snake.asm

;requires graphics
.code "main"
main_v:

    jal  scanDevices_v
    lb   $0, [dbg_after_scan_dvcs.]

    li   $t0, int_handler
    mts  intv, $t0
    li   $t0, -1
    mts  imsk, $t0
    li   $sp, 0x100000

    jal  swapBuffers_v

    jal  time_v
    jal  rseed_i

 .loop:

    lw   $t0, [food]
    bgt  $t0, $0, .else

    lw   $t0, [foodTimer]
    sub  $t0, 1
    sw   $t0, [foodTimer]

    bne  $t0, $0, .else
    jal  random_v
    modu $s0, $a0, $0, 25
    jal  random_v
    modu $t0, $a0, $0, 18
    shll $t0, 16
    or   $t0, $s0
    sw   $t0, [food]
 .else:

    lb   $0, [dbg_msg0.]
    jal  advanceSnake_v
    lw   $t0, [lost]
    bne  $t0, $0, .lost
    lb   $0, [dbg_msg1.]
    li   $a0, 0xff000000
    jal  clearScreen_i
    lb   $0, [dbg_msg2.]
    jal  drawSnake_v
    jal  drawFood_v
    jal  swapBuffers_v
    li   $a0, 250
    lb   $0, [dbg_msg3.]
    jal  sleep_i
    lb   $0, [dbg_msg4.]
    b    .loop

 .lost:
    li   $s0, 500

    li   $a0, 0xffff0000
    jal  clearScreen_i
    jal  swapBuffers_v
    mov  $a0, $s0
    jal  sleep_i
    jal  swapBuffers_v
 .die_loop:
    mov  $a0, $s0
    jal  sleep_i
    jal  swapBuffers_v
    b    .die_loop

    dw   0xffffffff


drawSnake_v:
    sw   $fp, ($sp)
    mov  $fp, $sp
    sw   $ra, $fp(-4)
    sw   $s0, $fp(-8)
    ~locals equ 44 ; fp + ra + s0 + a0-7 * 4
    sub  $sp, ~locals

    li   $s0, snake     ; $s0 = snakePtr
 .loop:
    lh   $t0, $s0(0)    ; $t0 = snake.x
    lh   $t1, $s0(2)    ; $t0 = snake.y
    blt  $t0, $0, .return

    `grid_cell_size     equ 32
    `grid_cell_padding  equ 3
    `grid_actual_size   equ 26 ;32 - 2*3
    ~snake_color        equ 0xffffffff ; white

    mul  $t0, `grid_cell_size
    add  $a0, $t0, `grid_cell_padding

    mul  $t1, `grid_cell_size
    add  $a1, $t1, `grid_cell_padding

    li   $a2, `grid_actual_size
    mov  $a3, $a2

    li   $a4, ~snake_color

    jal  drawRect_iiiii

    add  $s0, 4
    b    .loop

 .return:
    lw   $s0, $fp(-8)
    lw   $ra, $fp(-4)
    mov  $sp, $fp
    lw   $fp, ($sp)
    jr

drawFood_v:
    lw   $t0, [food]
    blt  $t0, $0, .return

    ~food_color equ 0xffffff00
    li   $t1, 0xffff
    and  $a0, $t0, $t1
    mul  $a0, `grid_cell_size
    add  $a0, `grid_cell_padding

    shrl $a1, $t0, $0, 16
    mul  $a1, `grid_cell_size
    add  $a1, `grid_cell_padding

    li   $a2, `grid_actual_size
    mov  $a3, $a2

    li   $a4, ~food_color

    j    drawRect_iiiii

 .return:
    jr

advanceSnake_v:
    sw   $fp, ($sp)
    mov  $fp, $sp
    sw   $ra, $fp(-4)
    sw   $s0, $fp(-8)
    sw   $s1, $fp(-12)
    sub  $sp, (2 + 3 + 2)*4


    lw   $t0, [snakeDir]
    shll $t0, 2
    li   $t1, snake

    mov  $s0, $0
    lw   $s1, ($t1)
    lw   $t2, [food]

    bne  $s1, $t2, .else
    li   $t2, -1
    sw   $t2, [food]
    li   $t2, 3
    sw   $t2, [foodTimer]
    li   $s0, 1
 .else:
    lh   $t2, $t1(0)
    lh   $t3, $t1(2)

    lw   $t4, .switch_table[$t0]
    jr   $t4
 .switch_table:
    dw   .sw_right
    dw   .sw_down
    dw   .sw_left
    dw   .sw_up
  .sw_right:
    add  $t2, 1
    b    .sw_def
  .sw_down:
    add  $t3, 1
    b    .sw_def
  .sw_left:
    sub  $t2, 1
    b    .sw_def
  .sw_up:
    sub  $t3, 1
 .sw_def:

    blt  $t2, $0, .setLose
    blt  $t3, $0, .setLose
    li   $t0, 25
    bge  $t2, $t0, .setLose
    li   $t0, 18
    bgt  $t3, $t0, .setLose

    sh   $t2, $t1(0)
    sh   $t3, $t1(2)

    li   $a0, snake
    add  $a0, 4
    mov  $a1, $s1
    jal  contains_ipi

    bne  $a0, $0, .setLose

 .loop:
    add  $t1, 4
    lw   $t2, ($t1)
    blt  $t2, $0, .end_snake

    sw   $s1, ($t1)
    mov  $s1, $t2
    b    .loop
 .end_snake:
    beq  $s0, $0, .return
    sw   $s1, ($t1)
 .return:
    mov  $sp, $fp
    lw   $ra, $fp(-4)
    lw   $s0, $fp(-8)
    lw   $s1, $fp(-12)
    lw   $fp, ($sp)
    jr
 .setLose:
    li   $t0, 1
    sw   $t0, [lost]
    b    .return

contains_ipi:
    dw   0x000000ff
 .loop:
    lw   $t0, ($a0)
    blt  $t0, $0, .return_false
    beq  $t0, $a1, .return_true

    add  $a0, 4
    b   .loop

 .return_false:
    mov  $a0, $0
    jr

 .return_true:
    li   $a0, 1
    jr


`key_right  equ 79
`key_left   equ 80
`key_down   equ 81
`key_up     equ 82

int_handler:
    lw   $k0, (keyboard_ptr)
    lw   $k1, ($k0)
    sw   $0,  ($k0)

    shrl $k0, $k1, $0, 16
    beq  $k0, $0, .return

    li   $k0, 0xffff
    and  $k0, $k1, $k0

    li   $k1, `key_right
    beq  $k0, $k1, .right
    li   $k1, `key_left
    beq  $k0, $k1, .left
    li   $k1, `key_down
    beq  $k0, $k1, .down
    li   $k1, `key_up
    beq  $k0, $k1, .up
    b    .return
 .right:
    li   $k0, `dir_right
    sw   $k0, [snakeDir]
    b    .return
 .left:
    li   $k0, `dir_left
    sw   $k0, [snakeDir]
    b    .return
 .up:
    li   $k0, `dir_up
    sw   $k0, [snakeDir]
    b    .return
 .down:
    li   $k0, `dir_down
    sw   $k0, [snakeDir]

 .return:
    mts  intd, $0
    mfs  $k0, rfin
    jr   $k0

snake:
    dw   0
    dw   0x00010000
    dw   0x00010001
    dw   -1 x 450

food: dw   0x00050005
foodTimer: dw 10

lost: dw   0

snakeDir: dw 0
`dir_right  equ 0
`dir_down   equ 1
`dir_left   equ 2
`dir_up     equ 3

dbg_after_scan_dvcs.:
    dz   "After scanning for devices"
dbg_msg0.: dz   "Before advanceSnake"
dbg_msg1.: dz   "After advanceSnake"
dgb_msg2.: dz   "Before drawSnake"
dbg_msg3.: dz   "Before sleep"
dbg_msg4.: dz   "After sleep"
    align 4