next.js/packages/font/src/google/validate-google-font-function-call.ts

import { allowedDisplayValues } from '../constants'
import { formatAvailableValues } from '../format-available-values'
import { nextFontError } from '../next-font-error'
import { googleFontsMetadata } from './google-fonts-metadata'

type FontOptions = {
  fontFamily: string
  weights: string[]
  styles: string[]
  display: string
  preload: boolean
  selectedVariableAxes?: string[]
  fallback?: string[]
  adjustFontFallback: boolean
  variable?: string
  subsets: string[]
}
/**
 * Validate the data received from next-swc next-transform-font on next/font/google calls
 */
export function validateGoogleFontFunctionCall(
  functionName: string,
  fontFunctionArgument: any
): FontOptions {
  let {
    weight,
    style,
    preload = true,
    display = 'swap',
    axes,
    fallback,
    adjustFontFallback = true,
    variable,
    subsets,
  } = fontFunctionArgument || ({} as any)
  if (functionName === '') {
    nextFontError(`next/font/google has no default export`)
  }

  const fontFamily = functionName.replace(/_/g, ' ')
  // Get the Google font metadata, we'll use this to validate the font arguments and to print better error messages
  const fontFamilyData = googleFontsMetadata[fontFamily]
  if (!fontFamilyData) {
    nextFontError(`Unknown font \`${fontFamily}\``)
  }

  const availableSubsets = fontFamilyData.subsets
  if (availableSubsets.length === 0) {
    // If the font doesn't have any preloadeable subsets, disable preload
    preload = false
  } else if (preload) {
    if (!subsets) {
      nextFontError(
        `Preload is enabled but no subsets were specified for font \`${fontFamily}\`. Please specify subsets or disable preloading if your intended subset can't be preloaded.\nAvailable subsets: ${formatAvailableValues(
          availableSubsets
        )}\n\nRead more: https://nextjs.org/docs/messages/google-fonts-missing-subsets`
      )
    }
    subsets.forEach((subset: string) => {
      if (!availableSubsets.includes(subset)) {
        nextFontError(
          `Unknown subset \`${subset}\` for font \`${fontFamily}\`.\nAvailable subsets: ${formatAvailableValues(
            availableSubsets
          )}`
        )
      }
    })
  }

  const fontWeights = fontFamilyData.weights
  const fontStyles = fontFamilyData.styles

  // Get the unique weights and styles from the function call
  const weights = !weight
    ? []
    : [...new Set(Array.isArray(weight) ? weight : [weight])]
  const styles = !style
    ? []
    : [...new Set(Array.isArray(style) ? style : [style])]

  if (weights.length === 0) {
    // Set variable as default, throw if not available
    if (fontWeights.includes('variable')) {
      weights.push('variable')
    } else {
      nextFontError(
        `Missing weight for font \`${fontFamily}\`.\nAvailable weights: ${formatAvailableValues(
          fontWeights
        )}`
      )
    }
  }

  if (weights.length > 1 && weights.includes('variable')) {
    nextFontError(
      `Unexpected \`variable\` in weight array for font \`${fontFamily}\`. You only need \`variable\`, it includes all available weights.`
    )
  }

  weights.forEach((selectedWeight) => {
    if (!fontWeights.includes(selectedWeight)) {
      nextFontError(
        `Unknown weight \`${selectedWeight}\` for font \`${fontFamily}\`.\nAvailable weights: ${formatAvailableValues(
          fontWeights
        )}`
      )
    }
  })

  if (styles.length === 0) {
    if (fontStyles.length === 1) {
      // Handle default style for fonts that only have italic
      styles.push(fontStyles[0])
    } else {
      // Otherwise set default style to normal
      styles.push('normal')
    }
  }

  styles.forEach((selectedStyle) => {
    if (!fontStyles.includes(selectedStyle)) {
      nextFontError(
        `Unknown style \`${selectedStyle}\` for font \`${fontFamily}\`.\nAvailable styles: ${formatAvailableValues(
          fontStyles
        )}`
      )
    }
  })

  if (!allowedDisplayValues.includes(display)) {
    nextFontError(
      `Invalid display value \`${display}\` for font \`${fontFamily}\`.\nAvailable display values: ${formatAvailableValues(
        allowedDisplayValues
      )}`
    )
  }

  if (axes) {
    if (!fontWeights.includes('variable')) {
      nextFontError('Axes can only be defined for variable fonts.')
    }

    if (weights[0] !== 'variable') {
      nextFontError(
        'Axes can only be defined for variable fonts when the weight property is nonexistent or set to `variable`.'
      )
    }
  }

  return {
    fontFamily,
    weights,
    styles,
    display,
    preload,
    selectedVariableAxes: axes,
    fallback,
    adjustFontFallback,
    variable,
    subsets,
  }
}