import { arrayFind } from 'element-ui/src/utils/util';
import { getRowIdentity } from '../util';

export default {
  data() {
    return {
      states: {
        // 不可响应的，设置 currentRowKey 时，data 不一定存在，也许无法算出正确的 currentRow
        // 把该值缓存一下，当用户点击修改 currentRow 时，把该值重置为 null
        _currentRowKey: null,
        currentRow: null
      }
    };
  },

  methods: {
    setCurrentRowKey(key) {
      this.assertRowKey();
      this.states._currentRowKey = key;
      this.setCurrentRowByKey(key);
    },

    restoreCurrentRowKey() {
      this.states._currentRowKey = null;
    },

    setCurrentRowByKey(key) {
      const { states } = this;
      const { data = [], rowKey } = states;
      let currentRow = null;
      if (rowKey) {
        currentRow = arrayFind(data, item => getRowIdentity(item, rowKey) === key);
      }
      states.currentRow = currentRow;
    },

    updateCurrentRow(currentRow) {
      const { states, table } = this;
      const oldCurrentRow = states.currentRow;
      if (currentRow && currentRow !== oldCurrentRow) {
        states.currentRow = currentRow;
        table.$emit('current-change', currentRow, oldCurrentRow);
        return;
      }
      if (!currentRow && oldCurrentRow) {
        states.currentRow = null;
        table.$emit('current-change', null, oldCurrentRow);
      }
    },

    updateCurrentRowData() {
      const { states, table } = this;
      const { rowKey, _currentRowKey } = states;
      // data 为 null 时，结构时的默认值会被忽略
      const data = states.data || [];
      const oldCurrentRow = states.currentRow;

      // 当 currentRow 不在 data 中时尝试更新数据
      if (data.indexOf(oldCurrentRow) === -1 && oldCurrentRow) {
        if (rowKey) {
          const currentRowKey = getRowIdentity(oldCurrentRow, rowKey);
          this.setCurrentRowByKey(currentRowKey);
        } else {
          states.currentRow = null;
        }
        if (states.currentRow === null) {
          table.$emit('current-change', null, oldCurrentRow);
        }
      } else if (_currentRowKey) {
        // 把初始时下设置的 rowKey 转化成 rowData
        this.setCurrentRowByKey(_currentRowKey);
        this.restoreCurrentRowKey();
      }
    }
  }
};
