import {
  isDigit,
  Delim,
  Number as NumberToken,
} from '../../tokenizer/index.js';

const SOLIDUS = 0x002f; // U+002F SOLIDUS (/)
const FULLSTOP = 0x002e; // U+002E FULL STOP (.)

// Terms of <ratio> should be a positive numbers (not zero or negative)
// (see https://drafts.csswg.org/mediaqueries-3/#values)
// However, -o-min-device-pixel-ratio takes fractional values as a ratio's term
// and this is using by various sites. Therefore we relax checking on parse
// to test a term is unsigned number without an exponent part.
// Additional checking may be applied on lexer validation.
function consumeNumber() {
  this.skipSC();

  const value = this.consume(NumberToken);

  for (let i = 0; i < value.length; i++) {
    const code = value.charCodeAt(i);
    if (!isDigit(code) && code !== FULLSTOP) {
      this.error(
        'Unsigned number is expected',
        this.tokenStart - value.length + i
      );
    }
  }

  if (Number(value) === 0) {
    this.error('Zero number is not allowed', this.tokenStart - value.length);
  }

  return value;
}

export const name = 'Ratio';
export const structure = {
  left: String,
  right: String,
};

// <positive-integer> S* '/' S* <positive-integer>
export function parse() {
  const start = this.tokenStart;
  const left = consumeNumber.call(this);
  let right;

  this.skipSC();
  this.eatDelim(SOLIDUS);
  right = consumeNumber.call(this);

  return {
    type: 'Ratio',
    loc: this.getLocation(start, this.tokenStart),
    left,
    right,
  };
}

export function generate(node) {
  this.token(NumberToken, node.left);
  this.token(Delim, '/');
  this.token(NumberToken, node.right);
}