<template>
  <div :style="style" aria-hidden="true">
    <!-- this img is not displayed; it is used to detect failure-to-load of div background image -->
    <img v-if="this.isImage" style="display: none" :src="this.src"/>
    <span v-show="!this.isImage">{{ userInitial }}</span>
  </div>
</template>


<script>
const getInitials = (username) => {
  let parts = username.split(/[ -]/)
  let initials = ''

  for (var i = 0; i < parts.length; i++) {
    initials += parts[i].charAt(0)
  }

  if (initials.length > 3 && initials.search(/[A-Z]/) !== -1) {
    initials = initials.replace(/[a-z]+/g, '')
  }

  initials = initials.substr(0, 3).toUpperCase()

  return initials
}

export default {
  name: 'avatar',
  props: {
    username: {
      type: String
    },
    inline: {
      type: Boolean
    },
    size: {
      type: Number,
      default: 50
    },
    src: {
      type: String
    },
    rounded: {
      type: Boolean,
      default: true
    },
    lighten: {
      type: Number,
      default: 80
    },
    parser: {
      type: Function,
      default: getInitials,
      validator: (parser) => typeof parser('John', getInitials) === 'string'
    }
  },

  data () {
    return {
      backgroundColor: 
        '#CCCCCC',
      imgError: false
    }
  },

  mounted () {
    if (!this.isImage) {
      this.$emit('avatar-initials', this.username, this.userInitial)
    }
  },

  computed: {
    background () {
      if (!this.isImage) {
        return this.backgroundColor || this.randomBackgroundColor(this.username.length, this.backgroundColors)
      }
      else {
        return "";
      }
    },
    isImage () {
      return !this.imgError && Boolean(this.src)
    },

    style () {
      const style = {
        display: 'flex',
        width: `${this.size}px`,
        height: `${this.size}px`,
        borderRadius: this.rounded ? '50%' : 0,
        lineHeight: `${(this.size + Math.floor(this.size / 20))}px`,
        fontWeight: 'bold',
        alignItems: 'center',
        justifyContent: 'center',
        textAlign: 'center',
        userSelect: 'none'
      }

      const imgBackgroundAndFontStyle = {
        background: `transparent url('${this.src}') no-repeat scroll 0% 0% / ${this.size}px ${this.size}px content-box border-box`
      }

      const initialBackgroundAndFontStyle = {
        backgroundColor: this.background,
        font: `${Math.floor(this.size / 2.5)}px/${this.size}px Helvetica, Arial, sans-serif`,
        color: this.fontColor
      }

      const backgroundAndFontStyle = (this.isImage)
        ? imgBackgroundAndFontStyle
        : initialBackgroundAndFontStyle

      Object.assign(style, backgroundAndFontStyle)

      return style
    },

    userInitial () {
      if (!this.isImage) {
        const initials = this.initials || this.parser(this.username, getInitials)
        return initials
      }
      return ''
    }
  },

  methods: {
    initial: getInitials,

    onImgError () {
      this.imgError = true
    },

    randomBackgroundColor (seed, colors) {
      return colors[seed % (colors.length)]
    },

    lightenColor (hex, amt) {
      // From https://css-tricks.com/snippets/javascript/lighten-darken-color/
      var usePound = false

      if (hex[0] === '#') {
        hex = hex.slice(1)
        usePound = true
      }

      var num = parseInt(hex, 16)
      var r = (num >> 16) + amt

      if (r > 255) r = 255
      else if (r < 0) r = 0

      var b = ((num >> 8) & 0x00FF) + amt

      if (b > 255) b = 255
      else if (b < 0) b = 0

      var g = (num & 0x0000FF) + amt

      if (g > 255) g = 255
      else if (g < 0) g = 0

      return (usePound ? '#' : '') + (g | (b << 8) | (r << 16)).toString(16)
    }
  }
}
</script>
