'''
BC1.py -- first of several incremental implementation of backward
chaining to illustrate incremental development in CS4100, Artificial
Intelligence.This first version works only with a KB of "facts",
meaning positive ground literals (with no variables). BC2 will introduce
variables and the possibility of having more than one return value.
We use a dictionary to store the KB and its keys are predicates symbols:
i.e., the goals we are trying to prove.

The incremental approach lets you create a basic structure for:
input/processing/output without getting bogged down by the details
of the multi-level recursion in the BC algorithm.
'''
from unify import *

Fdict = {}  #Here we will store the "facts" found in the knowledge base

def acquireKB(KBname):
    kbfile = open(KBname)
    for aline in kbfile.readlines():
        addClauseToFDict(FOLexp(aline))
        # now add the FOLexp to the dictionary with its key

def FOLBCtest(QFname):
    queryfile = open(QFname)
    for aline in queryfile.readlines():
        print 'Query: ' , aline[:-1]
        nextQ = FOLexp(aline)
        #now find everything the query matches in the KB
        if Fdict.has_key(nextQ.op):
            thetalist = runBC(nextQ, Fdict[nextQ.op], [])
            showResults(thetalist)
        else:
            print "RESULT>>>>>: False"
        
def addClauseToFDict(clause):
    #Adds a FOL sentence represented as a FOLexp to the KB dictionary
    if Fdict.has_key(clause.op):
        Fdict[clause.op] += [clause]   #append it to entry
    else:
        Fdict[clause.op] = [clause]    # make a new entry

def runBC(query, clauses, thetalist):
    # get all theta's that satisfy the query and display
    # them in a readable way
    for c in clauses:
        theta = unify(query, c)
        if theta != False:
            thetalist.append(theta)
    return thetalist
            
def showResults(thetalist):
    if len(thetalist) > 1:
        # Display the number of answers and each one
        print ">>> " , len(thetalist) , " answers found."
        i = 1
        for theta in thetalist:
            print ">>> ANSWER " , i
            printTheta(theta)
            i += 1
    else:
        print ">>> ANSWER: "
        printTheta(thetalist[0])