#include "Common.h"

#include <algorithm>
#include <cmath>
#include <filesystem>
#include <vector>

namespace bs {

const std::string& engineAssetDir() {
    static const std::string dir = [] {
        std::filesystem::path packaged = executableDir() / "engine";
        std::error_code ec;
        if (std::filesystem::exists(packaged / "shaders" / "common.glsl", ec)) return packaged.string();
        return std::string(HD2D_ENGINE_ASSET_DIR);
    }();
    return dir;
}

void UiTexture::upload(const hd2d::Image& img) {
    if (id_ && size_ != glm::ivec2(img.width, img.height)) reset();
    if (!id_) {
        glCreateTextures(GL_TEXTURE_2D, 1, &id_);
        glTextureStorage2D(id_, 1, GL_RGBA8, img.width, img.height);
        glTextureParameteri(id_, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTextureParameteri(id_, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTextureParameteri(id_, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTextureParameteri(id_, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        size_ = {img.width, img.height};
    }
    // Upload top row first so ImGui's (0,0) = top-left.
    std::vector<unsigned char> flipped(img.rgba.size());
    size_t row = size_t(img.width) * 4;
    for (int y = 0; y < img.height; ++y)
        std::copy_n(img.rgba.data() + size_t(img.height - 1 - y) * row, row, flipped.data() + size_t(y) * row);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTextureSubImage2D(id_, 0, 0, 0, img.width, img.height, GL_RGBA, GL_UNSIGNED_BYTE, flipped.data());
}

void UiTexture::reset() {
    if (id_) glDeleteTextures(1, &id_);
    id_ = 0;
    size_ = {0, 0};
}

void UiTexture::cellUV(glm::ivec2 cell, int col, int row, ImVec2& uv0, ImVec2& uv1) const {
    float w = float(std::max(size_.x, 1)), h = float(std::max(size_.y, 1));
    uv0 = ImVec2(float(col * cell.x) / w, float(row * cell.y) / h);
    uv1 = ImVec2(float((col + 1) * cell.x) / w, float((row + 1) * cell.y) / h);
}

float wrapAngle(float a) {
    constexpr float kTwoPi = 6.28318530718f;
    a = std::fmod(a + 3.14159265f, kTwoPi);
    if (a < 0.0f) a += kTwoPi;
    return a - 3.14159265f;
}

}  // namespace bs