interface Env {
  CONTENT_VAULT: R2Bucket;
  HF_WEBHOOK_SECRET: string;
  HF_TOKEN: string;
  HF_REPO: string;
  HF_BASE_URL: string;
}

interface HFTreeItem {
  type: string;
  path: string;
  size?: number;
}

interface HFWebhookPayload {
  event: { action: string; scope: string };
  repo: { name: string; type: string };
  updatedRefs?: Array<{ ref: string; oldSha: string; newSha: string }>;
}

const CONTENT_TYPES: Record<string, string> = {
  ".zip": "application/zip",
  ".yaml": "text/yaml",
  ".yml": "text/yaml",
  ".png": "image/png",
  ".jpg": "image/jpeg",
  ".jpeg": "image/jpeg",
  ".json": "application/json",
  ".md": "text/markdown",
  ".txt": "text/plain",
};

function getContentType(path: string): string {
  const ext = path.slice(path.lastIndexOf(".")).toLowerCase();
  return CONTENT_TYPES[ext] || "application/octet-stream";
}

function encodeFilePath(filePath: string): string {
  return filePath.split("/").map(encodeURIComponent).join("/");
}

async function listRepoFiles(baseUrl: string, repo: string, token: string): Promise<string[]> {
  const files: string[] = [];

  async function fetchTree(path: string) {
    const url = `${baseUrl}/api/models/${repo}/tree/main${path ? "/" + path : ""}`;
    const resp = await fetch(url, {
      headers: token ? { Authorization: `Bearer ${token}` } : {},
    });
    if (!resp.ok) {
      throw new Error(`Failed to list ${url}: ${resp.status} ${resp.statusText}`);
    }
    const items: HFTreeItem[] = await resp.json();
    for (const item of items) {
      if (item.type === "file") {
        files.push(item.path);
      } else if (item.type === "directory") {
        await fetchTree(item.path);
      }
    }
  }

  await fetchTree("");
  return files;
}

async function getChangedFiles(
  baseUrl: string,
  repo: string,
  token: string,
  newSha: string,
): Promise<{ added: string[]; deleted: string[] }> {
  const url = `${baseUrl}/${repo}/commit/${newSha}.diff`;
  const resp = await fetch(url, {
    headers: token ? { Authorization: `Bearer ${token}` } : {},
  });

  if (!resp.ok) {
    console.log(`Failed to get diff for ${newSha}: ${resp.status}, falling back to full sync`);
    return { added: [], deleted: [] };
  }

  const diff = await resp.text();
  const added: string[] = [];
  const deleted: string[] = [];

  for (const match of diff.matchAll(/^diff --git a\/(.+) b\/(.+)$/gm)) {
    added.push(match[2]);
  }

  // Detect deleted files: "deleted file mode" after the diff --git line
  const lines = diff.split("\n");
  for (let i = 0; i < lines.length; i++) {
    const diffMatch = lines[i].match(/^diff --git a\/(.+) b\/(.+)$/);
    if (diffMatch && i + 1 < lines.length && lines[i + 1].startsWith("deleted file mode")) {
      deleted.push(diffMatch[2]);
      // Remove from added since it's a deletion
      const idx = added.indexOf(diffMatch[2]);
      if (idx !== -1) added.splice(idx, 1);
    }
  }

  return { added, deleted };
}

async function syncFile(
  env: Env,
  filePath: string,
): Promise<{ path: string; status: string }> {
  const url = `${env.HF_BASE_URL}/${env.HF_REPO}/resolve/main/${encodeFilePath(filePath)}`;
  const resp = await fetch(url, {
    headers: env.HF_TOKEN ? { Authorization: `Bearer ${env.HF_TOKEN}` } : {},
  });

  if (!resp.ok) {
    return { path: filePath, status: `error: ${resp.status}` };
  }

  const body = resp.body ?? (await resp.arrayBuffer());

  await env.CONTENT_VAULT.put(filePath, body, {
    httpMetadata: {
      contentType: getContentType(filePath),
      cacheControl: "public, max-age=2592000",
    },
  });

  return { path: filePath, status: "ok" };
}

async function deleteFile(
  env: Env,
  filePath: string,
): Promise<{ path: string; status: string }> {
  await env.CONTENT_VAULT.delete(filePath);
  return { path: filePath, status: "deleted" };
}

const SKIP = (f: string) => f.startsWith(".git") || f === ".env" || f.startsWith("worker/");

const CONCURRENCY = 5;

async function runBatch<T>(items: T[], fn: (item: T) => Promise<void>): Promise<void> {
  const queue = [...items];
  const workers = Array.from({ length: Math.min(CONCURRENCY, queue.length) }, async () => {
    while (queue.length > 0) {
      const item = queue.shift()!;
      await fn(item);
    }
  });
  await Promise.all(workers);
}

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    if (request.method !== "POST") {
      return new Response("Method not allowed", { status: 405 });
    }

    const secret = request.headers.get("X-Webhook-Secret");
    if (!secret || secret !== env.HF_WEBHOOK_SECRET) {
      return new Response("Unauthorized", { status: 401 });
    }

    const payload: HFWebhookPayload = await request.json();
    console.log("Webhook event:", JSON.stringify(payload.event));

    const updatedRefs = payload.updatedRefs || [];
    const mainRef = updatedRefs.find((r) => r.ref === "refs/heads/main");

    ctx.waitUntil(
      (async () => {
        try {
          let filesToSync: string[] = [];
          let filesToDelete: string[] = [];

          if (mainRef) {
            const { added, deleted } = await getChangedFiles(
              env.HF_BASE_URL,
              env.HF_REPO,
              env.HF_TOKEN,
              mainRef.newSha,
            );

            if (added.length > 0 || deleted.length > 0) {
              filesToSync = added.filter((f) => !SKIP(f));
              filesToDelete = deleted.filter((f) => !SKIP(f));
              console.log(`Incremental sync: ${filesToSync.length} to sync, ${filesToDelete.length} to delete`);
            } else {
              const allFiles = await listRepoFiles(env.HF_BASE_URL, env.HF_REPO, env.HF_TOKEN);
              filesToSync = allFiles.filter((f) => !SKIP(f));
              console.log(`Full sync fallback: ${filesToSync.length} files`);
            }
          } else {
            const allFiles = await listRepoFiles(env.HF_BASE_URL, env.HF_REPO, env.HF_TOKEN);
            filesToSync = allFiles.filter((f) => !SKIP(f));
            console.log(`Full sync: ${filesToSync.length} files`);
          }

          await runBatch(filesToDelete, async (file) => {
            const result = await deleteFile(env, file);
            console.log(`${result.path}: ${result.status}`);
          });

          await runBatch(filesToSync, async (file) => {
            const result = await syncFile(env, file);
            console.log(`${result.path}: ${result.status}`);
          });

          console.log(`Sync complete: ${filesToSync.length} synced, ${filesToDelete.length} deleted`);
        } catch (err: unknown) {
          const message = err instanceof Error ? err.message : "Unknown error";
          console.error("Sync failed:", message);
        }
      })()
    );

    return new Response(JSON.stringify({ status: "sync started" }), {
      headers: { "Content-Type": "application/json" },
    });
  },
};