#pragma once
#include "hd2d/GL.h"

#include <glm/glm.hpp>
#include <string>
#include <vector>

namespace hd2d {

struct Image {
    int width = 0, height = 0;
    std::vector<unsigned char> rgba;  // row 0 = bottom (GL convention)
};

// Loads an RGBA8 image flipped to GL orientation. Colors of fully transparent
// pixels are replaced with their nearest opaque neighbour so that filtering
// never bleeds dark fringes into sprite edges.
bool loadImage(const std::string& path, Image& out);
// Decodes PNG bytes from memory. glTF images use flipY = false (their UV
// origin is top-left, which matches GL when rows are uploaded unflipped).
bool decodeImage(const unsigned char* data, size_t size, Image& out, bool flipY);
// Replaces the colors of fully transparent pixels with their nearest opaque
// neighbour (loadImage/decodeImage already do this). Call it on images you
// compose yourself so filtering never bleeds dark fringes into edges.
void bleedTransparentColors(Image& img);

// sRGB pixel-art texture. Sampled with "sharp bilinear" in shaders, so it uses
// linear filtering with mipmaps rather than GL_NEAREST. `nearest` = GL_NEAREST
// without mips instead (crisp ImGui previews of pixel art).
class Texture {
public:
    Texture() = default;
    Texture(const Texture&) = delete;
    Texture& operator=(const Texture&) = delete;
    Texture(Texture&& o) noexcept { *this = std::move(o); }
    Texture& operator=(Texture&& o) noexcept;
    ~Texture();

    bool load(const std::string& path, bool repeat = false, bool nearest = false);
    bool create(const Image& image, bool repeat = false, float anisotropy = 1.0f, bool nearest = false);
    // Fully transparent w x h texture (sRGB RGBA8, mipmapped, clamped) to fill with update().
    bool createEmpty(int w, int h);
    // Uploads `img` with its bottom-left pixel at (x, y) (GL orientation,
    // y = 0 is the bottom row) and regenerates the mips. Does not change
    // opaqueBounds(), which always describes the image given to create().
    void update(int x, int y, const Image& img);
    void bind(GLuint unit) const { glBindTextureUnit(unit, id_); }

    GLuint id() const { return id_; }
    glm::ivec2 size() const { return {width_, height_}; }
    // UV-space rectangle (minX, minY, maxX, maxY) of pixels with alpha >= 128.
    // Billboards use minY to plant the visible feet on the ground.
    glm::vec4 opaqueBounds() const { return opaqueBounds_; }

    // Grid sprite sheets authored top-down (row 0 = top row of the PNG), with
    // `cell` x `cell` pixel frames. cellUV is a BillboardInstance::uv rect;
    // cellAnchor is a BillboardInstance::anchor: the v of the bottom edge of
    // pixel row `feetRowFromCellTop` (0 = the cell's top row) of that cell.
    static glm::vec4 cellUV(glm::ivec2 texSize, glm::ivec2 cell, int col, int rowFromTop);
    static float cellAnchor(glm::ivec2 texSize, glm::ivec2 cell, int rowFromTop, int feetRowFromCellTop);

private:
    GLuint id_ = 0;
    int width_ = 0, height_ = 0, levels_ = 0;
    glm::vec4 opaqueBounds_{0, 0, 1, 1};
};

// 2D array of equally sized sRGB layers (terrain materials).
class TextureArray {
public:
    TextureArray() = default;
    TextureArray(const TextureArray&) = delete;
    TextureArray& operator=(const TextureArray&) = delete;
    ~TextureArray();

    bool load(const std::vector<std::string>& paths);
    void bind(GLuint unit) const { glBindTextureUnit(unit, id_); }
    glm::ivec2 size() const { return {width_, height_}; }
    int layers() const { return layers_; }

private:
    GLuint id_ = 0;
    int width_ = 0, height_ = 0, layers_ = 0;
};

}  // namespace hd2d