CSS Values

/**
 * Abstract base class for CSS values
 */
class CSSValue {
  constructor();
  
  /**
   * CSS text representation of the value
   * Abstract implementation - throws errors by default
   */
  cssText: string;
  
  /**
   * Internal helper for error messages
   * @returns {string} Constructor name for error context
   */
  _getConstructorName(): string;
}

const { CSSValue } = require("cssom");

const value = new CSSValue();

try {
  console.log(value.cssText);
} catch (error) {
  console.log(error.message); // 'getter "cssText" of "CSSValue" is not implemented!'
}

try {
  value.cssText = "some value";  
} catch (error) {
  console.log(error.message); // 'DOMException: property "cssText" of "CSSValue" is readonly and can not be replaced with "some value"!'
}

/**
 * CSS expression() value handler for IE-specific expressions
 */
class CSSValueExpression extends CSSValue {
  /**
   * Create a CSS expression parser
   * @param {string} token - Expression token string
   * @param {number} idx - Starting index in the token
   */
  constructor(token, idx);
  
  /** Expression token string */
  _token: string;
  
  /** Starting index in the token */
  _idx: number;
  
  /**
   * Parse the CSS expression
   * @returns {Object} Parse result with idx and expression, or error
   */
  parse(): Object;
  
  /**
   * Parse JavaScript comments within expressions
   * @param {string} token - Token string
   * @param {number} idx - Current index
   * @returns {number} Updated index after comment
   */
  _parseJSComment(token, idx): number;
  
  /**
   * Parse JavaScript strings within expressions
   * @param {string} token - Token string
   * @param {number} idx - Current index  
   * @param {string} sep - String delimiter (single or double quote)
   * @returns {number} Updated index after string
   */
  _parseJSString(token, idx, sep): number;
  
  /**
   * Parse JavaScript regular expressions within expressions
   * @param {string} token - Token string
   * @param {number} idx - Current index
   * @returns {number} Updated index after regex
   */
  _parseJSRexExp(token, idx): number;
  
  /**
   * Find matching delimiter for paired characters
   * @param {string} token - Token string
   * @param {number} idx - Current index
   * @param {string} sep - Delimiter to match
   * @returns {number} Index of matching delimiter
   */
  _findMatchedIdx(token, idx, sep): number;
}

const { CSSValueExpression } = require("cssom");

// Example IE CSS expression parsing
const token = 'expression(document.body.clientWidth + "px")';
const parser = new CSSValueExpression(token, 11); // Start after 'expression('

const result = parser.parse();

if (result.error) {
  console.log("Parse error:", result.error);
} else {
  console.log("Parsed expression:", result.expression);
  console.log("End index:", result.idx);
}

const { CSSValueExpression } = require("cssom");

// Complex expression with various JavaScript features
const expressions = [
  // Simple variable access
  'document.body.scrollTop',
  
  // String literals with escapes
  '"Hello \\"world\\""',
  
  // Regular expressions
  '/pattern/gi',
  
  // Comments
  '/* comment */ value',
  '// line comment\nvalue',
  
  // Function calls with nested parentheses
  'Math.max(window.innerWidth, document.body.clientWidth)',
  
  // Complex nested structures
  'obj.method("string", /regex/, /* comment */ 123)'
];

expressions.forEach((expr, i) => {
  console.log(`\nExpression ${i + 1}: ${expr}`);
  
  const fullToken = `expression(${expr})`;
  const parser = new CSSValueExpression(fullToken, 11);
  
  try {
    const result = parser.parse();
    if (result.error) {
      console.log("Error:", result.error);
    } else {
      console.log("Success:", result.expression);
    }
  } catch (error) {
    console.log("Exception:", error.message);
  }
});

const { CSSValueExpression } = require("cssom");

const malformedExpressions = [
  'unterminated string "hello',
  'unclosed comment /* comment',
  'unmatched parentheses ((',
  'invalid regex /[/'
];

malformedExpressions.forEach(expr => {
  const token = `expression(${expr})`;
  const parser = new CSSValueExpression(token, 11);
  
  const result = parser.parse();
  console.log(`Expression: ${expr}`);
  console.log(`Result:`, result.error ? `Error: ${result.error}` : `Success`);
});

const { parse } = require("cssom");

// CSS with IE expression (would be processed by CSSValueExpression internally)
const cssWithExpression = `
  .dynamic {
    width: expression(document.body.clientWidth + "px");
    height: expression(Math.max(300, window.innerHeight * 0.5) + "px");
  }
`;

// The parser automatically handles expressions during parsing
const sheet = parse(cssWithExpression);
const rule = sheet.cssRules[0];

// The expression is parsed and stored as the property value
console.log(rule.style.width);  // Processed expression value
console.log(rule.style.height); // Processed expression value

const { CSSValueExpression } = require("cssom");

// Nested function calls with multiple argument types
const complexExpression = `
  someFunction(
    "string argument",
    123,
    /regex-pattern/gi,
    /* inline comment */ anotherFunction(nested, "args"),
    // line comment
    finalArgument
  )
`;

const token = `expression(${complexExpression})`;
const parser = new CSSValueExpression(token, 11);

const result = parser.parse();
console.log("Complex expression parsed:", !result.error);
console.log("Result:", result.error || result.expression);

// Modern alternatives to CSS expressions:

// Instead of: width: expression(document.body.clientWidth + "px")
// Use CSS: width: calc(100vw - 20px)
// Or JavaScript: element.style.width = document.body.clientWidth + "px"

// The CSSOM library supports parsing these legacy expressions for compatibility
// and migration purposes, but modern CSS features are recommended for new development