import fs from "fs";
import path from "path";

const TOKEN_PATH = path.join(process.cwd(), "server/dropbox-token.json");
const DROPBOX_FOLDER = "/Folx News Gallery";

interface DropboxTokens {
  access_token: string;
  refresh_token: string;
  expires_at: number;
}

interface GalleryImage {
  folder: string;
  fileName: string;
  thumb: string;
  large: string;
  full: string;
}

function getAppKey(): string {
  return process.env.DROPBOX_APP_KEY || "";
}

function getAppSecret(): string {
  return process.env.DROPBOX_APP_SECRET || "";
}

export function getAuthUrl(redirectUri: string): string {
  const params = new URLSearchParams({
    client_id: getAppKey(),
    response_type: "code",
    redirect_uri: redirectUri,
    token_access_type: "offline",
  });
  return `https://www.dropbox.com/oauth2/authorize?${params.toString()}`;
}

export async function exchangeCodeForTokens(code: string, redirectUri: string): Promise<DropboxTokens> {
  const resp = await fetch("https://api.dropboxapi.com/oauth2/token", {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({
      code,
      grant_type: "authorization_code",
      redirect_uri: redirectUri,
      client_id: getAppKey(),
      client_secret: getAppSecret(),
    }),
  });

  if (!resp.ok) {
    const err = await resp.text();
    throw new Error(`Token exchange failed: ${err}`);
  }

  const data = await resp.json();
  const tokens: DropboxTokens = {
    access_token: data.access_token,
    refresh_token: data.refresh_token,
    expires_at: Date.now() + data.expires_in * 1000,
  };

  fs.writeFileSync(TOKEN_PATH, JSON.stringify(tokens, null, 2));
  return tokens;
}

function loadTokens(): DropboxTokens | null {
  try {
    if (fs.existsSync(TOKEN_PATH)) {
      return JSON.parse(fs.readFileSync(TOKEN_PATH, "utf-8"));
    }
  } catch {}
  return null;
}

async function refreshAccessToken(refreshToken: string): Promise<DropboxTokens> {
  const resp = await fetch("https://api.dropboxapi.com/oauth2/token", {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({
      grant_type: "refresh_token",
      refresh_token: refreshToken,
      client_id: getAppKey(),
      client_secret: getAppSecret(),
    }),
  });

  if (!resp.ok) {
    const err = await resp.text();
    throw new Error(`Token refresh failed: ${err}`);
  }

  const data = await resp.json();
  const tokens: DropboxTokens = {
    access_token: data.access_token,
    refresh_token: refreshToken,
    expires_at: Date.now() + data.expires_in * 1000,
  };

  fs.writeFileSync(TOKEN_PATH, JSON.stringify(tokens, null, 2));
  return tokens;
}

async function getValidAccessToken(): Promise<string | null> {
  let tokens = loadTokens();
  if (!tokens) return null;

  if (Date.now() > tokens.expires_at - 60000) {
    tokens = await refreshAccessToken(tokens.refresh_token);
  }

  return tokens.access_token;
}

export function isConnected(): boolean {
  return loadTokens() !== null;
}

async function listFolder(accessToken: string, folderPath: string): Promise<any[]> {
  const entries: any[] = [];
  let cursor: string | null = null;
  let hasMore = true;

  while (hasMore) {
    const url = cursor
      ? "https://api.dropboxapi.com/2/files/list_folder/continue"
      : "https://api.dropboxapi.com/2/files/list_folder";

    const body = cursor
      ? { cursor }
      : { path: folderPath, recursive: false, limit: 2000 };

    const resp = await fetch(url, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${accessToken}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify(body),
    });

    if (!resp.ok) {
      const err = await resp.text();
      throw new Error(`List folder failed: ${err}`);
    }

    const data = await resp.json();
    entries.push(...data.entries);
    hasMore = data.has_more;
    cursor = data.cursor;
  }

  return entries;
}

async function getThumbnailBatch(accessToken: string, paths: string[]): Promise<Map<string, string>> {
  const results = new Map<string, string>();
  const batchSize = 25;

  for (let i = 0; i < paths.length; i += batchSize) {
    const batch = paths.slice(i, i + batchSize);
    const entries = batch.map((p) => ({
      path: p,
      format: "jpeg",
      size: "w256h256",
      mode: "fitone_bestfit",
    }));

    try {
      const resp = await fetch("https://content.dropboxapi.com/2/files/get_thumbnail_batch", {
        method: "POST",
        headers: {
          Authorization: `Bearer ${accessToken}`,
          "Content-Type": "application/json",
        },
        body: JSON.stringify({ entries }),
      });

      if (resp.ok) {
        const data = await resp.json();
        for (const entry of data.entries) {
          if (entry[".tag"] === "success") {
            results.set(entry.metadata.path_lower, `data:image/jpeg;base64,${entry.thumbnail}`);
          }
        }
      }
    } catch {}
  }

  return results;
}

async function getTemporaryLinks(accessToken: string, paths: string[]): Promise<Map<string, string>> {
  const results = new Map<string, string>();

  for (const p of paths) {
    try {
      const resp = await fetch("https://api.dropboxapi.com/2/files/get_temporary_link", {
        method: "POST",
        headers: {
          Authorization: `Bearer ${accessToken}`,
          "Content-Type": "application/json",
        },
        body: JSON.stringify({ path: p }),
      });

      if (resp.ok) {
        const data = await resp.json();
        results.set(p.toLowerCase(), data.link);
      }
    } catch {}
  }

  return results;
}

const galleryCache: { data: GalleryImage[]; timestamp: number } = { data: [], timestamp: 0 };
const CACHE_DURATION = 30 * 60 * 1000;

export async function fetchGalleryFromDropbox(): Promise<GalleryImage[]> {
  if (galleryCache.data.length > 0 && Date.now() - galleryCache.timestamp < CACHE_DURATION) {
    return galleryCache.data;
  }

  const accessToken = await getValidAccessToken();
  if (!accessToken) return [];

  try {
    const topEntries = await listFolder(accessToken, DROPBOX_FOLDER);
    const folders = topEntries.filter((e: any) => e[".tag"] === "folder");
    const images: GalleryImage[] = [];

    for (const folder of folders) {
      const folderName = folder.name;
      const folderEntries = await listFolder(accessToken, folder.path_lower);
      const imageFiles = folderEntries.filter(
        (e: any) => e[".tag"] === "file" && /\.(jpg|jpeg|png|webp|gif)$/i.test(e.name)
      );

      const paths = imageFiles.map((f: any) => f.path_lower);
      const tempLinks = await getTemporaryLinks(accessToken, paths);

      for (const file of imageFiles) {
        const link = tempLinks.get(file.path_lower) || "";
        images.push({
          folder: folderName,
          fileName: file.name,
          thumb: link ? `${link}&size=256x256` : "",
          large: link,
          full: link,
        });
      }
    }

    galleryCache.data = images;
    galleryCache.timestamp = Date.now();

    const galleryPath = path.join(process.cwd(), "server/gallery-data.json");
    fs.writeFileSync(galleryPath, JSON.stringify(images, null, 2));

    return images;
  } catch (err: any) {
    console.error("Dropbox gallery fetch error:", err.message);
    return [];
  }
}