/*
 * Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
 * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
 * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
 * Copyright (c) 2024, Tim Ledbetter <timledbetter@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/GenericShorthands.h>
#include <AK/StringBuilder.h>
#include <AK/StringConversions.h>
#include <LibWeb/SVG/AttributeParser.h>
#include <ctype.h>

namespace Web::SVG {

AttributeParser::AttributeParser(StringView source)
    : m_lexer(source)
{
}

Optional<Vector<Transform>> AttributeParser::parse_transform(StringView input)
{
    AttributeParser parser { input };
    return parser.parse_transform();
}

Path AttributeParser::parse_path_data(StringView input)
{
    AttributeParser parser { input };
    parser.parse_whitespace();
    while (!parser.done()) {
        auto maybe_error = parser.parse_drawto();
        if (maybe_error.is_error())
            break;
    }
    if (!parser.m_instructions.is_empty() && parser.m_instructions[0].type != PathInstructionType::Move) {
        // Invalid. "A path data segment (if there is one) must begin with a "moveto" command."
        return Path { {} };
    }
    return Path { parser.m_instructions };
}

Optional<float> AttributeParser::parse_coordinate(StringView input)
{
    AttributeParser parser { input };
    parser.parse_whitespace();
    auto result_or_error = parser.parse_coordinate();
    if (result_or_error.is_error())
        return {};
    parser.parse_whitespace();
    if (parser.done())
        return result_or_error.value();
    return {};
}

Optional<float> AttributeParser::parse_length(StringView input)
{
    AttributeParser parser { input };
    parser.parse_whitespace();
    auto result_or_error = parser.parse_length();
    if (result_or_error.is_error())
        return {};
    parser.parse_whitespace();
    if (parser.done())
        return result_or_error.value();

    return {};
}

float NumberPercentage::resolve_relative_to(float length) const
{
    if (!m_is_percentage)
        return m_value;
    return m_value * length;
}

Optional<NumberPercentage> AttributeParser::parse_number_percentage(StringView input)
{
    AttributeParser parser { input };
    parser.parse_whitespace();

    auto number_or_error = parser.parse_number();
    if (number_or_error.is_error())
        return {};
    bool is_percentage = parser.match('%');
    if (is_percentage)
        parser.consume();
    parser.parse_whitespace();
    if (parser.done())
        return NumberPercentage(number_or_error.value(), is_percentage);

    return {};
}

Optional<float> AttributeParser::parse_positive_length(StringView input)
{
    // FIXME: Where this is used, the spec usually (always?) says "A negative value is an error (see Error processing)."
    //        So, implement error processing! Maybe this should return ErrorOr.
    auto result = parse_length(input);
    if (result.has_value() && result.value() < 0)
        result.clear();
    return result;
}

Vector<Gfx::FloatPoint> AttributeParser::parse_points(StringView input)
{
    AttributeParser parser { input };

    parser.parse_whitespace();

    auto coordinate_pair_sequence_or_error = parser.parse_coordinate_pair_sequence();
    if (coordinate_pair_sequence_or_error.is_error())
        return {};

    auto coordinate_pair_sequence = coordinate_pair_sequence_or_error.release_value();

    // FIXME: This is awkward. Can we return Gfx::FloatPoints from some of these parsing methods instead of Vector<float>?
    Vector<Gfx::FloatPoint> points;
    points.ensure_capacity(coordinate_pair_sequence.size());

    for (auto const& pair : coordinate_pair_sequence)
        points.empend(pair[0], pair[1]);

    return points;
}

ErrorOr<void> AttributeParser::parse_drawto()
{
    if (match('M') || match('m')) {
        return parse_moveto();
    } else if (match('Z') || match('z')) {
        parse_closepath();
        return {};
    } else if (match('L') || match('l')) {
        return parse_lineto();
    } else if (match('H') || match('h')) {
        return parse_horizontal_lineto();
    } else if (match('V') || match('v')) {
        return parse_vertical_lineto();
    } else if (match('C') || match('c')) {
        return parse_curveto();
    } else if (match('S') || match('s')) {
        return parse_smooth_curveto();
    } else if (match('Q') || match('q')) {
        return parse_quadratic_bezier_curveto();
    } else if (match('T') || match('t')) {
        return parse_smooth_quadratic_bezier_curveto();
    } else if (match('A') || match('a')) {
        return parse_elliptical_arc();
    }

    dbgln("AttributeParser::parse_drawto failed to match: '{}'", ch());
    return Error::from_string_literal("Invalid drawto command");
}

// https://www.w3.org/TR/SVG2/paths.html#PathDataMovetoCommands
ErrorOr<void> AttributeParser::parse_moveto()
{
    bool absolute = consume() == 'M';
    parse_whitespace();

    bool is_first = true;
    for (auto& pair : TRY(parse_coordinate_pair_sequence())) {
        // NOTE: "M 1 2 3 4" is equivalent to "M 1 2 L 3 4".
        auto type = is_first ? PathInstructionType::Move : PathInstructionType::Line;
        m_instructions.append({ type, absolute, pair });
        is_first = false;
    }

    return {};
}

void AttributeParser::parse_closepath()
{
    bool absolute = consume() == 'Z';
    parse_whitespace();
    m_instructions.append({ PathInstructionType::ClosePath, absolute, {} });
}

ErrorOr<void> AttributeParser::parse_lineto()
{
    bool absolute = consume() == 'L';
    parse_whitespace();
    for (auto& pair : TRY(parse_coordinate_pair_sequence()))
        m_instructions.append({ PathInstructionType::Line, absolute, pair });

    return {};
}

ErrorOr<void> AttributeParser::parse_horizontal_lineto()
{
    bool absolute = consume() == 'H';
    parse_whitespace();
    for (auto coordinate : TRY(parse_coordinate_sequence()))
        m_instructions.append({ PathInstructionType::HorizontalLine, absolute, { coordinate } });

    return {};
}

ErrorOr<void> AttributeParser::parse_vertical_lineto()
{
    bool absolute = consume() == 'V';
    parse_whitespace();
    for (auto coordinate : TRY(parse_coordinate_sequence()))
        m_instructions.append({ PathInstructionType::VerticalLine, absolute, { coordinate } });

    return {};
}

ErrorOr<void> AttributeParser::parse_curveto()
{
    bool absolute = consume() == 'C';
    parse_whitespace();

    while (true) {
        m_instructions.append({ PathInstructionType::Curve, absolute, TRY(parse_coordinate_pair_triplet()) });
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_coordinate())
            break;
    }

    return {};
}

ErrorOr<void> AttributeParser::parse_smooth_curveto()
{
    bool absolute = consume() == 'S';
    parse_whitespace();

    while (true) {
        m_instructions.append({ PathInstructionType::SmoothCurve, absolute, TRY(parse_coordinate_pair_double()) });
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_coordinate())
            break;
    }

    return {};
}

ErrorOr<void> AttributeParser::parse_quadratic_bezier_curveto()
{
    bool absolute = consume() == 'Q';
    parse_whitespace();

    while (true) {
        m_instructions.append({ PathInstructionType::QuadraticBezierCurve, absolute, TRY(parse_coordinate_pair_double()) });
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_coordinate())
            break;
    }

    return {};
}

ErrorOr<void> AttributeParser::parse_smooth_quadratic_bezier_curveto()
{
    bool absolute = consume() == 'T';
    parse_whitespace();

    while (true) {
        m_instructions.append({ PathInstructionType::SmoothQuadraticBezierCurve, absolute, TRY(parse_coordinate_pair()) });
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_coordinate())
            break;
    }

    return {};
}

ErrorOr<void> AttributeParser::parse_elliptical_arc()
{
    bool absolute = consume() == 'A';
    parse_whitespace();

    while (true) {
        auto argument = TRY(parse_elliptical_arc_argument());
        m_instructions.append({ PathInstructionType::EllipticalArc, absolute, move(argument) });
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_coordinate())
            break;
    }

    return {};
}

ErrorOr<float> AttributeParser::parse_length()
{
    // https://www.w3.org/TR/SVG11/types.html#DataTypeLength
    return parse_number();
}

ErrorOr<float> AttributeParser::parse_coordinate()
{
    // https://www.w3.org/TR/SVG11/types.html#DataTypeCoordinate
    // coordinate ::= length
    return parse_length();
}

ErrorOr<Vector<float>> AttributeParser::parse_coordinate_pair()
{
    Vector<float> coordinates;
    coordinates.append(TRY(parse_coordinate()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    coordinates.append(TRY(parse_coordinate()));
    return coordinates;
}

ErrorOr<Vector<float>> AttributeParser::parse_coordinate_sequence()
{
    Vector<float> sequence;
    bool is_first = true;
    while (true) {
        auto coordinate_or_error = parse_coordinate();
        if (coordinate_or_error.is_error()) {
            if (is_first)
                return Error::from_string_literal("Expected coordinate sequence");
        }
        is_first = false;
        sequence.append(coordinate_or_error.release_value());
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_comma_whitespace() && !match_coordinate())
            break;
    }
    return sequence;
}

ErrorOr<Vector<Vector<float>>> AttributeParser::parse_coordinate_pair_sequence()
{
    Vector<Vector<float>> sequence;
    bool is_first = true;
    while (true) {
        auto coordinate_pair_or_error = parse_coordinate_pair();
        if (coordinate_pair_or_error.is_error()) {
            if (is_first)
                return Error::from_string_literal("Expected coordinate pair sequence");
            break;
        }
        is_first = false;
        sequence.append(coordinate_pair_or_error.release_value());
        if (match_comma_whitespace())
            parse_comma_whitespace();
        if (!match_comma_whitespace() && !match_coordinate())
            break;
    }
    return sequence;
}

ErrorOr<Vector<float>> AttributeParser::parse_coordinate_pair_double()
{
    Vector<float> coordinates;
    coordinates.extend(TRY(parse_coordinate_pair()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    coordinates.extend(TRY(parse_coordinate_pair()));
    return coordinates;
}

ErrorOr<Vector<float>> AttributeParser::parse_coordinate_pair_triplet()
{
    Vector<float> coordinates;
    coordinates.extend(TRY(parse_coordinate_pair()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    coordinates.extend(TRY(parse_coordinate_pair()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    coordinates.extend(TRY(parse_coordinate_pair()));
    return coordinates;
}

ErrorOr<Vector<float>> AttributeParser::parse_elliptical_arc_argument()
{
    Vector<float> numbers;
    numbers.append(TRY(parse_number()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    numbers.append(TRY(parse_number()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    numbers.append(TRY(parse_number()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    numbers.append(TRY(parse_flag()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    numbers.append(TRY(parse_flag()));
    if (match_comma_whitespace())
        parse_comma_whitespace();
    numbers.extend(TRY(parse_coordinate_pair()));

    return numbers;
}

void AttributeParser::parse_whitespace(bool must_match_once)
{
    bool matched = false;
    while (!done() && match_whitespace()) {
        consume();
        matched = true;
    }

    VERIFY(!must_match_once || matched);
}

void AttributeParser::parse_comma_whitespace()
{
    if (match(',')) {
        consume();
        parse_whitespace();
    } else {
        parse_whitespace(1);
        if (match(','))
            consume();
        parse_whitespace();
    }
}

// https://www.w3.org/TR/SVG11/types.html#DataTypeNumber
ErrorOr<float> AttributeParser::parse_number()
{
    auto sign = parse_sign();
    return sign * TRY(parse_nonnegative_number());
}

// https://www.w3.org/TR/SVG11/paths.html#PathDataBNF
ErrorOr<float> AttributeParser::parse_nonnegative_number()
{
    // NOTE: The grammar is almost a floating point except we cannot have a sign
    //       at the start. That condition should have been checked by the caller.
    if (match('+') || match('-') || !match_number())
        return Error::from_string_literal("Expected number");

    auto parse_result = AK::parse_first_number<float>(m_lexer.remaining(), TrimWhitespace::No);
    VERIFY(parse_result.has_value());

    m_lexer.ignore(parse_result->characters_parsed);
    return parse_result->value;
}

ErrorOr<float> AttributeParser::parse_flag()
{
    if (!match('0') && !match('1'))
        return Error::from_string_literal("Expected flag");
    return consume() - '0';
}

int AttributeParser::parse_sign()
{
    if (match('-')) {
        consume();
        return -1;
    }
    if (match('+'))
        consume();
    return 1;
}

static bool whitespace(char c)
{
    // wsp:
    // Either a U+000A LINE FEED, U+000D CARRIAGE RETURN, U+0009 CHARACTER TABULATION, or U+0020 SPACE.
    return AK::first_is_one_of(c, '\n', '\r', '\t', '\f', ' ');
}

// https://svgwg.org/svg2-draft/coords.html#PreserveAspectRatioAttribute
Optional<PreserveAspectRatio> AttributeParser::parse_preserve_aspect_ratio(StringView input)
{
    // <align> <meetOrSlice>?
    GenericLexer lexer { input };
    lexer.ignore_while(whitespace);
    auto align_string = lexer.consume_until(whitespace);
    if (align_string.is_empty())
        return {};
    lexer.ignore_while(whitespace);
    auto meet_or_slice_string = lexer.consume_until(whitespace);

    // <align> =
    //     none
    //     | xMinYMin | xMidYMin | xMaxYMin
    //     | xMinYMid | xMidYMid | xMaxYMid
    //     | xMinYMax | xMidYMax | xMaxYMax
    auto align = [&]() -> Optional<PreserveAspectRatio::Align> {
        if (align_string == "none"sv)
            return PreserveAspectRatio::Align::None;
        if (align_string == "xMinYMin"sv)
            return PreserveAspectRatio::Align::xMinYMin;
        if (align_string == "xMidYMin"sv)
            return PreserveAspectRatio::Align::xMidYMin;
        if (align_string == "xMaxYMin"sv)
            return PreserveAspectRatio::Align::xMaxYMin;
        if (align_string == "xMinYMid"sv)
            return PreserveAspectRatio::Align::xMinYMid;
        if (align_string == "xMidYMid"sv)
            return PreserveAspectRatio::Align::xMidYMid;
        if (align_string == "xMaxYMid"sv)
            return PreserveAspectRatio::Align::xMaxYMid;
        if (align_string == "xMinYMax"sv)
            return PreserveAspectRatio::Align::xMinYMax;
        if (align_string == "xMidYMax"sv)
            return PreserveAspectRatio::Align::xMidYMax;
        if (align_string == "xMaxYMax"sv)
            return PreserveAspectRatio::Align::xMaxYMax;
        return {};
    }();

    if (!align.has_value())
        return {};

    // <meetOrSlice> = meet | slice
    auto meet_or_slice = [&]() -> Optional<PreserveAspectRatio::MeetOrSlice> {
        if (meet_or_slice_string.is_empty() || meet_or_slice_string == "meet"sv)
            return PreserveAspectRatio::MeetOrSlice::Meet;
        if (meet_or_slice_string == "slice"sv)
            return PreserveAspectRatio::MeetOrSlice::Slice;
        return {};
    }();

    if (!meet_or_slice.has_value())
        return {};

    return PreserveAspectRatio { *align, *meet_or_slice };
}

// https://svgwg.org/svg2-draft/pservers.html#LinearGradientElementGradientUnitsAttribute
// https://drafts.fxtf.org/css-masking/#element-attrdef-mask-maskunits
// https://drafts.fxtf.org/css-masking/#element-attrdef-mask-maskcontentunits
Optional<SVGUnits> AttributeParser::parse_units(StringView input)
{
    GenericLexer lexer { input };
    lexer.ignore_while(whitespace);
    auto gradient_units_string = lexer.consume_until(whitespace);
    if (gradient_units_string == "userSpaceOnUse"sv)
        return SVGUnits::UserSpaceOnUse;
    if (gradient_units_string == "objectBoundingBox"sv)
        return SVGUnits::ObjectBoundingBox;
    return {};
}

// https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementSpreadMethodAttribute
Optional<SpreadMethod> AttributeParser::parse_spread_method(StringView input)
{
    GenericLexer lexer { input };
    lexer.ignore_while(whitespace);
    auto spread_method_string = lexer.consume_until(whitespace);
    if (spread_method_string == "pad"sv)
        return SpreadMethod::Pad;
    if (spread_method_string == "repeat"sv)
        return SpreadMethod::Repeat;
    if (spread_method_string == "reflect"sv)
        return SpreadMethod::Reflect;
    return {};
}

// https://drafts.csswg.org/css-transforms/#svg-syntax
Optional<Vector<Transform>> AttributeParser::parse_transform()
{
    auto consume_whitespace = [&] {
        m_lexer.ignore_while(whitespace);
    };

    auto consume_comma_whitespace = [&] {
        consume_whitespace();
        m_lexer.consume_specific(',');
        consume_whitespace();
    };

    // FIXME: This parsing is quite lenient, so will accept (with default values) some transforms that should be rejected.
    auto parse_optional_number = [&](float default_value = 0.0f) {
        consume_comma_whitespace();
        auto number_or_error = parse_number();
        if (number_or_error.is_error())
            return default_value;
        return number_or_error.value();
    };

    auto try_parse_number = [&]() -> Optional<float> {
        auto number_or_error = parse_number();
        if (number_or_error.is_error())
            return {};
        return number_or_error.value();
    };

    auto parse_function = [&](auto body) -> Optional<Transform> {
        consume_whitespace();
        if (!m_lexer.consume_specific('('))
            return {};
        consume_whitespace();
        auto maybe_operation = body();
        if (!maybe_operation.has_value())
            return {};
        Transform transform { .operation = Transform::Operation { *maybe_operation } };
        consume_whitespace();
        if (m_lexer.consume_specific(')'))
            return transform;
        return {};
    };

    // NOTE: This looks very similar to the CSS transform but the syntax is not compatible.
    Vector<Transform> transform_list;
    consume_whitespace();
    while (!done()) {
        Optional<Transform> maybe_transform;
        if (m_lexer.consume_specific("translate"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::Translate> {
                Transform::Translate translate {};
                auto maybe_x = try_parse_number();
                if (!maybe_x.has_value())
                    return {};
                translate.x = *maybe_x;
                translate.y = parse_optional_number();
                return translate;
            });
        } else if (m_lexer.consume_specific("scale"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::Scale> {
                Transform::Scale scale {};
                auto maybe_x = try_parse_number();
                if (!maybe_x.has_value())
                    return {};
                scale.x = *maybe_x;
                scale.y = parse_optional_number(scale.x);
                return scale;
            });
        } else if (m_lexer.consume_specific("rotate"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::Rotate> {
                Transform::Rotate rotate {};
                auto maybe_a = try_parse_number();
                if (!maybe_a.has_value())
                    return {};
                rotate.a = *maybe_a;
                rotate.x = parse_optional_number();
                rotate.y = parse_optional_number();
                return rotate;
            });
        } else if (m_lexer.consume_specific("skewX"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::SkewX> {
                Transform::SkewX skew_x {};
                auto maybe_a = try_parse_number();
                if (!maybe_a.has_value())
                    return {};
                skew_x.a = *maybe_a;
                return skew_x;
            });
        } else if (m_lexer.consume_specific("skewY"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::SkewY> {
                Transform::SkewY skew_y {};
                auto maybe_a = try_parse_number();
                if (!maybe_a.has_value())
                    return {};
                skew_y.a = *maybe_a;
                return skew_y;
            });
        } else if (m_lexer.consume_specific("matrix"sv)) {
            maybe_transform = parse_function([&]() -> Optional<Transform::Matrix> {
                Transform::Matrix matrix;
                auto maybe_a = try_parse_number();
                if (!maybe_a.has_value())
                    return {};
                matrix.a = *maybe_a;
                consume_comma_whitespace();
                auto maybe_b = try_parse_number();
                if (!maybe_b.has_value())
                    return {};
                matrix.b = *maybe_b;
                consume_comma_whitespace();
                auto maybe_c = try_parse_number();
                if (!maybe_c.has_value())
                    return {};
                matrix.c = *maybe_c;
                consume_comma_whitespace();
                auto maybe_d = try_parse_number();
                if (!maybe_d.has_value())
                    return {};
                matrix.d = *maybe_d;
                consume_comma_whitespace();
                auto maybe_e = try_parse_number();
                if (!maybe_e.has_value())
                    return {};
                matrix.e = *maybe_e;
                consume_comma_whitespace();
                auto maybe_f = try_parse_number();
                if (!maybe_f.has_value())
                    return {};
                matrix.f = *maybe_f;
                return matrix;
            });
        }
        if (maybe_transform.has_value())
            transform_list.append(*maybe_transform);
        else
            return {};
        consume_comma_whitespace();
    }
    return transform_list;
}

Optional<ViewBox> AttributeParser::parse_viewbox(StringView input)
{
    AttributeParser parser { input };
    ViewBox viewbox;

    parser.parse_whitespace();
    auto maybe_min_x = parser.parse_coordinate();
    if (maybe_min_x.is_error())
        return {};
    viewbox.min_x = maybe_min_x.value();

    if (!parser.match_comma_whitespace())
        return {};
    parser.parse_comma_whitespace();
    auto maybe_min_y = parser.parse_coordinate();
    if (maybe_min_y.is_error())
        return {};
    viewbox.min_y = maybe_min_y.value();

    if (!parser.match_comma_whitespace())
        return {};
    parser.parse_comma_whitespace();
    auto maybe_width = parser.parse_length();
    if (maybe_width.is_error())
        return {};
    viewbox.width = maybe_width.value();

    if (!parser.match_comma_whitespace())
        return {};
    parser.parse_comma_whitespace();
    auto maybe_height = parser.parse_length();
    if (maybe_height.is_error())
        return {};
    viewbox.height = maybe_height.value();

    parser.parse_whitespace();
    if (!parser.done())
        return {};

    return viewbox;
}

bool AttributeParser::match_whitespace() const
{
    if (done())
        return false;
    char c = ch();
    return c == 0x9 || c == 0x20 || c == 0xa || c == 0xc || c == 0xd;
}

bool AttributeParser::match_comma_whitespace() const
{
    return match_whitespace() || match(',');
}

bool AttributeParser::match_coordinate() const
{
    return match_length();
}

bool AttributeParser::match_number() const
{
    return match_length();
}

bool AttributeParser::match_length() const
{
    if (done())
        return false;

    size_t offset = 0;
    if (ch() == '-' || ch() == '+')
        offset++;

    if (ch(offset) == '.')
        offset++;

    return !done() && isdigit(ch(offset));
}

}
