source: frontend/node_modules/source-list-map/lib/fromStringWithSourceMap.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/
"use strict";

const base64VLQ = require("./base64-vlq");
const SourceNode = require("./SourceNode");
const CodeNode = require("./CodeNode");
const SourceListMap = require("./SourceListMap");

module.exports = function fromStringWithSourceMap(code, map) {
        const sources = map.sources;
        const sourcesContent = map.sourcesContent;
        const mappings = map.mappings.split(";");
        const lines = code.split("\n");
        const nodes = [];
        let currentNode = null;
        let currentLine = 1;
        let currentSourceIdx = 0;
        let currentSourceNodeLine;
        function addCode(generatedCode) {
                if(currentNode && currentNode instanceof CodeNode) {
                        currentNode.addGeneratedCode(generatedCode);
                } else if(currentNode && currentNode instanceof SourceNode && !generatedCode.trim()) {
                        currentNode.addGeneratedCode(generatedCode);
                        currentSourceNodeLine++;
                } else {
                        currentNode = new CodeNode(generatedCode);
                        nodes.push(currentNode);
                }
        }
        function addSource(generatedCode, source, originalSource, linePosition) {
                if(currentNode && currentNode instanceof SourceNode &&
                        currentNode.source === source &&
                        currentSourceNodeLine === linePosition
                ) {
                        currentNode.addGeneratedCode(generatedCode);
                        currentSourceNodeLine++;
                } else {
                        currentNode = new SourceNode(generatedCode, source, originalSource, linePosition);
                        currentSourceNodeLine = linePosition + 1;
                        nodes.push(currentNode);
                }
        }
        mappings.forEach(function(mapping, idx) {
                let line = lines[idx];
                if(typeof line === 'undefined') return;
                if(idx !== lines.length - 1) line += "\n";
                if(!mapping)
                        return addCode(line);
                mapping = { value: 0, rest: mapping };
                let lineAdded = false;
                while(mapping.rest)
                        lineAdded = processMapping(mapping, line, lineAdded) || lineAdded;
                if(!lineAdded)
                        addCode(line);
        });
        if(mappings.length < lines.length) {
                let idx = mappings.length;
                while(!lines[idx].trim() && idx < lines.length-1) {
                        addCode(lines[idx] + "\n");
                        idx++;
                }
                addCode(lines.slice(idx).join("\n"));
        }
        return new SourceListMap(nodes);
        function processMapping(mapping, line, ignore) {
                if(mapping.rest && mapping.rest[0] !== ",") {
                        base64VLQ.decode(mapping.rest, mapping);
                }
                if(!mapping.rest)
                        return false;
                if(mapping.rest[0] === ",") {
                        mapping.rest = mapping.rest.substr(1);
                        return false;
                }

                base64VLQ.decode(mapping.rest, mapping);
                const sourceIdx = mapping.value + currentSourceIdx;
                currentSourceIdx = sourceIdx;

                let linePosition;
                if(mapping.rest && mapping.rest[0] !== ",") {
                        base64VLQ.decode(mapping.rest, mapping);
                        linePosition = mapping.value + currentLine;
                        currentLine = linePosition;
                } else {
                        linePosition = currentLine;
                }

                if(mapping.rest) {
                        const next = mapping.rest.indexOf(",");
                        mapping.rest = next === -1 ? "" : mapping.rest.substr(next);
                }

                if(!ignore) {
                        addSource(line, sources ? sources[sourceIdx] : null, sourcesContent ? sourcesContent[sourceIdx] : null, linePosition)
                        return true;
                }
        }
};