// Jeremy Lipschutz
// Reads in a .dot file and fills a Map to contain all the friendships in the Map
// After reading in the file we can find how many friends 'away' two people are
import java.io.*;
import java.util.*;

public class Friends {
   public static void main(String[] args) throws FileNotFoundException {
      System.out.println("Welcome to the cse143 friend finder.");
      Scanner input = new Scanner(new File("friends.dot"));
      // Each friend (String) has a corresponding friend group (Set<String>)
      Map<String, Set<String>> friendships = readFile(input);
      
      Scanner console = new Scanner(System.in);
      System.out.print("starting name: ");
      String name1 = console.nextLine();
      if(!friendships.containsKey(name1)) {
         System.out.println("That person is not in the .dot file");
      } else {
         System.out.print("target name? ");
         String name2 = console.nextLine();
         showMatches(friendships, name1, name2);
      }
      
   }

   // Constructs and returns a Map containing the friendships specified in the
   // given input. Friendships should be on separate lines with -- between the two names
   // that are friends with each other.
   public static Map<String, Set<String>> readFile(Scanner input) {
      Map<String, Set<String>> friendships = 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();  // this skips the "--" token
            String name2 = lineData.next();
            
            
            addToMap(friendships, name1, name2);
            addToMap(friendships, name2, name1);
            
         }
      }
      return friendships;
   }
   
   
   // Adds name2 as a friend of name1 in the map "friendships"
   public static void addToMap(Map<String, Set<String>> friendships, 
                               String name1, String name2) {
      // These two approaches are equivalent, but the second way is
      // much more concise
      /*
         if(friendships.containsKey(name1)) {
            Set<String> theirFriends = friendships.get(name1);
            theirFriends.add(name2);
            // friendships.put(name1, theirFriends);
         } else {
            Set<String> theirFriends = new TreeSet<String>();
            theirFriends.add(name2);
            friendships.put(name1, theirFriends);
         }
      */
      if(!friendships.containsKey(name1)) {
         /*
         Set<String> theirFriends = new TreeSet<String>();
         friendships.put(name1, theirFriends);
         */
         friendships.put(name1, new TreeSet<String>()); 
      }
      /*
      Set<String> theirFriends = friendships.get(name1);
      theirFriends.add(name2);
      */
      friendships.get(name1).add(name2);
   }
   
   // Using the friendships stored in the map 'friendships', finds how many freinds
   // away name2 is from name1. Prints out all the friends and their distances along
   // the way and prints out if the two cannot reach other through mutual friends.
   public static void showMatches(Map<String, Set<String>> friendships, 
                                  String name1, String name2) {
      System.out.println("Starting with " + name1);
      Set<String> currentGroup = new TreeSet<String>();
      currentGroup.add(name1);
      int distance = 0;
      
      // We need to keep track of which friends we've already seen so that we 
      // don't have duplicate names
      Set<String> alreadySeen = new TreeSet<String>();
      
      // Keep expanding our blob of friends until we've reached the person
      // we are looking for, or we don't find any new people
      while(!currentGroup.contains(name2) && !currentGroup.isEmpty()) {
         alreadySeen.addAll(currentGroup);
         
         // Update my current blob of friends to be all their friends
         Set<String> nextGroup = new TreeSet<String>();
         for(String person : currentGroup) {
            Set<String> friends = friendships.get(person);
            nextGroup.addAll(friends);
         }
         currentGroup = nextGroup;
         
         // We want to remove all the people we've already seen
         currentGroup.removeAll(alreadySeen);
         distance++;
         System.out.println("     " + distance + " away: " + currentGroup);
         
      }
      if(currentGroup.isEmpty()) {
         System.out.println("not found");
      } else {
         System.out.println("found at a distance of " + distance);
      }
   }
}