@x-govuk/govuk-eleventy-plugin/src/utils.js

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import fs from 'node:fs/promises'
import path from 'node:path'

/**
 * Get file contents
 *
 * @param {string} baseDirectory - Base directory for files
 * @param {string} filePath - Path to file
 * @returns {Promise<string>} File contents
 */
export async function getFileContents(baseDirectory, filePath) {
  filePath = path.join(baseDirectory, filePath)

  return await fs.readFile(filePath, { encoding: 'utf8' })
}

/**
 * Get navigation key for page
 *
 * @param {object} data - Page data
 * @returns {string|undefined} Page navigation key
 */
export const getNavigationKey = (data) => {
  const { homepage, eleventyExcludeFromCollections, eleventyNavigation } = data

  if (homepage) {
    // Use explicit navigation `key`, or `homeKey` set in plugin options
    return eleventyNavigation.key || data.options.homeKey
  } else if (!eleventyExcludeFromCollections) {
    // Use explicit navigation `key`, or page title
    return eleventyNavigation.key || data.title
  }
}

/**
 * Get navigation parent for page
 *
 * @param {object} data - Page data
 * @returns {string|undefined} Parent page key
 */
export const getNavigationParent = (data) => {
  const { homepage, eleventyExcludeFromCollections, eleventyNavigation } = data

  if (homepage) {
    // The homepage has no parent
    return false
  } else if (!eleventyExcludeFromCollections) {
    // Use explicit navigation `parent`, or `homeKey` set in plugin options
    return eleventyNavigation.parent || data.options.homeKey
  }
}

/**
 * Get virtual templates for default layouts
 * Uses users own named layout if exists, else provides a virtual template
 *
 * @param {object} eleventyConfig - Eleventy config
 * @param {Array} layoutFiles - Layout files
 * @param {string} baseDirectory - Base directory
 * @returns {object} Template names and strings
 */
export async function getLayoutTemplates(
  eleventyConfig,
  layoutFiles,
  baseDirectory
) {
  const { includes, layouts, input } = eleventyConfig.dir
  const layoutDir = layouts || includes
  const templates = {}
  baseDirectory = baseDirectory || path.join(import.meta.dirname, '..')

  for (const filename of layoutFiles) {
    try {
      const templatePath = path.join(input, layoutDir, filename)
      await fs.stat(templatePath)
    } catch {
      const templateString = await getFileContents(
        baseDirectory,
        `src/layouts/${filename}`
      )
      templates[`${layoutDir}/${filename}`] = templateString
    }
  }

  return templates
}

/**
 * Normalise value provided to a filter. Checks that a given value exists
 * before performing a transformation.
 *
 * @template T
 * @param {T} value - Input value
 * @param {T} defaultValue - Value to fallback to if no value given
 * @returns {T} defaultValue
 */
export function normalise(value, defaultValue) {
  if (value === null || value === undefined || value === false) {
    return defaultValue
  }

  return value
}