$gradient-start: #7166d9;
$gradient-end: #c86dd7;
$inverse-hover: #fafbff;
$base-class: 'button';

@mixin button-variant($color, $hover: null, $shadow: null) {
  @if not $shadow {
    $shadow: adjust-color($color, $lightness: -20%, $saturation: 20%);
  }

  @if not $hover {
    $hover: darken($color, 5%);
  }

  background-color: $color;
  box-shadow: 0 2px 0 $shadow, 0 3px 5px 0 rgba($black, 0.15);

  &.#{$base-class}--disabled {
    &:hover {
      background-color: $color;
    }
  }

  &:hover {
    background-color: $hover;
  }
}

.#{$base-class} {
  @include user-select(none);
  @include transition(color 150ms ease-in-out, background 150ms ease-in-out, top 50ms ease-in-out, box-shadow 50ms ease-in-out, border 50ms ease-in-out);
  @include button-variant($link);
  position: relative;
  height: 38px;
  text-align: center;
  color: $white;
  line-height: 36px;
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 1px;
  border-radius: 2px;
  font-size: $medium;
  font-family: 'Oxygen', $helvetica;
  font-weight: $bold;
  display: inline-block;
  padding: 0 $pad-large;
  top: 0;
  border: 0;
  cursor: pointer;
  box-sizing: border-box;

  &:focus {
    outline: none;
  }

  &--brand {
    @include button-variant($brand);
  }

  &--success {
    @include button-variant($success);
  }

  &--alert {
    @include button-variant($alert);
  }

  &--warning {
    @include button-variant($warning);
  }

  &--inverse {
    @include button-variant($white, $inverse-hover, $brand);
    color: $brand;
    border: 1px solid $brand;
    border-bottom-color: $white;

    &:active {
      border-bottom-color: $brand;
    }
  }

  &--inverse-alert {
    @include button-variant($white, $inverse-hover, $alert);
    color: $alert;
    border: 1px solid $alert;
    border-bottom-color: $white;

    &:active {
      border-bottom-color: $alert;
    }
  }

  &--block {
    display: block;
    width: 100%;
  }

  &--disabled {
    opacity: 0.4;
    cursor: default;
  }

  &--small {
    height: 28px;
    line-height: 26px;
    padding: 0 $pad-medium;
  }

  &--large {
    height: 48px;
    line-height: 46px;
  }

  &--gradient {
    background-color: transparent;
    background-image: linear-gradient(134deg, $gradient-start 0%, $gradient-end 100%);
    color: $white;
    font-size: $large;
    font-weight: $light;
    letter-spacing: 4px;
    padding: $medium;
    width: 100%;
    height: auto;
    box-shadow: inset 0 -3px 0 0 rgba(0, 0, 0, 0.25), 0 -2px 3px 0 rgba(0, 0, 0, 0.15);

    &:active {
      box-shadow: 0 1px 0 #734893, 0 -2px 0 #d1d9e9;
    }
  }

  &--unstyled {
    @include button-variant(transparent);
    border: 0;
    box-shadow: none;
    color: $text-dark;
    cursor: pointer;
    margin: 0;
    padding: 0;
    height: auto;
    line-height: normal;

    &:active {
      box-shadow: none;
      top: 0;
    }

    &:focus {
      outline: none;
    }

    &:hover {
      background-color: transparent;
      box-shadow: none;
    }
  }
}