// Hunter Schafer, CSE 143
// 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 {
      Map<String, Set<String>> friends = buildFriendMap("friends.dot");
      System.out.println(friends);

      Scanner console = new Scanner(System.in);
      System.out.print("First person? ");
      String name1 = console.next();

      System.out.print("Second person? ");
      String name2 = console.next();
      
      printLevels(name1, name2, friends);
   }

   // prints the friends at each level separating friend1 and friend2 in the
   // specified friendship graph.
   // pre: friends contains friend1
   private static void printLevels(String name1, String name2, Map<String, Set<String>> friends) {
       Set<String> currentLevel = new HashSet<String>();
       currentLevel.add(name1);
       int level = 0;
       
       Set<String> visited = new HashSet<String>();
       // stop when we found name2 or when we have no more names to explore
       while (!currentLevel.isEmpty() && !currentLevel.contains(name2)) {
           // move to the next level
           level++;
           visited.addAll(currentLevel);
           
           Set<String> nextLevel = new HashSet<String>();
           for (String name : currentLevel) {
               Set<String> friendsOfName = friends.get(name);
               nextLevel.addAll(friendsOfName);
           }
           nextLevel.removeAll(visited);
           
           System.out.println("\tDistance " + level + ": " + nextLevel);
           currentLevel = nextLevel;
       }

       if (!currentLevel.isEmpty()) {
           System.out.println(name2 + " is " + level + " away from " + name1);
        } else {
           System.out.println(name2 + " is not connected to " + name1);
        }
        
   }
   
   // Builds a map of friendships based on a file with the specified name.
   // pre: a file named filename exists and is in valid Graphviz format
   public static Map<String, Set<String>> buildFriendMap(String filename)
         throws FileNotFoundException {
      Scanner input = new Scanner(new File(filename));

      // key: names of people
      // value: Set<String> name's friends
      
      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();

            addToFriends(name1, name2, friends);
            addToFriends(name2, name1, friends);
       
         }
      }
      return friends;
   }
   
   // Adds name2 to name1's set of friends in the friends map.
   private static void addToFriends(String name1, String name2,
           Map<String, Set<String>> friends) {
       if (!friends.containsKey(name1)) {
           friends.put(name1, new TreeSet<String>());
       }
       // assume: there is a mapping for name1 
       Set<String> name1Friends = friends.get(name1);
       name1Friends.add(name2);       
   }
}