Intuitive DSL for Java

/*
 * This file is part of the Intuitive DSL project.
 * Copyright (c) 2026 DBA Labs - Switzerland. All rights reserved.
 *
 * This program is dual-licensed under a commercial license and the AGPLv3.
 * For commercial licensing, contact us at [email protected] or visit https://www.dbalabs.ch.
 *
 * AGPLv3 licensing:
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, version 3 (19 November 2007).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/agpl-3.0.html>.
 */

package ch.dbalabs.intuitivedsl.parser;

import ch.dbalabs.intuitivedsl.exception.DslSyntaxException;
import ch.dbalabs.intuitivedsl.grammar.GrammarCompiler;
import ch.dbalabs.intuitivedsl.grammar.GroupNode;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.util.List;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;

/**
 * Sentinel tests for syntax diagnostics.
 *
 * These tests focus on the quality of the feedback given to the caller, not just on
 * accept/reject behavior.
 */
class ErrorReportingSentinelTest {

    private GrammarCompiler compiler;
    private Lexer lexer;
    private AstNavigator navigator;

    @BeforeEach
    void setUp() {
        compiler = new GrammarCompiler();
        lexer = new Lexer();
        navigator = new AstNavigator();
    }

    @Test
    void shouldMergeExpectedTokensAcrossAlternativesAtSameFailurePositionWithinSingleGrammar() {
        GroupNode ast = compiler.compile("CREATE { USER username | ROLE role_name } ;");

        assertThatThrownBy(() -> navigator.parse(
                "CREATE GROUP admins ;",
                lexer.tokenize("CREATE GROUP admins ;"),
                ast,
                m -> List.of()
        )).isInstanceOf(DslSyntaxException.class)
                .satisfies(error -> {
                    DslSyntaxException ex = (DslSyntaxException) error;
                    assertThat(ex.getUnexpectedToken()).isNotNull();
                    assertThat(ex.getUnexpectedToken().value()).isEqualTo("GROUP");
                    assertThat(ex.getExpectedPossibilities()).contains("USER", "ROLE");
                });
    }

    @Test
    void shouldReportSyntheticEofTokenWhenInputEndsTooEarly() {
        GroupNode ast = compiler.compile("CREATE USER username ;");
        String input = "CREATE USER";

        assertThatThrownBy(() -> navigator.parse(
                input,
                lexer.tokenize(input),
                ast,
                m -> List.of()
        )).isInstanceOf(DslSyntaxException.class)
                .satisfies(error -> {
                    DslSyntaxException ex = (DslSyntaxException) error;
                    assertThat(ex.getUnexpectedToken()).isNotNull();
                    assertThat(ex.getUnexpectedToken().type()).isEqualTo(TokenType.EOF);
                    assertThat(ex.getUnexpectedToken().value()).isEqualTo("EOF");
                    assertThat(ex.getUnexpectedToken().position()).isEqualTo(input.length());
                    assertThat(ex.getExpectedPossibilities()).contains("<username>");
                });
    }

    @Test
    void shouldExposePreciseUnexpectedTokenPositionAndRichMessage() {
        GroupNode ast = compiler.compile("DEPLOY service_name TO environment ;");
        String input = "DEPLOY billing prod ;";

        assertThatThrownBy(() -> navigator.parse(input, lexer.tokenize(input), ast, m -> List.of()))
                .isInstanceOf(DslSyntaxException.class)
                .satisfies(error -> {
                    DslSyntaxException ex = (DslSyntaxException) error;
                    assertThat(ex.getUnexpectedToken()).isNotNull();
                    assertThat(ex.getUnexpectedToken().value()).isEqualTo("prod");
                    assertThat(ex.getUnexpectedToken().position()).isEqualTo(input.indexOf("prod"));
                    assertThat(ex.getExpectedPossibilities()).contains("TO");
                    assertThat(ex.getRichMessage()).contains("Unexpected token 'prod'");
                    assertThat(ex.getRichMessage()).contains("Expected: { TO }");
                });
    }

    @Test
    void shouldReportMissingGrammarDelimiterWhenTrailingTokensAppearBeforeCommandEnd() {
        GroupNode ast = compiler.compile("PING ;");

        assertThatThrownBy(() -> navigator.parse(
                "PING extra ;",
                lexer.tokenize("PING extra ;"),
                ast,
                m -> List.of()
        )).isInstanceOf(DslSyntaxException.class)
                .satisfies(error -> {
                    DslSyntaxException ex = (DslSyntaxException) error;
                    assertThat(ex.getUnexpectedToken()).isNotNull();
                    assertThat(ex.getUnexpectedToken().value()).isEqualTo("extra");
                    assertThat(ex.getExpectedPossibilities()).contains("';'");
                });
    }
}