#----------------------------------------------------------------------
# Basic command processor
#
# Copyright (C) October 11, 2017 -- Dr. William T. Verts
# Enhanced October 13, 2017 to be a graphics image processor
#
# This program ilustrates a number of new Python structures, including
# quoted strings that span lines, the string function to make all
# characters lower case, the raw_input function, the pass statement
# to act as a placeholder for future code, and the use of bool
# (Boolean) variables to control a loop.
#
# The new Python statements this time are the try-except block for
# error handling, and the ability to pass functions as parameters to
# other functions.
#
# In terms of command processor design, the main issues here are:
# A: Do I put action code inside the individual if-statements of the
#    command processor?
# B: Do I put action code inside individual functions called from
#    the command processor?
# C: Can I factor common code out of the functions to generalize?
#----------------------------------------------------------------------

# Approach B: Individual functions that do unique tasks

def Brighten (Canvas):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)):
            PX = getPixel(Canvas,X,Y)
            setRed(PX, getRed(PX) + 30)
            setGreen(PX, getGreen(PX) + 30)
            setBlue(PX, getBlue(PX) + 30)
        repaint(Canvas)
    return

def Darken (Canvas):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)):
            PX = getPixel(Canvas,X,Y)
            setRed(PX, getRed(PX) - 30)
            setGreen(PX, getGreen(PX) - 30)
            setBlue(PX, getBlue(PX) - 30)
        repaint(Canvas)
    return

def MoreRed(Canvas):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)):
            PX = getPixel(Canvas,X,Y)
            setRed(PX, getRed(PX) + 30)
        repaint(Canvas)
    return

#----------------------------------------------------------------------
# Approach C: Tiny pixel-handler functions passed
# in as parameters to the Process function.

def Brighten_Pixel (PX):
    setRed(PX, getRed(PX) + 30)
    setGreen(PX, getGreen(PX) + 30)
    setBlue(PX, getBlue(PX) + 30)
    return
    
def Darken_Pixel (PX):
    setRed(PX, getRed(PX) - 30)
    setGreen(PX, getGreen(PX) - 30)
    setBlue(PX, getBlue(PX) - 30)
    return

#--------------------------------------------------
# Process is responsible for scanning all pixels
# in an image and applying whatever is passed in
# as MyFunction to each pixel, and repainting the
# canvas after each line is completed.  If Process
# is passed Brighten_Pixel, then calling MyFunction
# is the same as calling Brighten_Pixel.  If Process
# is passed Darken_Pixel, then calling MyFunction
# is the same as calling Darken_Pixel. 

def Process(Canvas, MyFunction):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)):
            PX = getPixel(Canvas,X,Y)
            MyFunction(PX)
        repaint(Canvas)
    return

#----------------------------------------------------------------------

def Main():

    #--------------------------------------------------
    # Message uses the "triple-double-quote" of Python to build a
    # string that spans lines and contains line-breaks.  Between the
    # opening """ and the closing """ all characters are valid, so
    # indentation is not used. 
    
    Message = """
Stop Open
Brighten Darken
MoreRed MoreGreen MoreBlue
Enter a command --- """
    
    Canvas = makeEmptyPicture(100,100)
    show(Canvas)
    Stop = False
    while (not Stop):
        Command = requestString(Message)    # Use requestString(Message) for JES dialog, raw_input for pure Python box
        Command = Command.lower()           # Convert string to lower case (users may enter upper case by accident)
        
        if   (Command == "stop"):
            Stop = True
        elif (Command == "open"):
            Filename = pickAFile()
            try:                                                # If the user enters the name
                Canvas = makePicture(Filename)                  # of a file that isn't a graphic,
                repaint(Canvas)                                 # the repaint will fail, and throw
            except:                                             # an exception, picked up by the
                Canvas = makeEmptyPicture(100,100)              # except block.  If the try block
                showInformation(Filename + " is not a graphic") # succeeds, the except block won't run.
        
        #--------------------------------------------------
        # Approach C: each command calls a handler function (Process)
        # responsible for overall image scanning, but passes
        # in as a parameter the appropriate function to use to
        # process each pixel (Brighten_Pixel, Darken_Pixel).
                         
        elif (Command == "brighten"): Process(Canvas, Brighten_Pixel)
        elif (Command == "darken"):   Process(Canvas, Darken_Pixel)
        
        #--------------------------------------------------
        # Approach B: each command calls a unique function
        # dedicated to solving that one task.
        
        elif (Command == "morered"):  MoreRed(Canvas)

        #--------------------------------------------------
        # Approach A: each command in the command processor
        # does "its thing" right at the point that the new
        # command is known.  Effective, but makes the command
        # processor extremely lengthy and hard to debug (how
        # easy is it to line up the proper indentation if this
        # part of the code is 800 lines long?
        
        elif (Command == "moregreen"):
            for Y in range(getHeight(Canvas)):
                for X in range(getWidth(Canvas)):
                    PX = getPixel(Canvas,X,Y)
                    setGreen(PX, getGreen(PX) + 30)
                repaint(Canvas)
                
        elif (Command == "moreblue"):
            for Y in range(getHeight(Canvas)):
                for X in range(getWidth(Canvas)):
                    PX = getPixel(Canvas,X,Y)
                    setBlue(PX, getBlue(PX) + 30)
                repaint(Canvas)
        else:
            print Command + " is an illegal command"    # Use showMessage(...) for JES, print for pure Python dialog box
        
        repaint(Canvas)        
    return