@use "sass:color";
@use "sass:map";
@use "sass:math";
@use "sass:meta";
@use "sass:string";
@use "../settings/colours-palette" as *;

////
/// @group helpers/colour
////

///
/// Get colour
///
/// @param {String | Colour} $colour - Name of colour from the colour palette
///   (`$nhsuk-colours`)
/// @return {Colour} Representation of named colour
///
/// @throw if `$colour` is not a colour from the colour palette

@function nhsuk-colour($colour) {
  @if meta.type-of($colour) == "color" {
    $colour: string.quote("#{$colour}");
  }

  @if not map.has-key($nhsuk-colours, $colour) {
    @error "Unknown colour `#{$colour}`";
  }

  @return map.get($nhsuk-colours, $colour);
}

/// Converts a colour with potential float values for its RGB channels
/// into hexadecimal notation where possible (e.g. no alpha transparency)
///
/// This ensures the colour is rendered properly by Safari < 12
///
/// @param {String | Colour} $colour - The colour to convert or name from the colour palette
/// @return {Colour}

@function nhsuk-colour-compatible($colour) {
  @if meta.type-of($colour) == "string" {
    $colour: nhsuk-colour($colour);
  }

  $alpha: color.alpha($colour);
  $parts: ();

  // Maintain compatibility with Sass < v1.79.0 where colour space functions
  // are unavailable and RGB channels are automatically rounded to integers
  // https://github.com/sass/dart-sass/blob/1.79.0/CHANGELOG.md
  @if not meta.function-exists("channel", "color") {
    $parts: (
      "red": color.red($colour),
      "green": color.green($colour),
      "blue": color.blue($colour),
      "alpha": $alpha
    );
  } @else {
    $colour: color.to-space($colour, rgb);
    $alpha: color.channel($colour, "alpha");

    $parts: (
      "red": math.round(color.channel($colour, "red")),
      "green": math.round(color.channel($colour, "green")),
      "blue": math.round(color.channel($colour, "blue")),
      "alpha": $alpha
    );
  }

  @return color.change($colour, $parts...);
}

/// Make a colour darker by mixing it with black
///
/// @example scss
///   nhsuk-shade(color, percentage);
///   nhsuk-shade(nhsuk-colour("blue"), 50%);
///
/// @param {Colour} $colour - colour to shade
/// @param {Number} $percentage - percentage of black to mix with $colour
/// @return {Colour}

@function nhsuk-shade($colour, $percentage) {
  // Ensure the output is a hex string so that Safari <12 can render the colour
  // without issues from float values in `rgb()`
  @return nhsuk-colour-compatible(color.mix(black, $colour, $percentage));
}

/// Make a colour lighter by mixing it with white
///
/// @example scss
///   nhsuk-tint(color, percentage);
///   nhsuk-tint(nhsuk-colour("blue"), 10%);
///
/// @param {Colour} $colour - colour to tint
/// @param {Number} $percentage - percentage of white to mix with $colour
/// @return {Colour}

@function nhsuk-tint($colour, $percentage) {
  // Ensure the output is a hex string so that Safari <12 can render the colour
  // without issues from float values in `rgb()`
  @return nhsuk-colour-compatible(color.mix(white, $colour, $percentage));
}