#include "ImGui.h"                // https://github.com/ocornut/imgui
#include "imgui_markdown.h"       // https://github.com/juliettef/imgui_markdown
#include "IconsFontAwesome5.h"    // https://github.com/juliettef/IconFontCppHeaders

// Following includes for Windows LinkCallback
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include "Shellapi.h"
#include <string>

void LinkCallback( ImGui::MarkdownLinkCallbackData data_ );
inline ImGui::MarkdownImageData ImageCallback( ImGui::MarkdownLinkCallbackData data_ );

static ImFont* H1 = NULL;
static ImFont* H2 = NULL;
static ImFont* H3 = NULL;

static ImGui::MarkdownConfig mdConfig; 


void LinkCallback( ImGui::MarkdownLinkCallbackData data_ )
{
    std::string url( data_.link, data_.linkLength );
    if( !data_.isImage )
    {
        ShellExecuteA( NULL, "open", url.c_str(), NULL, NULL, SW_SHOWNORMAL );
    }
}

inline ImGui::MarkdownImageData ImageCallback( ImGui::MarkdownLinkCallbackData data_ )
{
    // In your application you would load an image based on data_ input. Here we just use the imgui font texture.
    ImTextureID image = ImGui::GetIO().Fonts->TexID;
    // > C++14 can use ImGui::MarkdownImageData imageData{ true, false, image, ImVec2( 40.0f, 20.0f ) };
    ImGui::MarkdownImageData imageData;
    imageData.isValid =         true;
    imageData.useLinkCallback = false;
    imageData.user_texture_id = image;
    imageData.size =            ImVec2( 40.0f, 20.0f );

    // For image resize when available size.x > image width, add
    ImVec2 const contentSize = ImGui::GetContentRegionAvail();
    if( imageData.size.x > contentSize.x )
    {
        float const ratio = imageData.size.y/imageData.size.x;
        imageData.size.x = contentSize.x;
        imageData.size.y = contentSize.x*ratio;
    }

    return imageData;
}

void LoadFonts( float fontSize_ = 12.0f )
{
    ImGuiIO& io = ImGui::GetIO();
    io.Fonts->Clear();
    // Base font
    io.Fonts->AddFontFromFileTTF( "myfont.ttf", fontSize_ );
    // Bold headings H2 and H3
    H2 = io.Fonts->AddFontFromFileTTF( "myfont-bold.ttf", fontSize_ );
    H3 = mdConfig.headingFormats[ 1 ].font;
    // bold heading H1
    float fontSizeH1 = fontSize_ * 1.1f;
    H1 = io.Fonts->AddFontFromFileTTF( "myfont-bold.ttf", fontSizeH1 );
}

void ExampleMarkdownFormatCallback( const ImGui::MarkdownFormatInfo& markdownFormatInfo_, bool start_ )
{
    // Call the default first so any settings can be overwritten by our implementation.
    // Alternatively could be called or not called in a switch statement on a case by case basis.
    // See defaultMarkdownFormatCallback definition for furhter examples of how to use it.
    ImGui::defaultMarkdownFormatCallback( markdownFormatInfo_, start_ );        
       
    switch( markdownFormatInfo_.type )
    {
    // example: change the colour of heading level 2
    case ImGui::MarkdownFormatType::HEADING:
    {
        if( markdownFormatInfo_.level == 2 )
        {
            if( start_ )
            {
                ImGui::PushStyleColor( ImGuiCol_Text, ImGui::GetStyle().Colors[ImGuiCol_TextDisabled] );
            }
            else
            {
                ImGui::PopStyleColor();
            }
        }
        break;
    }
    default:
    {
        break;
    }
    }
}

void Markdown( const std::string& markdown_ )
{
    // You can make your own Markdown function with your prefered string container and markdown config.
    // > C++14 can use ImGui::MarkdownConfig mdConfig{ LinkCallback, NULL, ImageCallback, ICON_FA_LINK, { { H1, true }, { H2, true }, { H3, false } }, NULL };
    mdConfig.linkCallback =         LinkCallback;
    mdConfig.tooltipCallback =      NULL;
    mdConfig.imageCallback =        ImageCallback;
    mdConfig.linkIcon =             ICON_FA_LINK;
    mdConfig.headingFormats[0] =    { H1, true };
    mdConfig.headingFormats[1] =    { H2, true };
    mdConfig.headingFormats[2] =    { H3, false };
    mdConfig.userData =             NULL;
    mdConfig.formatCallback =       ExampleMarkdownFormatCallback;
    ImGui::Markdown( markdown_.c_str(), markdown_.length(), mdConfig );
}

void MarkdownExample()
{
    const std::string markdownText = u8R"(
# H1 Header: Text and Links
You can add [links like this one to enkisoftware](https://www.enkisoftware.com/) and lines will wrap well.
You can also insert images ![image alt text](image identifier e.g. filename)
Horizontal rules:
***
___
*Emphasis* and **strong emphasis** change the appearance of the text.
## H2 Header: indented text.
  This text has an indent (two leading spaces).
    This one has two.
### H3 Header: Lists
  * Unordered lists
    * Lists can be indented with two extra spaces.
  * Lists can have [links like this one to Avoyd](https://www.avoyd.com/) and *emphasized text*
)";
    Markdown( markdownText );
}