| /** | |
| * Find all font files in the CSS response and determine which files should be preloaded. | |
| * In Google Fonts responses, the @font-face's subset is above it in a comment. | |
| * Walk through the CSS from top to bottom, keeping track of the current subset. | |
| */ | |
| export function findFontFilesInCss(css: string, subsetsToPreload?: string[]) { | |
| // Find font files to download | |
| const fontFiles: Array<{ | |
| googleFontFileUrl: string | |
| preloadFontFile: boolean | |
| }> = [] | |
| // Keep track of the current subset | |
| let currentSubset = '' | |
| for (const line of css.split('\n')) { | |
| const newSubset = /\/\* (.+?) \*\//.exec(line)?.[1] | |
| if (newSubset) { | |
| // Found new subset in a comment above the next @font-face declaration | |
| currentSubset = newSubset | |
| } else { | |
| const googleFontFileUrl = /src: url\((.+?)\)/.exec(line)?.[1] | |
| if ( | |
| googleFontFileUrl && | |
| !fontFiles.some( | |
| (foundFile) => foundFile.googleFontFileUrl === googleFontFileUrl | |
| ) | |
| ) { | |
| // Found the font file in the @font-face declaration. | |
| fontFiles.push({ | |
| googleFontFileUrl, | |
| preloadFontFile: !!subsetsToPreload?.includes(currentSubset), | |
| }) | |
| } | |
| } | |
| } | |
| return fontFiles | |
| } | |