/*
 * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/StringBuilder.h>
#include <AK/Utf8View.h>
#include <LibWeb/CSS/Serialize.h>

namespace Web::CSS {

// https://www.w3.org/TR/cssom-1/#escape-a-character
void escape_a_character(StringBuilder& builder, u32 character)
{
    builder.append('\\');
    builder.append_code_point(character);
}

// https://www.w3.org/TR/cssom-1/#escape-a-character-as-code-point
void escape_a_character_as_code_point(StringBuilder& builder, u32 character)
{
    builder.appendff("\\{:x} ", character);
}

// https://www.w3.org/TR/cssom-1/#serialize-an-identifier
void serialize_an_identifier(StringBuilder& builder, StringView ident)
{
    Utf8View characters { ident };
    auto first_character = characters.is_empty() ? 0 : *characters.begin();

    // To serialize an identifier means to create a string represented by the concatenation of,
    // for each character of the identifier:
    for (auto character : characters) {
        // If the character is NULL (U+0000), then the REPLACEMENT CHARACTER (U+FFFD).
        if (character == 0) {
            builder.append_code_point(0xFFFD);
            continue;
        }
        // If the character is in the range [\1-\1f] (U+0001 to U+001F) or is U+007F,
        // then the character escaped as code point.
        if ((character >= 0x0001 && character <= 0x001F) || (character == 0x007F)) {
            escape_a_character_as_code_point(builder, character);
            continue;
        }
        // If the character is the first character and is in the range [0-9] (U+0030 to U+0039),
        // then the character escaped as code point.
        if (builder.is_empty() && character >= '0' && character <= '9') {
            escape_a_character_as_code_point(builder, character);
            continue;
        }
        // If the character is the second character and is in the range [0-9] (U+0030 to U+0039)
        // and the first character is a "-" (U+002D), then the character escaped as code point.
        if (builder.length() == 1 && first_character == '-' && character >= '0' && character <= '9') {
            escape_a_character_as_code_point(builder, character);
            continue;
        }
        // If the character is the first character and is a "-" (U+002D), and there is no second
        // character, then the escaped character.
        if (builder.is_empty() && character == '-' && characters.length() == 1) {
            escape_a_character(builder, character);
            continue;
        }
        // If the character is not handled by one of the above rules and is greater than or equal to U+0080, is "-" (U+002D) or "_" (U+005F), or is in one of the ranges [0-9] (U+0030 to U+0039), [A-Z] (U+0041 to U+005A), or \[a-z] (U+0061 to U+007A), then the character itself.
        if ((character >= 0x0080)
            || (character == '-') || (character == '_')
            || (character >= '0' && character <= '9')
            || (character >= 'A' && character <= 'Z')
            || (character >= 'a' && character <= 'z')) {
            builder.append_code_point(character);
            continue;
        }
        // Otherwise, the escaped character.
        escape_a_character(builder, character);
    }
}

// https://www.w3.org/TR/cssom-1/#serialize-a-string
void serialize_a_string(StringBuilder& builder, StringView string)
{
    Utf8View characters { string };

    // To serialize a string means to create a string represented by '"' (U+0022), followed by the result
    // of applying the rules below to each character of the given string, followed by '"' (U+0022):
    builder.append('"');

    for (auto character : characters) {
        // If the character is NULL (U+0000), then the REPLACEMENT CHARACTER (U+FFFD).
        if (character == 0) {
            builder.append_code_point(0xFFFD);
            continue;
        }
        // If the character is in the range [\1-\1f] (U+0001 to U+001F) or is U+007F, the character escaped as code point.
        if ((character >= 0x0001 && character <= 0x001F) || (character == 0x007F)) {
            escape_a_character_as_code_point(builder, character);
            continue;
        }
        // If the character is '"' (U+0022) or "\" (U+005C), the escaped character.
        if (character == 0x0022 || character == 0x005C) {
            escape_a_character(builder, character);
            continue;
        }
        // Otherwise, the character itself.
        builder.append_code_point(character);
    }

    builder.append('"');
}

// https://www.w3.org/TR/cssom-1/#serialize-a-url
void serialize_a_url(StringBuilder& builder, StringView url)
{
    // To serialize a URL means to create a string represented by "url(",
    // followed by the serialization of the URL as a string, followed by ")".
    builder.append("url("sv);
    serialize_a_string(builder, url.to_string());
    builder.append(')');
}

// https://www.w3.org/TR/css-color-4/#serializing-sRGB-values
void serialize_a_srgb_value(StringBuilder& builder, Color color)
{
    // The serialized form is derived from the computed value and thus, uses either the rgb() or rgba() form
    // (depending on whether the alpha is exactly 1, or not), with lowercase letters for the function name.
    // NOTE: Since we use Gfx::Color, having an "alpha of 1" means its value is 255.
    if (color.alpha() == 255)
        builder.appendff("rgb({}, {}, {})"sv, color.red(), color.green(), color.blue());
    else
        builder.appendff("rgba({}, {}, {}, {})"sv, color.red(), color.green(), color.blue(), (float)(color.alpha()) / 255.0f);
}

String escape_a_character(u32 character)
{
    StringBuilder builder;
    escape_a_character(builder, character);
    return builder.to_string();
}

String escape_a_character_as_code_point(u32 character)
{
    StringBuilder builder;
    escape_a_character_as_code_point(builder, character);
    return builder.to_string();
}

String serialize_an_identifier(StringView ident)
{
    StringBuilder builder;
    serialize_an_identifier(builder, ident);
    return builder.to_string();
}

String serialize_a_string(StringView string)
{
    StringBuilder builder;
    serialize_a_string(builder, string);
    return builder.to_string();
}

String serialize_a_url(StringView url)
{
    StringBuilder builder;
    serialize_a_url(builder, url);
    return builder.to_string();
}

String serialize_a_srgb_value(Color color)
{
    StringBuilder builder;
    serialize_a_srgb_value(builder, color);
    return builder.to_string();
}

}