/**
 * S3-compatible storage abstraction.
 *
 * STORAGE_PROVIDER env controls which backend is used:
 *   local      – local filesystem (dev only, no CDN)
 *   uploadthing – UploadThing managed (default for quick start)
 *   s3          – AWS S3
 *   r2          – Cloudflare R2
 *   b2          – Backblaze B2 (S3-compatible endpoint)
 *   minio       – Self-hosted MinIO
 */

import {
  S3Client,
  PutObjectCommand,
  DeleteObjectCommand,
  GetObjectCommand,
  ListObjectsV2Command,
  HeadObjectCommand,
} from "@aws-sdk/client-s3";
import { getSignedUrl } from "@aws-sdk/s3-request-presigner";
import fs from "fs";
import path from "path";
import { randomUUID } from "crypto";
import { db } from "@/lib/db";

export type StorageProvider = "local" | "uploadthing" | "s3" | "r2" | "b2" | "minio";

function getProvider(): StorageProvider {
  return (process.env.STORAGE_PROVIDER as StorageProvider) ?? "uploadthing";
}

// ── S3 Client factory ────────────────────────────────────────────────────────

function buildS3Client(): S3Client {
  const provider = getProvider();

  if (provider === "r2") {
    return new S3Client({
      region: "auto",
      endpoint: `https://${process.env.R2_ACCOUNT_ID!}.r2.cloudflarestorage.com`,
      credentials: {
        accessKeyId: process.env.R2_ACCESS_KEY_ID!,
        secretAccessKey: process.env.R2_SECRET_ACCESS_KEY!,
      },
    });
  }

  if (provider === "b2") {
    return new S3Client({
      region: "auto",
      endpoint: process.env.B2_ENDPOINT!,
      credentials: {
        accessKeyId: process.env.B2_APPLICATION_KEY_ID!,
        secretAccessKey: process.env.B2_APPLICATION_KEY!,
      },
    });
  }

  if (provider === "minio") {
    return new S3Client({
      region: "us-east-1",
      endpoint: process.env.MINIO_ENDPOINT ?? "http://localhost:9000",
      forcePathStyle: true,
      credentials: {
        accessKeyId: process.env.MINIO_ACCESS_KEY!,
        secretAccessKey: process.env.MINIO_SECRET_KEY!,
      },
    });
  }

  // Default: AWS S3
  return new S3Client({
    region: process.env.AWS_REGION ?? "us-east-1",
    credentials: {
      accessKeyId: process.env.AWS_ACCESS_KEY_ID!,
      secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY!,
    },
  });
}

function getBucketName(): string {
  const provider = getProvider();
  const map: Record<string, string | undefined> = {
    s3: process.env.AWS_BUCKET_NAME,
    r2: process.env.R2_BUCKET_NAME,
    b2: process.env.B2_BUCKET_NAME,
    minio: process.env.MINIO_BUCKET_NAME,
  };
  return map[provider] ?? "vfx-review";
}

// ── Public API ───────────────────────────────────────────────────────────────

export interface UploadResult {
  url: string;
  key: string;
  provider: StorageProvider;
}

/**
 * Upload a file buffer to the configured storage backend.
 * Returns the public URL and storage key.
 */
export async function uploadFile(
  buffer: Buffer,
  fileName: string,
  contentType: string,
  folder: string = "uploads"
): Promise<UploadResult> {
  const provider = getProvider();
  const key = `${folder}/${randomUUID()}-${fileName}`;

  if (provider === "local") {
    return uploadLocal(buffer, key);
  }

  // All S3-compatible providers share the same logic
  const client = buildS3Client();
  const bucket = getBucketName();

  await client.send(
    new PutObjectCommand({
      Bucket: bucket,
      Key: key,
      Body: buffer,
      ContentType: contentType,
    })
  );

  const url = getPublicUrl(key, provider);
  return { url, key, provider };
}

/**
 * Generate a presigned URL for direct browser-to-storage upload.
 * Expires in 1 hour by default.
 */
export async function generatePresignedUploadUrl(
  key: string,
  contentType: string,
  expiresIn: number = 3600
): Promise<string> {
  const provider = getProvider();
  if (provider === "local" || provider === "uploadthing") {
    // Not applicable for local / uploadthing (use their own flow)
    throw new Error(`Presigned URLs not supported for provider: ${provider}`);
  }

  const client = buildS3Client();
  const command = new PutObjectCommand({
    Bucket: getBucketName(),
    Key: key,
    ContentType: contentType,
  });

  return getSignedUrl(client, command, { expiresIn });
}

/**
 * Generate a presigned download URL for a private object.
 */
export async function generatePresignedDownloadUrl(
  key: string,
  expiresIn: number = 3600
): Promise<string> {
  const provider = getProvider();
  if (provider === "local") {
    return `/api/files/${encodeURIComponent(key)}`;
  }

  const client = buildS3Client();
  const command = new GetObjectCommand({
    Bucket: getBucketName(),
    Key: key,
  });
  return getSignedUrl(client, command, { expiresIn });
}

/**
 * Delete a file from storage by key.
 */
export async function deleteFile(key: string): Promise<void> {
  const provider = getProvider();

  if (provider === "local") {
    const filePath = path.join(process.env.LOCAL_UPLOAD_DIR ?? "./uploads", key);
    if (fs.existsSync(filePath)) fs.unlinkSync(filePath);
    return;
  }

  const client = buildS3Client();
  await client.send(
    new DeleteObjectCommand({ Bucket: getBucketName(), Key: key })
  );
}

// ── Private helpers ──────────────────────────────────────────────────────────

function uploadLocal(buffer: Buffer, key: string): UploadResult {
  const uploadDir = process.env.LOCAL_UPLOAD_DIR ?? "./uploads";
  const filePath = path.join(uploadDir, key);
  const dir = path.dirname(filePath);

  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
  fs.writeFileSync(filePath, buffer);

  const url = `/api/files/${encodeURIComponent(key)}`;
  return { url, key, provider: "local" };
}

function getPublicUrl(key: string, provider: StorageProvider): string {
  if (provider === "r2" && process.env.R2_PUBLIC_URL) {
    return `${process.env.R2_PUBLIC_URL}/${key}`;
  }
  if (provider === "s3") {
    return `https://${process.env.AWS_BUCKET_NAME}.s3.${process.env.AWS_REGION ?? "us-east-1"}.amazonaws.com/${key}`;
  }
  if (provider === "minio") {
    return `${process.env.MINIO_ENDPOINT}/${getBucketName()}/${key}`;
  }
  // Fallback
  return `/${key}`;
}

// ── Hetzner Object Storage (dedicated high-res bucket) ───────────────────────

async function getHetznerConfig(): Promise<{
  endpoint: string;
  accessKey: string;
  secretKey: string;
  bucket: string;
}> {
  const rows = await db.systemConfig.findMany({
    where: { key: { in: ["hetzner_endpoint", "hetzner_access_key", "hetzner_secret_key", "hetzner_bucket_name"] } },
  });
  const map = Object.fromEntries(rows.map((r) => [r.key, r.value]));
  return {
    endpoint:  map["hetzner_endpoint"]    ?? process.env.HETZNER_ENDPOINT    ?? "",
    accessKey: map["hetzner_access_key"]  ?? process.env.HETZNER_ACCESS_KEY  ?? "",
    secretKey: map["hetzner_secret_key"]  ?? process.env.HETZNER_SECRET_KEY  ?? "",
    bucket:    map["hetzner_bucket_name"] ?? process.env.HETZNER_BUCKET_NAME ?? "vfx-review",
  };
}

async function buildHetznerClient(): Promise<{ client: S3Client; bucket: string }> {
  const cfg = await getHetznerConfig();
  const client = new S3Client({
    region: "auto",
    endpoint: cfg.endpoint,
    credentials: {
      accessKeyId: cfg.accessKey,
      secretAccessKey: cfg.secretKey,
    },
  });
  return { client, bucket: cfg.bucket };
}

/**
 * Upload a buffer directly to the Hetzner bucket (always uses Hetzner credentials,
 * regardless of the global STORAGE_PROVIDER setting).
 */
export async function uploadToHetzner(
  buffer: Buffer,
  fileName: string,
  contentType: string,
  folder: string = "highres"
): Promise<{ key: string }> {
  const key = `${folder}/${randomUUID()}-${fileName}`;
  const { client, bucket } = await buildHetznerClient();
  await client.send(
    new PutObjectCommand({
      Bucket: bucket,
      Key: key,
      Body: buffer,
      ContentType: contentType,
    })
  );
  return { key };
}

/**
 * Generate a presigned PUT URL for direct browser-to-Hetzner uploads.
 * The caller must use the returned `key` to commit the upload via the API.
 * Expires in 1 hour by default.
 */
export async function generateHetznerPresignedUploadUrl(
  key: string,
  contentType: string,
  expiresIn: number = 3600
): Promise<string> {
  const { client, bucket } = await buildHetznerClient();
  const command = new PutObjectCommand({
    Bucket: bucket,
    Key: key,
    ContentType: contentType,
  });
  return getSignedUrl(client, command, { expiresIn });
}

/**
 * In-process cache for Hetzner key existence checks.
 * Positive hits (key exists) are cached indefinitely for the process lifetime
 * since uploaded files are immutable UUID-named objects that never disappear.
 * Negative hits are not cached so newly-migrated files are picked up immediately.
 */
const hetznerExistsCache = new Map<string, true>();

/**
 * Returns true if the given key exists in the Hetzner bucket.
 * Results are cached in process memory after the first check.
 */
export async function hetznerKeyExists(key: string): Promise<boolean> {
  if (hetznerExistsCache.has(key)) return true;
  try {
    const { client, bucket } = await buildHetznerClient();
    await client.send(new HeadObjectCommand({ Bucket: bucket, Key: key }));
    hetznerExistsCache.set(key, true);
    return true;
  } catch {
    return false;
  }
}

/**
 * List all object keys currently stored in the Hetzner bucket.
 * Paginates automatically. Used by the migration tool.
 */
export async function listHetznerKeys(): Promise<Set<string>> {
  const { client, bucket } = await buildHetznerClient();
  const keys = new Set<string>();
  let continuationToken: string | undefined;

  do {
    const resp = await client.send(
      new ListObjectsV2Command({ Bucket: bucket, ContinuationToken: continuationToken })
    );
    for (const obj of resp.Contents ?? []) {
      if (obj.Key) keys.add(obj.Key);
    }
    continuationToken = resp.NextContinuationToken;
  } while (continuationToken);

  return keys;
}

/**
 * Upload a stream directly to Hetzner under an exact key (no UUID prefix).
 * Used by the migration tool to preserve existing file paths.
 */
export async function uploadToHetznerWithKey(
  body: NodeJS.ReadableStream,
  key: string,
  contentType: string,
  contentLength: number
): Promise<void> {
  const { client, bucket } = await buildHetznerClient();
  await client.send(
    new PutObjectCommand({
      Bucket: bucket,
      Key: key,
      Body: body as unknown as Blob,
      ContentType: contentType,
      ContentLength: contentLength,
    })
  );
}

/**
 * Generate a presigned URL for streaming a Hetzner object directly in the browser.
 * No Content-Disposition header — suitable for <video src="..."> playback.
 */
export async function generateHetznerStreamUrl(
  key: string,
  expiresIn: number = 3600
): Promise<string> {
  const { client, bucket } = await buildHetznerClient();
  const command = new GetObjectCommand({ Bucket: bucket, Key: key });
  return getSignedUrl(client, command, { expiresIn });
}

/**
 * Generate a presigned download URL from Hetzner that forces a file download
 * with the original filename preserved via Content-Disposition.
 */
export async function generateHetznerDownloadUrl(
  key: string,
  originalFilename: string,
  expiresIn: number = 3600
): Promise<string> {
  const { client, bucket } = await buildHetznerClient();
  const command = new GetObjectCommand({
    Bucket: bucket,
    Key: key,
    ResponseContentDisposition: `attachment; filename="${originalFilename}"`,
  });
  return getSignedUrl(client, command, { expiresIn });
}

/**
 * Delete a file from the Hetzner bucket by key.
 */
export async function deleteFromHetzner(key: string): Promise<void> {
  const { client, bucket } = await buildHetznerClient();
  await client.send(
    new DeleteObjectCommand({ Bucket: bucket, Key: key })
  );
}