#IFNDEF __lib_keyboard
#DEFINE __lib_keyboard 1

GOTO __skip_lib_keyboard

// ============================================================================
// KEYBOARD INPUT DRIVER FOR COMMODORE 64
// ============================================================================
// Direct CIA keyboard matrix reading (no IRQ required)
//
// C64 Keyboard Matrix:
//   $DC00 (Port A): Column select (write, active-low)
//   $DC01 (Port B): Row read (read, active-low)
//
// Usage:
//   #INCLUDE "keyboard.c65"
//   BYTE key
//   key_scan(key)
//   SWITCH key
//     CASE KEY_F1
//       // handle F1
//     CASE KEY_F3
//       // handle F3
//   ENDSWITCH
//
//   // Debouncing: wait for KEY_NONE
//   WHILE key != KEY_NONE
//     key_scan(key)
//   WEND
// ============================================================================

// CIA Port addresses
WORD CONST CIA_PORTA = $DC00     // Port A - ROW selection (write)
WORD CONST CIA_PORTB = $DC01     // Port B - COLUMN reading (read)
WORD CONST CIA_DDRA = $DC02      // Port A Data Direction Register
WORD CONST CIA_DDRB = $DC03      // Port B Data Direction Register

// Key constants
BYTE CONST KEY_NONE = 0
BYTE CONST KEY_F1 = 1
BYTE CONST KEY_F3 = 2
BYTE CONST KEY_F7 = 3
BYTE CONST KEY_F8 = 4       // F7 + SHIFT
BYTE CONST KEY_RETURN = 5
BYTE CONST KEY_LEFT_ARROW = 6

// ============================================================================
// FUNC key_scan
// Scan keyboard and return which key is pressed
// Returns KEY_* constant (KEY_NONE if no relevant key pressed)
// C64 Keyboard Matrix:
// - Write to $DC00 (Port A) to select ROW
// - Read from $DC01 (Port B) to detect COLUMN
// ============================================================================
FUNC key_scan(out:{BYTE key_pressed})
  BYTE col_data
  BYTE temp
  BYTE shift_held
  BYTE saved_ddra
  BYTE saved_ddrb
  BYTE saved_porta
  BYTE row0_data
  BYTE row1_data
  BYTE row6_data

  key_pressed = KEY_NONE
  shift_held = 0

  // Save current DDR state
  saved_ddra = PEEK CIA_DDRA
  saved_ddrb = PEEK CIA_DDRB
  saved_porta = PEEK CIA_PORTA

  // Set up DDR: Port A = output (rows), Port B = input (columns)
  POKE CIA_DDRA , $FF
  POKE CIA_DDRB , $00

  // Check F8 FIRST with two-read atomic check
  // Read 1: Select rows 0+1+6 simultaneously ($BC = 10111100)
  POKE CIA_PORTA , $BC
  BYTE multi_row_data
  multi_row_data = PEEK CIA_PORTB

  // Read 2: Select ONLY row 0 ($FE = 11111110)
  POKE CIA_PORTA , $FE
  col_data = PEEK CIA_PORTB

  // F8 detection: F7 pressed AND SHIFT pressed
  // F7 at Row 0, Col 3 - check in row0 data
  temp = col_data & $08
  IF temp == 0
    // F7 is pressed, now check if real SHIFT is pressed
    // Compare multi-row read vs row-0-only read for cols 4 and 7
    // If col 4 or 7 was low in multi-row but NOT in row-0-only, it's SHIFT
    BYTE shift_cols
    shift_cols = multi_row_data & $90  // Cols 4 and 7 in multi-row read
    temp = col_data & $90              // Cols 4 and 7 in row 0 only read
    // If multi-row has a low bit that row-0-only doesn't, it's from rows 1 or 6 (SHIFT)
    IF shift_cols != temp
      key_pressed = KEY_F8
    ENDIF
  ENDIF

  // If not F8, check other Row 0 keys (col_data already has row 0 from above)
  IF key_pressed == KEY_NONE

    // Check F1 (Row 0, Column 4)
    temp = col_data & $10
    IF temp == 0
      key_pressed = KEY_F1
    ENDIF

    // Check F3 (Row 0, Column 5)
    IF key_pressed == KEY_NONE
      temp = col_data & $20
      IF temp == 0
        key_pressed = KEY_F3
      ENDIF
    ENDIF

    // Check F7 (Row 0, Column 3)
    IF key_pressed == KEY_NONE
      temp = col_data & $08
      IF temp == 0
        key_pressed = KEY_F7
      ENDIF
    ENDIF

    // Check RETURN (Row 0, Column 1)
    IF key_pressed == KEY_NONE
      temp = col_data & $02
      IF temp == 0
        key_pressed = KEY_RETURN
      ENDIF
    ENDIF

    // Check Left Arrow (Row 0, Column 7)
    IF key_pressed == KEY_NONE
      temp = col_data & $80
      IF temp == 0
        key_pressed = KEY_LEFT_ARROW
      ENDIF
    ENDIF
  ENDIF

  // Always restore saved DDR and port state
  POKE CIA_PORTA , saved_porta
  POKE CIA_DDRA , saved_ddra
  POKE CIA_DDRB , saved_ddrb
FEND


LABEL __skip_lib_keyboard

#IFEND