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/* eslint-disable no-underscore-dangle */
import { Transform } from 'node:stream';
const NEW_LINE_CHAR = '\n'.codePointAt(0);
/**
* @typedef {Object} SourceMapTransformation
* @prop {number} line
* @prop {number} column
* @prop {string} content
*/
export default class SourceMapTransform extends Transform {
constructor() {
super({ objectMode: true });
}
/**
* @type {?{location:[number,number], buffers: Buffer[]}}
* buffer for the current incoming rule.
*/
#current = null;
/** track depth to handle rules nested in at-rules. */
#depth = 0;
/** track this and pass it downstream for source mapping. */
#line = 1;
/** track this and pass it downstream for source mapping. */
#column = 1;
/**
* @param {[string,Buffer]} chunk
* @param {any} encoding
* @param {Function} callback
*/
_transform([type, buf], encoding, callback) {
if ((type === 'rule_start' || type === 'atrule_start')) {
this.#depth += 1;
}
if (this.#depth > 0 && !this.#current) {
this.#current = { location: [this.#line, this.#column], buffers: [] };
}
if (type === 'rule_end' || type === 'atrule_end') {
this.#depth -= 1;
}
if (this.#current) {
this.#current.buffers.push(buf);
if (this.#depth === 0) {
// Push rule
this.push({
line: this.#current.location[0],
column: this.#current.location[1],
content: Buffer.concat(this.#current.buffers).toString(),
});
this.#current = null;
}
}
// Update position
for (const char of buf) {
if (char === NEW_LINE_CHAR) {
this.#line += 1;
this.#column = 1;
} else {
this.#column += 1;
}
}
callback();
}
}
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