/**
 * 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,
} 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";

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}`;
}