import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import org.junit.Test;
import static org.junit.Assert.*;
import org.junit.Before;

/**
 * @author Peter Wu
 */
public class SpellCorrectorTest {

    private CorpusReader fullCR;
    private ConfusionMatrixReader cmr;

    @Before
    public void setUp() throws IOException {
        fullCR = new MockCorpusReader();
        cmr = new ConfusionMatrixReader();
    }

    private void checkGetCandidateWords(CorpusReader cr, String word,
            Set<String> expResult)
            throws IOException {
        // ignore unchanged word
        expResult.remove(word);

        System.out.println("getCandidateWords(" + word + ")");
        SpellCorrector instance = new SpellCorrector(cr, cmr);
        Set<String> result = instance.getCandidateWords(word).keySet();

        assertFalse("Should not contain word " + word, result.contains(word));
        // quick check: are the results of the same size?
        assertEquals(expResult.size(), result.size());
        // verbose test: are all letters as expected?
        assertEquals(expResult, result);
    }

    @Test
    public void testGetCandidateWords0() throws IOException {
        Set<String> words = new HashSet<>();

        // test for empty word (only a letter can be inserted)
        for (char c : SpellCorrector.ALPHABET) {
            // insertion
            words.add("" + c);
        }
        checkGetCandidateWords(fullCR, "", words);
    }

    @Test
    public void testGetCandidateWords1() throws IOException {
        Set<String> words = new HashSet<>();

        // test for a single letter word
        for (char c : SpellCorrector.ALPHABET) {
            // insertion before and after
            words.add(c + "a");
            words.add("a" + c);
            // substitution should replace the letter.
            words.add("" + c);
        }
        // deletion should not yield a string
        //words.add("");
        checkGetCandidateWords(fullCR, "a", words);
    }

    @Test
    public void testGetCandidateWords2() throws IOException {
        Set<String> words = new HashSet<>();
        // test for a two letter word
        for (char c : SpellCorrector.ALPHABET) {
            // insertion before and after
            words.add(c + "up");
            words.add("u" + c + "p");
            words.add("up" + c);
            // substitution should replace the letter.
            words.add(c + "p");
            words.add("u" + c);
        }
        // deletion
        words.add("p");
        words.add("u");
        // transposition
        words.add("pu");
        checkGetCandidateWords(fullCR, "up", words);
    }

    @Test
    public void testGetCandidateWords3() throws IOException {
        Set<String> words = new HashSet<>();
        // test for a three letter word
        for (char c : SpellCorrector.ALPHABET) {
            // insertion before and after
            words.add(c + "ups");
            words.add("u" + c + "ps");
            words.add("up" + c + "s");
            words.add("ups" + c);
            // substitution should replace the letter.
            words.add(c + "ps");
            words.add("u" + c + "s");
            words.add("up" + c);
        }
        // deletion
        words.add("ps");
        words.add("us");
        words.add("up");
        // transposition
        words.add("pus");
        words.add("usp");
        checkGetCandidateWords(fullCR, "ups", words);
    }

    /**
     * Fake CorpusReader which tests whether getCandidateWords can produce all
     * words.
     */
    private class MockCorpusReader extends CorpusReader {

        public MockCorpusReader() throws IOException {
            super();
        }

        @Override
        public boolean inVocabulary(String word) {
            return true;
        }

        @Override
        public HashSet<String> inVocabulary(Set<String> set) {
            return new HashSet<>(set);
        }
    }
}