/**
 * HD44780 utf8-capable display buffer
 */

#ifndef HD44780UTF_LCDBUF_H
#define HD44780UTF_LCDBUF_H

#include <stdint.h>
#include "utf8.h"
#include "cgram.h"
#include "cgrom.h"

// --- settings ---

#define LINE_NUM 4
#define LINE_LEN 20

/// number of remembered dirty regions before giving up and just writing full display
#define LCDBUF_DIRTY_LIST_LEN 8

/// if a cell is marked dirty closer than this to an existing extent,
/// the extent can grows in the direction rather than creating a new one
#define LCDBUF_DIRTY_EXTEND 5

/// Char shown if the requested symbol is missing in lookup tables
#define LCDBUF_SUBSTITUTION_CHAR 0xDB // this is the katakana box (ro ロ?) in the codepage A00

/// this must contain the full width or height
typedef uint8_t lcdbuf_pos_t;

/// this must contain the total number of cells in the display
typedef uint8_t lcdbuf_count_t;
_Static_assert(LINE_NUM * LINE_LEN < 256, "LINE_NUM * LINE_LEN must fit in u8");

// ----------------

/// Number of custom CGRAM slots (always 8)
#define LCDBUF_CGRAM_CAPACITY 8

/** Indicates a range of screen cells that were changed and must be written to HW */
struct LcdBuf_DirtyExtent {
  lcdbuf_pos_t row;
  lcdbuf_pos_t col;
  lcdbuf_count_t count;
};

/** Struct for one CGRAM slot */
struct LcdBuf_CgramState {
  /** UTF8 uint shown in this slot */
  uint32_t uint;
  /** Array index in the custom symbols table, use for look-up when writing the font data to HW */
  uint16_t symbol_index;
  /** Number of occurrences of this symbol in the screen array */
  lcdbuf_count_t refcount;
  /** This CGRAM slot needs to be written to HW */
  bool dirty;
};

struct LcdBuffer {
  /** The raw screen buffer. Custom symbols are 0x00-0x07 */
  uint8_t screen[LINE_NUM][LINE_LEN];
  /** CGRAM state array */
  struct LcdBuf_CgramState cgram[LCDBUF_CGRAM_CAPACITY];
  /** Hardware CGROM lookup table, used to map UTF8 to existing ROM symbols */
  const struct LcdBuf_CGROM_Entry *cgrom;
  /** Defined custom display pattern of utf8 symbols */
  const struct LcdBuf_CGRAM_Symbol *custom_symbols;

  /** Array of dirty extents - ranges in the display that need to be flushed to HW */
  struct LcdBuf_DirtyExtent dirty_extents[LCDBUF_DIRTY_LIST_LEN];
  /** If the dirty extents array was not sufficient to hold all changes, this flag is set,
   * indicating the dirty_extents array should be disregarded. */
  bool full_repaint_required;

  /* Visible cursor - is restored after flushing */
  uint8_t cursor_style; // two bits - blink 0b01, bar 0b10
  lcdbuf_pos_t cursor_row;
  lcdbuf_pos_t cursor_col;
  bool cursor_dirty;
};

/** Initialize the struct */
void LcdBuffer_Init(struct LcdBuffer *self, const struct LcdBuf_CGROM_Entry *cgrom, const struct LcdBuf_CGRAM_Symbol *custom_symbols);

/** Clear the screen */
void LcdBuffer_Clear(struct LcdBuffer *self);

/** Write what needs to be written to the HW, clear all dirty marks */
void LcdBuffer_Flush(struct LcdBuffer *self);

/** Fully write everything to the display */
void LcdBuffer_FlushAll(struct LcdBuffer *self);

/** Set one utf8 character at a position */
void LcdBuffer_Set(struct LcdBuffer *self, lcdbuf_pos_t row, lcdbuf_pos_t col, struct Utf8Char ch);

/** Write a UTF8 string at a position */
void LcdBuffer_Write(struct LcdBuffer *self, lcdbuf_pos_t row, lcdbuf_pos_t col, char *utf_string);

/** Set visible cursor position and style. style is 2 bits: blink 0b01, bar 0b10 */
void LcdBuffer_SetCursor(struct LcdBuffer *self, lcdbuf_pos_t row, lcdbuf_pos_t col, uint8_t cursor_style);

/* Callbacks - need to be implemented by the application! */

/** Clear the entire screen (CGRAM can be left unchanged, but they will be written anew if needed) */
extern void LcdBuffer_IO_Clear();

/** Write character data at position */
extern void LcdBuffer_IO_WriteAt(lcdbuf_pos_t row, lcdbuf_pos_t col, const uint8_t *buf, lcdbuf_count_t len);

/** Write CGRAM data. Data is always 8 bytes long. */
extern void LcdBuffer_IO_WriteCGRAM(uint8_t position, const uint8_t *data);

/** Set cursor pos & style */
extern void LcdBuffer_IO_SetCursorPos(lcdbuf_pos_t cursor_row, lcdbuf_pos_t cursor_col);
extern void LcdBuffer_IO_SetCursorStyle(uint8_t cursor_style);

#endif //HD44780UTF_LCDBUF_H