// linux_fb_display.h — GfxCanvas subclass for Linux framebuffer devices.
//
// Supports XRGB8888 (32 bpp), RGB565 (16 bpp), 8-bit grayscale, and 1 bpp (SSD1306).
// Uses mmap for zero-copy access to the kernel framebuffer.

#ifndef LINUX_FB_DISPLAY_H
#define LINUX_FB_DISPLAY_H

#include "gfx_canvas.h"

#include <cstdint>
#include <linux/fb.h>

namespace gfx {

class LinuxFBDisplay : public GfxCanvas {
public:
    // Construct with the physical panel dimensions.
    LinuxFBDisplay(int16_t width, int16_t height);
    ~LinuxFBDisplay() override;

    // Open the framebuffer device.  Returns true on success.
    [[nodiscard]] bool open(const char* device);

    // Release the mmap and close the file descriptor.
    void close();

    // Is the framebuffer currently open and mapped?
    bool isOpen() const { return buf_ != nullptr; }

    // Copy the internal shadow buffer to the framebuffer, triggering a display refresh.
    void update();

protected:
    // Mandatory HAL: single pixel write.
    void drawPixelImpl(int16_t x, int16_t y, Color color) override;

    // Accelerated HAL overrides.
    void drawHLineImpl(int16_t x, int16_t y, int16_t w, Color color) override;
    void drawVLineImpl(int16_t x, int16_t y, int16_t h, Color color) override;
    void fillRectImpl(int16_t x, int16_t y,
                      int16_t w, int16_t h, Color color) override;

private:
    int      fd_       = -1;
    uint8_t* buf_      = nullptr;   // mmap'd framebuffer
    uint8_t* shadow_   = nullptr;   // internal draw target
    size_t   map_size_ = 0;
    uint32_t bpp_      = 0;
    uint32_t line_len_ = 0;

    fb_var_screeninfo vinfo_{};
    fb_fix_screeninfo finfo_{};

    // Convert XRGB8888 color to the native pixel value for this fb.
    // Returns the value and its byte width.
    void writePixel(uint8_t* dst, Color color) const;
};

} // namespace gfx

#endif // LINUX_FB_DISPLAY_H