import { serve } from "bun";
import { type Repo } from "./types.ts";

// --- Configuration Constants ---
const PORT = 7860;
const REFRESH_INTERVAL_MS = 30 * 60 * 1000; // 30 minutes in milliseconds
const MAX_SEARCH_RESULTS = 25;
const DEFAULT_PAGINATION_SIZE = 10;

// Changed to a single URL for packages
const PACKAGE_URL =
  "https://raw.githubusercontent.com/Zigistry/database/refs/heads/main/database/packages.json";
const PROGRAMS_URL =
  "https://raw.githubusercontent.com/Zigistry/database/refs/heads/main/database/programs.json";

// --- CORS Headers ---
const CORS_HEADERS: Record<string, string> = {
  "Content-Type": "application/json",
  "Access-Control-Allow-Origin": "*",
};

// --- Data Store ---
interface DataStore {
  packages: Repo[];
  programs: Repo[];
  sortedPackages: {
    latest: Repo[];
    mostUsed: Repo[];
  };
  sortedPrograms: {
    latest: Repo[];
    mostUsed: Repo[];
  };
  lastLoaded: number; // Timestamp of last successful data load
}

const dataStore: DataStore = {
  packages: [],
  programs: [],
  sortedPackages: { latest: [], mostUsed: [] },
  sortedPrograms: { latest: [], mostUsed: [] },
  lastLoaded: 0,
};

// --- Helper Functions ---
function removeReadmeContent(repos: Repo[]): Repo[] {
  return (repos.map((repo) => {
    const { readme_content, ...rest } = repo; // Destructure to exclude readme_content
    return rest;
  }) as Repo[]);
}

const sortByDate = (a: Repo, b: Repo) =>
  new Date(b.created_at ?? "").getTime() -
  new Date(a.created_at ?? "").getTime();

const sortByUsage = (a: Repo, b: Repo) =>
  (b.stargazers_count ?? 0) - (a.stargazers_count ?? 0);

function filterItems(
  items: Repo[],
  q: string | null,
  filter: string | null
): Repo[] {
  const lowerQ = q?.toLowerCase();
  const lowerFilter = filter?.toLowerCase();

  return items.filter(
    ({ name, full_name, description, topics, readme_content }) => {
      // Apply topic filter first
      if (
        lowerFilter &&
        !topics?.some((t) => t.toLowerCase() === lowerFilter)
      ) {
        return false;
      }

      // If no search query, all items passing the filter are included
      if (!lowerQ) {
        return true;
      }

      // Check if any relevant field includes the search query
      return [name, full_name, description, ...(topics ?? []), readme_content].some(
        (field) => field?.toLowerCase().includes(lowerQ)
      );
    }
  );
}

function getPaginated<T>(items: T[], page = 0, size = DEFAULT_PAGINATION_SIZE): T[] {
  const start = page * size;
  return items.slice(start, start + size);
}

function parseRange(str: string | null, max: number): [number, number] {
  const match = str?.match(/^(\d+)\.\.(\d+)$/);
  let start = 0;
  let end = DEFAULT_PAGINATION_SIZE; // Default range if no match

  if (match) {
    start = parseInt(match[1] ?? "0", 10);
    end = parseInt(match[2] ?? String(DEFAULT_PAGINATION_SIZE), 10);
  }

  return [Math.max(0, start), Math.min(max, end)];
}

// --- Data Loading and Caching ---
async function fetchData<T>(url: string): Promise<T | null> {
  try {
    const response = await fetch(url);
    if (!response.ok) {
      console.error(`Failed to fetch ${url}: ${response.statusText}`);
      return null;
    }
    return (await response.json()) as T;
  } catch (error) {
    console.error(`Error fetching or parsing ${url}:`, error);
    return null;
  }
}

async function loadData() {
  console.log("Attempting to load data...");
  try {
    // Fetch packages (now from a single URL)
    const newPackages = await fetchData<Repo[]>(PACKAGE_URL);

    // Fetch programs
    const newPrograms = await fetchData<Repo[]>(PROGRAMS_URL);

    if (newPackages && newPrograms) {
      dataStore.packages = newPackages;
      dataStore.programs = newPrograms;

      // Pre-sort data after successful load
      dataStore.sortedPackages.latest = [...newPackages].sort(sortByDate);
      dataStore.sortedPackages.mostUsed = [...newPackages].sort(sortByUsage);
      dataStore.sortedPrograms.latest = [...newPrograms].sort(sortByDate);
      dataStore.sortedPrograms.mostUsed = [...newPrograms].sort(sortByUsage);

      dataStore.lastLoaded = Date.now();
      console.log("Data loaded successfully.");
    } else {
      console.warn("Failed to load all data. Retaining old data if available.");
    }
  } catch (error) {
    console.error("Critical error during data loading:", error);
  }
}

async function ensureDataLoaded() {
  if (Date.now() - dataStore.lastLoaded > REFRESH_INTERVAL_MS) {
    console.log("Data is stale, refreshing...");
    await loadData();
  } else if (dataStore.lastLoaded === 0) {
    // Initial load if not already done
    console.log("Initial data load...");
    await loadData();
  }
}

// Perform initial data load immediately on server start
await loadData();

// Set up interval for refreshing data
setInterval(ensureDataLoaded, REFRESH_INTERVAL_MS / 2); // Check more frequently than refresh interval

// --- API Route Handlers ---
function handleSearch(items: Repo[], searchParams: URLSearchParams): Response {
  const q = searchParams.get("q")?.trim() ?? null;
  const filter = searchParams.get("filter")?.trim() ?? null;
  const result = filterItems(items, q, filter).slice(0, MAX_SEARCH_RESULTS);
  return Response.json(removeReadmeContent(result), { headers: CORS_HEADERS });
}

function handleInfiniteScroll(items: Repo[], searchParams: URLSearchParams): Response {
  const page = parseInt(searchParams.get("pageNumber") || "0", 10);
  if (isNaN(page) || page < 0) {
    return Response.json(
      { error: "Invalid page number. Must be a non-negative integer." },
      { status: 400, headers: CORS_HEADERS }
    );
  }
  const result = getPaginated(items, page);
  return Response.json(removeReadmeContent(result), { headers: CORS_HEADERS });
}

function handleSingleItem(
  items: Repo[],
  owner: string,
  repo: string,
  repoFrom: string | null = null
): Response {
  const found = items.find(
    (item) =>
      item.full_name?.toLowerCase() === `${owner}/${repo}` &&
      (repoFrom === null || item.repo_from?.toLowerCase() === repoFrom)
  );

  if (found) {
    // Return the full item, including readme_content, for single item requests
    return Response.json(found, { status: 200, headers: CORS_HEADERS });
  }
  return Response.json(
    { error: "Item not found" },
    { status: 404, headers: CORS_HEADERS }
  );
}

function handleIndexDetails(
  sortedData: { latest: Repo[]; mostUsed: Repo[] },
  searchParams: URLSearchParams
): Response {
  const section = searchParams.get("section");
  if (section !== "latestRepos" && section !== "mostUsed") {
    return Response.json(
      { error: "Invalid section. Must be 'latestRepos' or 'mostUsed'." },
      { status: 400, headers: CORS_HEADERS }
    );
  }

  const sortKey = section === "latestRepos" ? "latest" : "mostUsed";
  const data = sortedData[sortKey];
  const [start, end] = parseRange(searchParams.get("range"), data.length);
  const result = data.slice(start, end);
  return Response.json(removeReadmeContent(result), { headers: CORS_HEADERS });
}

// --- Router Mapping ---
const routes: Record<
  string,
  (url: URL) => Promise<Response> | Response
> = {
  "/api/searchPackages": (url) =>
    handleSearch(dataStore.packages, url.searchParams),
  "/api/searchPrograms": (url) =>
    handleSearch(dataStore.programs, url.searchParams),
  "/api/infiniteScrollPackages": (url) =>
    handleInfiniteScroll(dataStore.packages, url.searchParams),
  "/api/infiniteScrollPrograms": (url) =>
    handleInfiniteScroll(dataStore.programs, url.searchParams),
  "/api/indexDetailsPackages": (url) =>
    handleIndexDetails(dataStore.sortedPackages, url.searchParams),
  "/api/indexDetailsPrograms": (url) =>
    handleIndexDetails(dataStore.sortedPrograms, url.searchParams),
};

// --- Server ---
serve({
  port: PORT,
  async fetch(req) {
    const url = new URL(req.url);
    const { pathname, searchParams } = url;

    // Handle CORS preflight
    if (req.method === "OPTIONS") {
      return new Response(null, {
        status: 204,
        headers: {
          ...CORS_HEADERS,
          "Access-Control-Allow-Methods": "GET, POST, OPTIONS",
          "Access-Control-Allow-Headers": "Content-Type",
        },
      });
    }

    // Ensure data is loaded/refreshed before handling requests
    await ensureDataLoaded();

    // Direct route match
    if (routes[pathname]) {
      return routes[pathname](url);
    }

    // Regex-based routes for single items
    const programMatch = pathname.match(
      /^\/api\/programs\/([^/]+)\/([^/]+)\/([^/]+)$/
    );
    if (programMatch) {
      const repo_from = programMatch[1]?.toLowerCase() ?? "";
      const owner = programMatch[2]?.toLowerCase() ?? "";
      const repo = programMatch[3]?.toLowerCase() ?? "";
      return handleSingleItem(dataStore.programs, owner, repo, repo_from);
    }

    const packageMatch = pathname.match(
      /^\/api\/packages\/([^/]+)\/([^/]+)\/([^/]+)$/
    );
    if (packageMatch) {
      const repo_from = packageMatch[1]?.toLowerCase() ?? "";
      const owner = packageMatch[2]?.toLowerCase() ?? "";
      const repo = packageMatch[3]?.toLowerCase() ?? "";
      return handleSingleItem(dataStore.packages, owner, repo, repo_from);
    }

    // Not found
    return new Response("Not Found", {
      status: 404,
      headers: CORS_HEADERS,
    });
  },
});

console.log(`Server running on http://localhost:${PORT}`);