#
# recursive linear search for user-supplied word
# words in list can be in any order
# Matt Bishop, MHI 289I, Winter 2018
#

# this is global just to emphasize how that works
wordlist = [ "when", "in", "the", "course", "of", "human", "events" ]

# search a list of words for a word (linear search)
# parameters: word, the word to find in the list
# returns: index (+1) of word in list
#          -1 if not in list
def search(word, wordlist):
        # base case: list is empty or first element of list is word
        if wordlist == []:
                return -1
        # see if it's the current element
        # if it is, return position + 1 (the + 1 for humand)
        if word == wordlist[0]:
                return 1
        # recursive case: check rest of list
        k = search(word, wordlist[1:])
        # got it! Index is 1 more than previous
        if k != -1:
                return k + 1
        # return that you found nothing
        return -1

# append words to a list
# parameters: none
# returns: nothing
def addword(word, wordlist):
        # use existing routine to see if this is a duplicate
        found = search(word, wordlist)
        if (found == -1):
                # nope -- add it
                wordlist.append(word)
                print "Added word '%s' to list" % word
        else:   # yep -- say so
                print "'%s' is already in the list (word %d)" % (word, found)

# this puts it all together
def main():
        # declaration -- using the initial one
        global wordlist
        # loop
        instr = 'next'
        while len(instr) > 0:
                # read in word; quit on EOF
                try:
                        find = raw_input("what do I do (s word, a word, p)? ")
                except EOFError:
                        return
                # nothing typed?
                if len(find) == 0:
                        return
                # find the word if it's there
                l = find.split()
                #
                # now process the word and command
                #
                # first, be sure it's of the right form
                if len(l) == 0:
                        pass
                elif len(l) > 2:
                        print "Your input can have only 2 words!"
                # s word -- find word in the list
                elif l[0] == 's':
                        # be sure it is of the right form
                        if len(l) == 1:
                                print "s: what should I search for?"
                        else:
                                # look for the word in the list
                                found = search(l[1], wordlist)
                                # announce result
                                if found == -1:
                                        print "'%s' is not in the list" % l[1]
                                else:
                                        print "'%s' is word number %d" % (l[1], found)
                # a word -- append word to list
                elif l[0] == 'a':
                        # be sure it is of the right form
                        if len(l) == 1:
                                print "a: what should I add?"
                        else:
                                addword(l[1], wordlist)
                # p -- print list
                elif l[0] == 'p':
                        for i in range(len(wordlist)):
                                print "%2d. %s" % (i+1, wordlist[i])
                # you got me -- unknown command, so say so
                else:
                        print "Unknown command '%s'", find
                        
#
# and away we go!
#
main()