package lab.util;

import static org.junit.Assert.*;

import java.util.Date;
import java.util.NoSuchElementException;

import org.junit.Test;

public class StackTest {

  @Test
  public void testConstructor() {
    Stack<String> t = new Stack<String>();
    Node<String> top = t.getTop();
    assertNull("constructor should create an empty stack with no nodes", top);
  }
  
  @Test
  public void testIsEmpty() {
    Stack<String> t = new Stack<String>();
    assertTrue("isEmpty should return true for an empty stack",
        t.isEmpty());
    t.push("hi");
    assertFalse("isEmpty should return false for a non-empty stack",
        t.isEmpty());
  }

  @Test
  public void testSize() {
    Stack<String> t = new Stack<String>();
    assertEquals("size should return 0 for an empty stack",
        0, t.size());
    for (int i = 1; i < 100; i++) {
      t.push("push " + i);
      assertEquals("size should return " + i + " for a stack with " + i + " elements",
          i, t.size());
    }
  }

  @Test
  public void testPush() {
    Stack<Integer> t = new Stack<Integer>();
    for (int i = 1001; i < 2001; i++) {
      Integer exp = i;
      t.push(exp);
      Integer got = t.getTop().getElement();
      assertEquals("push failed to push the correct element to the top of the stack", exp, got);
    }
  }

  @Test
  public void testPopEmpty() {
    try {
      Stack<String> t = new Stack<String>();
      t.pop();
      fail("pop on an empty stack should have thrown an exception");
    }
    catch (NoSuchElementException x) {
      // ok, pop should throw this exception
    }
    catch (Exception x) {
      fail("pop threw the wrong kind of exception");
    }
  }
  
  @Test
  public void testPop() {
    Stack<Integer> t = new Stack<Integer>();
    for (int i = 1001; i < 2001; i++) {
      Integer exp = i;
      t.push(exp);
      Integer got = t.pop();
      assertEquals("pop failed to return the correct value", exp, got);
      t.push(got);
    }
    
  }

  @Test
  public void testPeek() {
    Stack<Integer> t = new Stack<Integer>();
    for (int i = 1001; i < 2001; i++) {
      Integer exp = i;
      t.push(exp);
      Integer got = t.peek();
      assertEquals("peek failed to return the correct value", exp, got);
    }
  }

  @Test
  public void testEqualsObject() {
    Date d = new Date();
    Stack<Integer> t = new Stack();
    Stack<Integer> u = new Stack();
    assertFalse("t.equals(null) should return false", t.equals(null));
    assertFalse("t.equals(d) should return false for a Stack t and a Date d", t.equals(d));
    assertTrue("t.equals(u) should return true for empty stacks t and u", t.equals(u));
    assertTrue("u.equals(t) should return true for empty stacks t and u", u.equals(t));
    
    for (int i = 0; i < 10; i++) {
      t.push(i);  
    }
    assertFalse("t.equals(u) should return false for different stacks t and u", t.equals(u));
    assertFalse("u.equals(t) should return false for different stacks t and u", u.equals(t));
    
    for (int i = 0; i < 10; i++) {
      u.push(i);  
    }
    assertTrue("t.equals(u) should return true for same stacks t and u", t.equals(u));
    assertTrue("u.equals(t) should return true for same stacks t and u", u.equals(t));
  }

}