadSize: number;
} {
  return {
    ragSize: ragCache.size,
    webFetchSize: webFetchCache.size,
    fileReadSize: fileReadCache.size,
  };
}