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"));

      Map<String, Set<String>> friendNetwork = readFile(input);
      
      Scanner console = new Scanner(System.in);
      System.out.print("starting name? ");
      String name1 = console.next();
      if (!friendNetwork.containsKey(name1)) {
         System.out.println("That person is not in the data file.");
      } else {
         System.out.print("target name? ");
         String name2 = console.next();
         showMatches(friendNetwork, name1, name2);
      }
      
   }
   
   // pre : input is open and contains a legal Graphviz file of friendship
   //       connections where each friend is listed as a single token
   // post: returns a map that contains for each person the set of friends for
   //       that person
   public static Map<String, Set<String>> readFile(Scanner input) {
      Map<String, Set<String>> friendNetwork = 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();
            
            // Add a friendship between name1 and name2 to our map
            // ex:  name1 = Raymond
            //      name2 = Anju
            updateMap(friendNetwork, name1, name2);
            updateMap(friendNetwork, name2, name1);
         }
      }
      return friendNetwork;
   }
   
   
   // post: records a friendship with name2 for name1
   public static void updateMap(Map<String, Set<String>> friendNetwork,
                                String name1, String name2) {                     
      /*
      if (!friendNetwork.containsKey(name1)) {  // first time we've seen a key
         Set<String> friendGroup = new TreeSet<>(); 
         friendGroup.add(name2);
         friendNetwork.put(name1, friendGroup);     
      } else { // we've seen this key already
         Set<String> friendGroup = friendNetwork.get(name1);
         friendGroup.add(name2);
         // We don't need to put the set back in the map!
         // The map stores a reference to the set, so the updates
         // are already there
      }*/
      
      if (!friendNetwork.containsKey(name1)) {
         friendNetwork.put(name1, new TreeSet<>());
      }
      friendNetwork.get(name1).add(name2);
                                               
   }
   
   // post: computes the distance between two people, printing the various
   //       lists of friends with their distance from name1
   public static void showMatches(Map<String, Set<String>> friendNetwork,
                                  String name1, String name2) {
      // Meta: The algorithm here is much more complicated than what I'd
      // expect you to come up with on your own
      // The important part is how we're using sets and maps.
      Set<String> currGroup = new TreeSet<>();
      currGroup.add(name1);
      int distance = 0;
      
      Set<String> visited = new HashSet<>();
      
      while (!currGroup.isEmpty() && !currGroup.contains(name2)) {
         visited.addAll(currGroup);
      
         Set<String> friendsOfCurrGroup = new TreeSet<>();
         for (String curr : currGroup) {
            Set<String> friendsOfCurr = friendNetwork.get(curr);
            for (String friend : friendsOfCurr) {
               if (!visited.contains(friend)) {
                  friendsOfCurrGroup.add(friend);
               }
            }
         }
         
         currGroup = friendsOfCurrGroup;
         distance += 1;
         System.out.println("    " + distance + " away: " + currGroup);
      }
   }

}