import org.junit.Before;
import org.junit.Test;

import java.util.HashMap;
import java.util.Map;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.nullValue;

public class HashMapTest {

    private Map<String, String> map1;

    @Before
    public void setUp() throws Exception {
        map1 = new HashMap<>();
    }

    @Test
    public void empty_after_init() {
        assertThat(map1.isEmpty(), is(true));
    }

    @Test
    public void compute() {
        map1.put("foo1", "bar1");
        map1.put("foo2", "bar2");

        map1.compute("foo1", (k, v) -> (v == null) ? "null value" : "not null value");
        assertThat(map1.get("foo1"), is("not null value"));
    }

    @Test
    public void computeIfAbsent() {
        map1.put("foo1", "bar1");

        map1.computeIfAbsent("foo2", k -> "null value");
        assertThat(map1.get("foo2"), is("null value"));
        assertThat(map1.size(), is(2));
    }

    @Test
    public void computeIfPresent() {
        map1.put("foo1", "bar1");

        map1.computeIfPresent("foo1", (k, v) -> "was " + v);
        assertThat(map1.get("foo1"), is("was bar1"));
        assertThat(map1.size(), is(1));

        map1.computeIfPresent("foo2", (k, v) -> "was " + v);
        assertThat(map1.size(), is(1));
    }

    @Test
    public void put_overwrite() {
        map1.put("foo1", "bar1");
        map1.put("foo1", "bar2");

        assertThat(map1.size(), is(1));
        assertThat(map1.get("foo1"), is("bar2"));
    }

    @Test
    public void putIfAbsent() {
        map1.put("foo1", "bar1");

        map1.putIfAbsent("foo1", "insert because of absence");
        map1.putIfAbsent("foo2", "insert becase of absence");

        assertThat(map1.size(), is(2));
        assertThat(map1.get("foo1"), is("bar1"));
        assertThat(map1.get("foo2"), is("insert becase of absence"));
    }

    @Test
    public void merge() {
        map1.put("foo1", "bar1");

        map1.merge("foo1", ": message", String::concat);
        map1.merge("foo2", ": message", String::concat);

        assertThat(map1.size(), is(2));
        assertThat(map1.get("foo1"), is("bar1: message"));
        assertThat(map1.get("foo2"), is(": message"));
    }

    @Test
    public void remove() {
        map1.put("foo1", "bar1");

        map1.remove("foo1", "bar2");
        assertThat(map1.size(), is(1));
        assertThat(map1.get("foo1"), is("bar1"));

        map1.remove("foo1");
        assertThat(map1.size(), is(0));
        assertThat(map1.get("foo1"), is(nullValue()));
    }

    @Test
    public void replace() {
        map1.replace("foo1", "bar1");
        assertThat(map1.size(), is(0));

        map1.put("key1", "bar1");
        map1.replace("key1", "value1");
        assertThat(map1.get("key1"), is("value1"));

        map1.replace("key1", "bar1", "newvalue");
        assertThat(map1.get("key1"), is("value1"));

        map1.replace("key1", "value1", "newvalue");
        assertThat(map1.get("key1"), is("newvalue"));
    }
}