/*
 * Copyright (C) 2010 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "HTMLParserIdioms.h"

#include "Decimal.h"
#include "HTMLIdentifier.h"
#include "KURL.h"
#include "QualifiedName.h"
#include <limits>
#include <wtf/MathExtras.h>
#include <wtf/text/AtomicString.h>
#include <wtf/text/StringBuilder.h>

namespace WebCore {

template <typename CharType>
static String stripLeadingAndTrailingHTMLSpaces(String string, CharType characters, unsigned length)
{
    unsigned numLeadingSpaces = 0;
    unsigned numTrailingSpaces = 0;

    for (; numLeadingSpaces < length; ++numLeadingSpaces) {
        if (isNotHTMLSpace(characters[numLeadingSpaces]))
            break;
    }

    if (numLeadingSpaces == length)
        return string.isNull() ? string : emptyAtom.string();

    for (; numTrailingSpaces < length; ++numTrailingSpaces) {
        if (isNotHTMLSpace(characters[length - numTrailingSpaces - 1]))
            break;
    }

    ASSERT(numLeadingSpaces + numTrailingSpaces < length);

    if (!(numLeadingSpaces | numTrailingSpaces))
        return string;

    return string.substring(numLeadingSpaces, length - (numLeadingSpaces + numTrailingSpaces));
}

String stripLeadingAndTrailingHTMLSpaces(const String& string)
{
    unsigned length = string.length();

    if (!length)
        return string.isNull() ? string : emptyAtom.string();

    if (string.is8Bit())
        return stripLeadingAndTrailingHTMLSpaces(string, string.characters8(), length);

    return stripLeadingAndTrailingHTMLSpaces(string, string.characters(), length);
}

String serializeForNumberType(const Decimal& number)
{
    if (number.isZero()) {
        // Decimal::toString appends exponent, e.g. "0e-18"
        return number.isNegative() ? "-0" : "0";
    }
    return number.toString();
}

String serializeForNumberType(double number)
{
    // According to HTML5, "the best representation of the number n as a floating
    // point number" is a string produced by applying ToString() to n.
    return String::numberToStringECMAScript(number);
}

Decimal parseToDecimalForNumberType(const String& string, const Decimal& fallbackValue)
{
    // See HTML5 2.5.4.3 `Real numbers.' and parseToDoubleForNumberType

    // String::toDouble() accepts leading + and whitespace characters, which are not valid here.
    const UChar firstCharacter = string[0];
    if (firstCharacter != '-' && firstCharacter != '.' && !isASCIIDigit(firstCharacter))
        return fallbackValue;

    const Decimal value = Decimal::fromString(string);
    if (!value.isFinite())
        return fallbackValue;

    // Numbers are considered finite IEEE 754 single-precision floating point values.
    // See HTML5 2.5.4.3 `Real numbers.'
    // FIXME: We should use numeric_limits<double>::max for number input type.
    const Decimal floatMax = Decimal::fromDouble(std::numeric_limits<float>::max());
    if (value < -floatMax || value > floatMax)
        return fallbackValue;

    // We return +0 for -0 case.
    return value.isZero() ? Decimal(0) : value;
}

Decimal parseToDecimalForNumberType(const String& string)
{
    return parseToDecimalForNumberType(string, Decimal::nan());
}

double parseToDoubleForNumberType(const String& string, double fallbackValue)
{
    // See HTML5 2.5.4.3 `Real numbers.'

    // String::toDouble() accepts leading + and whitespace characters, which are not valid here.
    UChar firstCharacter = string[0];
    if (firstCharacter != '-' && firstCharacter != '.' && !isASCIIDigit(firstCharacter))
        return fallbackValue;

    bool valid = false;
    double value = string.toDouble(&valid);
    if (!valid)
        return fallbackValue;

    // NaN and infinity are considered valid by String::toDouble, but not valid here.
    if (!std::isfinite(value))
        return fallbackValue;

    // Numbers are considered finite IEEE 754 single-precision floating point values.
    // See HTML5 2.5.4.3 `Real numbers.'
    if (-std::numeric_limits<float>::max() > value || value > std::numeric_limits<float>::max())
        return fallbackValue;

    // The following expression converts -0 to +0.
    return value ? value : 0;
}

double parseToDoubleForNumberType(const String& string)
{
    return parseToDoubleForNumberType(string, std::numeric_limits<double>::quiet_NaN());
}

template <typename CharacterType>
static bool parseHTMLIntegerInternal(const CharacterType* position, const CharacterType* end, int& value)
{
    // Step 3
    int sign = 1;

    // Step 4
    while (position < end) {
        if (!isHTMLSpace(*position))
            break;
        ++position;
    }

    // Step 5
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 6
    if (*position == '-') {
        sign = -1;
        ++position;
    } else if (*position == '+')
        ++position;
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 7
    if (!isASCIIDigit(*position))
        return false;

    // Step 8
    StringBuilder digits;
    while (position < end) {
        if (!isASCIIDigit(*position))
            break;
        digits.append(*position++);
    }

    // Step 9
    bool ok;
    if (digits.is8Bit())
        value = sign * charactersToIntStrict(digits.characters8(), digits.length(), &ok);
    else
        value = sign * charactersToIntStrict(digits.characters16(), digits.length(), &ok);
    return ok;
}

// http://www.whatwg.org/specs/web-apps/current-work/#rules-for-parsing-integers
bool parseHTMLInteger(const String& input, int& value)
{
    // Step 1
    // Step 2
    unsigned length = input.length();
    if (!length || input.is8Bit()) {
        const LChar* start = input.characters8();
        return parseHTMLIntegerInternal(start, start + length, value);
    }

    const UChar* start = input.characters16();
    return parseHTMLIntegerInternal(start, start + length, value);
}

template <typename CharacterType>
static bool parseHTMLNonNegativeIntegerInternal(const CharacterType* position, const CharacterType* end, unsigned& value)
{
    // Step 3
    while (position < end) {
        if (!isHTMLSpace(*position))
            break;
        ++position;
    }

    // Step 4
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 5
    if (*position == '+')
        ++position;

    // Step 6
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 7
    if (!isASCIIDigit(*position))
        return false;

    // Step 8
    StringBuilder digits;
    while (position < end) {
        if (!isASCIIDigit(*position))
            break;
        digits.append(*position++);
    }

    // Step 9
    bool ok;
    if (digits.is8Bit())
        value = charactersToUIntStrict(digits.characters8(), digits.length(), &ok);
    else
        value = charactersToUIntStrict(digits.characters16(), digits.length(), &ok);
    return ok;
}


// http://www.whatwg.org/specs/web-apps/current-work/#rules-for-parsing-non-negative-integers
bool parseHTMLNonNegativeInteger(const String& input, unsigned& value)
{
    // Step 1
    // Step 2
    unsigned length = input.length();
    if (length && input.is8Bit()) {
        const LChar* start = input.characters8();
        return parseHTMLNonNegativeIntegerInternal(start, start + length, value);
    }
    
    const UChar* start = input.characters();
    return parseHTMLNonNegativeIntegerInternal(start, start + length, value);
}

static bool threadSafeEqual(const StringImpl* a, const StringImpl* b)
{
    if (a == b)
        return true;
    if (a->hash() != b->hash())
        return false;
    return equalNonNull(a, b);
}

bool threadSafeMatch(const QualifiedName& a, const QualifiedName& b)
{
    return threadSafeEqual(a.localName().impl(), b.localName().impl());
}

#if ENABLE(THREADED_HTML_PARSER)
bool threadSafeMatch(const HTMLIdentifier& localName, const QualifiedName& qName)
{
    return threadSafeEqual(localName.asStringImpl(), qName.localName().impl());
}
#endif

struct ImageWithScale {
    String imageURL;
    float scaleFactor;
    bool operator==(const ImageWithScale& image) const
    {
        return scaleFactor == image.scaleFactor && imageURL == image.imageURL;
    }
};
typedef Vector<ImageWithScale> ImageCandidates;

static inline bool compareByScaleFactor(const ImageWithScale& first, const ImageWithScale& second)
{
    return first.scaleFactor < second.scaleFactor;
}

String bestFitSourceForImageAttributes(float deviceScaleFactor, const String& srcAttribute, const String& srcSetAttribute)
{
    ImageCandidates imageCandidates;

    const String srcSetAttributeValue = srcSetAttribute.simplifyWhiteSpace(isHTMLSpace);
    Vector<String> srcSetTokens;

    srcSetAttributeValue.split(',', srcSetTokens);
    for (size_t i = 0; i < srcSetTokens.size(); ++i) {
        Vector<String> data;
        float imgScaleFactor = 1.0;
        bool validScaleFactor = false;

        srcSetTokens[i].stripWhiteSpace().split(' ', data);
        // There must be at least one candidate descriptor, and the last one must
        // be a scale factor. Since we don't support descriptors other than scale,
        // it's better to discard any rule with such descriptors rather than accept
        // only the scale data.
        if (data.size() != 2)
            continue;
        if (!data.last().endsWith('x'))
            continue;

        imgScaleFactor = data.last().substring(0, data.last().length() - 1).toFloat(&validScaleFactor);
        if (!validScaleFactor)
            continue;

        ImageWithScale image;
        image.imageURL = decodeURLEscapeSequences(data[0]);
        image.scaleFactor = imgScaleFactor;

        imageCandidates.append(image);
    }

    const String src =  srcAttribute.simplifyWhiteSpace(isHTMLSpace);
    if (!src.isEmpty()) {
        ImageWithScale image;
        image.imageURL = decodeURLEscapeSequences(src);
        image.scaleFactor = 1.0;

        imageCandidates.append(image);
    }

    if (imageCandidates.isEmpty())
        return String();

    std::stable_sort(imageCandidates.begin(), imageCandidates.end(), compareByScaleFactor);

    for (size_t i = 0; i < imageCandidates.size() - 1; ++i) {
        if (imageCandidates[i].scaleFactor >= deviceScaleFactor)
            return imageCandidates[i].imageURL;
    }
    return imageCandidates.last().imageURL;
}

}