.data
	welcomeMessage: .asciiz "Welcome to a MIPS assembly Fibonacci Sequence calculator!\nThis will calculate the nth term of the Fibonacci Sequence.\n"
	prompt: .asciiz "Enter a number (n, input n > 2) to find the nth term:"
	foundTerm: .asciiz "The nth term is: "
	
.text

main:
	li $v0, 4 					# syscall 4 is to print a string
	la $a0, welcomeMessage				# store the ascii string in register a0
	syscall						# print
	
	jal getInput 					# get the user input
	
	jal fibonacci					# calculate the nth fibonacci term
	move $a0, $v0					# move the returned term to register a0
	li $v0, 1					# syscall 1 is to print an int
	syscall						# print
	
  	ori $v0, $0, 10       				# system call code 10 for exit
  	syscall               				# exit the program

getInput:
	li $v0, 4 					# syscall 4 is to print a string
	la $a0, prompt					# store the ascii string in register a0
	syscall						# print
	
	li $v0, 5 					# syscall 5 is for reading an int
	syscall						# read an int from the user
	move $a0, $v0 					# load input into register a0
	
	jr $ra 						# return to caller

fibonacci:
	move $s1, $a0 					# Copy the nth term
	li $t0, 2 					# Counter
	li $t1, 0					# Prev value
	li $t2, 1					# Current value
	li $t3, 0 					# Next value
	
	while:
		bge $t0, $s1, done 			# While the counter is less than n
			add $t3, $t1, $t2		# Sum the previous and current values and save in register t3
			move $t1, $t2			# Shift current value to previous value

			move $t2, $t3 			# Shift next value to current value
			addi $t0, $t0, 1 		# Increment counter
			
			b while 			# Jump back to start of while loop
			
	done:
		move $v0, $t2				# Move current value to register v0
		jr $ra					# Return to caller