import Accelerate
import Flutter
import MobileCoreServices
import Photos

class LocalImageApiImpl: LocalImageApi {
  private static let imageManager = PHImageManager.default()
  private static let fetchOptions = {
    let fetchOptions = PHFetchOptions()
    fetchOptions.fetchLimit = 1
    fetchOptions.wantsIncrementalChangeDetails = false
    return fetchOptions
  }()
  private static let requestOptions = {
    let requestOptions = PHImageRequestOptions()
    requestOptions.isNetworkAccessAllowed = true
    requestOptions.deliveryMode = .highQualityFormat
    requestOptions.resizeMode = .fast
    requestOptions.isSynchronous = true
    requestOptions.version = .current
    return requestOptions
  }()

  private static let registry = RequestRegistry<ImageRequest>()

  private static let rgbaFormat = vImage_CGImageFormat(
    bitsPerComponent: 8,
    bitsPerPixel: 32,
    colorSpace: CGColorSpaceCreateDeviceRGB(),
    bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue),
    renderingIntent: .defaultIntent
  )!
  private static let assetCache = {
    let assetCache = NSCache<NSString, PHAsset>()
    assetCache.countLimit = 10000
    return assetCache
  }()

  func getThumbhash(thumbhash: String, completion: @escaping (Result<[String : Int64], any Error>) -> Void) {
    ImageProcessing.queue.addOperation {
      guard let data = Data(base64Encoded: thumbhash)
      else { return completion(.failure(PigeonError(code: "", message: "Invalid base64 string: \(thumbhash)", details: nil)))}

      let (width, height, pointer) = thumbHashToRGBA(hash: data)
      completion(.success([
        "pointer": Int64(Int(bitPattern: pointer.baseAddress)),
        "width": Int64(width),
        "height": Int64(height),
        "rowBytes": Int64(width * 4)
      ]))
    }
  }

  func requestImage(assetId: String, requestId: Int64, width: Int64, height: Int64, isVideo: Bool, preferEncoded: Bool, completion: @escaping (Result<[String: Int64]?, any Error>) -> Void) {
    let request = ImageRequest(completion: completion)
    let operation = BlockOperation {
      if request.isCancelled {
        return request.completion(ImageProcessing.cancelledResult)
      }

      guard let asset = Self.requestAsset(assetId: assetId)
      else {
        Self.registry.remove(requestId: requestId)
        return request.completion(.failure(PigeonError(code: "", message: "Could not get asset data for \(assetId)", details: nil)))
      }

      if request.isCancelled {
        return request.completion(ImageProcessing.cancelledResult)
      }

      if preferEncoded {
        let dataOptions = PHImageRequestOptions()
        dataOptions.isNetworkAccessAllowed = true
        dataOptions.isSynchronous = true
        dataOptions.version = .current

        var imageData: Data?
        Self.imageManager.requestImageDataAndOrientation(
          for: asset,
          options: dataOptions,
          resultHandler: { (data, _, _, _) in
            imageData = data
          }
        )

        if request.isCancelled {
          return request.completion(ImageProcessing.cancelledResult)
        }

        guard let data = imageData else {
          Self.registry.remove(requestId: requestId)
          return request.completion(.failure(PigeonError(code: "", message: "Could not get image data for \(assetId)", details: nil)))
        }

        let length = data.count
        let pointer = malloc(length)!
        data.copyBytes(to: pointer.assumingMemoryBound(to: UInt8.self), count: length)

        if request.isCancelled {
          free(pointer)
          return request.completion(ImageProcessing.cancelledResult)
        }

        Self.registry.remove(requestId: requestId)
        return request.completion(.success([
          "pointer": Int64(Int(bitPattern: pointer)),
          "length": Int64(length),
        ]))
      }

      var image: UIImage?
      Self.imageManager.requestImage(
        for: asset,
        targetSize: width > 0 && height > 0 ? CGSize(width: Double(width), height: Double(height)) : PHImageManagerMaximumSize,
        contentMode: .aspectFill,
        options: Self.requestOptions,
        resultHandler: { (_image, info) -> Void in
          image = _image
        }
      )

      if request.isCancelled {
        return request.completion(ImageProcessing.cancelledResult)
      }

      guard let image = image,
            let cgImage = image.cgImage else {
        Self.registry.remove(requestId: requestId)
        return request.completion(.failure(PigeonError(code: "", message: "Could not get pixel data for \(assetId)", details: nil)))
      }

      if request.isCancelled {
        return request.completion(ImageProcessing.cancelledResult)
      }

      do {
        let buffer = try vImage_Buffer(cgImage: cgImage, format: Self.rgbaFormat)

        if request.isCancelled {
          buffer.free()
          return request.completion(ImageProcessing.cancelledResult)
        }

        Self.registry.remove(requestId: requestId)
        return request.completion(.success([
          "pointer": Int64(Int(bitPattern: buffer.data)),
          "width": Int64(buffer.width),
          "height": Int64(buffer.height),
          "rowBytes": Int64(buffer.rowBytes),
        ]))
      } catch {
        Self.registry.remove(requestId: requestId)
        return request.completion(.failure(PigeonError(code: "", message: "Failed to convert image for \(assetId): \(error)", details: nil)))
      }
    }

    Self.registry.add(requestId: requestId, request: request)
    ImageProcessing.queue.addOperation(operation)
  }

  func cancelRequest(requestId: Int64) {
    Self.registry.remove(requestId: requestId)?.cancel()
  }

  private static func requestAsset(assetId: String) -> PHAsset? {
    if let cached = assetCache.object(forKey: assetId as NSString) {
      return cached
    }

    guard let asset = PHAsset.fetchAssets(withLocalIdentifiers: [assetId], options: Self.fetchOptions).firstObject
    else { return nil }
    assetCache.setObject(asset, forKey: assetId as NSString)
    return asset
  }
}