#copied in from Assignment 2 solution
def numericInput(prompt):
    """Gets user input repeating until they enter a number"""
    accepted = False

    while not accepted:
        text = raw_input(prompt)
        try:
            #if the conversion fails, this will error before it returns
            return float(text)
        except:
            print "Please enter a number"


def readFile(filename):
    """reads the lines of a file and returns them in a list"""
    fileIn = file(filename,"r")
    lineList = []

    for line in fileIn:

        #remove the newline character
        if line[-1] == "\n":
            line = line[:-1]
            
        lineList.append(line)

    fileIn.close()
    return lineList


def writeFile(filename, lines):
    """write the contents in lines to a file"""
    fileOut = file(filename,"w")

    for line in lines:
        #add the newline character
        fileOut.write(line + "\n")

    fileOut.close()
    return



filename = raw_input("Please enter the file you'd like to work with: ")
print

fileLines = readFile(filename)
        
selection = 0
while selection != 4:
    if len(fileLines) == 0:
        print "***The file is empty***"
    else:
        lineIndex = 1
        for line in fileLines:
            print str(lineIndex) + "\t" + line
            lineIndex = lineIndex+1
    
    print
    print "1. Add a line to the end of the file."
    print "2. Delete a line from the file."
    print "3. Insert a line into the file."
    print "4. Exit, saving changes to the file."
    print "-----------------------------------------"
    selection = numericInput("Select an option: ")

    if selection==1:
        newLine = raw_input("Enter the new line: ")
        fileLines.append(newLine)

    elif selection==2:
        lineNum = int(numericInput("Which line would you like to delete: "))
        try:
            del fileLines[lineNum-1]
        except:
            print "You didn't select a valid line number."

    elif selection==3:
        newLine = raw_input("Enter the new line: ")
        lineNum = numericInput("On which line should it be inserted? ")
        fileLines.insert(lineNum-1,newLine)
    elif selection==4:
        print "Exiting."
    else:
        print "Please select a valid option."



writeFile(filename,fileLines)