/// Transforms a custom theme map into brand variables. See `_brand.scss`.
/// @access private
/// @param {map|null} $theme - A custom theme map.
/// @return {map} Brand variables.
@function _oFormsThemeToBrandVariants($theme) {
	@if not $theme {
		@return null;
	}

	// Get given base and border colour.
	$base: map-get($theme, 'controls-base');
	$base: if(type-of($base) == 'string', oPrivateFoundationGet($base), $base);
	$border: map-get($theme, 'controls-border');
	$border: if(type-of($border) == 'string', oPrivateFoundationGet($border), $border);

	// Get given checked base colour.
	$checked-base: map-get($theme, 'controls-checked-base');
	$checked-base: if(
		type-of($checked-base) == 'string',
		oPrivateFoundationGet($checked-base),
		$checked-base
	);

	// Get given negative checked colour.
	$negative-background: map-get($theme, 'controls-negative-checked-background');
	$negative-background: if(
		type-of($negative-background) == 'string',
		oPrivateFoundationGet($negative-background),
		$negative-background
	);

	// Error if no base colour.
	@if not $base {
		@error "The custom theme for box-styled controls is missing a 'controls-base' key.";
	}

	// Return brand options which the theme is a allowed to customise.
	@return (
		'controls-base': $base,
		'controls-checked-base': $checked-base,
		'controls-negative-checked-background':
			if($negative-background, $negative-background, $base),
		'default-border': $border
	);
}

/// @access private
/// Outputs base styling for custom icons
@mixin _oFormsCustomIconBase {
	.o-forms-input__label {
		min-width: unset;
	}

	a.o-forms-input__link.o-forms-input__link--current,
	input[type='radio']:checked + .o-forms-input__label {
		&:after {
			display: block;
		}
	}
}

/// @access public
/// @param {String} $icon Name of the icon to request from the image set
/// @param {String} $input Type of input to set icons on ('anchor' or radio)
/// @param {Map|null} $theme Custom theme map
@mixin _oFormsCustomIcon($icon, $input, $theme: null) {
	$theme: _oFormsThemeToBrandVariants($theme);
	$element: '';

	@if $input == 'radio' {
		$element: 'label .o-forms-input__label.o-forms-input__label__#{$icon}-icon';
	} @else {
		$element: 'a.o-forms-input__link--#{$icon}-icon';
	}

	#{$element} {
		padding-left: $_o-forms-checkbox-radio-width;
		padding-right: $_o-forms-spacing-two;
		text-align: left;

		&:after,
		&:before {
			content: '';
			background-repeat: no-repeat;
			background-position-y: 0.175em;
			position: absolute;
			top: 0;
			left: 0;
		}

		&:before {
			@include oPrivateIconsContent(
				$icon-name: $icon,
				$color: _oFormsGet('controls-base', $from: $theme),
				$size: $_o-forms-checkbox-radio-width,
				$include-base-styles: false
			);
		}

		&:after {
			@include oPrivateIconsContent(
				$icon-name: $icon,
				$color: _oFormsGet('controls-checked-base', $from: $theme),
				$size: $_o-forms-checkbox-radio-width,
				$include-base-styles: false
			);
			display: none;
		}
	}
}

/// @access public
/// @param {String} $input Type of input to customise, one of 'anchor' or 'radio'
/// @param {List} $icons A list of icons to render
/// @param {Map|null} $theme Custom theme map
@mixin oFormsAddCustom($input: null, $class: null, $icons: null, $theme: null) {
	@if not $input {
		@error ('Please specify whether you would like to customise radio inputs or anchors');
	}

	@if not $class {
		@error ('Please specify a name for the custom modifier (e.g. o-forms-input--{custom-modifier}).');
	}

	$theme: _oFormsThemeToBrandVariants($theme);

	.o-forms-input--#{$class} {
		@if $input == 'pseudo-radio-link' {
			// We can provide a notice here that pseudo-radio-links are deprecated,
			// as we know that the user is explicitly requesting and using it.
			@warn 'o-forms: Pseudo Radio Links are deprecated and will be removed in the next major release. This is due to accessibility issues, see the README for more information. Please use standard box-styled radio inputs instead. https://o2.origami.ft.com/?path=/story/o2-core_maintained-o-forms-pseudo-box-radio-links--pseudo-radio-box-links&globals=backgrounds:!undefined';
			@include _oFormsPseudoRadioLinkStyles($theme);
		} @else if $input == 'radio' {
			@include _oFormsRadioBoxInputStyles($theme);
		} @else {
			@error ('#{$input} inputs do not accept customisation. If you need to customise this type of input, please contact the Origami team.');
		}
	}

	@if $icons {
		@include _oFormsCustomIconBase();
		@each $icon in $icons {
			@include _oFormsCustomIcon($icon, $input, $theme);
		}
	}
}