// 分片切割邏輯
const chunkSize = 2 * 1024 * 1024 // 2MB分片
const totalChunks = Math.ceil(file.size / chunkSize)

for (let chunkNumber = 1; chunkNumber <= totalChunks; chunkNumber++) {
  const start = (chunkNumber - 1) * chunkSize
  const end = Math.min(start + chunkSize, file.size)
  const chunk = file.slice(start, end)
  
  // 構(gòu)造分片數(shù)據(jù)包
  const formData = new FormData()
  formData.append('file', chunk)
  formData.append('chunkNumber', chunkNumber)
  formData.append('totalChunks', totalChunks)
}

// 使用Map存儲(chǔ)上傳記錄
uploadedChunksMap = new Map() 

// 上傳前檢查已傳分片
if (!uploadedChunks.has(chunkNumber)) {
  // 執(zhí)行上傳
}

// 上傳成功記錄分片
uploadedChunks.add(chunkNumber)

const maxRetries = 3 // 最大重試次數(shù)
const baseDelay = 1000 // 基礎(chǔ)延遲

// 指數(shù)退避算法
const delay = Math.min(
  baseDelay * Math.pow(2, retries - 1) + Math.random() * 1000, 
  10000
)

createFileIdentifier(file) {
  // 文件名 + 大小 + 時(shí)間戳 生成唯一ID
  return `${file.name}-${file.size}-${new Date().getTime()}`
}

// 實(shí)時(shí)更新進(jìn)度
this.$set(this.uploadProgress, file.name, 
  Math.floor((uploadedChunks.size / totalChunks) * 100))

handleBeforeUpload(file) {
  // 類型校驗(yàn)
  const fileExt = file.name.split('.').pop()
  if (!this.fileType.includes(fileExt)) return false
  
  // 特殊字符校驗(yàn)
  if (file.name.includes(',')) return false
  
  // 大小校驗(yàn)（MB轉(zhuǎn)換）
  return file.size / 1024 / 1024 < this.fileSize
}

// 設(shè)置并行上傳數(shù)
const parallelUploads = 3 
const uploadQueue = []

for (let i=0; i<parallelUploads; i++) {
  uploadQueue.push(uploadNextChunk())
}

await Promise.all(uploadQueue)

// 分片上傳后立即釋放內(nèi)存
chunk = null
formData = null

// 計(jì)算文件哈希值
const fileHash = await calculateMD5(file)


// 查詢服務(wù)器是否存在相同文件
const res = await checkFileExist(fileHash)
if (res.exist) {
  this.handleUploadSuccess(res)
  return
}

<template>
  <div class="upload-file">
    <el-upload
      multiple
      :action="'#'"
      :http-request="customUpload"
      :before-upload="handleBeforeUpload"
      :file-list="fileList"
      :limit="limit"
      :on-error="handleUploadError"
      :on-exceed="handleExceed"
      :on-success="handleUploadSuccess"
      :show-file-list="false"
      :headers="headers"
      class="upload-file-uploader"
      ref="fileUpload"
      v-if="!disabled"
    >
      <!-- 上傳按鈕 -->
      <el-button size="mini" type="primary">選取文件</el-button>
      <!-- 上傳提示 -->
      <div class="el-upload__tip" slot="tip" v-if="showTip">
        請(qǐng)上傳
        <template v-if="fileSize">
          大小不超過(guò) <b style="color: #f56c6c">{{ fileSize }}MB</b>
        </template>
        <template v-if="fileType.length > 0">
          格式為 <b style="color: #f56c6c">{{ fileType.join("/") }}</b>
        </template>
        的文件
      </div>
    </el-upload>

    <!-- 文件列表 -->
    <transition-group
      class="upload-file-list el-upload-list el-upload-list--text"
      name="el-fade-in-linear"
      tag="ul"
    >
      <li
        :key="file.url"
        class="el-upload-list__item ele-upload-list__item-content"
        v-for="(file, index) in fileList"
      >
        <el-link
          :href="`${baseUrl}${file.url}`" rel="external nofollow" 
          :underline="false"
          target="_blank"
        >
          <span class="el-icon-document"> {{ getFileName(file.name) }} </span>
        </el-link>
        <div class="ele-upload-list__item-content-action">
          <el-link
            :underline="false"
            @click="handleDelete(index)"
            type="danger"
            v-if="!disabled"
            >刪除</el-link
          >
        </div>
      </li>
    </transition-group>
    <!-- 上傳進(jìn)度展示 -->
    <div
      v-for="(progress, fileName) in uploadProgress"
      :key="fileName"
      class="upload-progress"
    >
      <div class="progress-info">
        <span class="file-name">{{ fileName }}</span>
        <span class="percentage">{{ progress }}%</span>
      </div>
      <el-progress :percentage="progress" :show-text="false"></el-progress>
    </div>
  </div>
</template>

<script>
import { getToken } from "@/utils/auth";
import { uploadFileProgress } from "@/api/resource";
export default {
  name: "FileUpload",
  props: {
    // 值
    value: [String, Object, Array],
    // 數(shù)量限制
    limit: {
      type: Number,
      default: 5,
    },
    // 大小限制(MB)
    fileSize: {
      type: Number,
      default: 5,
    },
    // 文件類型, 例如['png', 'jpg', 'jpeg']
    fileType: {
      type: Array,
      default: () => [
        "doc",
        "docx",
        "xls",
        "xlsx",
        "ppt",
        "pptx",
        "txt",
        "pdf",
      ],
    },
    // 是否顯示提示
    isShowTip: {
      type: Boolean,
      default: true,
    },
    // 禁用組件（僅查看文件）
    disabled: {
      type: Boolean,
      default: false,
    },
  },
  data() {
    return {
      number: 0,
      uploadList: [],
      baseUrl: process.env.VUE_APP_BASE_API,
      uploadFileUrl: process.env.VUE_APP_BASE_API + "/common/upload", // 上傳文件服務(wù)器地址
      headers: {
        Authorization: "Bearer " + getToken(),
      },
      fileList: [],
      uploadProgress: {}, // 存儲(chǔ)文件上傳進(jìn)度
      uploadedChunksMap: new Map(), // 新增：存儲(chǔ)每個(gè)文件的已上傳分片記錄
    };
  },
  watch: {
    value: {
      handler(val) {
        if (val) {
          let temp = 1;
          // 首先將值轉(zhuǎn)為數(shù)組
          const list = Array.isArray(val) ? val : this.value.split(",");
          // 然后將數(shù)組轉(zhuǎn)為對(duì)象數(shù)組
          this.fileList = list.map((item) => {
            if (typeof item === "string") {
              item = { name: item, url: item };
            }
            item.uid = item.uid || new Date().getTime() + temp++;
            return item;
          });
        } else {
          this.fileList = [];
          return [];
        }
      },
      deep: true,
      immediate: true,
    },
  },
  computed: {
    // 是否顯示提示
    showTip() {
      return this.isShowTip && (this.fileType || this.fileSize);
    },
  },
  methods: {
    // 上傳前校檢格式和大小
    handleBeforeUpload(file) {
      // 校檢文件類型
      if (this.fileType && this.fileType.length > 0) {
        const fileName = file.name.split(".");
        const fileExt = fileName[fileName.length - 1];
        const isTypeOk = this.fileType.indexOf(fileExt) >= 0;
        if (!isTypeOk) {
          this.$modal.msgError(
            `文件格式不正確，請(qǐng)上傳${this.fileType.join("/")}格式文件!`
          );
          return false;
        }
      }
      // 校檢文件名是否包含特殊字符
      if (file.name.includes(",")) {
        this.$modal.msgError("文件名不正確，不能包含英文逗號(hào)!");
        return false;
      }
      // 校檢文件大小
      if (this.fileSize) {
        const isLt = file.size / 1024 / 1024 < this.fileSize;
        if (!isLt) {
          this.$modal.msgError(`上傳文件大小不能超過(guò) ${this.fileSize} MB!`);
          return false;
        }
      }
      // this.$modal.loading("正在上傳文件，請(qǐng)稍候...");
      this.number++;
      return true;
    },
    // 文件個(gè)數(shù)超出
    handleExceed() {
      this.$modal.msgError(`上傳文件數(shù)量不能超過(guò) ${this.limit} 個(gè)!`);
    },
    // 上傳失敗
    handleUploadError(err) {
      // 確保在上傳錯(cuò)誤時(shí)移除進(jìn)度條
      if (err.file && err.file.name) {
        this.$delete(this.uploadProgress, err.file.name);
      }
      this.$modal.msgError("上傳文件失敗，請(qǐng)重試");
      this.$modal.closeLoading();
    },
    // 上傳成功回調(diào)
    handleUploadSuccess(res, file) {
      if (res.code === 200) {
        this.uploadList.push({ name: res.fileName, url: res.fileName });
        this.uploadedSuccessfully();
      } else {
        this.number--;
        this.$modal.closeLoading();
        this.$modal.msgError(res.msg);
        this.$refs.fileUpload.handleRemove(file);
        this.uploadedSuccessfully();
      }
    },
    // 刪除文件
    handleDelete(index) {
      this.fileList.splice(index, 1);
      this.$emit("input", this.listToString(this.fileList));
    },
    // 上傳結(jié)束處理
    uploadedSuccessfully() {
      if (this.number > 0 && this.uploadList.length === this.number) {
        this.fileList = this.fileList.concat(this.uploadList);
        this.uploadList = [];
        this.number = 0;
        this.$emit("input", this.listToString(this.fileList));
        this.$modal.closeLoading();
      }
    },
    // 獲取文件名稱
    getFileName(name) {
      // 如果是url那么取最后的名字 如果不是直接返回
      if (name.lastIndexOf("/") > -1) {
        return name.slice(name.lastIndexOf("/") + 1);
      } else {
        return name;
      }
    },
    // 對(duì)象轉(zhuǎn)成指定字符串分隔
    listToString(list, separator) {
      let strs = "";
      separator = separator || ",";
      for (let i in list) {
        strs += list[i].url + separator;
      }
      return strs != "" ? strs.substr(0, strs.length - 1) : "";
    },
    // Create unique identifier for file
    createFileIdentifier(file) {
      return `${file.name}-${file.size}-${new Date().getTime()}`;
    },
    async customUpload({ file }) {
      try {
        const chunkSize = 2 * 1024 * 1024;
        const totalChunks = Math.ceil(file.size / chunkSize);
        const identifier = this.createFileIdentifier(file);
        const maxRetries = 3;
        const baseDelay = 1000;

        // 獲取或創(chuàng)建該文件的已上傳分片記錄
        if (!this.uploadedChunksMap.has(identifier)) {
          this.uploadedChunksMap.set(identifier, new Set());
        }
        const uploadedChunks = this.uploadedChunksMap.get(identifier);

        this.$set(this.uploadProgress, file.name,
          Math.floor((uploadedChunks.size / totalChunks) * 100));

        for (let chunkNumber = 1; chunkNumber <= totalChunks; chunkNumber++) {
          // 如果分片已上傳成功，跳過(guò)
          if (uploadedChunks.has(chunkNumber)) {
            continue;
          }

          let currentChunkSuccess = false;
          let retries = 0;

          while (!currentChunkSuccess && retries < maxRetries) {
            try {
              const start = (chunkNumber - 1) * chunkSize;
              const end = Math.min(start + chunkSize, file.size);
              const chunk = file.slice(start, end);

              const formData = new FormData();
              formData.append('file', chunk);
              formData.append('identifier', identifier);
              formData.append('totalChunks', totalChunks);
              formData.append('chunkNumber', chunkNumber);
              formData.append('fileName', file.name);

              const res = await uploadFileProgress(formData);

              if (res.code !== 200) {
                throw new Error(res.msg || '上傳失敗');
              }

              uploadedChunks.add(chunkNumber);
              this.$set(this.uploadProgress, file.name,
                Math.floor((uploadedChunks.size / totalChunks) * 100));

              currentChunkSuccess = true;

              // 所有分片上傳完成
              if (uploadedChunks.size === totalChunks) {
                const successRes = {
                  code: 200,
                  fileName: res.fileName,
                  url: res.url,
                };

                // 清理該文件的上傳記錄
                this.uploadedChunksMap.delete(identifier);
                // 立即移除進(jìn)度條
                this.$delete(this.uploadProgress, file.name);

                this.handleUploadSuccess(successRes, file);
                return;
              }
            } catch (error) {
              retries++;
              // if (retries === maxRetries) {
              //   throw new Error(`分片 ${chunkNumber} 上傳失敗，已重試 ${maxRetries} 次`);
              // }
              const delay = Math.min(baseDelay * Math.pow(2, retries - 1) + Math.random() * 1000, 10000);
              // this.$message.warning(`分片 ${chunkNumber} 上傳失敗，${retries}秒后重試...`);
              await new Promise(resolve => setTimeout(resolve, delay));
            }
          }

          if (!currentChunkSuccess) {
            throw new Error(`分片 ${chunkNumber} 上傳失敗`);
          }
        }
      } catch (error) {
        // 確保在錯(cuò)誤時(shí)也移除進(jìn)度條
        this.$delete(this.uploadProgress, file.name);
        this.uploadedChunksMap.delete(identifier); // 清理上傳記錄
        this.$modal.closeLoading();
        this.$modal.msgError(error.message || '上傳文件失敗，請(qǐng)重試');
      }
    },
  },
};
</script>

<style scoped lang="scss">
.upload-file-uploader {
  margin-bottom: 5px;
}
.upload-file-list .el-upload-list__item {
  border: 1px solid #e4e7ed;
  line-height: 2;
  margin-bottom: 10px;
  position: relative;
}
.upload-file-list .ele-upload-list__item-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: inherit;
}
.ele-upload-list__item-content-action .el-link {
  margin-right: 10px;
}

.upload-progress {
  margin: 10px 0;
  padding: 8px 12px;
  background-color: #f5f7fa;
  border-radius: 4px;

  .progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;

    .file-name {
      color: #606266;
      font-size: 14px;
      overflow: hidden;
      text-overflow: ellipsis;
      white-space: nowrap;
      max-width: 80%;
    }

    .percentage {
      color: #409eff;
      font-size: 13px;
      font-weight: 500;
    }
  }

  .el-progress {
    margin-bottom: 4px;
  }
}
</style>

<FileUpload 
  v-model="fileUrls"
  :limit="3"
  :fileSize="10"
  :fileType="['pdf','docx']"
/>