export function base64ToBlob(base64: string, mimeType: string = 'image/png'): Blob {
  const byteCharacters = atob(base64);
  const byteNumbers = new Array(byteCharacters.length);
  
  for (let i = 0; i < byteCharacters.length; i++) {
    byteNumbers[i] = byteCharacters.charCodeAt(i);
  }
  
  const byteArray = new Uint8Array(byteNumbers);
  return new Blob([byteArray], { type: mimeType });
}

export function blobToBase64(blob: Blob): Promise<string> {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = () => {
      const result = reader.result as string;
      const base64 = result.split(',')[1]; // Remove data:image/png;base64, prefix
      resolve(base64);
    };
    reader.onerror = reject;
    reader.readAsDataURL(blob);
  });
}

// 将URL转换为Blob
export async function urlToBlob(url: string): Promise<Blob> {
  const response = await fetch(url);
  return await response.blob();
}

export function createImageFromBase64(base64: string): Promise<HTMLImageElement> {
  return new Promise((resolve, reject) => {
    const img = new Image();
    img.onload = () => resolve(img);
    img.onerror = reject;
    img.src = `data:image/png;base64,${base64}`;
  });
}

export function resizeImageToFit(
  image: HTMLImageElement, 
  maxWidth: number, 
  maxHeight: number
): { width: number; height: number } {
  const ratio = Math.min(maxWidth / image.width, maxHeight / image.height);
  return {
    width: image.width * ratio,
    height: image.height * ratio
  };
}

export function generateId(): string {
  return `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
}

export function downloadImage(imageData: string, filename: string): void {
  if (imageData.startsWith('blob:')) {
    // 对于Blob URL，我们需要获取实际的Blob数据
    fetch(imageData)
      .then(response => response.blob())
      .then(blob => {
        const url = URL.createObjectURL(blob);
        const a = document.createElement('a');
        a.href = url;
        a.download = filename;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        URL.revokeObjectURL(url);
      });
  } else if (imageData.startsWith('data:')) {
    // 对于数据URL，直接下载
    const a = document.createElement('a');
    a.href = imageData;
    a.download = filename;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
  } else {
    // 对于其他URL，获取并转换为blob
    fetch(imageData)
      .then(response => response.blob())
      .then(blob => {
        const url = URL.createObjectURL(blob);
        const a = document.createElement('a');
        a.href = url;
        a.download = filename;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        URL.revokeObjectURL(url);
      });
  }
}

// 优化的图像压缩函数
export async function compressImage(blob: Blob, quality: number = 0.8): Promise<Blob> {
  return new Promise((resolve, reject) => {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    
    if (!ctx) {
      reject(new Error('无法获取canvas上下文'));
      return;
    }
    
    const img = new Image();
    img.onload = () => {
      // 设置canvas尺寸
      canvas.width = img.width;
      canvas.height = img.height;
      
      // 绘制图像
      ctx.drawImage(img, 0, 0);
      
      // 转换为Blob
      canvas.toBlob(
        (compressedBlob) => {
          if (compressedBlob) {
            resolve(compressedBlob);
          } else {
            reject(new Error('图像压缩失败'));
          }
        },
        'image/jpeg',
        quality
      );
    };
    
    img.onerror = reject;
    
    // 将Blob转换为URL以便加载到图像中
    const url = URL.createObjectURL(blob);
    img.src = url;
    
    // 清理URL
    img.onload = () => {
      URL.revokeObjectURL(url);
      // 调用原始的onload处理程序
      if (img.onload) {
        (img.onload as (() => void)).call(img);
      }
    };
  });
}