/*

 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>

 * Copyright (c) 2021, Max Wipfli <mail@maxwipfli.ch>

 *

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

 */

#include <AK/Base64.h>

#include <AK/CharacterTypes.h>

#include <AK/Debug.h>

#include <AK/LexicalPath.h>

#include <AK/StringBuilder.h>

#include <AK/Utf8View.h>

#include <LibURL/Parser.h>

#include <LibURL/URL.h>

namespace URL {

// FIXME: It could make sense to force users of URL to use URL::Parser::basic_parse() explicitly instead of using a constructor.

URL::URL(StringView string)

    : URL(Parser::basic_parse(string))

{

    if constexpr (URL_PARSER_DEBUG) {

        if (m_data->valid)

            dbgln("URL constructor: Parsed URL to be '{}'.", serialize());

        else

            dbgln("URL constructor: Parsed URL to be invalid.");

    }

}

URL URL::complete_url(StringView relative_url) const

{

    if (!is_valid())

        return {};

    return Parser::basic_parse(relative_url, *this);

}

ByteString URL::path_segment_at_index(size_t index) const

{

    VERIFY(index < path_segment_count());

    return percent_decode(m_data->paths[index]);

}

ByteString URL::basename() const

{

    if (!m_data->valid)

        return {};

    if (m_data->paths.is_empty())

        return {};

    auto& last_segment = m_data->paths.last();

    return percent_decode(last_segment);

}

void URL::set_scheme(String scheme)

{

    m_data->scheme = move(scheme);

    m_data->valid = compute_validity();

}

// https://url.spec.whatwg.org/#set-the-username

void URL::set_username(StringView username)

{

    // To set the username given a url and username, set url’s username to the result of running UTF-8 percent-encode on username using the userinfo percent-encode set.

    m_data->username = percent_encode(username, PercentEncodeSet::Userinfo);

    m_data->valid = compute_validity();

}

// https://url.spec.whatwg.org/#set-the-password

void URL::set_password(StringView password)

{

    // To set the password given a url and password, set url’s password to the result of running UTF-8 percent-encode on password using the userinfo percent-encode set.

    m_data->password = percent_encode(password, PercentEncodeSet::Userinfo);

    m_data->valid = compute_validity();

}

void URL::set_host(Host host)

{

    m_data->host = move(host);

    m_data->valid = compute_validity();

}

// https://url.spec.whatwg.org/#concept-host-serializer

ErrorOr<String> URL::serialized_host() const

{

    return Parser::serialize_host(m_data->host);

}

void URL::set_port(Optional<u16> port)

{

    if (port == default_port_for_scheme(m_data->scheme)) {

        m_data->port = {};

        return;

    }

    m_data->port = move(port);

    m_data->valid = compute_validity();

}

void URL::set_paths(Vector<ByteString> const& paths)

{

    m_data->paths.clear_with_capacity();

    m_data->paths.ensure_capacity(paths.size());

    for (auto const& segment : paths)

        m_data->paths.unchecked_append(percent_encode(segment, PercentEncodeSet::Path));

    m_data->valid = compute_validity();

}

void URL::append_path(StringView path)

{

    m_data->paths.append(percent_encode(path, PercentEncodeSet::Path));

}

// https://url.spec.whatwg.org/#cannot-have-a-username-password-port

bool URL::cannot_have_a_username_or_password_or_port() const

{

    // A URL cannot have a username/password/port if its host is null or the empty string, or its scheme is "file".

    return m_data->host.has<Empty>() || m_data->host == String {} || m_data->scheme == "file"sv;

}

// FIXME: This is by no means complete.

// NOTE: This relies on some assumptions about how the spec-defined URL parser works that may turn out to be wrong.

bool URL::compute_validity() const

{

    if (m_data->scheme.is_empty())

        return false;

    if (m_data->cannot_be_a_base_url) {

        if (m_data->paths.size() != 1)

            return false;

        if (m_data->paths[0].is_empty())

            return false;

    } else {

        if (m_data->scheme.is_one_of("about", "mailto"))

            return false;

        // NOTE: Maybe it is allowed to have a zero-segment path.

        if (m_data->paths.size() == 0)

            return false;

    }

    // NOTE: A file URL's host should be the empty string for localhost, not null.

    if (m_data->scheme == "file" && m_data->host.has<Empty>())

        return false;

    return true;

}

// https://url.spec.whatwg.org/#default-port

Optional<u16> default_port_for_scheme(StringView scheme)

{

    // Spec defined mappings with port:

    if (scheme == "ftp")

        return 21;

    if (scheme == "http")

        return 80;

    if (scheme == "https")

        return 443;

    if (scheme == "ws")

        return 80;

    if (scheme == "wss")

        return 443;

    // NOTE: not in spec, but we support these too

    if (scheme == "gemini")

        return 1965;

    if (scheme == "irc")

        return 6667;

    if (scheme == "ircs")

        return 6697;

    return {};

}

URL create_with_file_scheme(ByteString const& path, ByteString const& fragment, ByteString const& hostname)

{

    LexicalPath lexical_path(path);

    if (!lexical_path.is_absolute())

        return {};

    URL url;

    url.set_scheme("file"_string);

    url.set_host(hostname == "localhost" ? String {} : String::from_byte_string(hostname).release_value_but_fixme_should_propagate_errors());

    url.set_paths(lexical_path.parts());

    if (path.ends_with('/'))

        url.append_slash();

    if (!fragment.is_empty())

        url.set_fragment(String::from_byte_string(fragment).release_value_but_fixme_should_propagate_errors());

    return url;

}

URL create_with_help_scheme(ByteString const& path, ByteString const& fragment, ByteString const& hostname)

{

    LexicalPath lexical_path(path);

    URL url;

    url.set_scheme("help"_string);

    url.set_host(hostname == "localhost" ? String {} : String::from_byte_string(hostname).release_value_but_fixme_should_propagate_errors());

    url.set_paths(lexical_path.parts());

    if (path.ends_with('/'))

        url.append_slash();

    if (!fragment.is_empty())

        url.set_fragment(String::from_byte_string(fragment).release_value_but_fixme_should_propagate_errors());

    return url;

}

URL create_with_url_or_path(ByteString const& url_or_path)

{

    URL url = url_or_path;

    if (url.is_valid())

        return url;

    ByteString path = LexicalPath::canonicalized_path(url_or_path);

    return create_with_file_scheme(path);

}

URL create_with_data(StringView mime_type, StringView payload, bool is_base64)

{

    URL url;

    url.set_cannot_be_a_base_url(true);

    url.set_scheme("data"_string);

    StringBuilder builder;

    builder.append(mime_type);

    if (is_base64)

        builder.append(";base64"sv);

    builder.append(',');

    builder.append(payload);

    url.set_paths({ builder.to_byte_string() });

    return url;

}

// https://url.spec.whatwg.org/#special-scheme

bool is_special_scheme(StringView scheme)

{

    return scheme.is_one_of("ftp", "file", "http", "https", "ws", "wss");

}

// https://url.spec.whatwg.org/#url-path-serializer

String URL::serialize_path() const

{

    // 1. If url has an opaque path, then return url’s path.

    // FIXME: Reimplement this step once we modernize the URL implementation to meet the spec.

    if (cannot_be_a_base_url())

        return m_data->paths[0];

    // 2. Let output be the empty string.

    StringBuilder output;

    // 3. For each segment of url’s path: append U+002F (/) followed by segment to output.

    for (auto const& segment : m_data->paths) {

        output.append('/');

        output.append(segment);

    }

    // 4. Return output.

    return output.to_string_without_validation();

}

// https://url.spec.whatwg.org/#concept-url-serializer

ByteString URL::serialize(ExcludeFragment exclude_fragment) const

{

    // 1. Let output be url’s scheme and U+003A (:) concatenated.

    StringBuilder output;

    output.append(m_data->scheme);

    output.append(':');

    // 2. If url’s host is non-null:

    if (!m_data->host.has<Empty>()) {

        // 1. Append "//" to output.

        output.append("//"sv);

        // 2. If url includes credentials, then:

        if (includes_credentials()) {

            // 1. Append url’s username to output.

            output.append(m_data->username);

            // 2. If url’s password is not the empty string, then append U+003A (:), followed by url’s password, to output.

            if (!m_data->password.is_empty()) {

                output.append(':');

                output.append(m_data->password);

            }

            // 3. Append U+0040 (@) to output.

            output.append('@');

        }

        // 3. Append url’s host, serialized, to output.

        output.append(serialized_host().release_value_but_fixme_should_propagate_errors());

        // 4. If url’s port is non-null, append U+003A (:) followed by url’s port, serialized, to output.

        if (m_data->port.has_value())

            output.appendff(":{}", *m_data->port);

    }

    // 3. If url’s host is null, url does not have an opaque path, url’s path’s size is greater than 1, and url’s path[0] is the empty string, then append U+002F (/) followed by U+002E (.) to output.

    // 4. Append the result of URL path serializing url to output.

    // FIXME: Implement this closer to spec steps.

    if (cannot_be_a_base_url()) {

        output.append(m_data->paths[0]);

    } else {

        if (m_data->host.has<Empty>() && m_data->paths.size() > 1 && m_data->paths[0].is_empty())

            output.append("/."sv);

        for (auto& segment : m_data->paths) {

            output.append('/');

            output.append(segment);

        }

    }

    // 5. If url’s query is non-null, append U+003F (?), followed by url’s query, to output.

    if (m_data->query.has_value()) {

        output.append('?');

        output.append(*m_data->query);

    }

    // 6. If exclude fragment is false and url’s fragment is non-null, then append U+0023 (#), followed by url’s fragment, to output.

    if (exclude_fragment == ExcludeFragment::No && m_data->fragment.has_value()) {

        output.append('#');

        output.append(*m_data->fragment);

    }

    // 7. Return output.

    return output.to_byte_string();

}

// https://url.spec.whatwg.org/#url-rendering

// NOTE: This does e.g. not display credentials.

// FIXME: Parts of the URL other than the host should have their sequences of percent-encoded bytes replaced with code points

//        resulting from percent-decoding those sequences converted to bytes, unless that renders those sequences invisible.

ByteString URL::serialize_for_display() const

{

    VERIFY(m_data->valid);

    StringBuilder builder;

    builder.append(m_data->scheme);

    builder.append(':');

    if (!m_data->host.has<Empty>()) {

        builder.append("//"sv);

        builder.append(serialized_host().release_value_but_fixme_should_propagate_errors());

        if (m_data->port.has_value())

            builder.appendff(":{}", *m_data->port);

    }

    if (cannot_be_a_base_url()) {

        builder.append(m_data->paths[0]);

    } else {

        if (m_data->host.has<Empty>() && m_data->paths.size() > 1 && m_data->paths[0].is_empty())

            builder.append("/."sv);

        for (auto& segment : m_data->paths) {

            builder.append('/');

            builder.append(segment);

        }

    }

    if (m_data->query.has_value()) {

        builder.append('?');

        builder.append(*m_data->query);

    }

    if (m_data->fragment.has_value()) {

        builder.append('#');

        builder.append(*m_data->fragment);

    }

    return builder.to_byte_string();

}

ErrorOr<String> URL::to_string() const

{

    return String::from_byte_string(serialize());

}

// https://url.spec.whatwg.org/#concept-url-origin

Origin URL::origin() const

{

    // The origin of a URL url is the origin returned by running these steps, switching on url’s scheme:

    // -> "blob"

    if (scheme() == "blob"sv) {

        auto url_string = to_string().release_value_but_fixme_should_propagate_errors();

        // 1. If url’s blob URL entry is non-null, then return url’s blob URL entry’s environment’s origin.

        if (blob_url_entry().has_value())

            return blob_url_entry()->environment_origin;

        // 2. Let pathURL be the result of parsing the result of URL path serializing url.

        auto path_url = Parser::basic_parse(serialize_path());

        // 3. If pathURL is failure, then return a new opaque origin.

        if (!path_url.is_valid())

            return Origin {};

        // 4. If pathURL’s scheme is "http", "https", or "file", then return pathURL’s origin.

        if (path_url.scheme().is_one_of("http"sv, "https"sv, "file"sv))

            return path_url.origin();

        // 5. Return a new opaque origin.

        return Origin {};

    }

    // -> "ftp"

    // -> "http"

    // -> "https"

    // -> "ws"

    // -> "wss"

    if (scheme().is_one_of("ftp"sv, "http"sv, "https"sv, "ws"sv, "wss"sv)) {

        // Return the tuple origin (url’s scheme, url’s host, url’s port, null).

        return Origin(scheme().to_byte_string(), host(), port());

    }

    // -> "file"

    // AD-HOC: Our resource:// is basically an alias to file://

    if (scheme() == "file"sv || scheme() == "resource"sv) {

        // Unfortunate as it is, this is left as an exercise to the reader. When in doubt, return a new opaque origin.

        // Note: We must return an origin with the `file://' protocol for `file://' iframes to work from `file://' pages.

        return Origin(scheme().to_byte_string(), String {}, {});

    }

    // -> Otherwise

    // Return a new opaque origin.

    return Origin {};

}

bool URL::equals(URL const& other, ExcludeFragment exclude_fragments) const

{

    if (this == &other)

        return true;

    if (!m_data->valid || !other.m_data->valid)

        return false;

    return serialize(exclude_fragments) == other.serialize(exclude_fragments);

}

void append_percent_encoded(StringBuilder& builder, u32 code_point)

{

    if (code_point <= 0x7f)

        builder.appendff("%{:02X}", code_point);

    else if (code_point <= 0x07ff)

        builder.appendff("%{:02X}%{:02X}", ((code_point >> 6) & 0x1f) | 0xc0, (code_point & 0x3f) | 0x80);

    else if (code_point <= 0xffff)

        builder.appendff("%{:02X}%{:02X}%{:02X}", ((code_point >> 12) & 0x0f) | 0xe0, ((code_point >> 6) & 0x3f) | 0x80, (code_point & 0x3f) | 0x80);

    else if (code_point <= 0x10ffff)

        builder.appendff("%{:02X}%{:02X}%{:02X}%{:02X}", ((code_point >> 18) & 0x07) | 0xf0, ((code_point >> 12) & 0x3f) | 0x80, ((code_point >> 6) & 0x3f) | 0x80, (code_point & 0x3f) | 0x80);

    else

        VERIFY_NOT_REACHED();

}

// https://url.spec.whatwg.org/#c0-control-percent-encode-set

bool code_point_is_in_percent_encode_set(u32 code_point, PercentEncodeSet set)

{

    // NOTE: Once we've checked for presence in the C0Control set, we know that the code point is

    //       a valid ASCII character in the range 0x20..0x7E, so we can safely cast it to char.

    switch (set) {

    case PercentEncodeSet::C0Control:

        return code_point < 0x20 || code_point > 0x7E;

    case PercentEncodeSet::Fragment:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::C0Control) || " \"<>`"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::Query:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::C0Control) || " \"#<>"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::SpecialQuery:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::Query) || code_point == '\'';

    case PercentEncodeSet::Path:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::Query) || "?`{}"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::Userinfo:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::Path) || "/:;=@[\\]^|"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::Component:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::Userinfo) || "$%&+,"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::ApplicationXWWWFormUrlencoded:

        return code_point_is_in_percent_encode_set(code_point, PercentEncodeSet::Component) || "!'()~"sv.contains(static_cast<char>(code_point));

    case PercentEncodeSet::EncodeURI:

        // NOTE: This is the same percent encode set that JS encodeURI() uses.

        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURI

        return code_point > 0x7E || (!is_ascii_alphanumeric(code_point) && !";,/?:@&=+$-_.!~*'()#"sv.contains(static_cast<char>(code_point)));

    default:

        VERIFY_NOT_REACHED();

    }

}

void append_percent_encoded_if_necessary(StringBuilder& builder, u32 code_point, PercentEncodeSet set)

{

    if (code_point_is_in_percent_encode_set(code_point, set))

        append_percent_encoded(builder, code_point);

    else

        builder.append_code_point(code_point);

}

String percent_encode(StringView input, PercentEncodeSet set, SpaceAsPlus space_as_plus)

{

    StringBuilder builder;

    for (auto code_point : Utf8View(input)) {

        if (space_as_plus == SpaceAsPlus::Yes && code_point == ' ')

            builder.append('+');

        else

            append_percent_encoded_if_necessary(builder, code_point, set);

    }

    return MUST(builder.to_string());

}

ByteString percent_decode(StringView input)

{

    if (!input.contains('%'))

        return input;

    StringBuilder builder;

    Utf8View utf8_view(input);

    for (auto it = utf8_view.begin(); !it.done(); ++it) {

        if (*it != '%') {

            builder.append_code_point(*it);

        } else if (!is_ascii_hex_digit(it.peek(1).value_or(0)) || !is_ascii_hex_digit(it.peek(2).value_or(0))) {

            builder.append_code_point(*it);

        } else {

            ++it;

            u8 byte = parse_ascii_hex_digit(*it) << 4;

            ++it;

            byte += parse_ascii_hex_digit(*it);

            builder.append(byte);

        }

    }

    return builder.to_byte_string();

}

}