$masthead-height: 180px;
$masthead-image-blur: 1px;
$menu-link-background-color-active: rgba(255, 255, 255, 0.3);
$menu-link-background-color-hover: rgba(255, 255, 255, 0.15);

@mixin masthead-background-containers() {
  position: absolute;
  left: 0;
  right: 0;
  display: block;
  width: auto;
  height: inherit;
}

@mixin masthead-navigation-menu() {
  border: 0;
  border-radius: 0;

  ul.nav.navbar-nav {
    > li {
      text-transform: uppercase;

      a {
        color: $gray-lighter;
        letter-spacing: 1.2px;
      }
    }

    a:hover {
      background-color: $menu-link-background-color-hover;
    }

    > .active > a {
      background-color: $menu-link-background-color-active;
      color: $white;
    }

    .dropdown-menu {
      text-transform: none;

      > li a {
        color: $black;

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

  // Curated Features menu link when it has dropdown menu
  .navbar-nav > .open > a,
  .navbar-nav > .open > a:hover,
  .navbar-nav > .open > a:focus {
    background-color: $menu-link-background-color-hover;
  }
}

#exhibit-masthead,
#exhibit-navbar {
  z-index: 1;
}

#exhibit-navbar {
  z-index: 100;

  &.page-masthead {
    @include masthead-navigation-menu();
    background-color: rgba(0, 0, 0, 0.5);
    border-bottom: 1px solid $gray;
    margin-bottom: 0;
    margin-top: 0;

    .navbar-nav {
      float: right;
    }

    .navbar-brand,
    .navbar-nav li {
      color: $gray-lighter;

      &.active a {
        color: $gray;
      }

      a {
        color: $gray-lighter;
      }
    }
  }

  .navbar-form {
    text-align: right;
  }
}

#exhibit-masthead.with-image + #exhibit-navbar.navbar-default {
  @include masthead-navigation-menu();
  background-color: rgba(0, 0, 0, 0.2);
  border-top: 1px solid $gray;
}

.navbar + .navbar {
  margin-top: 0;
}

#header-navbar {
  margin-bottom: 0;
}

#exhibit-masthead {
  height: $masthead-height;
  margin-bottom: -50px;
  padding: 0;
  position: static;

  & > .container {
    position: relative;
    top: 33%;
    -webkit-transform: translateY(-50%);
    transform: translateY(-50%);
  }

  &.with-page-masthead {
    margin-bottom: $padding-base-vertical;
    margin-top: -51px;

    > .container {
      top: 60%;
    }

    .navbar-brand {
      font-size: $font-size-large;
      text-shadow: 1px 1px 0 $black;
    }

    .search-title {
      text-align: center;

      small {
        text-transform: uppercase;
      }
    }
  }

  .site-title {
    font-size: 30px;
  }

  small {
    display: block;
    padding-top: $padding-base-vertical;
    @extend .hidden-xs;
  }

  &.with-image {
    .site-title,
    .search-title {
      color: $white;
      text-shadow: 1px 1px 0 $black;
    }

    small {
      color: $white;
    }

    .more-exhibits {
      a {
        color: $gray-lighter;
        background: rgba(0, 0, 0, 0.4);
        border-top-left-radius: $border-radius-base;
        border-top-right-radius: $border-radius-base;
      }

      a:hover,
      a:focus,
      a:active {
        background: rgba(0, 0, 0, 0.6);
      }

      .dropdown-menu a {
        background: none;
        color: $gray;

        &:hover,
        &:focus,
        &:active {
          background-color: $gray-lighter;
        }
      }
    }
  }

  .more-exhibits {
    @extend .navbar-right;
  }

  &.with-page-masthead {
    .site-title {
      margin-top: $padding-large-vertical * 3;
    }

    .more-exhibits {
      @extend .navbar-left;
      padding-top: $padding-base-vertical;

      .dropdown-menu {
        left: 0;
        right: auto;
      }
    }
  }

  // This is to add a background image to the masthead, in a way that
  // enables the site title and subtitle text to be visible above it.
  .background-container {
    @include masthead-background-containers();
    background-repeat: no-repeat;
    background-size: cover;
    // Add small amount of blur to help text stand out
    //filter: url(masthead/blur.svg#blur); // for older versions of FF
    -webkit-filter: blur($masthead-image-blur);
    filter: blur($masthead-image-blur);
    // Shift image slightly to hide blurred edge of image
    margin-left: -$masthead-image-blur;
    margin-top: -$masthead-image-blur;
    overflow: hidden;
    // Add right border to image to hide lighter blurred edge
    border-right: 1px solid $black;
  }

  // Include gradient to improve text legibility,
  // especially on light background images.
  .background-container-gradient {
    @include masthead-background-containers();
    background:
     linear-gradient(
       rgba(0, 0, 0, 0.0),
       rgba(0, 0, 0, 0.4),
       rgba(0, 0, 0, 0.5)
     );
  }
}

// Margin between bottom of masthead and start of page content.
// Need to apply bottom margin to different element, depending on
// whether it is a regular masthead or a browse category masthead
#exhibit-masthead + #exhibit-navbar,
#exhibit-navbar + #exhibit-masthead {
  margin-bottom: $padding-large-vertical * 2.5;
}

.col-md-4 {
  .submit-search-text {
    // hide 'search' label
    // copied from .sr-only, sadly can't seem to use @extend in a media
    // query like this, have to copy.
    border: 0;
    clip: rect(0, 0, 0, 0);
    height: 1px;
    margin: -1px;
    overflow: hidden;
    position: absolute;
    width: 1px;
  }

  .glyphicon-search {
    line-height: $line-height-computed;
  }
}