// js/storage/s3-multipart.js

import { requireAwsSdk } from "./s3-client.js";
import logger from "../utils/logger.js";

const DEFAULT_CACHE_CONTROL = "public, max-age=3600";

function normalizeRegion(region) {
  if (!region) {
    return "";
  }
  const trimmed = String(region).trim();
  if (!trimmed || trimmed.toLowerCase() === "auto") {
    return "";
  }
  return trimmed;
}

function getCreateBucketConfig(region) {
  const normalized = normalizeRegion(region);
  if (!normalized || normalized === "us-east-1") {
    return {};
  }
  return {
    CreateBucketConfiguration: {
      LocationConstraint: normalized,
    },
  };
}

// Exported for tests. Upload keys are content-addressed (buildR2Key namespaces
// by the file's infohash), so media at a given key never changes — a long
// immutable Cache-Control is safe and makes browsers keep thumbnails/avatars/
// videos across visits instead of re-fetching them. Playlists (m3u8/mpd) stay
// short-lived because live/HLS manifests DO mutate in place.
export function computeCacheControl(key) {
  if (!key) {
    return DEFAULT_CACHE_CONTROL;
  }

  const lower = String(key).toLowerCase();
  if (/(?:\.)(m3u8|mpd)$/.test(lower)) {
    return "public, max-age=60, must-revalidate";
  }

  if (
    /\.(m4s|ts|mp4|webm|mov|mkv|png|jpg|jpeg|gif|svg|webp|avif|ico|vtt|srt|mpg|mpeg|torrent)$/.test(
      lower
    )
  ) {
    return "public, max-age=31536000, immutable";
  }

  return DEFAULT_CACHE_CONTROL;
}

export async function ensureBucketExists({ s3, bucket, region } = {}) {
  if (!s3) {
    throw new Error("S3 client is required to ensure buckets");
  }
  if (!bucket) {
    throw new Error("Bucket name is required to ensure buckets");
  }

  const { CreateBucketCommand, HeadBucketCommand } = requireAwsSdk();

  try {
    await s3.send(new HeadBucketCommand({ Bucket: bucket }));
    return;
  } catch (error) {
    const status = error?.$metadata?.httpStatusCode || 0;
    const code = error?.name || error?.Code || "";
    if (status !== 404 && code !== "NotFound" && code !== "NoSuchBucket") {
      throw error;
    }
  }

  try {
    await s3.send(
      new CreateBucketCommand({
        Bucket: bucket,
        ...getCreateBucketConfig(region),
      })
    );
  } catch (error) {
    const status = error?.$metadata?.httpStatusCode || 0;
    const code = error?.name || error?.Code || "";
    if (
      status === 409 ||
      code === "BucketAlreadyOwnedByYou" ||
      code === "BucketAlreadyExists"
    ) {
      return;
    }
    throw error;
  }
}

export async function ensureBucketCors({ s3, bucket, origins, region } = {}) {
  if (!s3) {
    throw new Error("S3 client is required to configure CORS");
  }
  if (!bucket) {
    throw new Error("Bucket name is required to configure CORS");
  }

  const allowedOrigins = [...new Set((origins || []).filter(Boolean))];
  if (allowedOrigins.length === 0) {
    return;
  }

  const { GetBucketCorsCommand, PutBucketCorsCommand } = requireAwsSdk();
  await ensureBucketExists({ s3, bucket, region });

  let existingRules;
  try {
    const response = await s3.send(new GetBucketCorsCommand({ Bucket: bucket }));
    existingRules = response.CORSRules || [];
  } catch (error) {
    // A denied or failed read must never turn into a destructive replacement.
    if (error?.name !== "NoSuchCORSConfiguration") {
      throw error;
    }
    existingRules = [];
  }

  const defaultRule = {
    AllowedHeaders: ["*"],
    AllowedMethods: ["GET", "HEAD", "PUT", "POST", "DELETE", "OPTIONS"],
    ExposeHeaders: ["ETag", "Content-Length", "Content-Range", "Accept-Ranges"],
    MaxAgeSeconds: 3600,
  };
  const equivalentRules = existingRules.filter((rule) =>
    // Only explicit origins in equivalent default rules count as coverage.
    // Arbitrary rules (including wildcard rules) remain completely untouched.
    Object.keys(rule).every((key) =>
      key === "AllowedOrigins" || key === "ID" || key in defaultRule
    ) &&
    rule.MaxAgeSeconds === defaultRule.MaxAgeSeconds &&
    ["AllowedHeaders", "AllowedMethods", "ExposeHeaders"].every((key) =>
      Array.isArray(rule[key]) &&
      rule[key].length === defaultRule[key].length &&
      defaultRule[key].every((value) => rule[key].includes(value))
    )
  );
  const uncoveredOrigins = allowedOrigins.filter((origin) =>
    !equivalentRules.some((rule) => rule.AllowedOrigins?.includes(origin))
  );
  if (uncoveredOrigins.length === 0) {
    return;
  }

  const command = new PutBucketCorsCommand({
    Bucket: bucket,
    CORSConfiguration: {
      CORSRules: [
        ...existingRules,
        { ...defaultRule, AllowedOrigins: uncoveredOrigins },
      ],
    },
  });

  await s3.send(command);
}

export async function deleteObject({ s3, bucket, key } = {}) {
  if (!s3 || !bucket || !key) {
    throw new Error("Missing required parameters for deleteObject");
  }

  const { DeleteObjectCommand } = requireAwsSdk();

  try {
    await s3.send(
      new DeleteObjectCommand({
        Bucket: bucket,
        Key: key,
      })
    );
  } catch (error) {
    // We treat 404 (NoSuchKey) as success since the object is gone.
    const status = error?.$metadata?.httpStatusCode || 0;
    const code = error?.name || error?.Code || "";
    if (status !== 404 && code !== "NoSuchKey") {
      throw error;
    }
  }
}

/**
 * List object keys under a prefix, following pagination. Returns plain key
 * strings. `maxKeys` is a safety cap so an enormous bucket can't run unbounded.
 */
export async function listObjects({ s3, bucket, prefix = "", maxKeys = 5000 } = {}) {
  if (!s3 || !bucket) {
    throw new Error("Missing required parameters for listObjects");
  }

  const { ListObjectsV2Command } = requireAwsSdk();
  const keys = [];
  let continuationToken;

  do {
    const response = await s3.send(
      new ListObjectsV2Command({
        Bucket: bucket,
        Prefix: prefix || undefined,
        ContinuationToken: continuationToken,
      })
    );
    const contents = Array.isArray(response?.Contents) ? response.Contents : [];
    for (const item of contents) {
      if (item && typeof item.Key === "string" && item.Key) {
        keys.push(item.Key);
      }
    }
    continuationToken = response?.IsTruncated
      ? response.NextContinuationToken
      : undefined;
  } while (continuationToken && keys.length < maxKeys);

  return keys;
}

export async function multipartUpload({
  s3,
  bucket,
  key,
  file,
  contentType,
  onProgress,
  createBucketIfMissing = false,
  region,
} = {}) {
  if (!s3) {
    throw new Error("S3 client is required");
  }
  if (!bucket) {
    throw new Error("Bucket is required");
  }
  if (!key) {
    throw new Error("Object key is required");
  }
  if (!file) {
    throw new Error("File is required");
  }
  // A 0-byte file produces a multipart upload with zero parts, which S3/R2
  // rejects with a cryptic CompleteMultipartUpload error. Fail fast and clearly.
  if (typeof file.size === "number" && file.size === 0) {
    throw new Error("File is empty (0 bytes). Choose a non-empty file to upload.");
  }

  const {
    CreateMultipartUploadCommand,
    UploadPartCommand,
    CompleteMultipartUploadCommand,
    AbortMultipartUploadCommand,
  } = requireAwsSdk();

  if (createBucketIfMissing) {
    try {
      await ensureBucketExists({ s3, bucket, region });
    } catch (error) {
      logger.dev.warn(
        "[S3 multipart] Bucket creation check failed, continuing anyway.",
        error
      );
    }
  }

  logger.dev.debug("[S3 multipart] Starting multipart upload for:", key);

  const createCommand = new CreateMultipartUploadCommand({
    Bucket: bucket,
    Key: key,
    ContentType: contentType || file.type || "application/octet-stream",
    CacheControl: computeCacheControl(key),
  });

  const { UploadId } = await s3.send(createCommand);

  if (!UploadId) {
    throw new Error("Failed to start multipart upload");
  }

  const MIN_PART = 5 * 1024 * 1024;
  const maxParts = 10000;
  const calculated = Math.ceil(file.size / maxParts);
  const partSize = Math.max(MIN_PART, calculated);
  const total = file.size;
  const parts = [];
  let uploadedBytes = 0;
  let partNumber = 1;

  if (typeof onProgress === "function") {
    onProgress(0);
  }

  try {
    while (uploadedBytes < total) {
      const start = uploadedBytes;
      const end = Math.min(start + partSize, total);
      const chunk = file.slice(start, end);

      const { ETag } = await s3.send(
        new UploadPartCommand({
          Bucket: bucket,
          Key: key,
          UploadId,
          PartNumber: partNumber,
          Body: chunk,
        })
      );

      parts.push({ ETag, PartNumber: partNumber });
      uploadedBytes = end;
      partNumber += 1;

      if (typeof onProgress === "function") {
        onProgress(uploadedBytes / total);
      }
    }

    await s3.send(
      new CompleteMultipartUploadCommand({
        Bucket: bucket,
        Key: key,
        UploadId,
        MultipartUpload: { Parts: parts },
      })
    );
  } catch (error) {
    await s3
      .send(
        new AbortMultipartUploadCommand({
          Bucket: bucket,
          Key: key,
          UploadId,
        })
      )
      .catch(() => {});
    throw error;
  }
}