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/* @test
 * @summary Basic tests for StableMap methods
 * @modules java.base/jdk.internal.lang.stable
 * @enablePreview
 * @run junit StableMapTest
 */

import jdk.internal.lang.stable.StableUtil;
import jdk.internal.lang.stable.StableValueImpl;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;

import java.io.Serializable;
import java.util.AbstractMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.Set;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static org.junit.jupiter.api.Assertions.*;

final class StableMapTest {

    private static final int NOT_PRESENT = 147;
    private static final int KEY = 7;
    private static final Set<Integer> KEYS = Set.of(0, KEY, 13);
    private static final Set<Integer> EMPTY = Set.of();
    private static final Function<Integer, Integer> IDENTITY = Function.identity();

    @Test
    void factoryInvariants() {
        assertThrows(NullPointerException.class, () -> StableValue.map(KEYS, null));
        assertThrows(NullPointerException.class, () -> StableValue.map(null, IDENTITY));
    }

    @Test
    void isEmpty() {
        assertFalse(newMap().isEmpty());
        assertTrue(newEmptyMap().isEmpty());
    }

    @Test
    void size() {
        assertEquals(KEYS.size(), newMap().size());
        assertEquals(EMPTY.size(), newEmptyMap().size());
    }

    @Test
    void get() {
        StableTestUtil.CountingFunction<Integer, Integer> cf = new StableTestUtil.CountingFunction<>(IDENTITY);
        var lazy = StableValue.map(KEYS, cf);
        int cnt = 1;
        for (int i : KEYS) {
            assertEquals(i, lazy.get(i));
            assertEquals(cnt, cf.cnt());
            assertEquals(i, lazy.get(i));
            assertEquals(cnt++, cf.cnt());
        }
        assertNull(lazy.get(NOT_PRESENT));
    }

    @Test
    void getException() {
        StableTestUtil.CountingFunction<Integer, Integer> cf = new StableTestUtil.CountingFunction<>(_ -> {
            throw new UnsupportedOperationException();
        });
        var lazy = StableValue.map(KEYS, cf);
        assertThrows(UnsupportedOperationException.class, () -> lazy.get(KEY));
        assertEquals(1, cf.cnt());
        assertThrows(UnsupportedOperationException.class, () -> lazy.get(KEY));
        assertEquals(2, cf.cnt());
    }

    @Test
    void containsKey() {
        var lazy = newMap();
        for (int i : KEYS) {
            assertTrue(lazy.containsKey(i));
        }
        assertFalse(lazy.containsKey(NOT_PRESENT));
    }

    @Test
    void containsValue() {
        var lazy = newMap();
        for (int i : KEYS) {
            assertTrue(lazy.containsValue(i));
        }
        assertFalse(lazy.containsValue(NOT_PRESENT));
    }

    @Test
    void forEach() {
        var lazy = newMap();
        Set<Map.Entry<Integer, Integer>> expected = KEYS.stream()
                .map(i -> new AbstractMap.SimpleImmutableEntry<>(i , i))
                .collect(Collectors.toSet());
        Set<Map.Entry<Integer, Integer>> actual = new HashSet<>();
        lazy.forEach((k, v) -> actual.add(new AbstractMap.SimpleImmutableEntry<>(k , v)));
        assertEquals(expected, actual);
    }

    @Test
    void toStringTest() {
        assertEquals("{}", newEmptyMap().toString());
        var map = StableValue.map(Set.of(KEY), IDENTITY);
        assertEquals("{" + KEY + "=.unset}", map.toString());
        map.get(KEY);
        assertEquals("{" + KEY + "=" + KEY + "}", map.toString());
        String actual = newMap().toString();
        assertTrue(actual.startsWith("{"));
        for (int key : KEYS) {
            assertTrue(actual.contains(key + "=.unset"));
        }
        assertTrue(actual.endsWith("}"));
    }

    @Test
    void hashCodeTest() {
        assertEquals(Map.of().hashCode(), newEmptyMap().hashCode());
        assertEquals(newRegularMap().hashCode(), newMap().hashCode());
    }

    @Test
    void equalsTest() {
        assertTrue(newEmptyMap().equals(Map.of()));
        assertTrue(Map.of().equals(newEmptyMap()));
        assertTrue(newMap().equals(newRegularMap()));
        assertTrue(newRegularMap().equals(newMap()));
        assertFalse(newMap().equals("A"));
    }

    @Test
    void entrySet() {
        var regular = newRegularMap().entrySet();
        var actual = newMap().entrySet();
        assertTrue(regular.equals(actual));
        assertTrue(actual.equals(regular));
        assertTrue(regular.equals(actual));
    }

    @Test
    void entrySetToString() {
        var map = newMap();
        var entrySet = map.entrySet();
        var toString = entrySet.toString();
        for (var key : KEYS) {
            assertTrue(toString.contains(key + "=.unset"));
        }
        assertTrue(toString.startsWith("["));
        assertTrue(toString.endsWith("]"));

        map.get(KEY);
        for (var key : KEYS) {
            if (key.equals(KEY)) {
                continue;
            }
            assertTrue(entrySet.toString().contains(key + "=.unset"));
        }
        assertTrue(entrySet.toString().contains(KEY + "=" + KEY));
    }

    @Test
    void values() {
        var map = newMap();
        var values = map.values();
        // Look at one of the elements
        var val = values.stream().iterator().next();
        var toString = map.toString();
        for (var key : KEYS) {
            if (key.equals(val)) {
                assertTrue(toString.contains(key + "=" + key));
            } else {
                assertTrue(toString.contains(key + "=.unset"));
            }
        }

        // Mod ops
        assertThrows(UnsupportedOperationException.class, () -> values.remove(KEY));
        assertThrows(UnsupportedOperationException.class, () -> values.add(KEY));
        assertThrows(UnsupportedOperationException.class, values::clear);
        assertThrows(UnsupportedOperationException.class, () -> values.addAll(Set.of(1)));
        assertThrows(UnsupportedOperationException.class, () -> values.removeIf(i -> true));
        assertThrows(UnsupportedOperationException.class, () -> values.retainAll(Set.of(KEY)));
    }

    @Test
    void valuesToString() {
        var map = newMap();
        var values = map.values();
        assertEquals("[.unset, .unset, .unset]", values.toString());
        map.get(KEY);
        var afterGet = values.toString();
        assertTrue(afterGet.contains(Integer.toString(KEY)), afterGet);
    }

    @Test
    void iteratorNext() {
        Set<Integer> encountered = new HashSet<>();
        var iterator = newMap().entrySet().iterator();
        while (iterator.hasNext()) {
            var entry = iterator.next();
            assertEquals(entry.getKey(), entry.getValue());
            encountered.add(entry.getValue());
        }
        assertEquals(KEYS, encountered);
    }

    @Test
    void iteratorForEachRemaining() {
        Set<Integer> encountered = new HashSet<>();
        var iterator = newMap().entrySet().iterator();
        var entry = iterator.next();
        assertEquals(entry.getKey(), entry.getValue());
        encountered.add(entry.getValue());
        iterator.forEachRemaining(e -> {
            assertEquals(e.getKey(), e.getValue());
            encountered.add(e.getValue());
        });
        assertEquals(KEYS, encountered);
    }

    @Test
    void stableEntry() {
        var map = newMap();
        var entry = map.entrySet().stream()
                .filter(e -> e.getKey().equals(KEY))
                .findAny()
                .orElseThrow();

        assertEquals(KEY + "=.unset", entry.toString());
        var otherDifferent = Map.entry(-1, -1);
        assertNotEquals(entry, otherDifferent);
        assertEquals(KEY + "=.unset", entry.toString());
        var otherEqual = Map.entry(KEY, KEY);
        assertEquals(entry, otherEqual);
        assertEquals(KEY + "=" + KEY, entry.toString());
        assertEquals(entry.hashCode(), otherEqual.hashCode());
    }

    @Test
    void stableForEachEntry() {
        var map = newMap();
        // Only touch the key.
        map.entrySet().iterator().forEachRemaining(Map.Entry::getKey);
        map.entrySet().iterator()
                .forEachRemaining(e -> assertTrue(e.toString().contains(".unset")));
        // Only touch the value.
        map.entrySet().iterator().forEachRemaining(Map.Entry::getValue);
        map.entrySet().iterator()
                .forEachRemaining(e -> assertFalse(e.toString().contains(".unset")));
    }

    // Immutability
    @ParameterizedTest
    @MethodSource("unsupportedOperations")
    void unsupported(Operation operation) {
        assertThrowsForOperation(UnsupportedOperationException.class, operation);
    }

    // Method parameter invariant checking

    @ParameterizedTest
    @MethodSource("nullAverseOperations")
    void nullAverse(Operation operation) {
        assertThrowsForOperation(NullPointerException.class, operation);
    }

    static <T extends Throwable> void assertThrowsForOperation(Class<T> expectedType, Operation operation) {
        var lazy = newMap();
        assertThrows(expectedType, () -> operation.accept(lazy));
    }

    // Implementing interfaces

    @Test
    void serializable() {
        serializable(newMap());
        serializable(newEmptyMap());
    }

    void serializable(Map<Integer, Integer> map) {
        assertFalse(map instanceof Serializable);
        assertFalse(map.entrySet() instanceof Serializable);
        assertFalse(map.keySet() instanceof Serializable);
        assertFalse(map.values() instanceof Serializable);
    }

    @Test
    void distinct() {
        Map<Integer, StableValueImpl<Integer>> map = StableUtil.map(Set.of(1, 2, 3));
        assertEquals(3, map.size());
        // Check, every StableValue is distinct
        Map<StableValue<Integer>, Boolean> idMap = new IdentityHashMap<>();
        map.forEach((k, v) -> idMap.put(v, true));
        assertEquals(3, idMap.size());
    }

    @Test
    void nullResult() {
        var map = StableValue.map(Set.of(0), _ -> null);
        assertNull(map.getOrDefault(0, 1));;
        assertTrue(map.containsKey(0));
        assertNull(map.get(0));
    }

    @Test
    void nullKeys() {
        Set<Integer> inputs = new HashSet<>();
        inputs.add(0);
        inputs.add(null);
        assertThrows(NullPointerException.class, () -> StableValue.map(inputs, IDENTITY));
    }

    // Support constructs

    record Operation(String name,
                     Consumer<Map<Integer, Integer>> consumer) implements Consumer<Map<Integer, Integer>> {
        @java.lang.Override
        public void accept(Map<Integer, Integer> map) { consumer.accept(map); }
        @java.lang.Override
        public String toString() { return name; }
    }

    static Stream<Operation> nullAverseOperations() {
        return Stream.of(
            new Operation("forEach",     m -> m.forEach(null))
        );
    }

    static Stream<Operation> unsupportedOperations() {
        return Stream.of(
            new Operation("clear",             Map::clear),
            new Operation("compute",           m -> m.compute(KEY, (_, _) -> 1)),
            new Operation("computeIfAbsent",   m -> m.computeIfAbsent(KEY, _ -> 1)),
            new Operation("computeIfPresent",  m -> m.computeIfPresent(KEY, (_, _) -> 1)),
            new Operation("merge",             m -> m.merge(KEY, KEY, (a, _) -> a)),
            new Operation("put",               m -> m.put(0, 0)),
            new Operation("putAll",            m -> m.putAll(Map.of())),
            new Operation("remove1",           m -> m.remove(KEY)),
            new Operation("remove2",           m -> m.remove(KEY, KEY)),
            new Operation("replace2",          m -> m.replace(KEY, 1)),
            new Operation("replace3",          m -> m.replace(KEY, KEY, 1)),
            new Operation("replaceAll",        m -> m.replaceAll((a, _) -> a))
        );
    }

    static Map<Integer, Integer> newMap() {
        return StableValue.map(KEYS, IDENTITY);
    }

    static Map<Integer, Integer> newEmptyMap() {
        return StableValue.map(EMPTY, IDENTITY);
    }

    static Map<Integer, Integer> newRegularMap() {
        return KEYS.stream().collect(Collectors.toMap(IDENTITY, IDENTITY));
    }

}