feat: font specification flexibility

quartz/util/theme.ts

@@ -15,11 +15,19 @@ interface Colors {
   darkMode: ColorScheme
 }
 
+type FontSpecification =
+  | string
+  | {
+      name: string
+      weights?: number[]
+      includeItalic?: boolean
+    }
+
 export interface Theme {
   typography: {
-    header: string
-    body: string
-    code: string
+    header: FontSpecification
+    body: FontSpecification
+    code: FontSpecification
   }
   cdnCaching: boolean
   colors: Colors
@@ -32,9 +40,54 @@ const DEFAULT_SANS_SERIF =
   'system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol"'
 const DEFAULT_MONO = "ui-monospace, SFMono-Regular, SF Mono, Menlo, monospace"
 
+export function getFontSpecificationName(spec: FontSpecification): string {
+  if (typeof spec === "string") {
+    return spec
+  }
+
+  return spec.name
+}
+
+function formatFontSpecification(type: "header" | "body" | "code", spec: FontSpecification) {
+  if (typeof spec === "string") {
+    spec = { name: spec }
+  }
+
+  const defaultIncludeWeights = type === "header" ? [400, 700] : [400, 600]
+  const defaultIncludeItalic = type === "body"
+  const weights = spec.weights ?? defaultIncludeWeights
+  const italic = spec.includeItalic ?? defaultIncludeItalic
+
+  const features: string[] = []
+  if (italic) {
+    features.push("ital")
+  }
+
+  if (weights.length > 1) {
+    const weightSpec = italic
+      ? weights
+          .flatMap((w) => [`0,${w}`, `1,${w}`])
+          .sort()
+          .join(";")
+      : weights.join(";")
+
+    features.push(`wght@${weightSpec}`)
+  }
+
+  if (features.length > 0) {
+    return `${spec.name}:${features.join(",")}`
+  }
+
+  return spec.name
+}
+
 export function googleFontHref(theme: Theme) {
   const { code, header, body } = theme.typography
-  return `https://fonts.googleapis.com/css2?family=${code}&family=${header}:wght@400;700&family=${body}:ital,wght@0,400;0,600;1,400;1,600&display=swap`
+  const headerFont = formatFontSpecification("header", header)
+  const bodyFont = formatFontSpecification("body", body)
+  const codeFont = formatFontSpecification("code", code)
+
+  return `https://fonts.googleapis.com/css2?family=${bodyFont}&family=${headerFont}&family=${codeFont}&display=swap`
 }
 
 export function joinStyles(theme: Theme, ...stylesheet: string[]) {