#include "XCUIBackend/ImGuiTextAtlasProvider.h"

#include <imgui.h>
#include <imgui_internal.h>

namespace XCEngine {
namespace Editor {
namespace XCUIBackend {

namespace {

IXCUITextAtlasProvider::FontHandle MakeFontHandle(const ImFont* font) {
    IXCUITextAtlasProvider::FontHandle handle = {};
    handle.value = reinterpret_cast<std::uintptr_t>(font);
    return handle;
}

ImFont* ResolveFontHandle(IXCUITextAtlasProvider::FontHandle handle) {
    return reinterpret_cast<ImFont*>(handle.value);
}

ImFontAtlas* ResolveAtlas(::ImGuiContext* context) {
    if (context == nullptr) {
        return nullptr;
    }
    return context->IO.Fonts;
}

ImFont* ResolveDefaultFont(::ImGuiContext* context) {
    ImFontAtlas* atlas = ResolveAtlas(context);
    if (atlas == nullptr) {
        return nullptr;
    }

    ImFont* font = context->IO.FontDefault;
    if (font == nullptr && atlas->Fonts.Size > 0) {
        font = atlas->Fonts[0];
    }
    return font;
}

float ResolveNominalFontSize(const ImFont& font) {
    return font.LegacySize > 0.0f ? font.LegacySize : 16.0f;
}

float ResolveRequestedFontSize(const ImFont& font, float requestedFontSize) {
    return requestedFontSize > 0.0f ? requestedFontSize : ResolveNominalFontSize(font);
}

bool IsFontOwnedByAtlas(const ImFont* font, const ImFontAtlas* atlas) {
    return font != nullptr && atlas != nullptr && font->OwnerAtlas == atlas;
}

ImFontBaked* ResolveBakedFont(
    IXCUITextAtlasProvider::FontHandle fontHandle,
    ImFontAtlas* atlas,
    float requestedFontSize) {
    ImFont* font = ResolveFontHandle(fontHandle);
    if (!IsFontOwnedByAtlas(font, atlas)) {
        return nullptr;
    }

    const float resolvedFontSize = ResolveRequestedFontSize(*font, requestedFontSize);
    if (resolvedFontSize <= 0.0f) {
        return nullptr;
    }

    return font->GetFontBaked(resolvedFontSize);
}

} // namespace

ImGuiTextAtlasProvider::ImGuiTextAtlasProvider(::ImGuiContext* context)
    : m_context(context) {
}

void ImGuiTextAtlasProvider::SetContext(::ImGuiContext* context) {
    m_context = context;
}

::ImGuiContext* ImGuiTextAtlasProvider::GetContext() const {
    return m_context;
}

bool ImGuiTextAtlasProvider::GetAtlasTextureView(
    PixelFormat preferredFormat,
    AtlasTextureView& outView) const {
    outView = {};

    ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    if (atlas == nullptr) {
        return false;
    }

    unsigned char* pixels = nullptr;
    int width = 0;
    int height = 0;
    int bytesPerPixel = 0;
    PixelFormat resolvedFormat = preferredFormat;

    switch (preferredFormat) {
    case PixelFormat::Alpha8:
        atlas->GetTexDataAsAlpha8(&pixels, &width, &height, &bytesPerPixel);
        break;
    case PixelFormat::RGBA32:
    case PixelFormat::Unknown:
    default:
        atlas->GetTexDataAsRGBA32(&pixels, &width, &height, &bytesPerPixel);
        resolvedFormat = PixelFormat::RGBA32;
        break;
    }

    if (pixels == nullptr || width <= 0 || height <= 0 || bytesPerPixel <= 0) {
        return false;
    }

    outView.pixels = pixels;
    outView.width = width;
    outView.height = height;
    outView.stride = width * bytesPerPixel;
    outView.bytesPerPixel = bytesPerPixel;
    outView.format = resolvedFormat;
    outView.atlasStorageKey = reinterpret_cast<std::uintptr_t>(atlas);
    outView.pixelDataKey = reinterpret_cast<std::uintptr_t>(pixels);
    return true;
}

std::size_t ImGuiTextAtlasProvider::GetFontCount() const {
    const ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    return atlas != nullptr ? static_cast<std::size_t>(atlas->Fonts.Size) : 0u;
}

IXCUITextAtlasProvider::FontHandle ImGuiTextAtlasProvider::GetFont(std::size_t index) const {
    const ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    if (atlas == nullptr || index >= static_cast<std::size_t>(atlas->Fonts.Size)) {
        return {};
    }

    return MakeFontHandle(atlas->Fonts[static_cast<int>(index)]);
}

IXCUITextAtlasProvider::FontHandle ImGuiTextAtlasProvider::GetDefaultFont() const {
    return MakeFontHandle(ResolveDefaultFont(ResolveContext()));
}

bool ImGuiTextAtlasProvider::GetFontInfo(FontHandle fontHandle, FontInfo& outInfo) const {
    outInfo = {};

    ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    ImFont* font = ResolveFontHandle(fontHandle);
    if (!IsFontOwnedByAtlas(font, atlas)) {
        return false;
    }

    outInfo.handle = fontHandle;
    outInfo.nominalSize = ResolveNominalFontSize(*font);
    return true;
}

bool ImGuiTextAtlasProvider::GetBakedFontInfo(
    FontHandle fontHandle,
    float fontSize,
    BakedFontInfo& outInfo) const {
    outInfo = {};

    ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    ImFontBaked* bakedFont = ResolveBakedFont(fontHandle, atlas, fontSize);
    if (bakedFont == nullptr) {
        return false;
    }

    outInfo.lineHeight = bakedFont->Size;
    outInfo.ascent = bakedFont->Ascent;
    outInfo.descent = bakedFont->Descent;
    outInfo.rasterizerDensity = bakedFont->RasterizerDensity;
    return true;
}

bool ImGuiTextAtlasProvider::FindGlyph(
    FontHandle fontHandle,
    float fontSize,
    std::uint32_t codepoint,
    GlyphInfo& outInfo) const {
    outInfo = {};

    if (codepoint > IM_UNICODE_CODEPOINT_MAX) {
        return false;
    }

    ImFontAtlas* atlas = ResolveAtlas(ResolveContext());
    ImFontBaked* bakedFont = ResolveBakedFont(fontHandle, atlas, fontSize);
    if (bakedFont == nullptr) {
        return false;
    }

    ImFontGlyph* glyph = bakedFont->FindGlyph(static_cast<ImWchar>(codepoint));
    if (glyph == nullptr) {
        return false;
    }

    outInfo.requestedCodepoint = codepoint;
    outInfo.resolvedCodepoint = glyph->Codepoint;
    outInfo.visible = glyph->Visible != 0;
    outInfo.colored = glyph->Colored != 0;
    outInfo.advanceX = glyph->AdvanceX;
    outInfo.x0 = glyph->X0;
    outInfo.y0 = glyph->Y0;
    outInfo.x1 = glyph->X1;
    outInfo.y1 = glyph->Y1;
    outInfo.u0 = glyph->U0;
    outInfo.v0 = glyph->V0;
    outInfo.u1 = glyph->U1;
    outInfo.v1 = glyph->V1;
    return true;
}

::ImGuiContext* ImGuiTextAtlasProvider::ResolveContext() const {
    return m_context != nullptr ? m_context : ImGui::GetCurrentContext();
}

} // namespace XCUIBackend
} // namespace Editor
} // namespace XCEngine