139 lines
3.2 KiB
Plaintext
139 lines
3.2 KiB
Plaintext
/**
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* @typedef {import('micromark-util-types').Chunk} Chunk
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* @typedef {import('micromark-util-types').Code} Code
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* @typedef {import('micromark-util-types').Encoding} Encoding
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* @typedef {import('micromark-util-types').Value} Value
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*/
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/**
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* @callback Preprocessor
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* @param {Value} value
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* @param {Encoding | null | undefined} [encoding]
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* @param {boolean | null | undefined} [end=false]
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* @returns {Array<Chunk>}
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*/
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import {codes, constants} from 'micromark-util-symbol'
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const search = /[\0\t\n\r]/g
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/**
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* @returns {Preprocessor}
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*/
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export function preprocess() {
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let column = 1
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let buffer = ''
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/** @type {boolean | undefined} */
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let start = true
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/** @type {boolean | undefined} */
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let atCarriageReturn
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return preprocessor
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/** @type {Preprocessor} */
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// eslint-disable-next-line complexity
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function preprocessor(value, encoding, end) {
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/** @type {Array<Chunk>} */
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const chunks = []
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/** @type {RegExpMatchArray | null} */
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let match
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/** @type {number} */
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let next
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/** @type {number} */
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let startPosition
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/** @type {number} */
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let endPosition
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/** @type {Code} */
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let code
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value =
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buffer +
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(typeof value === 'string'
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? value.toString()
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: new TextDecoder(encoding || undefined).decode(value))
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startPosition = 0
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buffer = ''
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if (start) {
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// To do: `markdown-rs` actually parses BOMs (byte order mark).
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if (value.charCodeAt(0) === codes.byteOrderMarker) {
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startPosition++
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}
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start = undefined
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}
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while (startPosition < value.length) {
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search.lastIndex = startPosition
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match = search.exec(value)
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endPosition =
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match && match.index !== undefined ? match.index : value.length
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code = value.charCodeAt(endPosition)
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if (!match) {
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buffer = value.slice(startPosition)
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break
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}
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if (
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code === codes.lf &&
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startPosition === endPosition &&
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atCarriageReturn
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) {
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chunks.push(codes.carriageReturnLineFeed)
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atCarriageReturn = undefined
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} else {
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if (atCarriageReturn) {
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chunks.push(codes.carriageReturn)
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atCarriageReturn = undefined
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}
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if (startPosition < endPosition) {
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chunks.push(value.slice(startPosition, endPosition))
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column += endPosition - startPosition
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}
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switch (code) {
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case codes.nul: {
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chunks.push(codes.replacementCharacter)
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column++
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break
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}
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case codes.ht: {
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next = Math.ceil(column / constants.tabSize) * constants.tabSize
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chunks.push(codes.horizontalTab)
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while (column++ < next) chunks.push(codes.virtualSpace)
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break
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}
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case codes.lf: {
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chunks.push(codes.lineFeed)
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column = 1
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break
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}
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default: {
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atCarriageReturn = true
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column = 1
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}
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}
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}
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startPosition = endPosition + 1
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}
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if (end) {
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if (atCarriageReturn) chunks.push(codes.carriageReturn)
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if (buffer) chunks.push(buffer)
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chunks.push(codes.eof)
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}
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return chunks
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}
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}
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