/*
 * 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.command;

import org.elasticsearch.ElasticsearchParseException;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.cluster.routing.allocation.RoutingExplanations;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.xcontent.ToXContentFragment;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;

/**
 * A simple {@link AllocationCommand} composite managing several
 * {@link AllocationCommand} implementations
 */
public class AllocationCommands implements ToXContentFragment {
    private final List<AllocationCommand> commands = new ArrayList<>();

    /**
     * Creates a new set of {@link AllocationCommands}
     *
     * @param commands {@link AllocationCommand}s that are wrapped by this instance
     */
    public AllocationCommands(AllocationCommand... commands) {
        if (commands != null) {
            this.commands.addAll(Arrays.asList(commands));
        }
    }

    /**
     * Adds a set of commands to this collection
     * @param commands Array of commands to add to this instance
     * @return {@link AllocationCommands} with the given commands added
     */
    public AllocationCommands add(AllocationCommand... commands) {
        if (commands != null) {
            this.commands.addAll(Arrays.asList(commands));
        }
        return this;
    }

    /**
     * Get the commands wrapped by this instance
     * @return {@link List} of commands
     */
    public List<AllocationCommand> commands() {
        return this.commands;
    }

    /**
     * Executes all wrapped commands on a given {@link RoutingAllocation}
     * @param allocation {@link RoutingAllocation} to apply this command to
     * @throws org.elasticsearch.ElasticsearchException if something happens during execution
     */
    public RoutingExplanations execute(RoutingAllocation allocation, boolean explain) {
        RoutingExplanations explanations = new RoutingExplanations();
        for (AllocationCommand command : commands) {
            explanations.add(command.execute(allocation, explain));
        }
        return explanations;
    }

    /**
     * Reads a {@link AllocationCommands} from a {@link StreamInput}
     * @param in {@link StreamInput} to read from
     * @return {@link AllocationCommands} read
     *
     * @throws IOException if something happens during read
     */
    public static AllocationCommands readFrom(StreamInput in) throws IOException {
        AllocationCommands commands = new AllocationCommands();
        int size = in.readVInt();
        for (int i = 0; i < size; i++) {
            commands.add(in.readNamedWriteable(AllocationCommand.class));
        }
        return commands;
    }

    /**
     * Writes {@link AllocationCommands} to a {@link StreamOutput}
     *
     * @param commands Commands to write
     * @param out {@link StreamOutput} to write the commands to
     * @throws IOException if something happens during write
     */
    public static void writeTo(AllocationCommands commands, StreamOutput out) throws IOException {
        out.writeNamedWriteableList(commands.commands);
    }

    /**
     * Reads {@link AllocationCommands} from a {@link XContentParser}
     * <pre>
     *     {
     *         "commands" : [
     *              {"allocate" : {"index" : "test", "shard" : 0, "node" : "test"}}
     *         ]
     *     }
     * </pre>
     * @param parser {@link XContentParser} to read the commands from
     * @return {@link AllocationCommands} read
     * @throws IOException if something bad happens while reading the stream
     */
    public static AllocationCommands fromXContent(XContentParser parser) throws IOException {
        AllocationCommands commands = new AllocationCommands();

        XContentParser.Token token = parser.currentToken();
        if (token == null) {
            throw new ElasticsearchParseException("No commands");
        }
        if (token == XContentParser.Token.FIELD_NAME) {
            if (parser.currentName().equals("commands") == false) {
                throw new ElasticsearchParseException("expected field name to be named [commands], got [{}] instead", parser.currentName());
            }
            token = parser.nextToken();
            if (token != XContentParser.Token.START_ARRAY) {
                throw new ElasticsearchParseException("commands should follow with an array element");
            }
        } else if (token == XContentParser.Token.START_ARRAY) {
            // ok...
        } else {
            throw new ElasticsearchParseException("expected either field name [commands], or start array, got [{}] instead", token);
        }
        while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
            if (token == XContentParser.Token.START_OBJECT) {
                // move to the command name
                token = parser.nextToken();
                String commandName = parser.currentName();
                token = parser.nextToken();
                commands.add(parser.namedObject(AllocationCommand.class, commandName, null));
                // move to the end object one
                if (parser.nextToken() != XContentParser.Token.END_OBJECT) {
                    throw new ElasticsearchParseException(
                        "allocation command is malformed, done parsing a command," + " but didn't get END_OBJECT, got [{}] instead",
                        token
                    );
                }
            } else {
                throw new ElasticsearchParseException("allocation command is malformed, got [{}] instead", token);
            }
        }
        return commands;
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startArray("commands");
        for (AllocationCommand command : commands) {
            builder.startObject();
            builder.field(command.name(), command);
            builder.endObject();
        }
        builder.endArray();
        return builder;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        AllocationCommands other = (AllocationCommands) obj;
        // Override equals and hashCode for testing
        return Objects.equals(commands, other.commands);
    }

    @Override
    public int hashCode() {
        // Override equals and hashCode for testing
        return Objects.hashCode(commands);
    }

    @Override
    public String toString() {
        return Strings.toString(this, true, true);
    }
}
