/*

 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>

 * Copyright (c) 2021, Max Wipfli <max.wipfli@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/FlyString.h>

#include <AK/Function.h>

#include <AK/OwnPtr.h>

#include <AK/Types.h>

#include <AK/Variant.h>

#include <AK/Vector.h>

namespace Web::HTML {

class HTMLTokenizer;

class HTMLToken {

    AK_MAKE_NONCOPYABLE(HTMLToken);

    AK_MAKE_DEFAULT_MOVABLE(HTMLToken);

public:

    enum class Type : u8 {

        Invalid,

        DOCTYPE,

        StartTag,

        EndTag,

        Comment,

        Character,

        EndOfFile,

    };

    struct Position {

        size_t line { 0 };

        size_t column { 0 };

        size_t byte_offset { 0 };

    };

    struct Attribute {

        Optional<FlyString> prefix;

        FlyString local_name;

        Optional<FlyString> namespace_;

        String value;

        Position name_start_position;

        Position value_start_position;

        Position name_end_position;

        Position value_end_position;

    };

    struct DoctypeData {

        // NOTE: "Missing" is a distinct state from the empty string.

        String name;

        String public_identifier;

        String system_identifier;

        bool missing_name { true };

        bool missing_public_identifier { true };

        bool missing_system_identifier { true };

        bool force_quirks { false };

    };

    static HTMLToken make_character(u32 code_point)

    {

        HTMLToken token { Type::Character };

        token.set_code_point(code_point);

        return token;

    }

    static HTMLToken make_start_tag(FlyString const& tag_name)

    {

        HTMLToken token { Type::StartTag };

        token.set_tag_name(tag_name);

        return token;

    }

    HTMLToken() = default;

    HTMLToken(Type type)

        : m_type(type)

    {

        switch (m_type) {

        case Type::Character:

            m_data.set(0u);

            break;

        case Type::DOCTYPE:

            m_data.set(OwnPtr<DoctypeData> {});

            break;

        case Type::StartTag:

        case Type::EndTag:

            m_data.set(OwnPtr<Vector<Attribute>>());

            break;

        default:

            break;

        }

    }

    bool is_doctype() const { return m_type == Type::DOCTYPE; }

    bool is_start_tag() const { return m_type == Type::StartTag; }

    bool is_end_tag() const { return m_type == Type::EndTag; }

    bool is_comment() const { return m_type == Type::Comment; }

    bool is_character() const { return m_type == Type::Character; }

    bool is_end_of_file() const { return m_type == Type::EndOfFile; }

    u32 code_point() const

    {

        VERIFY(is_character());

        return m_data.get<u32>();

    }

    bool is_parser_whitespace() const

    {

        // NOTE: The parser considers '\r' to be whitespace, while the tokenizer does not.

        if (!is_character())

            return false;

        switch (code_point()) {

        case '\t':

        case '\n':

        case '\f':

        case '\r':

        case ' ':

            return true;

        default:

            return false;

        }

    }

    void set_code_point(u32 code_point)

    {

        VERIFY(is_character());

        m_data.get<u32>() = code_point;

    }

    String const& comment() const

    {

        VERIFY(is_comment());

        return m_comment_data;

    }

    void set_comment(String comment)

    {

        VERIFY(is_comment());

        m_comment_data = move(comment);

    }

    FlyString const& tag_name() const

    {

        VERIFY(is_start_tag() || is_end_tag());

        return m_string_data;

    }

    void set_tag_name(FlyString name)

    {

        VERIFY(is_start_tag() || is_end_tag());

        m_string_data = move(name);

    }

    bool is_self_closing() const

    {

        VERIFY(is_start_tag() || is_end_tag());

        return m_tag_self_closing;

    }

    void set_self_closing(bool self_closing)

    {

        VERIFY(is_start_tag() || is_end_tag());

        m_tag_self_closing = self_closing;

    }

    bool has_acknowledged_self_closing_flag() const

    {

        VERIFY(is_self_closing());

        return m_tag_self_closing_acknowledged;

    }

    void acknowledge_self_closing_flag_if_set()

    {

        if (is_self_closing())

            m_tag_self_closing_acknowledged = true;

    }

    bool has_attributes() const

    {

        VERIFY(is_start_tag() || is_end_tag());

        auto* ptr = tag_attributes();

        return ptr && !ptr->is_empty();

    }

    size_t attribute_count() const

    {

        VERIFY(is_start_tag() || is_end_tag());

        if (auto* ptr = tag_attributes())

            return ptr->size();

        return 0;

    }

    void add_attribute(Attribute attribute)

    {

        VERIFY(is_start_tag() || is_end_tag());

        ensure_tag_attributes().append(move(attribute));

    }

    Attribute const& last_attribute() const

    {

        VERIFY(is_start_tag() || is_end_tag());

        VERIFY(has_attributes());

        return tag_attributes()->last();

    }

    Attribute& last_attribute()

    {

        VERIFY(is_start_tag() || is_end_tag());

        VERIFY(has_attributes());

        return tag_attributes()->last();

    }

    void drop_attributes()

    {

        VERIFY(is_start_tag() || is_end_tag());

        m_data.get<OwnPtr<Vector<Attribute>>>().clear();

    }

    void for_each_attribute(Function<IterationDecision(Attribute const&)> callback) const

    {

        VERIFY(is_start_tag() || is_end_tag());

        auto* ptr = tag_attributes();

        if (!ptr)

            return;

        for (auto& attribute : *ptr) {

            if (callback(attribute) == IterationDecision::Break)

                break;

        }

    }

    void for_each_attribute(Function<IterationDecision(Attribute&)> callback)

    {

        VERIFY(is_start_tag() || is_end_tag());

        auto* ptr = tag_attributes();

        if (!ptr)

            return;

        for (auto& attribute : *ptr) {

            if (callback(attribute) == IterationDecision::Break)

                break;

        }

    }

    Optional<String> attribute(FlyString const& attribute_name) const

    {

        if (auto result = raw_attribute(attribute_name); result.has_value())

            return result->value;

        return {};

    }

    Optional<Attribute const&> raw_attribute(FlyString const& attribute_name) const

    {

        VERIFY(is_start_tag() || is_end_tag());

        auto* ptr = tag_attributes();

        if (!ptr)

            return {};

        for (auto const& attribute : *ptr) {

            if (attribute_name == attribute.local_name)

                return attribute;

        }

        return {};

    }

    bool has_attribute(FlyString const& attribute_name) const

    {

        return attribute(attribute_name).has_value();

    }

    void adjust_tag_name(FlyString const& old_name, FlyString const& new_name)

    {

        VERIFY(is_start_tag() || is_end_tag());

        if (old_name == tag_name())

            set_tag_name(new_name);

    }

    void adjust_attribute_name(FlyString const& old_name, FlyString const& new_name)

    {

        VERIFY(is_start_tag() || is_end_tag());

        for_each_attribute([&](Attribute& attribute) {

            if (old_name == attribute.local_name)

                attribute.local_name = new_name;

            return IterationDecision::Continue;

        });

    }

    void adjust_foreign_attribute(FlyString const& old_name, Optional<FlyString> const& prefix, FlyString const& local_name, Optional<FlyString> const& namespace_)

    {

        VERIFY(is_start_tag() || is_end_tag());

        for_each_attribute([&](Attribute& attribute) {

            if (old_name == attribute.local_name) {

                attribute.prefix = prefix;

                attribute.local_name = local_name;

                attribute.namespace_ = namespace_;

            }

            return IterationDecision::Continue;

        });

    }

    DoctypeData const& doctype_data() const

    {

        VERIFY(is_doctype());

        auto* ptr = m_data.get<OwnPtr<DoctypeData>>().ptr();

        VERIFY(ptr);

        return *ptr;

    }

    DoctypeData& ensure_doctype_data()

    {

        VERIFY(is_doctype());

        auto& ptr = m_data.get<OwnPtr<DoctypeData>>();

        if (!ptr)

            ptr = make<DoctypeData>();

        return *ptr;

    }

    Type type() const { return m_type; }

    String to_string() const;

    Position const& start_position() const { return m_start_position; }

    Position const& end_position() const { return m_end_position; }

    void set_start_position(Badge<HTMLTokenizer>, Position start_position) { m_start_position = start_position; }

    void set_end_position(Badge<HTMLTokenizer>, Position end_position) { m_end_position = end_position; }

    void normalize_attributes();

private:

    Vector<Attribute> const* tag_attributes() const

    {

        return m_data.get<OwnPtr<Vector<Attribute>>>().ptr();

    }

    Vector<Attribute>* tag_attributes()

    {

        return m_data.get<OwnPtr<Vector<Attribute>>>().ptr();

    }

    Vector<Attribute>& ensure_tag_attributes()

    {

        VERIFY(is_start_tag() || is_end_tag());

        auto& ptr = m_data.get<OwnPtr<Vector<Attribute>>>();

        if (!ptr)

            ptr = make<Vector<Attribute>>();

        return *ptr;

    }

    Type m_type { Type::Invalid };

    // Type::StartTag and Type::EndTag

    bool m_tag_self_closing { false };

    bool m_tag_self_closing_acknowledged { false };

    // Type::StartTag and Type::EndTag (tag name)

    FlyString m_string_data;

    // Type::Comment (comment data)

    String m_comment_data;

    Variant<Empty, u32, OwnPtr<DoctypeData>, OwnPtr<Vector<Attribute>>> m_data {};

    Position m_start_position;

    Position m_end_position;

};

}