/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2023, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Debug.h>
#include <AK/LexicalPath.h>
#include <LibGemini/Document.h>
#include <LibGfx/ImageFormats/ImageDecoder.h>
#include <LibMarkdown/Document.h>
#include <LibTextCodec/Decoder.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/DocumentLoading.h>
#include <LibWeb/HTML/Navigable.h>
#include <LibWeb/HTML/NavigationParams.h>
#include <LibWeb/HTML/Parser/HTMLEncodingDetection.h>
#include <LibWeb/HTML/Parser/HTMLParser.h>
#include <LibWeb/Loader/GeneratedPagesLoader.h>
#include <LibWeb/Namespace.h>
#include <LibWeb/Platform/ImageCodecPlugin.h>
#include <LibWeb/XML/XMLDocumentBuilder.h>

namespace Web {

static bool build_markdown_document(DOM::Document& document, ByteBuffer const& data)
{
    auto markdown_document = Markdown::Document::parse(data);
    if (!markdown_document)
        return false;

    auto extra_head_contents = R"~~~(
<style>
    .zoomable {
        cursor: zoom-in;
        max-width: 100%;
    }
    .zoomable.zoomed-in {
        cursor: zoom-out;
        max-width: none;
    }
</style>
<script>
    function imageClickEventListener(event) {
        let image = event.target;
        if (image.classList.contains("zoomable")) {
            image.classList.toggle("zoomed-in");
        }
    }
    function processImages() {
        let images = document.querySelectorAll("img");
        let windowWidth = window.innerWidth;
        images.forEach((image) => {
            if (image.naturalWidth > windowWidth) {
                image.classList.add("zoomable");
            } else {
                image.classList.remove("zoomable");
                image.classList.remove("zoomed-in");
            }

            image.addEventListener("click", imageClickEventListener);
        });
    }

    document.addEventListener("load", () => {
        processImages();
    });

    window.addEventListener("resize", () => {
        processImages();
    });
</script>
)~~~"sv;

    auto parser = HTML::HTMLParser::create(document, markdown_document->render_to_html(extra_head_contents), "utf-8");
    parser->run(document.url());
    return true;
}

static bool build_text_document(DOM::Document& document, ByteBuffer const& data)
{
    auto html_element = DOM::create_element(document, HTML::TagNames::html, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(document.append_child(html_element));

    auto head_element = DOM::create_element(document, HTML::TagNames::head, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(head_element));
    auto title_element = DOM::create_element(document, HTML::TagNames::title, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(head_element->append_child(title_element));

    auto title_text = document.create_text_node(MUST(String::from_byte_string(document.url().basename())));
    MUST(title_element->append_child(title_text));

    auto body_element = DOM::create_element(document, HTML::TagNames::body, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(body_element));

    auto pre_element = DOM::create_element(document, HTML::TagNames::pre, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(body_element->append_child(pre_element));

    MUST(pre_element->append_child(document.create_text_node(String::from_utf8(StringView { data }).release_value_but_fixme_should_propagate_errors())));
    return true;
}

static bool build_image_document(DOM::Document& document, ByteBuffer const& data)
{
    auto image = Platform::ImageCodecPlugin::the().decode_image(data);
    if (!image.has_value() || image->frames.is_empty())
        return false;
    auto const& frame = image->frames[0];
    auto const& bitmap = frame.bitmap;
    if (!bitmap)
        return false;

    auto html_element = DOM::create_element(document, HTML::TagNames::html, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(document.append_child(html_element));

    auto head_element = DOM::create_element(document, HTML::TagNames::head, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(head_element));
    auto title_element = DOM::create_element(document, HTML::TagNames::title, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(head_element->append_child(title_element));

    auto basename = LexicalPath::basename(document.url().serialize_path());
    auto title_text = document.heap().allocate<DOM::Text>(document.realm(), document, MUST(String::formatted("{} [{}x{}]", basename, bitmap->width(), bitmap->height())));
    MUST(title_element->append_child(*title_text));

    auto body_element = DOM::create_element(document, HTML::TagNames::body, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(body_element));

    auto image_element = DOM::create_element(document, HTML::TagNames::img, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(image_element->set_attribute(HTML::AttributeNames::src, MUST(document.url().to_string())));
    MUST(body_element->append_child(image_element));

    return true;
}

static bool build_gemini_document(DOM::Document& document, ByteBuffer const& data)
{
    StringView gemini_data { data };
    auto gemini_document = Gemini::Document::parse(gemini_data, document.url());
    ByteString html_data = gemini_document->render_to_html();

    dbgln_if(GEMINI_DEBUG, "Gemini data:\n\"\"\"{}\"\"\"", gemini_data);
    dbgln_if(GEMINI_DEBUG, "Converted to HTML:\n\"\"\"{}\"\"\"", html_data);

    auto parser = HTML::HTMLParser::create(document, html_data, "utf-8");
    parser->run(document.url());
    return true;
}

bool build_xml_document(DOM::Document& document, ByteBuffer const& data, Optional<String> content_encoding)
{
    Optional<TextCodec::Decoder&> decoder;
    // The actual HTTP headers and other metadata, not the headers as mutated or implied by the algorithms given in this specification,
    // are the ones that must be used when determining the character encoding according to the rules given in the above specifications.
    if (content_encoding.has_value())
        decoder = TextCodec::decoder_for(*content_encoding);
    if (!decoder.has_value()) {
        auto encoding = HTML::run_encoding_sniffing_algorithm(document, data);
        decoder = TextCodec::decoder_for(encoding);
    }
    VERIFY(decoder.has_value());
    // Well-formed XML documents contain only properly encoded characters
    if (!decoder->validate(data))
        return false;
    auto source = decoder->to_utf8(data).release_value_but_fixme_should_propagate_errors();
    XML::Parser parser(source, { .resolve_external_resource = resolve_xml_resource });
    XMLDocumentBuilder builder { document };
    auto result = parser.parse_with_listener(builder);
    return !result.is_error() && !builder.has_error();
}

static bool build_video_document(DOM::Document& document)
{
    auto html_element = DOM::create_element(document, HTML::TagNames::html, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(document.append_child(html_element));

    auto head_element = DOM::create_element(document, HTML::TagNames::head, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(head_element));

    auto body_element = DOM::create_element(document, HTML::TagNames::body, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(body_element));

    auto video_element = DOM::create_element(document, HTML::TagNames::video, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(video_element->set_attribute(HTML::AttributeNames::src, MUST(document.url().to_string())));
    MUST(video_element->set_attribute(HTML::AttributeNames::autoplay, String {}));
    MUST(video_element->set_attribute(HTML::AttributeNames::controls, String {}));
    MUST(body_element->append_child(video_element));

    return true;
}

static bool build_audio_document(DOM::Document& document)
{
    auto html_element = DOM::create_element(document, HTML::TagNames::html, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(document.append_child(html_element));

    auto head_element = DOM::create_element(document, HTML::TagNames::head, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(head_element));

    auto body_element = DOM::create_element(document, HTML::TagNames::body, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(html_element->append_child(body_element));

    auto video_element = DOM::create_element(document, HTML::TagNames::audio, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
    MUST(video_element->set_attribute(HTML::AttributeNames::src, MUST(document.url().to_string())));
    MUST(video_element->set_attribute(HTML::AttributeNames::autoplay, String {}));
    MUST(video_element->set_attribute(HTML::AttributeNames::controls, String {}));
    MUST(body_element->append_child(video_element));

    return true;
}

bool parse_document(DOM::Document& document, ByteBuffer const& data, Optional<String> content_encoding)
{
    auto& mime_type = document.content_type();
    if (mime_type == "text/html") {
        auto parser = HTML::HTMLParser::create_with_uncertain_encoding(document, data);
        parser->run(document.url());
        return true;
    }
    if (mime_type.ends_with_bytes("+xml"sv) || mime_type.is_one_of("text/xml", "application/xml"))
        return build_xml_document(document, data, move(content_encoding));
    if (mime_type.starts_with_bytes("image/"sv))
        return build_image_document(document, data);
    if (mime_type.starts_with_bytes("video/"sv))
        return build_video_document(document);
    if (mime_type.starts_with_bytes("audio/"sv))
        return build_audio_document(document);
    if (mime_type == "text/plain" || mime_type == "application/json")
        return build_text_document(document, data);
    if (mime_type == "text/markdown")
        return build_markdown_document(document, data);
    if (mime_type == "text/gemini")
        return build_gemini_document(document, data);

    return false;
}

static bool is_supported_document_mime_type(StringView mime_type)
{
    if (mime_type == "text/html")
        return true;
    if (mime_type.ends_with("+xml"sv) || mime_type.is_one_of("text/xml", "application/xml"))
        return true;
    if (mime_type.starts_with("image/"sv))
        return true;
    if (mime_type.starts_with("video/"sv))
        return true;
    if (mime_type.starts_with("audio/"sv))
        return true;
    if (mime_type == "text/plain" || mime_type == "application/json")
        return true;
    if (mime_type == "text/markdown")
        return true;
    if (mime_type == "text/gemini")
        return true;
    return false;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#loading-a-document
JS::GCPtr<DOM::Document> load_document(HTML::NavigationParams navigation_params)
{
    // To load a document given navigation params navigationParams, source snapshot params sourceSnapshotParams,
    // and origin initiatorOrigin, perform the following steps. They return a Document or null.

    // 1. Let type be the computed type of navigationParams's response.
    auto extracted_mime_type = navigation_params.response->header_list()->extract_mime_type().release_value_but_fixme_should_propagate_errors();
    if (!extracted_mime_type.has_value())
        return nullptr;
    auto type = extracted_mime_type.release_value();

    VERIFY(navigation_params.response->body());

    // 2. If the user agent has been configured to process resources of the given type using some mechanism other than
    //    rendering the content in a navigable, then skip this step.
    //    Otherwise, if the type is one of the following types:

    // -> an HTML MIME type
    if (type.is_html()) {
        // FIXME: Return the result of loading an HTML document, given navigationParams.
    }

    // -> an XML MIME type that is not an explicitly supported XML MIME type
    //    FIXME: that is not an explicitly supported XML MIME type
    if (type.is_xml()) {
        // FIXME: Return the result of loading an XML document given navigationParams and type.
    }

    // -> a JavaScript MIME type
    // -> a JSON MIME type that is not an explicitly supported JSON MIME type
    // -> "text/css"
    // -> "text/plain"
    // -> "text/vtt"
    if (type.is_javascript()
        || type.is_json()
        || type.essence() == "text/css"_string
        || type.essence() == "text/plain"_string
        || type.essence() == "text/vtt"_string) {
        // FIXME: Return the result of loading a text document given navigationParams and type.
    }

    // -> "multipart/x-mixed-replace"
    if (type.essence() == "multipart/x-mixed-replace"_string) {
        // FIXME: Return the result of loading a multipart/x-mixed-replace document, given navigationParams,
        //        sourceSnapshotParams, and initiatorOrigin.
    }

    // -> A supported image, video, or audio type
    if (type.is_image()
        || type.is_audio_or_video()) {
        // FIXME: Return the result of loading a media document given navigationParams and type.
    }

    // -> "application/pdf"
    // -> "text/pdf"
    if (type.essence() == "application/pdf"_string
        || type.essence() == "text/pdf"_string) {
        // FIXME: If the user agent's PDF viewer supported is true, return the result of creating a document for inline
        //        content that doesn't have a DOM given navigationParams's navigable.
    }

    // Otherwise, proceed onward.

    // FIXME: 3. If, given type, the new resource is to be handled by displaying some sort of inline content, e.g., a
    //        native rendering of the content or an error message because the specified type is not supported, then
    //        return the result of creating a document for inline content that doesn't have a DOM given navigationParams's
    //        navigable, navigationParams's id, and navigationParams's navigation timing type.

    // FIXME: 4. Otherwise, the document's type is such that the resource will not affect navigationParams's navigable,
    //        e.g., because the resource is to be handed to an external application or because it is an unknown type
    //        that will be processed as a download. Hand-off to external software given navigationParams's response,
    //        navigationParams's navigable, navigationParams's final sandboxing flag set, sourceSnapshotParams's has
    //        transient activation, and initiatorOrigin.

    // FIXME: Start of old, ad-hoc code

    if (!is_supported_document_mime_type(type.essence()))
        return nullptr;

    auto document = DOM::Document::create_and_initialize(DOM::Document::Type::HTML, "text/html"_string, navigation_params).release_value_but_fixme_should_propagate_errors();
    document->set_content_type(type.essence());

    auto& realm = document->realm();

    if (navigation_params.response->body()) {
        Optional<String> content_encoding = type.parameters().get("charset"sv);
        auto process_body = [document, url = navigation_params.response->url().value(), encoding = move(content_encoding)](ByteBuffer bytes) {
            if (parse_document(*document, bytes, move(encoding)))
                return;
            document->remove_all_children(true);
            auto error_html = load_error_page(url).release_value_but_fixme_should_propagate_errors();
            auto parser = HTML::HTMLParser::create(document, error_html, "utf-8");
            document->set_url(AK::URL("about:error"));
            parser->run();
        };

        auto process_body_error = [](auto) {
            dbgln("FIXME: Load html page with an error if read of body failed.");
        };

        navigation_params.response->body()->fully_read(
                                              realm,
                                              move(process_body),
                                              move(process_body_error),
                                              JS::NonnullGCPtr { realm.global_object() })
            .release_value_but_fixme_should_propagate_errors();
    }

    return document;

    // FIXME: End of old, ad-hoc code

    // 5. Return null.
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/document-lifecycle.html#read-ua-inline
JS::GCPtr<DOM::Document> create_document_for_inline_content(JS::GCPtr<HTML::Navigable> navigable, Optional<String> navigation_id, StringView content_html)
{
    auto& vm = navigable->vm();

    // 1. Let origin be a new opaque origin.
    HTML::Origin origin {};

    // 2. Let coop be a new cross-origin opener policy.
    auto coop = HTML::CrossOriginOpenerPolicy {};

    // 3. Let coopEnforcementResult be a new cross-origin opener policy enforcement result with
    //    url: response's URL
    //    origin: origin
    //    cross-origin opener policy: coop
    HTML::CrossOriginOpenerPolicyEnforcementResult coop_enforcement_result {
        .url = AK::URL("about:error"), // AD-HOC
        .origin = origin,
        .cross_origin_opener_policy = coop
    };

    // 4. Let navigationParams be a new navigation params with
    //    id: navigationId
    //    navigable: navigable
    //    request: null
    //    response: a new response
    //    origin: origin
    //    fetch controller: null
    //    commit early hints: null
    //    COOP enforcement result: coopEnforcementResult
    //    reserved environment: null
    //    policy container: a new policy container
    //    final sandboxing flag set: an empty set
    //    cross-origin opener policy: coop
    //    FIXME: navigation timing type: navTimingType
    //    about base URL: null
    auto response = Fetch::Infrastructure::Response::create(vm);
    response->url_list().append(AK::URL("about:error")); // AD-HOC: https://github.com/whatwg/html/issues/9122
    HTML::NavigationParams navigation_params {
        .id = navigation_id,
        .navigable = navigable,
        .request = {},
        .response = *response,
        .fetch_controller = nullptr,
        .commit_early_hints = nullptr,
        .coop_enforcement_result = move(coop_enforcement_result),
        .reserved_environment = {},
        .origin = move(origin),
        .policy_container = HTML::PolicyContainer {},
        .final_sandboxing_flag_set = HTML::SandboxingFlagSet {},
        .cross_origin_opener_policy = move(coop),
        .about_base_url = {},
    };

    // 5. Let document be the result of creating and initializing a Document object given "html", "text/html", and navigationParams.
    auto document = DOM::Document::create_and_initialize(DOM::Document::Type::HTML, "text/html"_string, navigation_params).release_value_but_fixme_should_propagate_errors();

    // 6. Either associate document with a custom rendering that is not rendered using the normal Document rendering rules, or mutate document until it represents the content the
    //    user agent wants to render.
    auto parser = HTML::HTMLParser::create(document, content_html, "utf-8");
    document->set_url(AK::URL("about:error"));
    parser->run();

    // 7. Return document.
    return document;
}

}