import static org.junit.Assert.*;

import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

import org.junit.Test;

public class HuffmanTest {

    private Huffman h;

    @Test(expected = IllegalArgumentException.class)
    public void huffmanFromNullStringTest() {
	String s = null;
	new Huffman(s);
    }

    @Test(expected = IllegalArgumentException.class)
    public void huffManFromEmptyStringTest() {
	new Huffman("");
    }

    @Test(expected = IllegalArgumentException.class)
    public void huffmanFromOneCharacterStringTest() {
	new Huffman("aaaaaaaa");
    }

    @Test(expected = IllegalArgumentException.class)
    public void huffmanFromNullMapTest() {
	Map<Character, Integer> myMap = null;
	new Huffman(myMap);
    }

    @Test(expected = IllegalArgumentException.class)
    public void huffManFromEmptyMapTest() {
	new Huffman(new HashMap<Character, Integer>());
    }

    @Test(expected = IllegalArgumentException.class)
    public void huffmanFromOneCharacterTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 5);
	new Huffman(myMap);
    }

    @Test(expected = IllegalArgumentException.class)
    public void compressNullTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 5);
	myMap.put('b', 4);
	new Huffman(myMap).compress(null);
    }

    @Test(expected = IllegalArgumentException.class)
    public void compressIllegalTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 5);
	myMap.put('b', 4);
	new Huffman(myMap).compress("c");
    }

    @Test(expected = IllegalArgumentException.class)
    public void decompressNullTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 5);
	myMap.put('b', 4);
	new Huffman(myMap).decompress(null);
    }

    @Test(expected = IllegalArgumentException.class)
    public void decompressIllegalTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 5);
	myMap.put('b', 4);
	new Huffman(myMap).decompress("010120101");
    }

    @Test(expected = IllegalArgumentException.class)
    public void decompressNotFoundTest() {
	Map<Character, Integer> myMap = new HashMap<Character, Integer>();
	myMap.put('a', 1);
	myMap.put('b', 1);
	myMap.put('c', 1);
	myMap.put('d', 1);
	// odd length should throw an exception
	new Huffman(myMap).decompress("00110");
    }

    @Test(expected = IllegalStateException.class)
    public void noRatioYetTest() {
	new Huffman("ab").compressionRatio();
    }

    @Test
    public void compressSimpleTest() {
	h = new Huffman("ab");
	assertEquals("0", h.compress("a"));
	assertEquals("1", h.compress("b"));
    }

    @Test
    public void compressMediumTest() {
	h = new Huffman("abcc");
	assertEquals("00", h.compress("a"));
	assertEquals("01", h.compress("b"));
	assertEquals("1", h.compress("c"));
	assertEquals("0001110100", h.compress("abccba"));
    }

    @Test
    public void decompressSimpleTest() {
	h = new Huffman("ab");
	assertEquals("a", h.decompress("0"));
	assertEquals("b", h.decompress("1"));
    }

    @Test
    public void decompressMediumTest() {
	h = new Huffman("abcc");
	assertEquals("a", h.decompress("00"));
	assertEquals("b", h.decompress("01"));
	assertEquals("c", h.decompress("1"));
	assertEquals("abccba", h.decompress("0001110100"));
    }

    @Test
    public void simpleRatioTest() {
	h = new Huffman("abc");
	h.compress("a");
	assertEquals(1.0 / 8.0, h.compressionRatio(), 0);
    }

    @Test
    public void complexRatioTest() {
	h = new Huffman("abc");
	h.compress("abcababcabbaacb");
	assertEquals(27.0 / 240.0, h.compressionRatio(), 0);
    }

    @Test
    public void identityTest() {
	h = new Huffman("sagfcafascweprouwqepoityolmaznxmknjdbdchdgvagasdfawiefuifnarfnsfij");
	Function<String, String> compress = h::compress;
	Function<String, String> decompress = h::decompress;

	Function<String, String> identity = compress.andThen(decompress);

	String[] strings = { "abc", "dfsadfsd", "werwqwewqqwwwwwwererrtopskvd",
		"sgsfswordoiojmomcsdacioansiond", "sdafsa", "helloworld",
		"thisisnotasubliminalmessage",
		"sakfdjaslvnsajdklcnskljcmaijfnjsdkasknfjskaldnfsjakfdsdkfsklfdnsadklfh" };

	for (String s : strings) {
	    assertEquals(s, identity.apply(s));
	}

    }

    @Test
    public void expectedEncodingLengthSmallTest() {
	h = new Huffman("ab");
	assertEquals(1, h.expectedEncodingLength(), 0);
    }

    @Test
    public void expectedEncodingLengthMediumTest() {
	h = new Huffman("abc");
	assertEquals(5.0 / 3.0, h.expectedEncodingLength(), Math.ulp(2));
    }

    @Test
    public void expectedEncodingLengthLongTest() {
	h = new Huffman("aaaaaaaaaaaaaaaaaabcde");
	assertEquals(13.0 / 5.0, h.expectedEncodingLength(), Math.ulp(3));
    }

    @Test
    public void expectedEncodingLengthAlphabetTest() {
	h = new Huffman("qwertyuiopasdfghjklzxcvbnm");
	// 20 chars have a length 5 encoding
	// 6 chars have a length 4 encoding
	assertEquals((20 * 5 + 6 * 4) / 26.0, h.expectedEncodingLength(), 0);
    }

}