// Prompts the user for two names and prints how distant of friends they are.
// This version fixes a couple of bugs.

import java.util.*;
import java.io.*;

public class Friends {
    
    public static void main(String[] args) throws FileNotFoundException {
        System.out.println("Welcome to the cse143 friend finder.");
        Map<String, Set<String>> friends = readFile("friends.dot");
        System.out.println(friends);
        
        Scanner console = new Scanner(System.in);
        System.out.print("starting name? ");
        String name1 = console.next();
        
        
        if (!friends.containsKey(name1)) {
            System.out.println("That person is not in the data file.");
        } else {
            System.out.print("target name? ");
            String name2 = console.next();
            
            if (!friends.containsKey(name2)) {
                System.out.println("That person is not in the data file.");
            } else {
                findFriends(friends, name1, name2);
            }
        }
        
    }
    
    // pre : filename is the name of a legal GraphViz file of friendship connections
    // post: returns a map that contains for each person, the set of friends for that person
    public static Map<String, Set<String>> readFile(String filename) throws FileNotFoundException {
        Scanner input = new Scanner(new File(filename));
        
        Map<String, Set<String>> friends = new TreeMap<String, Set<String>>();
        
        while (input.hasNextLine()) {
            String line = input.nextLine();
            if (line.contains("--")) {
                Scanner lineData = new Scanner(line);
                String name1 = lineData.next();
                lineData.next(); // skip "--"
                String name2 = lineData.next();
                
                addFriend(friends, name1, name2);
                addFriend(friends, name2, name1);
            }
        }
        return friends;
    }
    
    // post: records a frienship for name1 and name2. If name1 is not in the map,
    //       a set is added to the map containing name2.
    public static void addFriend(Map<String, Set<String>> friends,
                                 String name1, String name2) {
        /* Hunter: More verbose way to handle this
         * if (!friends.containsKey(name1)) {
         *     Set<String> theFriends = new TreeSet<String>();
         *     theFriends.add(name2);
         *     friends.put(name1, theFriends);
         * } else {
         *     Set<String> theFriends = friends.get(name1);
         *     theFriends.add(name2);
         *     // Why isn't this necessary?
         *     // friends.put(name1, theFriends);
         * }
         */
         
        if (!friends.containsKey(name1)) {
            friends.put(name1, new TreeSet<String>());
        }
        Set<String> theFriends = friends.get(name1);
        theFriends.add(name2);
    }
    
    // post: computes the distance between two people, printing out 
    //       the set of friends that are certain "degrees" away from name1
    public static void findFriends(Map<String, Set<String>> friends,
                                   String name1, String name2) {
        int distance = 0;
        Set<String> currGroup = new TreeSet<String>();
        Set<String> visited = new HashSet<String>();
        currGroup.add(name1);
        while (!currGroup.contains(name2) && !currGroup.isEmpty()) {
            // make sure we don't visit someone we've already visisted
            visited.addAll(currGroup);
            
            // find next group 
            Set<String> nextGroup = new TreeSet<String>();
            for (String name : currGroup) {
                nextGroup.addAll(friends.get(name));
            }
            
            nextGroup.removeAll(visited);
            
            // update curr group and other info
            currGroup = nextGroup;
            distance++;
            System.out.println("    " + distance + " away: " + currGroup);
        }  
        System.out.println("found at distance of " + distance);                            
    }
}