# AreaCalculator_4_1171.py - version 4
#
# This program allows us to compute the area of
# a triangle, a circle, a rectangle, a square and an ellipse.
#
# Anne Lavergne:
# Created June 2015 - Modified March 2017
#
# Liaqat Ali:
# Modified July 2018
#
# Demonstrating "Incremental Development"
# -> Refactoring repeated code from the functions square( ) and rectangle( )
#    and encapsulating it into their own function:
#    - getUserInput( whichData, shape ) -> called from square( ) and rectangle( ) to get and validate
#           side, width or height from user
#    - areaOfParallelogram( base, height ) -> called from square( ) and rectangle( ) to compute their area
#           since square and rectangle are both parallelograms and therefore use the same area equation.
#    - displayResult( theShape, area ) -> called from the main part of the program to display the result
#           since all shapes will have a resulting area to display.


# Set variables
exitProgram  = 'X'

          
def printMenu( ) :
    """
       Print description of program and menu displaying selection of shapes.
       Parameters: none.
       Returned value: none.
    """
    print("Welcome to my Area Calculator.\n")
    print("""This AreaCalculator allows us to compute the area of:\n
      \ta triangle\tEnter T
      \ta circle\tEnter C
      \ta rectangle\tEnter R
      \ta square\tEnter S
      \tan ellipse\tEnter E
      \tto exit\t\tEnter X""")
    return


def getSelection(  ) :
    """
       Print input instruction to user, read user input (selection) then validate user input.
       Parameter: "notASelectionCode" - a letter indicating that the user has entered an invalid input.
       Returned value: "selectedShape" - either contains a valid selection or the value of parameter "notASelectionCode".
    """
    # Print input instruction to user and read user input
    selectedShape = input("\nPlease, enter your selection: ")
    # Validate input
    # Transform the user's input into an upper case letter in case
    # the user has entered a lower case letter as an selection
    selectedShape = selectedShape.upper( )
    return selectedShape

def getUserInput( whichData, shape ) :
    """
       Get user input needed to calculate the area of a shape and validate it.
       Parameter: "whichData" - a string (either "width", "height", "side" or "radius").
                  "shape" - a string representing the shape selected by the user.
       Returned value: "returnedValue" - either contains a valid user input or 0 if the user entered either a letter or nothing.
    """
    returnedValue = 0
    theInput = input("\nPlease, enter the {0} of the {1} as a positive integer number: ".format(whichData, shape))
    # Make sure the user has entered positive integer number (valid input)
    if not theInput.isalpha() and int(theInput) > 0:
        returnedValue = int(theInput)
    else:
        print("\nThe {0} you entered for the {1} ({2}) is invalid.\n".format(whichData, shape, theInput))
    return returnedValue


def areaOfParallelogram( base, height ):
    """
       Returns the area of a parallelogram (generalization).
    """
    area = base * height
    return area


def rectangle():
    """
       Deals with the area computation of a rectangle.       
    """
    print("You have selected Rectangle.")
    # Ask for the width and height
    width = getUserInput( "width", "rectangle" )
    if width != 0 :
        height = getUserInput( "height", "rectangle" )
        if height != 0 :
            # Compute area = width * height
            area = areaOfParallelogram(int(width), int(height))
    return area



def square():
    """
       Deals with the area computation of a square.   
    """
    print("You have selected Square.")
    # Ask for the side
    side = getUserInput( "side", "square" )
    if side != 0 :
        # Compute area = side * side
        area = areaOfParallelogram(int(side), int(side))
    return area


def displayResult( theShape, area ):
    """
       Display the result, i.e., the shape and the area.
       Parameters: "theSshape" - a string representing the shape selected by the user
                   "area" is its computed area or 0 if seomthing wrong happened.
       Returned value: none.
    """
    if area > 0 :
        # Print the shape and the area
        print("\nThe area of the {} is {}.\n".format(theShape, area))
    return


# Main part of the program - top level (of execution)
# Print description of program and menu displaying selection of shapes
printMenu( )

# Get selection from user (+ validate input)
selectedShape = getSelection(  )

# As long as the user enters a valid selection ...
while selectedShape != exitProgram: 
    area = 0
    # If "triangle" is selected?
    if selectedShape == "T":
        theShape = "triangle"
        print(theShape)
    # If "circle" is selected?
    elif selectedShape == "C":
        theShape = "circle"
        print(theShape)
    # If "rectangle" is selected?
    elif selectedShape == "R":
        theShape = "rectangle"
        area = rectangle()
    # If "square" is selected?
    elif selectedShape == "S":
        theShape = "square"
        area = square()
    # If "ellipse" is selected?
    elif selectedShape == "E" :
        theShape = "ellipse"
        print(theShape)
    elif len(selectedShape) == 0 :
        print("You have not entered anything. Please, try again!")
        theShape = ""
    # Has the user entered valid input (1 letter either T, C, R, S or E)
    elif not (selectedShape in ["T", "C", "R", "S", "E"] ) :  
        print("You have not entered valid input. Please, try again!")
        theShape = ""

    # Print the shape and the area
    if theShape != "":
        displayResult( theShape, area )

    # Get the next selection
    selectedShape = getSelection(  )

# For testing purposes:
# print("Exiting Main: selectedShape = ", selectedShape)
print("---")


# NOT YET IMPLEMENTED
# Based on selection selected by user, get appropriate input from user (validate input)
    # If "triangle" is selected, then ask for the base and height
    # If "circle" is selected, then ask for the radius
    # If "elipse" is selected, then ask for both radii
    # Validate input
    
# Compute desired area
    # If "triangle" is selected, then compute area = 0.5 ( base * height )
    # If "circle" is selected, then compute area = pi * radius squared
    # If "elipse" is selected, then compute area = pi * radius1 * radius2