package function.builtin.special;

import static org.junit.Assert.fail;
import static testutil.TestUtilities.assertSExpressionsMatch;
import static testutil.TestUtilities.evaluateString;
import static testutil.TestUtilities.parseString;

import org.junit.Test;

import function.ArgumentValidator.BadArgumentTypeException;
import function.ArgumentValidator.TooManyArgumentsException;
import function.builtin.special.RECUR.NestedRecurException;
import function.builtin.special.RECUR.RecurNotInTailPositionException;
import function.builtin.special.RECUR.RecurOutsideOfFunctionException;
import sexpression.SExpression;
import testutil.SymbolAndFunctionCleaner;

public class RECURTest extends SymbolAndFunctionCleaner {

    @Test(expected = RecurOutsideOfFunctionException.class)
    public void recurOutsideOfFunction_ThrowsException() {
        evaluateString("(recur)");
    }

    @Test(expected = RecurOutsideOfFunctionException.class)
    public void recurOutsideOfFunction_AfterFunctionCall_ThrowsException() {
        evaluateString("(defun f (n) (if (= n  0) 'ZERO n))");
        evaluateString("(f 2)");
        evaluateString("(recur)");
    }

    @Test(expected = BadArgumentTypeException.class)
    public void recurInSpecialFunction_DoesNotEvaluateArguments() {
        evaluateString("(define-special tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");
        evaluateString("(tail-recursive 900)");
    }

    @Test(expected = BadArgumentTypeException.class)
    public void recurInMacro_DoesNotEvaluateArguments() {
        evaluateString("(defmacro tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");
        evaluateString("(tail-recursive 900)");
    }

    @Test(expected = NestedRecurException.class)
    public void nestedRecur_ThrowsException() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (recur (- n 1)))))");
        evaluateString("(tail-recursive 900)");
    }

    @Test(expected = TooManyArgumentsException.class)
    public void functionCallValidatesRecurArguments() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1) 23)))");
        evaluateString("(tail-recursive 900)");
    }

    @Test(expected = RecurNotInTailPositionException.class)
    public void recurInNonTailPositionInArgumentList() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (list (recur (- n 1)))))");
        evaluateString("(tail-recursive 900)");
    }

    @Test(expected = RecurNotInTailPositionException.class)
    public void recurInNonTailPositionInBegin() {
        evaluateString("(defun tail-recursive (n) (begin (recur) 2))");
        evaluateString("(tail-recursive 900)");
    }

    @Test
    public void recurCallsCurrentFunction() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurCallsCurrentFunction_InBegin() {
        evaluateString("(defun tail-recursive (n) (if (> n 1) (begin 1 2 (recur (- n 1))) 'PASS))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurInTailPositionWithApply() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (apply 'recur (list (- n 1)))))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurInTailPositionWithFuncall() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (call 'recur (- n 1))))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurCallsCurrentFunction_WithApply() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(apply 'tail-recursive '(900))"));
    }

    @Test
    public void recurCallsCurrentFunction_WithFuncall() {
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(call 'tail-recursive '900)"));
    }

    @Test
    public void recurWorksAfterFailure() {
        evaluateString("(defun bad-tail-recursive (n) (if (= n  0) 'PASS (list (recur (- n 1)))))");
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");

        try {
            evaluateString("(bad-tail-recursive 900)");
            fail("expectedException");
        } catch (RecurNotInTailPositionException e) {}

        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurWorksAfterFailure2() {
        evaluateString("(defun bad-tail-recursive (n) (begin (recur) 2))");
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");

        try {
            evaluateString("(bad-tail-recursive 900)");
            fail("expectedException");
        } catch (RecurNotInTailPositionException e) {}

        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurWorksAfterNestedFailure() {
        evaluateString("(defun bad-tail-recursive (n) (if (= n  0) 'PASS (recur (recur (- n 1)))))");
        evaluateString("(defun tail-recursive (n) (if (= n  0) 'PASS (recur (- n 1))))");

        try {
            evaluateString("(bad-tail-recursive 900)");
            fail("expectedException");
        } catch (NestedRecurException e) {}

        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive 900)"));
    }

    @Test
    public void recurWithNoArgs_AltersGlobalVariable() {
        evaluateString("(defun tail-recursive () (if (= n  0) 'PASS (begin (setq n (- n 1)) (recur))))");
        evaluateString("(setq n 200)");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(tail-recursive)"));
    }

    @Test
    public void recurWithLambda() {
        SExpression lambdaTailCall = evaluateString("((lambda (n) (if (= n  0) 'PASS (recur (- n 1)))) 2020)");
        assertSExpressionsMatch(parseString("PASS"), lambdaTailCall);
    }

    @Test
    public void recurWithNestedLambda() {
        evaluateString("(defun nested-tail () ((lambda (n) (if (= n  0) 'PASS (recur (- n 1)))) 2020))");
        assertSExpressionsMatch(parseString("PASS"), evaluateString("(nested-tail)"));
    }

}