<style scoped>
  .headerWrapper {
    height: 80px;
  }
  .header {
    height: 80px;
    background-color: rgba(32, 160, 255, 1);
    color: #fff;
    top: 0;
    left: 0;
    width: 100%;
    line-height: @height;
    z-index: 100;
    position: relative;

    .container {
      height: 100%;
    }

    h1 {
      margin: 0;
      float: left;
      font-size: 32px;
      font-weight: normal;

      a {
        color: #fff;
        text-decoration: none;
        display: block;
      }

      span {
        font-size: 12px;
        display: inline-block;
        width: 34px;
        height: 18px;
        border: 1px solid rgba(255, 255, 255, .5);
        text-align: center;
        line-height: 18px;
        vertical-align: middle;
        margin-left: 10px;
        border-radius: 3px;
      }
    }
    .nav {
      float: right;
      height: 100%;
      line-height: 80px;
      background: transparent;
      @utils-clearfix;
      padding: 0;
      margin: 0;
    }
    .nav-logo {
      vertical-align: sub;
    }
    .nav-item {
      margin: 0;
      float: left;
      list-style: none;
      position: relative;
      cursor: pointer;
      margin-left: 20px;
    
      &:last-child {
        cursor: default;
        margin-left: 34px;
        span {
          opacity: .8;
        }

        .nav-lang {
          cursor: pointer;
          display: inline-block;
          height: 100%;
          &:hover {
            opacity: 1;
          }
          &.active {
            font-weight: 700;
            opacity: 1;
          }
        }
      }

      a {
        text-decoration: none;
        color: #fff;
        display: block;
        padding: 0 20px;
        opacity: .8;
        &.active,
        &:hover {
          opacity: 1;
        }
         
        &.active {
          font-weight: 700;
        }

        &.active::before {
          content: '';
          display: block;
          position: absolute;
          bottom: 0;
          left: 0;
          width: 100%;
          height: 4px;
          background:#99d2fc;
        }
      }
    }
  }
  .header-home {
    position: fixed;
    top: 0;
    background-color: rgba(32, 160, 255, 0);
  }
</style>
<template>
  <div class="headerWrapper">
    <header class="header"
    ref="header"
    :style="headerStyle"
    :class="{
      'header-home': isHome
    }">
      <div class="container">
        <h1><router-link :to="`/${ lang }`">
          <img
            src="../assets/images/element-logo.svg"
            alt="element-logo"
            class="nav-logo">
        </router-link></h1>
        <ul class="nav">
          <li class="nav-item">
            <router-link
              active-class="active"
              :to="`/${ lang }/guide`">{{ langConfig.guide }}
            </router-link>
          </li>
          <li class="nav-item">
            <router-link
              active-class="active"
              :to="`/${ lang }/component`">{{ langConfig.components }}
            </router-link>
          </li>
          <li class="nav-item">
            <router-link
              active-class="active"
              :to="`/${ lang }/resource`"
              exact>{{ langConfig.resource }}
            </router-link>
          </li>
          <li class="nav-item">
            <span
              class="nav-lang"
              :class="{ 'active': lang === 'zh-CN' }"
              @click="switchLang('zh-CN')">
              中文
            </span>
            <span> / </span>
            <span
              class="nav-lang"
              :class="{ 'active': lang === 'en-US' }"
              @click="switchLang('en-US')">
              En
            </span>
          </li>
        </ul>
      </div>
    </header>
  </div>
</template>
<script>
  import compoLang from '../i18n/component.json';

  export default {
    data() {
      return {
        active: '',
        isHome: false,
        headerStyle: {}
      };
    },
    watch: {
      '$route.path'() {
        this.isHome = this.$route.name === 'home';
        this.headerStyle.backgroundColor = `rgba(32, 160, 255, ${ this.isHome ? '0' : '1' })`;
      }
    },
    computed: {
      lang() {
        return this.$route.path.split('/')[1] || 'zh-CN';
      },
      langConfig() {
        return compoLang.filter(config => config.lang === this.lang)[0]['header'];
      }
    },
    methods: {
      switchLang(targetLang) {
        if (this.lang === targetLang) return;
        this.$router.push(this.$route.path.replace(this.lang, targetLang));
      }
    },
    mounted() {
      this.isHome = this.$route.name === 'home';
      function scroll(fn) {
        window.addEventListener('scroll', () => {
          fn();
        }, false);
      }
      scroll(() => {
        if (this.isHome) {
          const threshold = 200;
          let alpha = Math.min(document.body.scrollTop, threshold) / threshold;
          this.$refs.header.style.backgroundColor = `rgba(32, 160, 255, ${ alpha })`;
        }
      });
    }
  };
</script>
