/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.cluster.routing.allocation.decider;

import org.elasticsearch.Version;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.cluster.ClusterModule;
import org.elasticsearch.cluster.ClusterName;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.ESAllocationTestCase;
import org.elasticsearch.cluster.EmptyClusterInfoService;
import org.elasticsearch.cluster.TestShardRoutingRoleStrategies;
import org.elasticsearch.cluster.metadata.IndexMetadata;
import org.elasticsearch.cluster.metadata.Metadata;
import org.elasticsearch.cluster.node.DiscoveryNodes;
import org.elasticsearch.cluster.routing.RoutingNode;
import org.elasticsearch.cluster.routing.RoutingTable;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.ShardRoutingState;
import org.elasticsearch.cluster.routing.allocation.AllocationService;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.cluster.routing.allocation.allocator.BalancedShardsAllocator;
import org.elasticsearch.common.settings.ClusterSettings;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.plugins.ClusterPlugin;
import org.elasticsearch.snapshots.EmptySnapshotsInfoService;
import org.elasticsearch.test.gateway.TestGatewayAllocator;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import static org.elasticsearch.cluster.routing.RoutingNodesHelper.shardsWithState;
import static org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider.CLUSTER_ROUTING_ALLOCATION_ENABLE_SETTING;
import static org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider.CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING;
import static org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider.INDEX_ROUTING_REBALANCE_ENABLE_SETTING;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThan;

public class EnableAllocationShortCircuitTests extends ESAllocationTestCase {

    private static ClusterState createClusterStateWithAllShardsAssigned() {
        AllocationService allocationService = createAllocationService(Settings.EMPTY);

        final int numberOfNodes = randomIntBetween(1, 5);
        final DiscoveryNodes.Builder discoveryNodesBuilder = DiscoveryNodes.builder();
        for (int i = 0; i < numberOfNodes; i++) {
            discoveryNodesBuilder.add(newNode("node" + i));
        }

        final Metadata.Builder metadataBuilder = Metadata.builder();
        final RoutingTable.Builder routingTableBuilder = RoutingTable.builder(TestShardRoutingRoleStrategies.DEFAULT_ROLE_ONLY);
        for (int i = randomIntBetween(1, 10); i >= 0; i--) {
            final IndexMetadata indexMetadata = IndexMetadata.builder("test" + i)
                .settings(settings(Version.CURRENT))
                .numberOfShards(1)
                .numberOfReplicas(randomIntBetween(0, numberOfNodes - 1))
                .build();
            metadataBuilder.put(indexMetadata, true);
            routingTableBuilder.addAsNew(indexMetadata);
        }

        ClusterState clusterState = ClusterState.builder(ClusterName.DEFAULT)
            .nodes(discoveryNodesBuilder)
            .metadata(metadataBuilder)
            .routingTable(routingTableBuilder.build())
            .build();

        while (clusterState.getRoutingNodes().hasUnassignedShards()
            || shardsWithState(clusterState.getRoutingNodes(), ShardRoutingState.INITIALIZING).isEmpty() == false) {
            clusterState = startInitializingShardsAndReroute(allocationService, clusterState);
        }

        return clusterState;
    }

    public void testRebalancingAttemptedIfPermitted() {
        ClusterState clusterState = createClusterStateWithAllShardsAssigned();

        final RebalanceShortCircuitPlugin plugin = new RebalanceShortCircuitPlugin();
        AllocationService allocationService = createAllocationService(
            Settings.builder()
                .put(
                    CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(),
                    randomFrom(
                        EnableAllocationDecider.Rebalance.ALL,
                        EnableAllocationDecider.Rebalance.PRIMARIES,
                        EnableAllocationDecider.Rebalance.REPLICAS
                    ).name()
                ),
            plugin
        );
        allocationService.reroute(clusterState, "reroute", ActionListener.noop()).routingTable();
        assertThat(plugin.rebalanceAttempts, greaterThan(0));
    }

    public void testRebalancingSkippedIfDisabled() {
        ClusterState clusterState = createClusterStateWithAllShardsAssigned();

        final RebalanceShortCircuitPlugin plugin = new RebalanceShortCircuitPlugin();
        AllocationService allocationService = createAllocationService(
            Settings.builder().put(CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Allocation.NONE.name()),
            plugin
        );
        allocationService.reroute(clusterState, "reroute", ActionListener.noop()).routingTable();
        assertThat(plugin.rebalanceAttempts, equalTo(0));
    }

    public void testRebalancingSkippedIfDisabledIncludingOnSpecificIndices() {
        ClusterState clusterState = createClusterStateWithAllShardsAssigned();
        final IndexMetadata indexMetadata = randomFrom(clusterState.metadata().indices().values().toArray(IndexMetadata[]::new));
        clusterState = ClusterState.builder(clusterState)
            .metadata(
                Metadata.builder(clusterState.metadata())
                    .put(
                        IndexMetadata.builder(indexMetadata)
                            .settings(
                                Settings.builder()
                                    .put(indexMetadata.getSettings())
                                    .put(INDEX_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Rebalance.NONE.name())
                            )
                    )
                    .build()
            )
            .build();

        final RebalanceShortCircuitPlugin plugin = new RebalanceShortCircuitPlugin();
        AllocationService allocationService = createAllocationService(
            Settings.builder().put(CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Rebalance.NONE.name()),
            plugin
        );
        allocationService.reroute(clusterState, "reroute", ActionListener.noop()).routingTable();
        assertThat(plugin.rebalanceAttempts, equalTo(0));
    }

    public void testRebalancingAttemptedIfDisabledButOverridenOnSpecificIndices() {
        ClusterState clusterState = createClusterStateWithAllShardsAssigned();
        final IndexMetadata indexMetadata = randomFrom(clusterState.metadata().indices().values());
        clusterState = ClusterState.builder(clusterState)
            .metadata(
                Metadata.builder(clusterState.metadata())
                    .put(
                        IndexMetadata.builder(indexMetadata)
                            .settings(
                                Settings.builder()
                                    .put(indexMetadata.getSettings())
                                    .put(
                                        INDEX_ROUTING_REBALANCE_ENABLE_SETTING.getKey(),
                                        randomFrom(
                                            EnableAllocationDecider.Rebalance.ALL,
                                            EnableAllocationDecider.Rebalance.PRIMARIES,
                                            EnableAllocationDecider.Rebalance.REPLICAS
                                        ).name()
                                    )
                            )
                    )
                    .build()
            )
            .build();

        final RebalanceShortCircuitPlugin plugin = new RebalanceShortCircuitPlugin();
        AllocationService allocationService = createAllocationService(
            Settings.builder().put(CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Rebalance.NONE.name()),
            plugin
        );
        allocationService.reroute(clusterState, "reroute", ActionListener.noop()).routingTable();
        assertThat(plugin.rebalanceAttempts, greaterThan(0));
    }

    public void testAllocationSkippedIfDisabled() {
        final AllocateShortCircuitPlugin plugin = new AllocateShortCircuitPlugin();
        AllocationService allocationService = createAllocationService(
            Settings.builder().put(CLUSTER_ROUTING_ALLOCATION_ENABLE_SETTING.getKey(), EnableAllocationDecider.Allocation.NONE.name()),
            plugin
        );

        Metadata metadata = Metadata.builder()
            .put(IndexMetadata.builder("test").settings(settings(Version.CURRENT)).numberOfShards(1).numberOfReplicas(0))
            .build();

        RoutingTable routingTable = RoutingTable.builder(TestShardRoutingRoleStrategies.DEFAULT_ROLE_ONLY)
            .addAsNew(metadata.index("test"))
            .build();

        ClusterState clusterState = ClusterState.builder(ClusterName.DEFAULT)
            .metadata(metadata)
            .routingTable(routingTable)
            .nodes(DiscoveryNodes.builder().add(newNode("node1")))
            .build();

        allocationService.reroute(clusterState, "reroute", ActionListener.noop()).routingTable();
        assertThat(plugin.canAllocateAttempts, equalTo(0));
    }

    private static AllocationService createAllocationService(Settings.Builder settingsBuilder, ClusterPlugin plugin) {
        var settings = settingsBuilder.build();
        var clusterSettings = ClusterSettings.createBuiltInClusterSettings(settings);
        List<AllocationDecider> deciders = new ArrayList<>(
            ClusterModule.createAllocationDeciders(settings, clusterSettings, Collections.singletonList(plugin))
        );
        return new MockAllocationService(
            new AllocationDeciders(deciders),
            new TestGatewayAllocator(),
            new BalancedShardsAllocator(clusterSettings),
            EmptyClusterInfoService.INSTANCE,
            EmptySnapshotsInfoService.INSTANCE
        );
    }

    private static class RebalanceShortCircuitPlugin implements ClusterPlugin {
        int rebalanceAttempts;

        @Override
        public Collection<AllocationDecider> createAllocationDeciders(Settings settings, ClusterSettings clusterSettings) {
            return Collections.singletonList(new RebalanceShortCircuitAllocationDecider());
        }

        private class RebalanceShortCircuitAllocationDecider extends AllocationDecider {

            @Override
            public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation allocation) {
                rebalanceAttempts++;
                return super.canRebalance(shardRouting, allocation);
            }

            @Override
            public Decision canRebalance(RoutingAllocation allocation) {
                rebalanceAttempts++;
                return super.canRebalance(allocation);
            }
        }
    }

    private static class AllocateShortCircuitPlugin implements ClusterPlugin {
        int canAllocateAttempts;

        @Override
        public Collection<AllocationDecider> createAllocationDeciders(Settings settings, ClusterSettings clusterSettings) {
            return Collections.singletonList(new AllocateShortCircuitAllocationDecider());
        }

        private class AllocateShortCircuitAllocationDecider extends AllocationDecider {

            @Override
            public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) {
                canAllocateAttempts++;
                return super.canAllocate(shardRouting, node, allocation);
            }

            @Override
            public Decision canAllocate(ShardRouting shardRouting, RoutingAllocation allocation) {
                canAllocateAttempts++;
                return super.canAllocate(shardRouting, allocation);
            }

            @Override
            public Decision canAllocate(IndexMetadata indexMetadata, RoutingNode node, RoutingAllocation allocation) {
                canAllocateAttempts++;
                return super.canAllocate(indexMetadata, node, allocation);
            }
        }
    }
}
