<template>
  <el-color-picker
    v-model="theme"
    :predefine="[
      '#409EFF',
      '#1890ff',
      '#304156',
      '#212121',
      '#11a983',
      '#13c2c2',
      '#6959CD',
      '#f5222d'
    ]"
    class="theme-picker"
    popper-class="theme-picker-dropdown"
  />
</template>

<script lang="ts">
import { Component, Prop, Vue, Watch } from "vue-property-decorator";
import { SettingsModule } from "@/store/modules/settings";

const version = require("element-ui/package.json").version; // element-ui version from node_modules
const ORIGINAL_THEME = "#409EFF"; // default color

@Component({
  name: "ThemePicker"
})
export default class extends Vue {
  private chalk = ""; // The content of theme-chalk css
  private theme = "";

  get defaultTheme() {
    return SettingsModule.theme;
  }

  @Watch("defaultTheme", { immediate: true })
  private onDefaultThemeChange(value: string) {
    this.theme = value;
  }

  @Watch("theme")
  private async onThemeChange(value: string) {
    if (!value) return;
    const oldValue = this.chalk ? this.theme : ORIGINAL_THEME;
    const themeCluster = this.getThemeCluster(value.replace("#", ""));
    const originalCluster = this.getThemeCluster(oldValue.replace("#", ""));
    const message = this.$message({
      message: "  Compiling the theme",
      customClass: "theme-message",
      type: "success",
      duration: 0,
      iconClass: "el-icon-loading"
    });

    if (!this.chalk) {
      const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`;
      await this.getCSSString(url, "chalk");
    }

    const getHandler = (variable: string, id: string) => {
      return () => {
        const originalCluster = this.getThemeCluster(
          ORIGINAL_THEME.replace("#", "")
        );
        const newStyle = this.updateStyle(
          (this as any)[variable],
          originalCluster,
          themeCluster
        );

        let styleTag = document.getElementById(id);
        if (!styleTag) {
          styleTag = document.createElement("style");
          styleTag.setAttribute("id", id);
          document.head.appendChild(styleTag);
        }
        styleTag.innerText = newStyle;
      };
    };
    const chalkHandler = getHandler("chalk", "chalk-style");
    chalkHandler();

    let styles: HTMLElement[] = [].slice.call(
      document.querySelectorAll("style")
    );
    styles = styles.filter(style => {
      const text = style.innerText;
      return (
        new RegExp(oldValue, "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("change", value);
    message.close();
  }

  private updateStyle(
    style: string,
    oldCluster: string[],
    newCluster: string[]
  ) {
    let newStyle = style;
    oldCluster.forEach((color, index) => {
      newStyle = newStyle.replace(new RegExp(color, "ig"), newCluster[index]);
    });
    return newStyle;
  }

  private getCSSString(url: string, variable: string) {
    return new Promise(resolve => {
      const xhr = new XMLHttpRequest();
      xhr.onreadystatechange = () => {
        if (xhr.readyState === 4 && xhr.status === 200) {
          (this as any)[variable] = xhr.responseText.replace(
            /@font-face{[^}]+}/,
            ""
          );
          resolve();
        }
      };
      xhr.open("GET", url);
      xhr.send();
    });
  }

  private getThemeCluster(theme: string) {
    const tintColor = (color: string, tint: number) => {
      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) {
        // when primary color is in its rgb space
        return [red, green, blue].join(",");
      } else {
        red += Math.round(tint * (255 - red));
        green += Math.round(tint * (255 - green));
        blue += Math.round(tint * (255 - blue));
        return `#${red.toString(16)}${green.toString(16)}${blue.toString(16)}`;
      }
    };

    const shadeColor = (color: string, shade: number) => {
      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);
      return `#${red.toString(16)}${green.toString(16)}${blue.toString(16)}`;
    };

    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>

<style lang="scss">
.theme-message,
.theme-picker-dropdown {
  z-index: 99999 !important;
}

.theme-picker .el-color-picker__trigger {
  height: 26px !important;
  width: 26px !important;
  padding: 2px;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
  display: none;
}
</style>
