/**
 * 通用多列排序 Mixin
 * 用法：在页面 data() 中声明 sortableColumns，在 loadList() 中加入 sortParams，
 *       在 el-table-column 的 slot="header" 中调用 this.sortHeader(col)。
 */
export default {
  data() {
    return {
      sortState: [],          // [{column, order:'asc'|'desc'}]
    }
  },
  computed: {
    sortLabel() {
      if (!this.sortState || this.sortState.length === 0) return ''
      const labels = this.sortableColumns || {}
      return this.sortState.map(s => {
        const label = labels[s.column] || s.column
        return (s.order === 'asc' ? label + '↑' : label + '↓')
      }).join(' > ')
    }
  },
  methods: {
    /**
     * 渲染排序列头 HTML 字符串（供 slot 内联使用）
     * 用法: <span v-html="sortHeader('name')"></span>
     */
    sortHeader(col, label) {
      const icon = this.sortIcon(col)
      const cls = this.sortClass(col)
      const safeCol = col.replace(/[."']/g, '')
      return `<span class="sort-header ${cls}" `
        + `onclick="window.__sortClick && window.__sortClick('${safeCol}', event)" `
        + `ondblclick="window.__sortToggle && window.__sortToggle('${safeCol}')" `
        + `>${label || col}${icon}</span>`
    },
    sortClass(col) {
      const s = this.sortState.find(x => x.column === col)
      if (!s) return ''
      return s.order === 'asc' ? 'sort-asc' : 'sort-desc'
    },
    sortIcon(col) {
      const s = this.sortState.find(x => x.column === col)
      if (!s) return ''
      return s.order === 'asc' ? ' ↑' : ' ↓'
    },
    onSortClick(col, event) {
      if (event.shiftKey) {
        this.shiftAppendSort(col)
      } else {
        this.setPrimarySort(col)
      }
      if (typeof this.loadList === 'function') this.loadList()
    },
    onSortToggle(col) {
      const idx = this.sortState.findIndex(s => s.column === col)
      if (idx >= 0) {
        this.sortState[idx].order = this.sortState[idx].order === 'asc' ? 'desc' : 'asc'
      } else {
        this.sortState = [{ column: col, order: 'asc' }]
      }
      if (typeof this.loadList === 'function') this.loadList()
    },
    setPrimarySort(col) {
      const idx = this.sortState.findIndex(s => s.column === col)
      if (idx >= 0) {
        const item = this.sortState.splice(idx, 1)[0]
        this.sortState.unshift(item)
      } else {
        this.sortState = [{ column: col, order: 'asc' }]
      }
    },
    shiftAppendSort(col) {
      const idx = this.sortState.findIndex(s => s.column === col)
      if (idx >= 0) {
        this.sortState[idx].order = this.sortState[idx].order === 'asc' ? 'desc' : 'asc'
      } else if (this.sortState.length < 3) {
        this.sortState.push({ column: col, order: 'asc' })
      }
    },
    clearSort() {
      this.sortState = []
      if (typeof this.loadList === 'function') this.loadList()
    },
    /** 将当前 sortState 注入到请求参数中 */
    applySortToParams(params) {
      if (this.sortState.length > 0) {
        params.sort = this.sortState
      }
      return params
    }
  }
}