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/**
* @typedef {import('micromark-util-types').Chunk} Chunk
* @typedef {import('micromark-util-types').Code} Code
* @typedef {import('micromark-util-types').Encoding} Encoding
* @typedef {import('micromark-util-types').Value} Value
*/
/**
* @callback Preprocessor
* @param {Value} value
* @param {Encoding | null | undefined} [encoding]
* @param {boolean | null | undefined} [end=false]
* @returns {Array<Chunk>}
*/
const search = /[\0\t\n\r]/g
/**
* @returns {Preprocessor}
*/
export function preprocess() {
let column = 1
let buffer = ''
/** @type {boolean | undefined} */
let start = true
/** @type {boolean | undefined} */
let atCarriageReturn
return preprocessor
/** @type {Preprocessor} */
function preprocessor(value, encoding, end) {
/** @type {Array<Chunk>} */
const chunks = []
/** @type {RegExpMatchArray | null} */
let match
/** @type {number} */
let next
/** @type {number} */
let startPosition
/** @type {number} */
let endPosition
/** @type {Code} */
let code
// @ts-expect-error `Buffer` does allow an encoding.
value = buffer + value.toString(encoding)
startPosition = 0
buffer = ''
if (start) {
// To do: `markdown-rs` actually parses BOMs (byte order mark).
if (value.charCodeAt(0) === 65279) {
startPosition++
}
start = undefined
}
while (startPosition < value.length) {
search.lastIndex = startPosition
match = search.exec(value)
endPosition =
match && match.index !== undefined ? match.index : value.length
code = value.charCodeAt(endPosition)
if (!match) {
buffer = value.slice(startPosition)
break
}
if (code === 10 && startPosition === endPosition && atCarriageReturn) {
chunks.push(-3)
atCarriageReturn = undefined
} else {
if (atCarriageReturn) {
chunks.push(-5)
atCarriageReturn = undefined
}
if (startPosition < endPosition) {
chunks.push(value.slice(startPosition, endPosition))
column += endPosition - startPosition
}
switch (code) {
case 0: {
chunks.push(65533)
column++
break
}
case 9: {
next = Math.ceil(column / 4) * 4
chunks.push(-2)
while (column++ < next) chunks.push(-1)
break
}
case 10: {
chunks.push(-4)
column = 1
break
}
default: {
atCarriageReturn = true
column = 1
}
}
}
startPosition = endPosition + 1
}
if (end) {
if (atCarriageReturn) chunks.push(-5)
if (buffer) chunks.push(buffer)
chunks.push(null)
}
return chunks
}
}
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