Week 7 Libraries and More Python/21. Own programming language, Part 4: Condition clause

'''Condition clause

Implement the function
execute(code: str) -> str
in addition to the properties of the previous functions:


JUMP place IF variable==value
Code execution will continue from the named location after the command if the value of the given variable satisfies the condition. 
You can assume that the value is a constant value (not another variable). 
Also, the program does not need to understand anything other than the equality operator. 



Example programs for testing instructions:

Program:
LET a=13
JUMP end IF a==13
INC a 10
INC a 15
LABEL end
PRINT a

Execution of the program returns:
13





Program:
LET a=27
LABEL start
PRINT a
INC a 1
JUMP end IF a==32
GOTO start
LABEL end

Program execution returns:
27
28
29
30
31





Programme:
LET c=12
LET d=1
LABEL loop
PRINT c
DEC c d
JUMP continue IF c==1
GOTO loop
LABEL continue

Program execution returns:
12
11
10
9
8
7
6
5
4
3
2
'''










def execute(code: str) -> str:
    variables = {'a': 0, 'b': 0, 'c': 0, 'd': 0}
    output = []

    ###################
    # Refactored for this exercise to keep track of line number for LABEL 
    ###################
    # Split the code into lines and strip whitespace
    lines = [line.strip() for line in code.split('\n')]
    
    # Track labels and their corresponding line numbers
    labels = {}
    for i, line in enumerate(lines):
        if line.startswith('LABEL'):
            _, location = line.split()
            labels[location] = i  # Store the line number of the label


    i = 0
    while i < len(lines):
        line = lines[i]
        
        # Skip empty lines
        if not line:
            i += 1
            continue
        ###################
        
        if line.startswith('LET'):
            _, assignment = line.split(' ', 1)
            var, value = assignment.split('=')
            if var in variables:
                variables[var] = int(value)
                i += 1
            else:
                raise ValueError(f"Invalid variable name: {var}")
        elif line.startswith('PRINT'):
            _, var = line.split()
            if var in variables:
                output.append(str(variables[var]))
                i += 1
            else:
                raise ValueError(f"Undefined variable: {var}")
        ##########################################
        # 19. part 2
        ##########################################
        elif line.startswith('INC') or line.startswith('DEC'):
            # Handle INC and DEC commands
            parts = line.split()
            command = parts[0]
            var1 = parts[1]
            
            if var1 not in variables:
                raise ValueError(f"Invalid variable name: {var1}")
            if len(parts) == 3:
                # Check if parts[2] is an integer
                try:
                    value = int(parts[2])  # Try to convert parts[2] to an integer
                    
                    # If conversion succeeds
                    # INC/DEC variable number
                    if command == 'INC':
                        variables[var1] += value
                    elif command == 'DEC':
                        variables[var1] -= value
                    i += 1
                        
                # parts[2] is NOT an integer
                except ValueError:
                    # INC/DEC variable1 variable2
                    var2 = parts[2]
                    if var2 not in variables:
                        raise ValueError(f"Invalid variable name: {var2}")
                    
                    if command == 'INC':
                        variables[var1] += variables[var2]
                    elif command == 'DEC':
                        variables[var1] -= variables[var2]  
                    i += 1
            
            else:
                raise ValueError(f"Invalid command format: {line}")
        ##########################################
        ##########################################
        # 20. part 3
        ##########################################
        elif line.startswith('LABEL'):
            # Labels are already processed, so just 'skip' the line
            i += 1
        
        elif line.startswith('GOTO'):
            _, location = line.split()
            if location in labels:
                i = labels[location]  # Jump to the line number of the label
            else:
                raise ValueError(f"Undefined label: {location}")
        ##########################################
        
        else:
            raise ValueError(f"Invalid command: {line}")
            
    
    joined_output = '\n'.join(output)
    joined_output+='\n'
    return joined_output






eg1='''LET a=13
JUMP end IF a==13
INC a 10
INC a 15
LABEL end
PRINT a'''





eg2='''LET a=27
LABEL start
PRINT a
INC a 1
JUMP end IF a==32
GOTO start
LABEL end'''





eg3='''LET c=12
LET d=1
LABEL loop
PRINT c
DEC c d
JUMP continue IF c==1
GOTO loop
LABEL continue'''