//
// Copyright 2020 Google Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
@use 'sass:map';
@use 'sass:meta';
@use './css';
@use './gss';

/// Returns true if the parameter is a custom property Map.
///
/// @param {*} $value - the value to test.
/// @return true if the value is a custom property Map, or false if not.
@function is-custom-prop($value) {
  @return meta.type-of($value) == 'map' and map.has-key($value, 'varname');
}

/// Returns true if $prop1's varname and fallback values are deeply equal to
/// $prop2's varname and fallback values.
///
/// @param {Map} $prop1 - the first value to test.
/// @param {Map} $prop2 - the second value to test.
/// @return true if both properties are deeply equal
@function are-equal($prop1, $prop2) {
  @return create-var($prop1) == create-var($prop2);
}

/// Creates a custom property Map.
///
/// @param {String} $varname - the custom property name.
/// @param {String | Number | Map} - the fallback value (may be another custom
///     property Map). May be null.
/// @return a custom property Map.
@function create($varname, $fallback: null) {
  @return (varname: $varname, fallback: $fallback);
}

/// Returns the custom property variable name of a custom property Map.
///
/// @param {Map} $custom-prop - a custom property Map.
/// @return the custom property variable name defined by the Map.
@function get-varname($custom-prop) {
  @return map.get($custom-prop, 'varname');
}

/// Returns the fallback value of a custom property Map. May be null if the
/// custom property does not have a fallback.
///
/// @param {Map} $custom-prop - a custom property Map.
/// @param {Bool} $shallow - if true, return the first fallback value, which
///     may be another custom property Map. Defaults to false, which will return
///     the deep final fallback value.
/// @return the fallback value of a custom property Map. May be null.
@function get-fallback($custom-prop, $shallow: false) {
  $fallback: map.get($custom-prop, 'fallback');
  @if is-custom-prop($fallback) and not $shallow {
    @return get-fallback($fallback);
  }

  @return $fallback;
}

/// Creates a new custom property Map and returns it with the specified new
/// fallback value.
///
/// @param {Map} $custom-prop - the custom property Map to copy.
/// @param {String | Number | Map} $new-fallback - the new fallback value of the
///     custom property Map. May be null.
/// @param {Bool} $shallow - if true, set the first fallback value. Defaults to
///     false, which will set the deep final fallback value.
/// @return a new custom property Map with the new fallback value.
@function set-fallback($custom-prop, $new-fallback, $shallow: false) {
  $varname: get-varname($custom-prop);
  $first-fallback: get-fallback($custom-prop, $shallow: true);

  @if is-custom-prop($first-fallback) and not $shallow {
    // The first fallback is a custom property and $shallow is false. Deeply
    // set the fallback value of the custom property and get the new custom
    // property Map returned.
    $new-fallback: set-fallback($first-fallback, $new-fallback);
  }

  @return create($varname, $new-fallback);
}

/// Creates and returns a `var()` function declaration represented by the
/// provided custom property Map.
///
/// @param {Map} $custom-prop - a custom property Map.
/// @return a `var()` function declaration using the custom property Map's
///     varname and fallback value.
@function create-var($custom-prop) {
  $varname: get-varname($custom-prop);
  $fallback: get-fallback($custom-prop, $shallow: true);

  @if is-custom-prop($fallback) {
    @return var($varname, create-var($fallback));
  } @else if $fallback != null {
    @return var($varname, $fallback);
  } @else {
    @return var($varname);
  }
}

/// Applies a custom property value to the specified property.
///
/// @param {String} $property - the name of the CSS property.
/// @param {Map} $custom-prop - a custom property Map for the property's value.
/// @param {Map} $gss - optional Map of GSS annotations to set.
/// @param {Bool} $important - set to true to add an `!important` rule. Defaults
///     to false.
@mixin apply($property, $custom-prop, $gss: (), $important: false) {
  @if not is-custom-prop($custom-prop) {
    @error "mdc-theme: Invalid custom property: #{$custom-prop}. Must be a Map with 'varname' and 'fallback'.";
  }

  @include css.declaration(
    $property,
    $value: create-var($custom-prop),
    $fallback-value: get-fallback($custom-prop),
    $gss: $gss,
    $important: $important
  );
}