<template>
  <el-color-picker v-model="theme" />
</template>
<script>
const version = require("element-ui/package.json").version;
const ORIGINAL_THEME = "#409EFF";
export default {
  props: {
    color: String,
  },
  data() {
    return {
      chalk: "",
      theme: "",
    };
  },
  computed: {
    defaultTheme() {
      return this.color;
    },
  },
  watch: {
    defaultTheme: {
      handler: function (val, oldVal) {
        this.theme = val;
      },
      immediate: true,
    },
    async theme(val) {
      const oldVal = this.chalk ? this.theme : ORIGINAL_THEME;
      if (typeof val !== "string") return;
      const themeCluster = this.getThemeCluster(val.replace("#", ""));
      const originalCluster = this.getThemeCluster(oldVal.replace("#", ""));
      if (!this.chalk) {
        await this.getCSSString();
      }
      this.getHandler(themeCluster);
      const styles = [].slice
        .call(document.querySelectorAll("style"))
        .filter((style) => {
          const text = style.innerText;
          return (
            new RegExp(oldVal, "i").test(text) && !/Chalk Variables/.test(text)
          );
        });
      styles.forEach((style) => {
        const { innerText } = style;
        if (typeof innerText !== "string") return;
        style.innerText = this.updateStyle(
          innerText,
          originalCluster,
          themeCluster
        );
      });
      this.$emit("color-update", val);
    },
  },
  methods: {
    // 修改element-ui主题样式表颜色
    updateStyle(style, oldCluster, newCluster) {
      let newStyle = style;
      oldCluster.forEach((color, index) => {
        newStyle = newStyle.replace(new RegExp(color, "ig"), newCluster[index]);
      });
      return newStyle;
    },
    // 生成新的样式表
    getHandler(themeCluster) {
      const originalCluster = this.getThemeCluster(
        ORIGINAL_THEME.replace("#", "")
      );
      const newStyle = this.updateStyle(
        this.chalk,
        originalCluster,
        themeCluster
      );
      let styleTag = document.getElementById("chalk-style");
      if (!styleTag) {
        styleTag = document.createElement("style");
        styleTag.setAttribute("id", "chalk-style");
        document.head.appendChild(styleTag);
      }
      styleTag.innerText = newStyle;
    },
    // 获取element-ui主题样式
    getCSSString() {
      const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`;
      return new Promise((resolve) => {
        const xhr = new XMLHttpRequest();
        xhr.onreadystatechange = () => {
          if (xhr.readyState === 4 && xhr.status === 200) {
            this.chalk = xhr.responseText.replace(/@font-face{[^}]+}/, "");
            resolve();
          }
        };
        xhr.open("GET", url);
        xhr.send();
      });
    },
    getThemeCluster(theme) {
      const tintColor = (color, tint) => {
        let red = parseInt(color.slice(0, 2), 16);
        let green = parseInt(color.slice(2, 4), 16);
        let blue = parseInt(color.slice(4, 6), 16);
        if (tint === 0) {
          return [red, green, blue].join(",");
        } else {
          red += Math.round(tint * (255 - red));
          green += Math.round(tint * (255 - green));
          blue += Math.round(tint * (255 - blue));
          red = red.toString(16);
          green = green.toString(16);
          blue = blue.toString(16);
          return `#${red}${green}${blue}`;
        }
      };
      const shadeColor = (color, shade) => {
        let red = parseInt(color.slice(0, 2), 16);
        let green = parseInt(color.slice(2, 4), 16);
        let blue = parseInt(color.slice(4, 6), 16);
        red = Math.round((1 - shade) * red);
        green = Math.round((1 - shade) * green);
        blue = Math.round((1 - shade) * blue);
        red = red.toString(16);
        green = green.toString(16);
        blue = blue.toString(16);
        return `#${red}${green}${blue}`;
      };
      const clusters = [theme];
      for (let i = 0; i <= 9; i++) {
        clusters.push(tintColor(theme, Number((i / 10).toFixed(2))));
      }
      clusters.push(shadeColor(theme, 0.1));
      return clusters;
    },
  },
};
</script>


