.data
input:                 .space  20
input_string:          .asciiz "Saisir un mot ? "
msg_palindrome_part_1: .asciiz "Le mot "
msg_palindrome_part_2: .asciiz " un palindrome"
msg_is_palindrome:     .asciiz "est"
msg_is_not_palindrome: .asciiz "n'est pas"
newline:               .asciiz "\n"
 
.text
main:
    jal input_word
    jal clean_and_length_word
    jal isPalindrome
    li  $v0, 10
    syscall
   
input_word:
    la  $a0, input_string
    li  $v0, 4
    syscall
    li  $v0, 8
    la  $a0, input
    li  $a1, 20
    syscall
    jr  $ra

clean_and_length_word:
    la   $s4, ($zero)
    la   $s0, input	# $s0 contains base address of the string buffer
    addi $s3, $0, '\n'	# $s3 = '\n'
loop1:
    lb   $s1, 0($s0)	# load character into $s1
    beq  $s1, $s3, end1	# break if byte is newline
    addi $s0, $s0, 1	# increment buffer address
    addi $s4, $s4, 1
    j    loop1
end1:
    la   $a2, ($s4)
    jr   $ra
    
isPalindrome:
    # Check base case
    slti $t0, $a2, 2
    bne	 $t0, $zero, returnTrue

    # Make sure first and last are equal
    lb	 $t0, 0($a0)
    addi $t1, $a2, -1
    add	 $t1, $t1, $a0
    lb	 $t1, 0($t1)
    bne	 $t0, $t1, returnFalse
    
    # Shift pointer, length, recurse
    addi $a2, $a2, -2
    addi $a0, $a0, 1
    j	 isPalindrome
 
returnFalse:
    addi $v0, $zero, 0
    addi $sp, $sp, -4
    sw   $ra, 0($sp)
    jal  display_not_palindrome
    lw   $ra, 0($sp)
    addi $sp, $sp, 4
    jr	 $ra

returnTrue:
    addi $v0, $zero, 1
    addi $sp, $sp, -4
    sw   $ra, 0($sp)
    jal  display_palindrome
    lw   $ra, 0($sp)
    addi $sp, $sp, 4
    jr	 $ra
 
display_palindrome:
    la   $a0, msg_palindrome_part_1
    li   $v0, 4
    syscall
    la   $a0, input
    li   $v0, 4
    syscall
    la   $a0, msg_is_palindrome
    li   $v0, 4
    syscall 
    la   $a0, msg_palindrome_part_2
    li   $v0, 4
    syscall
    la   $a0, newline
    li   $v0, 4
    syscall
    jr   $ra   
          
display_not_palindrome:
    la   $a0, msg_palindrome_part_1
    li   $v0, 4
    syscall
    la   $a0, input
    li   $v0, 4
    syscall
    la   $a0, msg_is_not_palindrome
    li   $v0, 4
    syscall 
    la   $a0, msg_palindrome_part_2
    li   $v0, 4
    syscall
    la   $a0, newline
    li   $v0, 4
    syscall
    jr   $ra