#!/usr/bin/python
## C463 Artificial Intelligence
## Dana Vrajitoru
## An expert system that will help the user choose a car appropriate
## to their needs and preferences.

# declare these to be able to answer without the quotes
yes = "yes"
no = "no"
y = "yes"
n = "no"

## Organizing the database for a car expert system in a dictionary so
## we can make the process more automatic.
## The list associates with each state contains the question to be
## asked when we are in that state, the state to go to from there if
## the answer is "yes",a nd the state to go to from there if the
## answer is "no".
def make_car_db():
    car_db = {}
    car_db["initial"] = ["Will you have more than 5 passengers?",
                         "bus_state", "carry_state"]
    car_db["carry_state"] = ["Do you need to cary a lot of stuff?",
                             "suv_state", "size_state"]
    car_db["size_state"] = ["Do you want a big car?",
                            "speed_state", "vwb_state"]
    car_db["speed_state"] = ["Do you want a fast car?", "", ""]
    car_db["bus_state"] = ["I suggest a bus."]
    car_db["suv_state"] = ["I sugest a SUV."]
    car_db["vwb_state"] = ["I suggest a VW Beetle."]
    return car_db

   ## to be completed by the student
## A simple general purpose expert system that executes a loop doing
## the following:
## (1) ask the user a question
## (2) reading the asnwer and transforming it into a standard form
## (3) going from the current state to another one based on the answer
## starting from the initial state and until we reach a terminal state
## or leaf in the decision tree.
def expert_system (db):
    state = "initial"
    question = ""
    answer = ""
    res = ""
    while state:
        question = get_text(db, state)
        print question
        if is_terminal(db, state):
            res = state
            state = ""
	else:
            user_input = input()
            answer = trans_answer(user_input)
##             if answer:
##                 print "yes\n"
##             else:
##                 print "no\n"
            state = process_answer(db, state, answer)
    return res
	

## Transforming a text into something simpler to test: true or false.
## The argument must be of type text or character, anything else will
## be discarded.  If the text starts with "y" or "Y" then the result
## will be true (t), everything else is interpreted as nil.
def trans_answer (text):
    if not text:
        return False
    elif type(text) == type(" ") and (text[0] == "y" or text[0] == "Y"):
        return True
    else:
        return False

## Checks if a state is terminal. We're making the convention that
## states with associated text ending with a question mark are not
## terminal, all of the others are terminal.
def is_terminal (db, state):
    text = get_text(db, state)
    if text[len(text)-1] == "?":
        return False
    else:
        return True

## Returns the text to be displayed for each of the possible states of
## the system.
def get_text (db, state):
    if not db or not state or not (state in db.keys()):
        return ""
    elif not len(db[state]):
        return ""
    else:
        return db[state][0]

## Returns a new state for every state of the system based on the
## answer.
def process_answer (db, state, answer):
    if not db or not state or not (state in db.keys()):
        return ""
    elif len(db[state]) < 3:
        return ""
    elif answer:
        return db[state][1]
    else:
        return db[state][2]

if __name__ == '__main__':
    db = make_car_db()
    expert_system(db)

## Will you have more than 5 passengers?
## yes
## I suggest a bus.
## bus_state


## Will you have more than 5 passengers?
## no
## Do you need to cary a lot of stuff?
## yes
## I sugest a SUV.
## suv_state