package com.strkk.other.graph.other;

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.time.Instant;
import java.util.*;
import java.util.Map.Entry;

public class Planner {

    public static void main(String[] args) throws IOException {

        if(args.length < 1){
            System.out.println("Need a path to file, exit...");
            System.exit(1);
        }

        long start = Instant.now().getEpochSecond();
        Map<String, Node> map = new HashMap<>();
        try (BufferedReader br = Files.newBufferedReader(Paths.get(args[0]))) {
            String line = null;
            while ((line = br.readLine()) != null) {
                int i = line.indexOf(' ');
                String source = line.substring(0, i);
                String dest = line.substring(i + 1);

                Node s;
                if (map.containsKey(source)) {
                    s = map.get(source);
                } else {
                    s = new Node();
                    map.put(source, s);
                }

                Node d;
                if (map.containsKey(dest)) {
                    d = map.get(dest);
                } else {
                    d = new Node();
                    map.put(dest, d);
                }
                d.counter++;
                s.nodes.add(d);
            }
        }

        List<List<String>> result = new ArrayList<>();
        while (true) {
            List<String> list = new ArrayList<>();
            for (Iterator<Entry<String, Node>> it = map.entrySet().iterator(); it.hasNext(); ) {
                Entry<String, Node> e = it.next();
                Node value = e.getValue();
                if (!value.visited && value.counter == 0) {
                    list.add(e.getKey());
                    for (Node n : value.nodes) {
                        n.counter--;
                        n.visited = true;
                    }
                    it.remove();
                }
            }
            map.values().forEach(n -> n.visited = false);

            if (list.isEmpty()) {
                break;
            }
            result.add(list);
        }
        if (map.size() != 0) {
            throw new IllegalArgumentException("Tasks graph contains cycles!");
        }
        System.out.println((Instant.now().getEpochSecond() - start) + " seconds");
//        uncomment to see result
//        result.forEach(System.out::println);
        System.out.println("lists: " + result.size());
    }
}

class Node {
    int counter;
    List<Node> nodes = new ArrayList<>();
    boolean visited;
}