/*
Crafter®.Graphics
Copyright (C) 2026 Catcrafts®
catcrafts.net
*/

// Backend-agnostic UIRenderer methods. FillHeader and ShapeText do not
// touch any GPU API; they only read window dimensions and (for ShapeText)
// the CPU-side font atlas. Split out so both Vulkan and WebGPU impls
// share the same source.

module Crafter.Graphics:UI_shared_impl;
import :UI;
import :Window;
import :Font;
import :FontAtlas;
import :GraphicsTypes;
import std;

using namespace Crafter;

UIDispatchHeader UIRenderer::FillHeader(std::uint32_t itemBufferSlot,
                                        std::uint32_t itemCount,
                                        std::array<float,4> clipRectPx,
                                        std::uint32_t flags) const noexcept {
    UIDispatchHeader h{};
    h.outImage      = outImageSlot_;
    h.itemBuffer    = itemBufferSlot;
    h.surfaceWidth  = window_->width;
    h.surfaceHeight = window_->height;
    h.clipX = clipRectPx[0];
    h.clipY = clipRectPx[1];
    h.clipW = clipRectPx[2];
    h.clipH = clipRectPx[3];
    h.itemCount = itemCount;
#ifndef CRAFTER_GRAPHICS_WINDOW_DOM
    h.frameIdx  = window_->currentBuffer;
#else
    h.frameIdx  = 0;
#endif
    h.flags     = flags;
    h._pad      = 0;
    return h;
}

std::uint32_t UIRenderer::ShapeText(Font& font, float pxSize,
                                    float x, float baselineY,
                                    std::string_view utf8,
                                    std::array<float,4> color,
                                    GlyphItem* out, std::uint32_t outCapacity,
                                    float* outAdvance) {
    if (fontAtlas == nullptr) {
        std::println("UIRenderer::ShapeText: no FontAtlas (set fontAtlas before Initialize)");
        std::abort();
    }

    const float scale = pxSize / FontAtlas::kBaseSize;
    float cursor = x;
    std::uint32_t written = 0;

    std::size_t i = 0;
    while (i < utf8.size() && written < outCapacity) {
        std::uint32_t cp = DecodeUtf8(utf8, i);
        if (cp == 0) break;
        if (cp == '\n') { continue; }

        fontAtlas->Ensure(font, cp);
        const Glyph* g = fontAtlas->Lookup(font, cp);
        if (g == nullptr) continue;

        if (g->w > 0 && g->h > 0) {
            GlyphItem& gi = out[written++];
            gi.x  = cursor + g->xoff * scale;
            gi.y  = baselineY + g->yoff * scale;
            gi.w  = g->w * scale;
            gi.h  = g->h * scale;
            gi.u0 = g->u0; gi.v0 = g->v0;
            gi.u1 = g->u1; gi.v1 = g->v1;
            gi.r = color[0]; gi.g = color[1]; gi.b = color[2]; gi.a = color[3];
        }
        cursor += g->advance * scale;
    }

    if (outAdvance) *outAdvance = cursor - x;
    return written;
}