tailwindcss/src/lib/evaluateTailwindFunctions.js

import dlv from 'dlv'
import didYouMean from 'didyoumean'
import transformThemeValue from '../util/transformThemeValue'
import parseValue from 'postcss-value-parser'
import { normalizeScreens } from '../util/normalizeScreens'
import buildMediaQuery from '../util/buildMediaQuery'
import { toPath } from '../util/toPath'

function isObject(input) {
  return typeof input === 'object' && input !== null
}

function findClosestExistingPath(theme, path) {
  let parts = toPath(path)
  do {
    parts.pop()

    if (dlv(theme, parts) !== undefined) break
  } while (parts.length)

  return parts.length ? parts : undefined
}

function pathToString(path) {
  if (typeof path === 'string') return path
  return path.reduce((acc, cur, i) => {
    if (cur.includes('.')) return `${acc}[${cur}]`
    return i === 0 ? cur : `${acc}.${cur}`
  }, '')
}

function list(items) {
  return items.map((key) => `'${key}'`).join(', ')
}

function listKeys(obj) {
  return list(Object.keys(obj))
}

function validatePath(config, path, defaultValue) {
  const pathString = Array.isArray(path)
    ? pathToString(path)
    : path.replace(/^['"]+/g, '').replace(/['"]+$/g, '')
  const pathSegments = Array.isArray(path) ? path : toPath(pathString)
  const value = dlv(config.theme, pathString, defaultValue)

  if (value === undefined) {
    let error = `'${pathString}' does not exist in your theme config.`
    const parentSegments = pathSegments.slice(0, -1)
    const parentValue = dlv(config.theme, parentSegments)

    if (isObject(parentValue)) {
      const validKeys = Object.keys(parentValue).filter(
        (key) => validatePath(config, [...parentSegments, key]).isValid
      )
      const suggestion = didYouMean(pathSegments[pathSegments.length - 1], validKeys)
      if (suggestion) {
        error += ` Did you mean '${pathToString([...parentSegments, suggestion])}'?`
      } else if (validKeys.length > 0) {
        error += ` '${pathToString(parentSegments)}' has the following valid keys: ${list(
          validKeys
        )}`
      }
    } else {
      const closestPath = findClosestExistingPath(config.theme, pathString)
      if (closestPath) {
        const closestValue = dlv(config.theme, closestPath)
        if (isObject(closestValue)) {
          error += ` '${pathToString(closestPath)}' has the following keys: ${listKeys(
            closestValue
          )}`
        } else {
          error += ` '${pathToString(closestPath)}' is not an object.`
        }
      } else {
        error += ` Your theme has the following top-level keys: ${listKeys(config.theme)}`
      }
    }

    return {
      isValid: false,
      error,
    }
  }

  if (
    !(
      typeof value === 'string' ||
      typeof value === 'number' ||
      typeof value === 'function' ||
      value instanceof String ||
      value instanceof Number ||
      Array.isArray(value)
    )
  ) {
    let error = `'${pathString}' was found but does not resolve to a string.`

    if (isObject(value)) {
      let validKeys = Object.keys(value).filter(
        (key) => validatePath(config, [...pathSegments, key]).isValid
      )
      if (validKeys.length) {
        error += ` Did you mean something like '${pathToString([...pathSegments, validKeys[0]])}'?`
      }
    }

    return {
      isValid: false,
      error,
    }
  }

  const [themeSection] = pathSegments

  return {
    isValid: true,
    value: transformThemeValue(themeSection)(value),
  }
}

function extractArgs(node, vNodes, functions) {
  vNodes = vNodes.map((vNode) => resolveVNode(node, vNode, functions))

  let args = ['']

  for (let vNode of vNodes) {
    if (vNode.type === 'div' && vNode.value === ',') {
      args.push('')
    } else {
      args[args.length - 1] += parseValue.stringify(vNode)
    }
  }

  return args
}

function resolveVNode(node, vNode, functions) {
  if (vNode.type === 'function' && functions[vNode.value] !== undefined) {
    let args = extractArgs(node, vNode.nodes, functions)
    vNode.type = 'word'
    vNode.value = functions[vNode.value](node, ...args)
  }

  return vNode
}

function resolveFunctions(node, input, functions) {
  return parseValue(input)
    .walk((vNode) => {
      resolveVNode(node, vNode, functions)
    })
    .toString()
}

let nodeTypePropertyMap = {
  atrule: 'params',
  decl: 'value',
}

export default function ({ tailwindConfig: config }) {
  let functions = {
    theme: (node, path, ...defaultValue) => {
      const { isValid, value, error } = validatePath(
        config,
        path,
        defaultValue.length ? defaultValue : undefined
      )

      if (!isValid) {
        throw node.error(error)
      }

      return value
    },
    screen: (node, screen) => {
      screen = screen.replace(/^['"]+/g, '').replace(/['"]+$/g, '')
      let screens = normalizeScreens(config.theme.screens)
      let screenDefinition = screens.find(({ name }) => name === screen)

      if (!screenDefinition) {
        throw node.error(`The '${screen}' screen does not exist in your theme.`)
      }

      return buildMediaQuery(screenDefinition)
    },
  }
  return (root) => {
    root.walk((node) => {
      let property = nodeTypePropertyMap[node.type]

      if (property === undefined) {
        return
      }

      node[property] = resolveFunctions(node, node[property], functions)
    })
  }
}