#define c_print_int 1
#define c_print_str 4
#define c_atoi 5
#define c_sbrk 9
#define c_exit 10
#define c_print_char 11
#define c_exit2 17


.data
error_msg   : .asciiz "\nProgram expects two arguments. \n Usage:    main.s input0 input1 [1:Add,0:Mul] \n"
i0     : .asciiz "\nInput0 :"
i1     : .asciiz "\nInput1 :"
res    : .asciiz "\nResult :"


.globl main

.text
#================================================================
# void print_int(int a1)
# Prints the integer in a1.
# args:
#   a1 = integer to print
# return:
#   void
#================================================================
print_int:
    li a0 c_print_int
    ecall
    jr ra


#================================================================
# void print_str(char *a1)
# Prints the null-terminated string at address a1.
# args:
#   a1 = address of the string you want printed.
# return:
#   void
#================================================================
print_str:
    li a0 c_print_str
    ecall
    jr ra


#================================================================
# int atoi(char* a1)
# Returns the integer version of the string at address a1.
# args:
#   a1 = address of the string you want to turn into an integer.
# return:
#   a0 = Integer representation of string 
#================================================================
atoi:
    li a0 c_atoi
    ecall
    jr ra


#================================================================
# void print_char(char a1)
# Prints the ASCII character in a1 to the console.
# args:
#   a1 = character to print
# return:
#   void
#================================================================
print_char:
    li a0 c_print_char
    ecall
    jr ra


#================================================================
# void noreturn exit()
# Exits the program with a zero exit code.
# args:
#   None
# return:
#   No Return
#================================================================
exit:
    li a0 c_exit
    ecall

#================================================================
# void noreturn exit2(int a1)
# Exits the program with error code a1.
# args:
#   a1 = Exit code.
# return:
#   This program does not return.
#================================================================
exit2:
    li a0 c_exit2
    ecall
    jr ra




.text
main:
    # =====================================
    # COMMAND LINE ARGUMENTS
    # =====================================
    # Args:
    #   a0: int argc
    #   a1: char** argv
    #
    # Exit if incorrect number of command line args
    li s2, 3 # Expect 3 arguments
    mv s3, a0 # (argc)
    blt a0, s2, error # if argc < 3 jump to exit
    
    # argv[1]
    mv s4, a1 # (char** argv). s4 char* argv[] 

    # 1st Argument
    addi s4,s4,4 # Dereferencing the first string (Why is this required ? )
    lw a1, 0 (s4)   # s4[0]. (pointer to string containing argument 0 value)
    jal atoi # (convert string to integer)
    mv s0,a0 # (store return result in s0)

    # 2nd argument
    addi s4,s4,4
    lw a1, 0(s4) # (pointer to string containing argument 1 value)
    jal atoi  # (convert string to integer)
    mv s1,a0 # (store return result in s0)

    # 3rd argument
    addi s4,s4,4
    lw a1, 0(s4)
    jal atoi
    mv s2,a0


    # S0 - argument 0, S1 - argument 1, S2 - 1 - do + 0 - do *

    beq s2,zero, multiply # Jump to multiply routine
    add s3,s0,s1 # add routine
    j exit_prog # jump over multiply to exit
multiply:
    mul s3,s0,s1

exit_prog:
    la a1, i0     # Print str
    jal print_str  
    mv a1,s0       # Print value
    jal print_int

    la a1,i1
    jal print_str
    mv a1,s1
    jal print_int


    la a1,res
    jal print_str
    mv a1,s3
    jal print_int

    # Print newline afterwards for clarity
    li a1 '\n'
    jal print_char
    j exit

error: 
    la a1, error_msg
    jal print_str
    li a1, 1
    jal exit2