reduce_v1.js

const fs = require('fs');
const readline = require('readline');

const FILE_PATH = './src/app/assets/css/phillip/styles.css';
const OUTPUT_PATH = './src/app/assets/css/phillip/styles.css';
const NEW_LINE = '\n';

const lineReader = readline.createInterface({
    input: fs.createReadStream(FILE_PATH)
});
const lineProcessor = getLineProcessor(ruleFilter, cssFilter);
let outputText = '';


lineReader.on('line', (line) => {
    lineProcessor(line);
}).on('close', () => {
    fs.writeFileSync(OUTPUT_PATH, outputText);
});


// true -> leave it as it is
function ruleFilter(rule, css, headerPassed) {
    // @textColor, @linkColor, @bullishColor, @bearishColor
    if (rule.indexOf('@textColor') !== -1 || rule.indexOf('@linkColor') !== -1 || rule.indexOf('@bullishColor') !== -1 || rule.indexOf('@bearishColor') !== -1) {
        return true;
    }
    // .tc-presto li, .tc-presto p, .tc-presto input, .tc-presto textarea, .tc-presto select ...
    if (-1 !== css.selectors.indexOf('.tc-presto li, .tc-presto p, .tc-presto input, .tc-presto textarea, .tc-presto select, .tc-presto td, .tc-presto th, .tc-presto button, .tc-presto div, .tc-presto h1, .tc-presto span')) {
        return true;
    }
    // .tc-search-bar-button-container {}, .tc-search-bar-button-icon {}
    if (-1 !== css.selectors.indexOf('.tc-search-bar-button-container') || -1 !== css.selectors.indexOf('.tc-search-bar-button-icon')) {
        return true;
    }
    // All "text" styles at top of file
    if (!headerPassed && (rule.indexOf('color:') !== -1 && rule.indexOf('-color:') === -1 || rule.indexOf('font-') !== -1 || rule.indexOf('text-') !== -1)) {
        return true;
    }
    return false;
}

// true -> leave it as it is
function cssFilter(css, headerPassed) {
    // .tc-presto li, .tc-presto p, .tc-presto input, .tc-presto textarea, .tc-presto select ...
    if (-1 !== css.selectors.indexOf('.tc-presto li, .tc-presto p, .tc-presto input, .tc-presto textarea, .tc-presto select, .tc-presto td, .tc-presto th, .tc-presto button, .tc-presto div, .tc-presto h1, .tc-presto span')) {
        return true;
    }
    // .tc-search-bar-button-container {}, .tc-search-bar-button-icon {}
    if (-1 !== css.selectors.indexOf('.tc-search-bar-button-container') || -1 !== css.selectors.indexOf('.tc-search-bar-button-icon')) {
        return true;
    }
    // filter out all empty css style like: selector {}
    // 1 here, because ending bracket is in the rule array
    return css.rules.length > 1;
}

function getLineProcessor(ruleFilter, cssFilter) {
    let headerPassed = false;
    const scanStates = {
        selectorsDone: false,
    };
    let css = null;

    function resetScanStates() {
        scanStates.selectorsDone = false;
    }

    function isRuleLine(line) {
        return line.indexOf(';') !== -1;
    }

    function isEndingBracket(line) {
        return line.indexOf('}') !== -1;
    }

    // assume no empty css style in source files
    return (line) => {
        if (line.indexOf('.tc-auto-suggest {') !== -1) {
            headerPassed = true;
        }
        if (!scanStates.selectorsDone) {
            if (css) {
                if (isRuleLine(line)) {
                    scanStates.selectorsDone = true;
                    if (ruleFilter(line, css, headerPassed)) { css.appendRule(line); }
                } else {
                    css.appendSelector(line);
                }
            } else {
                css = new Css();
                css.appendSelector(line);
            }
        } else {
            if (isRuleLine(line)) {
                if (ruleFilter(line, css, headerPassed)) { css.appendRule(line); }
            } else if (isEndingBracket(line)) {
                css.appendRule(line);

                // have read a whole css ..
                if (cssFilter(css, headerPassed)) { outputText += css.toString(); }
                css = null;
                resetScanStates();
            } else {
                css.appendRule(line);
            }
        }
    };
}

function Css() {
    // including comments
    this.selectors = '';
    // including comments and ending bracket
    this.rules = [];
    this.emptyCss = true;
}
Css.prototype.appendSelector = function(selector) {
    this.selectors += selector + NEW_LINE;
};
Css.prototype.appendRule = function(rule) {
    this.rules.push(rule + NEW_LINE);
    this.emptyCss = false;
};
Css.prototype.toString = function() {
    return this.selectors + this.rules.reduce((rule1, rule2) => rule1 + rule2);
}