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A utility-first CSS framework for rapidly building custom user interfaces.
// @ts-check
import bigSign from '../util/bigSign'
import { remapBitfield } from './remap-bitfield.js'
/**
* @typedef {'base' | 'defaults' | 'components' | 'utilities' | 'variants' | 'user'} Layer
*/
/**
* @typedef {object} VariantOption
* @property {number} id An unique identifier to identify `matchVariant`
* @property {function | undefined} sort The sort function
* @property {string|null} value The value we want to compare
* @property {string|null} modifier The modifier that was used (if any)
* @property {bigint} variant The variant bitmask
*/
/**
* @typedef {object} RuleOffset
* @property {Layer} layer The layer that this rule belongs to
* @property {Layer} parentLayer The layer that this rule originally belonged to. Only different from layer if this is a variant.
* @property {bigint} arbitrary 0n if false, 1n if true
* @property {bigint} variants Dynamic size. 1 bit per registered variant. 0n means no variants
* @property {bigint} parallelIndex Rule index for the parallel variant. 0 if not applicable.
* @property {bigint} index Index of the rule / utility in its given *parent* layer. Monotonically increasing.
* @property {bigint} propertyOffset Offset for the arbitrary property. Only valid after sorting.
* @property {string} property Name/Value of the arbitrary property.
* @property {VariantOption[]} options Some information on how we can sort arbitrary variants
*/
export class Offsets {
constructor() {
/**
* Offsets for the next rule in a given layer
*
* @type {Record}
*/
this.offsets = {
defaults: 0n,
base: 0n,
components: 0n,
utilities: 0n,
variants: 0n,
user: 0n,
}
/**
* Positions for a given layer
*
* @type {Record}
*/
this.layerPositions = {
defaults: 0n,
base: 1n,
components: 2n,
utilities: 3n,
// There isn't technically a "user" layer, but we need to give it a position
// Because it's used for ordering user-css from @apply
user: 4n,
variants: 5n,
}
/**
* The total number of functions currently registered across all variants (including arbitrary variants)
*
* @type {bigint}
*/
this.reservedVariantBits = 0n
/**
* Positions for a given variant
*
* @type {Map}
*/
this.variantOffsets = new Map()
}
/**
* @param {Layer} layer
* @returns {RuleOffset}
*/
create(layer) {
return {
layer,
parentLayer: layer,
arbitrary: 0n,
variants: 0n,
parallelIndex: 0n,
index: this.offsets[layer]++,
propertyOffset: 0n,
property: '',
options: [],
}
}
/**
* @param {string} name
* @returns {RuleOffset}
*/
arbitraryProperty(name) {
return {
...this.create('utilities'),
arbitrary: 1n,
property: name,
}
}
/**
* Get the offset for a variant
*
* @param {string} variant
* @param {number} index
* @returns {RuleOffset}
*/
forVariant(variant, index = 0) {
let offset = this.variantOffsets.get(variant)
if (offset === undefined) {
throw new Error(`Cannot find offset for unknown variant ${variant}`)
}
return {
...this.create('variants'),
variants: offset << BigInt(index),
}
}
/**
* @param {RuleOffset} rule
* @param {RuleOffset} variant
* @param {VariantOption} options
* @returns {RuleOffset}
*/
applyVariantOffset(rule, variant, options) {
options.variant = variant.variants
return {
...rule,
layer: 'variants',
parentLayer: rule.layer === 'variants' ? rule.parentLayer : rule.layer,
variants: rule.variants | variant.variants,
options: options.sort ? [].concat(options, rule.options) : rule.options,
// TODO: Technically this is wrong. We should be handling parallel index on a per variant basis.
// We'll take the max of all the parallel indexes for now.
// @ts-ignore
parallelIndex: max([rule.parallelIndex, variant.parallelIndex]),
}
}
/**
* @param {RuleOffset} offset
* @param {number} parallelIndex
* @returns {RuleOffset}
*/
applyParallelOffset(offset, parallelIndex) {
return {
...offset,
parallelIndex: BigInt(parallelIndex),
}
}
/**
* Each variant gets 1 bit per function / rule registered.
* This is because multiple variants can be applied to a single rule and we need to know which ones are present and which ones are not.
* Additionally, every unique group of variants is grouped together in the stylesheet.
*
* This grouping is order-independent. For instance, we do not differentiate between `hover:focus` and `focus:hover`.
*
* @param {string[]} variants
* @param {(name: string) => number} getLength
*/
recordVariants(variants, getLength) {
for (let variant of variants) {
this.recordVariant(variant, getLength(variant))
}
}
/**
* The same as `recordVariants` but for a single arbitrary variant at runtime.
* @param {string} variant
* @param {number} fnCount
*
* @returns {RuleOffset} The highest offset for this variant
*/
recordVariant(variant, fnCount = 1) {
this.variantOffsets.set(variant, 1n << this.reservedVariantBits)
// Ensure space is reserved for each "function" in the parallel variant
// by offsetting the next variant by the number of parallel variants
// in the one we just added.
// Single functions that return parallel variants are NOT handled separately here
// They're offset by 1 (or the number of functions) as usual
// And each rule returned is tracked separately since the functions are evaluated lazily.
// @see `RuleOffset.parallelIndex`
this.reservedVariantBits += BigInt(fnCount)
return {
...this.create('variants'),
variants: this.variantOffsets.get(variant),
}
}
/**
* @param {RuleOffset} a
* @param {RuleOffset} b
* @returns {bigint}
*/
compare(a, b) {
// Sort layers together
if (a.layer !== b.layer) {
return this.layerPositions[a.layer] - this.layerPositions[b.layer]
}
// When sorting the `variants` layer, we need to sort based on the parent layer as well within
// this variants layer.
if (a.parentLayer !== b.parentLayer) {
return this.layerPositions[a.parentLayer] - this.layerPositions[b.parentLayer]
}
// Sort based on the sorting function
for (let aOptions of a.options) {
for (let bOptions of b.options) {
if (aOptions.id !== bOptions.id) continue
if (!aOptions.sort || !bOptions.sort) continue
let maxFnVariant = max([aOptions.variant, bOptions.variant]) ?? 0n
// Create a mask of 0s from bits 1..N where N represents the mask of the Nth bit
let mask = ~(maxFnVariant | (maxFnVariant - 1n))
let aVariantsAfterFn = a.variants & mask
let bVariantsAfterFn = b.variants & mask
// If the variants the same, we _can_ sort them
if (aVariantsAfterFn !== bVariantsAfterFn) {
continue
}
let result = aOptions.sort(
{
value: aOptions.value,
modifier: aOptions.modifier,
},
{
value: bOptions.value,
modifier: bOptions.modifier,
}
)
if (result !== 0) return result
}
}
// Sort variants in the order they were registered
if (a.variants !== b.variants) {
return a.variants - b.variants
}
// Make sure each rule returned by a parallel variant is sorted in ascending order
if (a.parallelIndex !== b.parallelIndex) {
return a.parallelIndex - b.parallelIndex
}
// Always sort arbitrary properties after other utilities
if (a.arbitrary !== b.arbitrary) {
return a.arbitrary - b.arbitrary
}
// Always sort arbitrary properties alphabetically
if (a.propertyOffset !== b.propertyOffset) {
return a.propertyOffset - b.propertyOffset
}
// Sort utilities, components, etc… in the order they were registered
return a.index - b.index
}
/**
* Arbitrary variants are recorded in the order they're encountered.
* This means that the order is not stable between environments and sets of content files.
*
* In order to make the order stable, we need to remap the arbitrary variant offsets to
* be in alphabetical order starting from the offset of the first arbitrary variant.
*/
recalculateVariantOffsets() {
// Sort the variants by their name
let variants = Array.from(this.variantOffsets.entries())
.filter(([v]) => v.startsWith('['))
.sort(([a], [z]) => fastCompare(a, z))
// Sort the list of offsets
// This is not necessarily a discrete range of numbers which is why
// we're using sort instead of creating a range from min/max
let newOffsets = variants.map(([, offset]) => offset).sort((a, z) => bigSign(a - z))
// Create a map from the old offsets to the new offsets in the new sort order
/** @type {[bigint, bigint][]} */
let mapping = variants.map(([, oldOffset], i) => [oldOffset, newOffsets[i]])
// Remove any variants that will not move letting us skip
// remapping if everything happens to be in order
return mapping.filter(([a, z]) => a !== z)
}
/**
* @template T
* @param {[RuleOffset, T][]} list
* @returns {[RuleOffset, T][]}
*/
remapArbitraryVariantOffsets(list) {
let mapping = this.recalculateVariantOffsets()
// No arbitrary variants? Nothing to do.
// Everyhing already in order? Nothing to do.
if (mapping.length === 0) {
return list
}
// Remap every variant offset in the list
return list.map((item) => {
let [offset, rule] = item
offset = {
...offset,
variants: remapBitfield(offset.variants, mapping),
}
return [offset, rule]
})
}
/**
* @template T
* @param {[RuleOffset, T][]} list
* @returns {[RuleOffset, T][]}
*/
sortArbitraryProperties(list) {
// Collect all known arbitrary properties
let known = new Set()
for (let [offset] of list) {
if (offset.arbitrary === 1n) {
known.add(offset.property)
}
}
// No arbitrary properties? Nothing to do.
if (known.size === 0) {
return list
}
// Sort the properties alphabetically
let properties = Array.from(known).sort()
// Create a map from the property name to its offset
let offsets = new Map()
let offset = 1n
for (let property of properties) {
offsets.set(property, offset++)
}
// Apply the sorted offsets to the list
return list.map((item) => {
let [offset, rule] = item
offset = {
...offset,
propertyOffset: offsets.get(offset.property) ?? 0n,
}
return [offset, rule]
})
}
/**
* @template T
* @param {[RuleOffset, T][]} list
* @returns {[RuleOffset, T][]}
*/
sort(list) {
// Sort arbitrary variants so they're in alphabetical order
list = this.remapArbitraryVariantOffsets(list)
// Sort arbitrary properties so they're in alphabetical order
list = this.sortArbitraryProperties(list)
return list.sort(([a], [b]) => bigSign(this.compare(a, b)))
}
}
/**
*
* @param {bigint[]} nums
* @returns {bigint|null}
*/
function max(nums) {
let max = null
for (const num of nums) {
max = max ?? num
max = max > num ? max : num
}
return max
}
/**
* A fast ASCII order string comparison function.
*
* Using `.sort()` without a custom compare function is faster
* But you can only use that if you're sorting an array of
* only strings. If you're sorting strings inside objects
* or arrays, you need must use a custom compare function.
*
* @param {string} a
* @param {string} b
*/
function fastCompare(a, b) {
let aLen = a.length
let bLen = b.length
let minLen = aLen < bLen ? aLen : bLen
for (let i = 0; i < minLen; i++) {
let cmp = a.charCodeAt(i) - b.charCodeAt(i)
if (cmp !== 0) return cmp
}
return aLen - bLen
}