<?php
/**
* WP_Font_Face class.
*
* @package WordPress
* @subpackage Fonts
* @since 6.4.0
*/

/**
* Font Face generates and prints `@font-face` styles for given fonts.
*
* @since 6.4.0
*/
class WP_Font_Face {

/**
* The font-face property defaults.
*
* @since 6.4.0
*
* @var string[]
*/
private $font_face_property_defaults = array(
'font-family' => '',
'font-style' => 'normal',
'font-weight' => '400',
'font-display' => 'fallback',
);

/**
* Valid font-face property names.
*
* @since 6.4.0
*
* @var string[]
*/
private $valid_font_face_properties = array(
'ascent-override',
'descent-override',
'font-display',
'font-family',
'font-stretch',
'font-style',
'font-weight',
'font-variant',
'font-feature-settings',
'font-variation-settings',
'line-gap-override',
'size-adjust',
'src',
'unicode-range',
);

/**
* Valid font-display values.
*
* @since 6.4.0
*
* @var string[]
*/
private $valid_font_display = array( 'auto', 'block', 'fallback', 'swap', 'optional' );

/**
* Array of font-face style tag's attribute(s)
* where the key is the attribute name and the
* value is its value.
*
* @since 6.4.0
*
* @var string[]
*/
private $style_tag_attrs = array();

/**
* Creates and initializes an instance of WP_Font_Face.
*
* @since 6.4.0
*/
public function __construct() {
if (
function_exists( 'is_admin' ) && ! is_admin()
&&
function_exists( 'current_theme_supports' ) && ! current_theme_supports( 'html5', 'style' )
) {
$this->style_tag_attrs = array( 'type' => 'text/css' );
}
}

/**
* Generates and prints the `@font-face` styles for the given fonts.
*
* @since 6.4.0
*
* @param array[][] $fonts Optional. The font-families and their font variations.
* See {@see wp_print_font_faces()} for the supported fields.
* Default empty array.
*/
public function generate_and_print( array $fonts ) {
$fonts = $this->validate_fonts( $fonts );

// Bail out if there are no fonts are given to process.
if ( empty( $fonts ) ) {
return;
}

$css = $this->get_css( $fonts );

/*
* The font-face CSS is contained within <style> tags and can only be interpreted
* as CSS in the browser. Using wp_strip_all_tags() is sufficient escaping
* to avoid malicious attempts to close </style> and open a <script>.
*/
$css = wp_strip_all_tags( $css );

// Bail out if there is no CSS to print.
if ( empty( $css ) ) {
return;
}

printf( $this->get_style_element(), $css );
}

/**
* Validates each of the font-face properties.
*
* @since 6.4.0
*
* @param array $fonts The fonts to valid.
* @return array Prepared font-faces organized by provider and font-family.
*/
private function validate_fonts( array $fonts ) {
$validated_fonts = array();

foreach ( $fonts as $font_faces ) {
foreach ( $font_faces as $font_face ) {
$font_face = $this->validate_font_face_declarations( $font_face );
// Skip if failed validation.
if ( false === $font_face ) {
continue;
}

$validated_fonts[] = $font_face;
}
}

return $validated_fonts;
}

/**
* Validates each font-face declaration (property and value pairing).
*
* @since 6.4.0
*
* @param array $font_face Font face property and value pairings to validate.
* @return array|false Validated font-face on success, or false on failure.
*/
private function validate_font_face_declarations( array $font_face ) {
$font_face = wp_parse_args( $font_face, $this->font_face_property_defaults );

// Check the font-family.
if ( empty( $font_face['font-family'] ) || ! is_string( $font_face['font-family'] ) ) {
// @todo replace with `wp_trigger_error()`.
_doing_it_wrong(
__METHOD__,
__( 'Font font-family must be a non-empty string.' ),
'6.4.0'
);
return false;
}

// Make sure that local fonts have 'src' defined.
if ( empty( $font_face['src'] ) || ( ! is_string( $font_face['src'] ) && ! is_array( $font_face['src'] ) ) ) {
// @todo replace with `wp_trigger_error()`.
_doing_it_wrong(
__METHOD__,
__( 'Font src must be a non-empty string or an array of strings.' ),
'6.4.0'
);
return false;
}

// Validate the 'src' property.
foreach ( (array) $font_face['src'] as $src ) {
if ( empty( $src ) || ! is_string( $src ) ) {
// @todo replace with `wp_trigger_error()`.
_doing_it_wrong(
__METHOD__,
__( 'Each font src must be a non-empty string.' ),
'6.4.0'
);
return false;
}
}

// Check the font-weight.
if ( ! is_string( $font_face['font-weight'] ) && ! is_int( $font_face['font-weight'] ) ) {
// @todo replace with `wp_trigger_error()`.
_doing_it_wrong(
__METHOD__,
__( 'Font font-weight must be a properly formatted string or integer.' ),
'6.4.0'
);
return false;
}

// Check the font-display.
if ( ! in_array( $font_face['font-display'], $this->valid_font_display, true ) ) {
$font_face['font-display'] = $this->font_face_property_defaults['font-display'];
}

// Remove invalid properties.
foreach ( $font_face as $property => $value ) {
if ( ! in_array( $property, $this->valid_font_face_properties, true ) ) {
unset( $font_face[ $property ] );
}
}

return $font_face;
}

/**
* Gets the style element for wrapping the `@font-face` CSS.
*
* @since 6.4.0
*
* @return string The style element.
*/
private function get_style_element() {
$attributes = $this->generate_style_element_attributes();

return "<style class='wp-fonts-local'{$attributes}>\n%s\n</style>\n";
}

/**
* Gets the defined <style> element's attributes.
*
* @since 6.4.0
*
* @return string A string of attribute=value when defined, else, empty string.
*/
private function generate_style_element_attributes() {
$attributes = '';
foreach ( $this->style_tag_attrs as $name => $value ) {
$attributes .= " {$name}='{$value}'";
}
return $attributes;
}

/**
* Gets the `@font-face` CSS styles for locally-hosted font files.
*
* This method does the following processing tasks:
* 1. Orchestrates an optimized `src` (with format) for browser support.
* 2. Generates the `@font-face` for all its fonts.
*
* @since 6.4.0
*
* @param array[] $font_faces The font-faces to generate @font-face CSS styles.
* @return string The `@font-face` CSS styles.
*/
private function get_css( $font_faces ) {
$css = '';

foreach ( $font_faces as $font_face ) {
// Order the font's `src` items to optimize for browser support.
$font_face = $this->order_src( $font_face );

// Build the @font-face CSS for this font.
$css .= '@font-face{' . $this->build_font_face_css( $font_face ) . '}' . "\n";
}

// Don't print the last newline character.
return rtrim( $css, "\n" );
}

/**
* Orders `src` items to optimize for browser support.
*
* @since 6.4.0
*
* @param array $font_face Font face to process.
* @return array Font-face with ordered src items.
*/
private function order_src( array $font_face ) {
if ( ! is_array( $font_face['src'] ) ) {
$font_face['src'] = (array) $font_face['src'];
}

$src = array();
$src_ordered = array();

foreach ( $font_face['src'] as $url ) {
// Add data URIs first.
if ( str_starts_with( trim( $url ), 'data:' ) ) {
$src_ordered[] = array(
'url' => $url,
'format' => 'data',
);
continue;
}
$format = pathinfo( $url, PATHINFO_EXTENSION );
$src[ $format ] = $url;
}

// Add woff2.
if ( ! empty( $src['woff2'] ) ) {
$src_ordered[] = array(
'url' => $src['woff2'],
'format' => 'woff2',
);
}

// Add woff.
if ( ! empty( $src['woff'] ) ) {
$src_ordered[] = array(
'url' => $src['woff'],
'format' => 'woff',
);
}

// Add ttf.
if ( ! empty( $src['ttf'] ) ) {
$src_ordered[] = array(
'url' => $src['ttf'],
'format' => 'truetype',
);
}

// Add eot.
if ( ! empty( $src['eot'] ) ) {
$src_ordered[] = array(
'url' => $src['eot'],
'format' => 'embedded-opentype',
);
}

// Add otf.
if ( ! empty( $src['otf'] ) ) {
$src_ordered[] = array(
'url' => $src['otf'],
'format' => 'opentype',
);
}
$font_face['src'] = $src_ordered;

return $font_face;
}

/**
* Builds the font-family's CSS.
*
* @since 6.4.0
*
* @param array $font_face Font face to process.
* @return string This font-family's CSS.
*/
private function build_font_face_css( array $font_face ) {
$css = '';

/*
* Wrap font-family in quotes if it contains spaces
* and is not already wrapped in quotes.
*/
if (
str_contains( $font_face['font-family'], ' ' ) &&
! str_contains( $font_face['font-family'], '"' ) &&
! str_contains( $font_face['font-family'], "'" )
) {
$font_face['font-family'] = '"' . $font_face['font-family'] . '"';
}

foreach ( $font_face as $key => $value ) {
// Compile the "src" parameter.
if ( 'src' === $key ) {
$value = $this->compile_src( $value );
}

// If font-variation-settings is an array, convert it to a string.
if ( 'font-variation-settings' === $key && is_array( $value ) ) {
$value = $this->compile_variations( $value );
}

if ( ! empty( $value ) ) {
$css .= "$key:$value;";
}
}

return $css;
}

/**
* Compiles the `src` into valid CSS.
*
* @since 6.4.0
*
* @param array $value Value to process.
* @return string The CSS.
*/
private function compile_src( array $value ) {
$src = '';

foreach ( $value as $item ) {
$src .= ( 'data' === $item['format'] )
? ", url({$item['url']})"
: ", url('{$item['url']}') format('{$item['format']}')";
}

$src = ltrim( $src, ', ' );
return $src;
}

/**
* Compiles the font variation settings.
*
* @since 6.4.0
*
* @param array $font_variation_settings Array of font variation settings.
* @return string The CSS.
*/
private function compile_variations( array $font_variation_settings ) {
$variations = '';

foreach ( $font_variation_settings as $key => $value ) {
$variations .= "$key $value";
}

return $variations;
}
}