// CSE 143, Winter 2009, Daniel Otero
// This program hires and fires teaching assistants based on their experience.
// It is a demonstration of the PriorityQueue class.

import java.io.*;
import java.util.*;

public class FiringSquad {
    private static final int MINIMUM_EXP = 3;
    private static final String TAS_FILE = "tas.txt";
    private static final String REPLACEMENTS_FILE = "replacements.txt";

    public static void main(String[] args) throws IOException {
        List<TA> taList = getTAsFromFile(TAS_FILE);
        System.out.println(taList);
        System.out.println();
        
        // Get TAs into sorted order somehow
        Queue<TA> queue = new PriorityQueue<TA>();
        for (TA ta : taList) {
            System.out.println("Just added TA: " + ta);
            queue.add(ta);
            printQueue(queue);
            System.out.println();
        }
                
        // Find all the TAs with < MINIMUM_EXP quarters of experience
        // (Elements come out of the queue in sorted order, least to greatest,
        // regardless of the order in which they were inserted.)
        while (!queue.isEmpty() && queue.peek().getExperience() < MINIMUM_EXP) {
            TA ta = queue.remove();
            System.out.println("Removed TA: " + ta);
        }
        
        // Replace fired TAs with new ones from the replacements file
        List<TA> replacements = getTAsFromFile(REPLACEMENTS_FILE);
        for (TA replacement : replacements) {
            queue.add(replacement);
        }
        
        System.out.println();
        System.out.println("Final queue:");
        printQueue(queue);
    }
    
    // Given a file name, attempts to read the names and experience levels of
    // TAs from that file. Each TAs data is inserted into a TA object, and the
    // lot are returned in a list.
    private static List<TA> getTAsFromFile(String filename) throws IOException {
        Scanner fileScanner = new Scanner(new File(filename));
        List<TA> tas = new ArrayList<TA>();
        while (fileScanner.hasNext()) {
            String taName = fileScanner.next();
            int taExp = fileScanner.nextInt();
            tas.add(new TA(taName, taExp));
        }
        
        return tas;
    }
    
    // Prints contents of given priority queue in order they would be removed.
    // PriorityQueue#toString() doesn't suffice: doesn't show ordering.
    private static void printQueue(Queue<TA> queue) {
        Queue<TA> backup = new LinkedList<TA>();
        System.out.print("[");
        if (!queue.isEmpty()) {
            System.out.print(queue.remove());
            while (!queue.isEmpty()) {
                TA ta = queue.remove();
                System.out.print(", " + ta);
                backup.add(ta);
            }
        }
        System.out.println("]");
        
        while (!backup.isEmpty()) {
            queue.add(backup.remove());
        }
    }
}