package org.shedlang.compiler.parser;

import org.junit.jupiter.api.Test;
import org.shedlang.compiler.tokeniser.UnexpectedTokenException;

import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.shedlang.compiler.ast.untyped.UntypedNodeMatchers.*;
import static org.shedlang.compiler.parser.ParserTesting.parseString;
import static org.zwobble.precisely.AssertThat.assertThat;
import static org.zwobble.precisely.Matchers.*;

public class ParserFunctionExpressionTests {
    @Test
    public void canParseMinimalFunction() {
        var source = """
            fn () -> Unit {
            }""";

        var node = parseString(source, Parser::parseTopLevelExpression);

        assertThat(
            node,
            isUntypedFunctionExpressionNode()
                .withSignature(
                    isUntypedFunctionSignatureNode()
                        .withParams(isUntypedParamsNode(isSequence(), isSequence()))
                        .withEffect(isOptionalEmpty())
                        .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
                )
                .withBody(isUntypedBlockNode(isSequence()))
        );
    }

    @Test
    public void canParseFunctionWithBodyWithoutReturn() {
        var source = """
            fn () -> Unit {
                a;
                b;
                c;
            }""";

        var node = parseString(source, Parser::parseTopLevelExpression);

        assertThat(
            node,
            isUntypedFunctionExpressionNode()
                .withBody(isUntypedBlockNode(isSequence(
                    isUntypedExpressionStatementNode(isUntypedReferenceNode("a")),
                    isUntypedExpressionStatementNode(isUntypedReferenceNode("b")),
                    isUntypedExpressionStatementNode(isUntypedReferenceNode("c"))
                )))
        );
    }

    @Test
    public void canParseFunctionWithBodyWithBlockReturn() {
        var source = """
            fn () -> Unit {
                a;
                b;
                c
            }""";

        var node = parseString(source, Parser::parseTopLevelExpression);

        assertThat(
            node,
            isUntypedFunctionExpressionNode()
                .withBody(isUntypedBlockNode(isSequence(
                    isUntypedExpressionStatementNode(isUntypedReferenceNode("a")),
                    isUntypedExpressionStatementNode(isUntypedReferenceNode("b")),
                    isUntypedBlockReturnNode(isUntypedReferenceNode("c"))
                )))
        );
    }

    @Test
    public void blockReturnEndsFunction() {
        var source = """
            fn () -> Unit {
                a;
                b
                c
            }""";

        var error = assertThrows(
            UnexpectedTokenException.class,
            () -> parseString(source, Parser::parseTopLevelExpression)
        );

        assertThat(error.getActual().value().toString(), equalTo("c"));
        assertThat(error.getExpected(), equalTo(TokenType.SYMBOL_BRACE_CLOSE.toString()));
    }
}