package sexpression;

import static error.ErrorManager.Severity.ERROR;
import static org.junit.Assert.*;
import static sexpression.Nil.NIL;

import java.math.BigInteger;

import org.junit.*;

import function.UserDefinedFunction;
import sexpression.LispNumber.InvalidNumberException;

public class SExpressionTester {

    private void assertSExpressionMatchesString(String expected, SExpression sExpression) {
        assertEquals(expected, sExpression.toString());
    }

    @Before
    public void setUp() throws Exception {}

    @Test
    public void nilToString() {
        String input = "NIL";

        assertSExpressionMatchesString(input, NIL);
    }

    @Test
    public void numberToString() {
        String input = "12";

        assertSExpressionMatchesString(input, new LispNumber(input));
    }

    @Test
    public void numberValueToString() {
        String expected = "12";

        assertSExpressionMatchesString(expected, new LispNumber("12"));
    }

    @Test
    public void stringToString() {
        String input = "\"hi\"";

        assertSExpressionMatchesString(input, new LispString(input));
    }

    @Test
    public void symbolToString() {
        String input = "symbol";

        assertSExpressionMatchesString(input.toUpperCase(), new Symbol(input));
    }

    @Test
    public void simpleConsToString() {
        String expected = "(1)";
        Cons cons = new Cons(new LispNumber("1"), NIL);

        assertSExpressionMatchesString(expected, cons);
    }

    @Test
    public void complexConsToString() {
        String expected = "(1 A \"string\")";
        Cons list = new Cons(new LispNumber("1"),
                             new Cons(new Symbol("a"), new Cons(new LispString("\"string\""), NIL)));

        assertSExpressionMatchesString(expected, list);
    }

    @Test
    public void improperListToString() {
        String expected = "(A . B)";
        Cons list = new Cons(new Symbol("A"), new Symbol("B"));

        assertSExpressionMatchesString(expected, list);
    }

    @Test
    public void lambdaExpressionToString() {
        String expected = "(LAMBDA)";
        LambdaExpression lambda = new LambdaExpression(new Cons(new Symbol("lambda"), NIL), null);

        assertSExpressionMatchesString(expected, lambda);
    }

    @Test
    public void lambdaExpressionGetLambdaExpression() {
        String expected = "(LAMBDA)";
        LambdaExpression lambda = new LambdaExpression(new Cons(new Symbol("lambda"), NIL), null);

        assertSExpressionMatchesString(expected, lambda.getLambdaExpression());
    }

    @Test
    public void lambdaExpressionGetFunction() {
        String expected = "(LAMBDA)";
        UserDefinedFunction function = new UserDefinedFunction(expected, NIL, NIL);
        LambdaExpression lambda = new LambdaExpression(new Cons(new Symbol("lambda"), NIL), function);

        assertEquals(function, lambda.getFunction());
    }

    @Test
    public void firstOfNilIsNil() {
        assertEquals(NIL, NIL.getFirst());
    }

    @Test
    public void restOfNilIsNil() {
        assertEquals(NIL, NIL.getRest());
    }

    @Test
    public void afterSettingFirstOfNil_ShouldStillBeNil() {
        Cons nil = NIL;
        nil.setFirst(new LispNumber("2"));

        assertEquals(NIL, nil.getFirst());
    }

    @Test
    public void afterSettingRestOfNil_ShouldStillBeNil() {
        Cons nil = NIL;
        nil.setRest(new LispNumber("2"));

        assertEquals(NIL, nil.getRest());
    }

    @Test
    public void numberValue() {
        BigInteger value = new BigInteger("12");
        LispNumber number = new LispNumber(value.toString());

        assertEquals(value, number.getValue());
    }

    @Test(expected = InvalidNumberException.class)
    public void invalidNumberText_ThrowsException() {
        new LispNumber("a");
    }

    @Test
    public void invalidNumberException_HasCorrectSeverity() {
        try {
            new LispNumber("a");
        } catch (InvalidNumberException e) {
            assertEquals(ERROR, e.getSeverity());
        }
    }

    @Test
    public void invalidNumberException_HasMessageText() {
        try {
            new LispNumber("a");
        } catch (InvalidNumberException e) {
            String message = e.getMessage();

            assertNotNull(message);
            assertTrue(message.length() > 0);
        }
    }

    @Test
    public void lispNumberConstants() {
        assertEquals(BigInteger.ZERO, LispNumber.ZERO.getValue());
        assertEquals(BigInteger.ONE, LispNumber.ONE.getValue());
    }

}