# CSE 143, Winter 2009, Marty Stepp
# Homework 5 (Grammar Solver), in Python
#
# Instructor-provided testing program, by Marty Stepp
# A client program that prompts a user for the name of a
# grammar file and then gives the user the opportunity to generate random
# versions of various elements of the grammar.

from grammarsolver import *

# Displays all non-terminal symbols, prompts for a symbol to generate,
# and returns the symbol as a string.
def get_symbol(solver):
    print("")
    print("Available symbols to generate are:")
    print(solver.symbols())
    target = raw_input("What do you want to generate (Enter to quit)? ").strip()
    return target

# Generates some number of instances of the given symbol.
def do_generate(solver, symbol):
    number = int(raw_input("How many do you want me to generate? "))
    if number >= 0:
        print("")
        for i in range(number):
            print(solver.generate(symbol))
    else:
        print("No negatives allowed.")


# main
print("Welcome to the CSE 143 random sentence generator!")
print("")

# open grammar file; read its lines into a list
filename = raw_input("What is the name of the grammar file? ")
lines = [line.strip() for line in file(filename)]

# construct grammar solver and begin user input loop
solver = GrammarSolver(lines)

# repeatedly prompt for symbols to generate, and generate them
symbol = get_symbol(solver)
while len(symbol) > 0:
    if solver.contains(symbol):
        do_generate(solver, symbol)
    else:
        print("Illegal symbol.")
    symbol = get_symbol(solver)