/*#############################################################################
## Author: Shaun Reed                                                        ##
## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
##                                                                           ##
## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
##############################################################################
*/
#ifndef PANEL_DEVICE_H
#define PANEL_DEVICE_H

#include <esp_lcd_panel_dev.h>
#include <esp_lcd_panel_io.h>
#include <esp_log.h>

#include <display/lv_display.h>

// LVGL reserves 2x4 bytes in the buffer to be used as a palette.
// This additional space must be added to the IPanelDevice::buf_size_.
#define LVGL_PALETTE_SIZE 8
#define LVGL_TICK_PERIOD_MS 5
#define LVGL_TASK_STACK_SIZE (4 * 1024)
#define LVGL_TASK_PRIORITY 2

#define LCD_H_RES 128
#define LCD_V_RES 64

/**
 * Calculate byte offset for the pixel at [x,y] within a horizontally-mapped
 * monochrome uint8 draw buffer, using the initialized horizontal resolution.
 *
 * We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
 * buffer can hold 8 bits. To find the uint8 value in our draw buffer that
 * stores this pixel's value we must compensate for this when using pixel
 * coordinates in byte math.
 *
 * Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
 * Below is an example of calculating for [x, y] pixel coordinates [20, 10].
 * The example uses a horizontal resolution of 128.
 *
 * For the horizontal case, each row (y) of the image is represented by
 * `hor_res >> 3` bytes (16). The byte-offset of the first pixel in the 10th
 * row for example is `16 * 10` = 160.
 *
 * Since the pixels are stored horizontally we must calculate the 20th pixel
 * column (x) as `160 + (20 >> 3)`, or `160 + (20 / 8)` to get a final offset
 * of 162.
 *
 * @param x X pixel coordinate to find byte offset.
 * @param y Y pixel coordinate to find byte offset.
 * @param hor_res horizontal resolution of the display.
 * @return byte offset for a single-byte monochrome pixel at [x,y].
 */
static ptrdiff_t horizontal_byte_offset_long(const int32_t x, const int32_t y,
                                             const int32_t hor_res)
{
    // Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
    return (hor_res >> 3) * y + (x >> 3);
}

static ptrdiff_t horizontal_byte_offset(const int32_t x, const int32_t y)
{
    return horizontal_byte_offset_long(x, y, LCD_V_RES);
}

/**
 * Calculate byte offset for the pixel at [x,y] within a vertically-mapped
 * monochrome uint8 draw buffer, using the initialized horizontal resolution.
 *
 * We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
 * buffer can hold 8 bits. To find the uint8 value in our draw buffer that
 * stores this pixel's value we must compensate for this when using pixel
 * coordinates in byte math.
 *
 * Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
 * Below is an example of calculating for [x, y] pixel coordinates [20, 10].
 * The example uses a horizontal resolution of 128.
 *
 * For the vertical case, each row (y) of the image is represented by
 * `hor_res` bytes (128) - one for each column (x). Because the pixels are
 * stored vertically, the byte-offset of the first pixel in the 10th row is
 * `128 * (10 >> 3)` or * `128 * (10 / 8)` = 128.
 *
 * From this location we can simply calculate the 20th pixel column (x) as
 * `128 + 20` to get a final offset of 148, because the pixels are stored in a
 * columnar format.
 *
 * @param x X pixel coordinate to find byte offset.
 * @param y Y pixel coordinate to find byte offset.
 * @param hor_res horizontal resolution of the display.
 * @return byte offset for a single-byte monochrome pixel at [x,y].
 */
static ptrdiff_t vertical_byte_offset_long(const int32_t x, const int32_t y,
                                           const int32_t hor_res)
{
    // Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
    return hor_res * (y >> 3) + x;
}

static ptrdiff_t vertical_byte_offset(const int32_t x, const int32_t y)
{
    return vertical_byte_offset_long(x, y, LCD_V_RES);
}

/**
 * Finds the Most Significant Bit location of bit `i` in a byte.
 *
 *          MSB           LSB
 * bits      7 6 5 4 3 2 1 0
 * data      8 7 6 5 4 3 2 1
 *          Left         Right
 *
 * @return bitmask for MSB location of `i`.
 */
static uint8_t msb_mask(const int32_t i) { return 1 << (7 - i % 8); }

/**
 * Finds the Least Significant Bit location of bit `i` in a byte.
 *
 *          LSB           MSB
 * bits      0 1 2 3 4 5 6 7
 * data      1 2 3 4 5 6 7 8
 *          Left         Right
 *
 * @return bitmask for LSB location of `i`.
 */
static uint8_t lsb_mask(const int32_t i) { return 1 << (i % 8); }

static uint8_t* get_additional_draw_buffer()
{
    // Static to the scope of this function, not the compilation unit.
    // For LV_COLOR_FORMAT_I1 we need an extra buffer to hold converted data.
    static uint8_t oled_buffer[LCD_H_RES * LCD_V_RES / 8];
    return oled_buffer;
}

/**
 * Retrieve the device specific vendor configuration structure.
 *
 * @return Address of vendor configuration structure.
 */
typedef void* (*vendor_config_cb_t)();

/**
 * Registers LVGL ticker timer callback for rendering this display.
 *
 * An implementation of the interface can optionally override this method to
 * provide custom LVGL callbacks and tick configurations.
 */
typedef void (*register_lvgl_tick_timer_cb_t)();

/**
 * Initializes the ESP panel using vendor specific APIs and configurations.
 * This method should implement any setup logic specific to the device.
 *
 * @param config ESP LCD panel configuration.
 * @param io ESP LCD panel IO handle.
 * @param [out] panel ESP LCD panel handle output pointer location.
 */
typedef void (*init_panel_cb_t)(esp_lcd_panel_dev_config_t* config,
                                esp_lcd_panel_io_handle_t io,
                                esp_lcd_panel_handle_t* panel);

/**
 * Registers LVGL draw buffers and callbacks for this display.
 *
 * An implementation of the interface can optionally override this method to
 * provide custom LVGL callbacks and display configurations.
 *
 * @param display_handle LVGL display handle to use for rendering.
 * @param io_handle IO handle for the ESP LCD panel.
 */
typedef void (*register_rendering_data_cb_t)(
    lv_display_t* display_handle, esp_lcd_panel_io_handle_t io_handle, void*,
    size_t);

/**
 * Encapsulates vendor specific ESP LCD panel initialization logic.
 * This pure virtual interface can be inherited from for using new LCD devices.
 * See SSD1306 as an example to implement IPanelDevice for NT35510 or ST7789.
 *
 * At this time only I2C is supported.
 * Classes that inherit from this interface should likely be marked final.
 */
struct IPanelDevice
{
    /// Width of the device screen in pixels.
    int32_t width_;

    /// Height of the device screen in pixels.
    int32_t height_;

    /// RST GPIO pin number.
    int rst_num_;

    /// LVGL draw buffer size for the device.
    size_t lv_buf_size_;

    /// ESP LCD panel IO configuration.
    esp_lcd_panel_io_i2c_config_t esp_io_config_;

    /// LVGL draw buffer associated with this Display's lv_display_t.
    void* lv_buf_;

    /// Callback used to initialize the ESP panel.
    /// TODO: Assert by default?
    init_panel_cb_t init_panel_cb;

    /// Callback used to register LVGL tick timer.
    register_lvgl_tick_timer_cb_t register_lvgl_tick_timer_cb;

    /// Callback used to register LVGL draw buffers.
    register_rendering_data_cb_t register_rendering_data_cb;

    /// Callback used to fetch the display vendor configuration.
    vendor_config_cb_t vendor_config_cb;
};

/**
 * Static accessor to a static buffer to store draw buffer data for the panel.
 *
 * This method is protected to allow an implementation to provide a custom
 * callback method similar to IPanelDevice::lvgl_flush_cb.
 *
 * The buffer is allocated statically within the scope of this function to
 * allow creating multiple panels that _each_ manage their own statically
 * allocated draw buffer data. This simplifies implementing the interface by
 * taking this responsibility off of the implementor. The buffer will only be
 * allocated if this method is called, so the memory is only used if required.
 *
 * @return Pointer to uint8 draw buffer data.
 * @sa register_rendering_data for overriding LVGL rendering callbacks.
 */


/**
 * The callback invoked when panel IO finishes transferring color data.
 * This signals that the panel is ready to flush image data to the display.
 *
 * @param panel LCD panel IO handles.
 * @param data Panel IO event data, fed by driver.
 * @param user_ctx User data, passed from `esp_lcd_panel_io_xxx_config_t`.
 * @return Whether a high priority task has been waken up by this function.
 * @sa register_rendering_data for overriding this callback.
 */
static bool lvgl_flush_ready_cb(esp_lcd_panel_io_handle_t panel,
                                esp_lcd_panel_io_event_data_t* data,
                                void* user_ctx);

/**
 * The callback invoked for flushing the rendered image to the display.
 *
 * `px_map` contains the rendered image as raw pixel map and it should be
 *  copied to `area` on the display.
 *
 * The following details are crucial for understanding the logic surrounding
 * flushing to the display in this example.
 *
 * The order of bits within the px_map from _LVGL_ is MSB first.
 *              MSB           LSB
 *     bits      7 6 5 4 3 2 1 0
 *     pixels    0 1 2 3 4 5 6 7
 *              Left         Right
 *
 * The bytes from _LVGL_ are mapped to pixel rows of the display
 * 8 bits (pixels) per byte -
 * [0, 0, 0, 0, 0, 0, 0, 0]
 * [0, 0, 0, 0, 0, 0, 0, 0]
 * [0, 0, 0, 0, 0, 0, 0, 0]
 *
 * The order of bits expected by the _display driver_ is LSB first.
 * We must preserve pairing of each bit and pixel when writing to the display.
 *              LSB           MSB
 *     bits      0 1 2 3 4 5 6 7
 *     pixels    7 6 5 4 3 2 1 0
 *              Left         Right
 *
 * Bytes expected by the _display driver_ map to pixel columns of the display.
 * 8 bits (pixels) per byte -
 * [0, [0, [0, [0,
 *  0,  0,  0,  0,
 *  0,  0,  0,  0,
 *  0,  0,  0,  0,
 *  0,  0,  0,  0,
 *  0,  0,  0,  0,
 *  0,  0,  0,  0,
 *  0]  0]  0]  0]
 *
 * These layouts in memory have no opinion on the shape of the image. The
 * beginning and end of a row or a column for example is entirely dependent
 * on how the data is accessed. The vertical and horitzontal resolution may
 * vary between displays.
 *
 * For the LV_COLOR_FORMAT_I1 color format we are using, an additional buffer
 * is needed for transposing the bits to the vertical arrangement required by
 * the display driver that is outlined above.
 *
 * This callback implementation is an example of handling this transposition
 * and flushing the data to the display in the expected format.
 *
 * @param display LVGL display handle to use for rendering.
 * @param area Area of the display being flushed.
 * @param px_map Rendered image data for writing to the display area.
 * @sa register_rendering_data for overriding this callback.
 * @sa get_additional_draw_buffer
 */
static void lvgl_flush_cb(lv_display_t* display, const lv_area_t* area,
                          uint8_t* px_map);

/**
 * Callback invoked for every period of the timer.
 *
 * This callback _must_ call lv_tick_inc to inform LVGL how much time has
 * elapsed since the last period of the timer.
 *
 * @param data User data passed to the callback.
 * @sa register_lvgl_tick_timer for setting user data and the tick period of
 *        the timer, or overriding this callback entirely.
 */
static void lvgl_increase_tick_cb(void* data);

/**
 * FreeRTOS task callback invoked for handling LVGL events or updating the UI.
 *
 * This function is intentionally an endless loop and should never return.
 * LVGL initialization logic can optionally be added before entering the loop.
 * Input logic can optionally be handled within the loop.
 *
 * This callback _must_ call lv_timer_handler to handle LVGL periodic timers.
 *
 * @param data User data passed to the callback.
 * @sa register_lvgl_tick_timer for overriding this callback.
 */
[[noreturn]] static void lvgl_port_task(void* data);

/**
 * Registers LVGL ticker timer callback for rendering this display.
 *
 * An implementation of the interface can optionally override this method to
 * provide custom LVGL callbacks and tick configurations.
 */
void register_lvgl_tick_timer();

void register_rendering_data(lv_display_t* display_handle,
                             esp_lcd_panel_io_handle_t io_handle, void* lv_buf,
                             size_t lv_buf_size);

inline struct IPanelDevice LCD_new_panel()
{
    return (struct IPanelDevice){
        .width_ = LCD_H_RES,
        .height_ = LCD_V_RES,
        .rst_num_ = -1,
        .init_panel_cb = NULL, // Must be assigned by caller
        .register_lvgl_tick_timer_cb = register_lvgl_tick_timer,
        .register_rendering_data_cb = register_rendering_data,
        .vendor_config_cb = NULL, // Must be assigned by caller
    };
}

#endif // PANEL_DEVICE_H