// Josh Ervin, thanks to Erika Wolfe :)
// This program reads a Graphviz graph file of friendships and allows the user
// to find the distance between two people in the graph.

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>> friends = readFile(input);
        
        System.out.println("On average, each TA has " + computeAverage(friends) + " 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();
            showMatches(friends, name1, name2);
        }
        
                
    }
    
    // pre : friends is a mapping from a person to a set of their friends
    // post: computes the average number of friends that each person has 
    public static double computeAverage(Map<String, Set<String>> friends) {
        int total = 0;
        for (String name : friends.keySet()) {
            Set<String> theirFriends = friends.get(name);
            total += theirFriends.size(); 
        }
        
        return (double) total / friends.size(); 
    }

    // 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>> 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();  // this skips the "--" token
                String name2 = lineData.next();
                
                // Added since Wednesday's lecture
                addTo(friends, name1, name2);
                addTo(friends, name2, name1);
            }
        }
        return friends;
    }

    // post: computes the distance between two people, printing the various
    //       lists of friends with their distance from name1
    // showMatches(friends, "hunter", "mitchell");
    public static void showMatches(Map<String, Set<String>> friends, 
                                   String name1, String name2) {
        
        Set<String> currGroup = new TreeSet<>();
        Set<String> visited = new HashSet<>();
        currGroup.add(name1);
        int distance = 0;
        
        while (!currGroup.isEmpty() && !currGroup.contains(name2)) {
            Set<String> nextGroup = new TreeSet<>();
            for (String person : currGroup) {
                Set<String> neighbors = friends.get(person);
                for (String neighbor : neighbors) {
                    if (!visited.contains(neighbor)) {
                        nextGroup.add(neighbor);
                    }
                }
            }
            
            visited.addAll(currGroup);
            currGroup = nextGroup;
            distance++;
            System.out.println("  " + distance + " away: " + currGroup);
        }
        
        

    }

    // post: records a friendship for name1.  If name1 is not in the map, a new
    //       set is added to the map
    public static void addTo(Map<String, Set<String>> friends, String name1, 
                             String name2) {
        /*
        if (!friends.containsKey(name1)) {
            Set<String> theFriends = new TreeSet<String>();
            friends.put(name1, theFriends);
            theFriends.add(name2);
        } else {
            Set<String> theFriends = friends.get(name1);
            theFriends.add(name2);
        }
        */
        
        if (!friends.containsKey(name1)) {
            friends.put(name1, new TreeSet<String>());
        }
        
        friends.get(name1).add(name2);
    }
}