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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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package com.oracle.truffle.js.builtins.helper;

import com.oracle.truffle.api.CompilerDirectives.*;
import com.oracle.truffle.api.profiles.*;
import com.oracle.truffle.js.runtime.JSRuntime;

public class FloatParser {

    private final String input;
    private int pos;
    private boolean isNaN;
    private final double value;

    private final BranchProfile exponentBranch;

    public FloatParser(String s, BranchProfile exponentBranch) {
        input = s;
        pos = 0;
        isNaN = false;
        this.exponentBranch = exponentBranch;
        value = parse();
    }

    public double getResult() {
        return value;
    }

    @TruffleBoundary
    private double parse() {
        strDecimalLiteral();
        if (isNaN) {
            return Double.NaN;
        }
        return parseValidSubstring();
    }

    @TruffleBoundary
    private double parseValidSubstring() {
        return Double.parseDouble(input.substring(0, pos));
    }

    private void strDecimalLiteral() {
        char currentChar = current();
        if (currentChar == '+' || currentChar == '-') {
            next();
            currentChar = current();
        }
        if (JSRuntime.isAsciiDigit(currentChar) || currentChar == '.') {
            strUnsignedDecimalLiteral();
        } else {
            isNaN = true;
        }
    }

    private void strUnsignedDecimalLiteral() {
        if (JSRuntime.isAsciiDigit(current())) {
            decimalDigits();
        }
        int prevPos = pos;
        if (hasNext() && current() == '.') {
            next();
            if (JSRuntime.isAsciiDigit(current())) {
                decimalDigits();
            }
        }
        if (isNaN) {
            pos = prevPos;
            isNaN = false;
            return;
        }
        prevPos = pos;
        if (isExponentPart()) {
            exponentPart();
        }
        if (isNaN) {
            pos = prevPos;
            isNaN = false;
            return;
        }
    }

    private void next() {
        pos++;
    }

    private char current() {
        if (hasNext()) {
            return input.charAt(pos);
        } else {
            return 0;
        }
    }

    private boolean hasNext() {
        return pos < input.length();
    }

    private void exponentPart() {
        exponentBranch.enter();
        assert current() == 'e' || current() == 'E';
        next();
        char currentChar = current();
        if (JSRuntime.isAsciiDigit(currentChar)) {
            decimalDigits();
        } else if (currentChar == '+' || currentChar == '-') {
            next();
            decimalDigits();
        } else {
            isNaN = true;
        }
    }

    private boolean isExponentPart() {
        if (hasNext()) {
            char firstChar = current();
            return firstChar == 'e' || firstChar == 'E';
        }
        return false;
    }

    private void decimalDigits() {
        char currentChar = current();
        boolean valid = false;
        while (JSRuntime.isAsciiDigit(currentChar) && hasNext()) {
            valid = true;
            next();
            currentChar = current();
        }
        if (!valid) {
            isNaN = true;
        }
    }
}