/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.elasticsearch.script;

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import static java.util.Collections.unmodifiableMap;
import static java.util.Collections.unmodifiableSet;

/**
 * Registry for operations that use scripts as part of their execution. Can be standard operations of custom defined ones (via plugin).
 * Allows plugins to register custom operations that they use scripts for,
 * via {@link org.elasticsearch.plugins.ScriptPlugin}
 * Scripts can be enabled/disabled via fine-grained settings for each single registered operation.
 */
public final class ScriptContextRegistry {
    static final Set<String> RESERVED_SCRIPT_CONTEXTS = reservedScriptContexts();

    private final Map<String, ScriptContext> scriptContexts;

    public ScriptContextRegistry(Collection<ScriptContext.Plugin> customScriptContexts) {
        Map<String, ScriptContext> scriptContexts = new HashMap<>();
        for (ScriptContext.Standard scriptContext : ScriptContext.Standard.values()) {
            scriptContexts.put(scriptContext.getKey(), scriptContext);
        }
        for (ScriptContext.Plugin customScriptContext : customScriptContexts) {
            validateScriptContext(customScriptContext);
            ScriptContext previousContext = scriptContexts.put(customScriptContext.getKey(), customScriptContext);
            if (previousContext != null) {
                throw new IllegalArgumentException("script context [" + customScriptContext.getKey() + "] cannot be registered twice");
            }
        }
        this.scriptContexts = unmodifiableMap(scriptContexts);
    }

    /**
     * @return a list that contains all the supported {@link ScriptContext}s, both standard ones and registered via plugins
     */
    Collection<ScriptContext> scriptContexts() {
        return scriptContexts.values();
    }

    /**
     * @return <tt>true</tt> if the provided {@link ScriptContext} is supported, <tt>false</tt> otherwise
     */
    boolean isSupportedContext(ScriptContext scriptContext) {
        return scriptContexts.containsKey(scriptContext.getKey());
    }

    //script contexts can be used in fine-grained settings, we need to be careful with what we allow here
    private void validateScriptContext(ScriptContext.Plugin scriptContext) {
        if (RESERVED_SCRIPT_CONTEXTS.contains(scriptContext.getPluginName())) {
            throw new IllegalArgumentException("[" + scriptContext.getPluginName() + "] is a reserved name, it cannot be registered as a custom script context");
        }
        if (RESERVED_SCRIPT_CONTEXTS.contains(scriptContext.getOperation())) {
            throw new IllegalArgumentException("[" + scriptContext.getOperation() + "] is a reserved name, it cannot be registered as a custom script context");
        }
    }

    private static Set<String> reservedScriptContexts() {
        Set<String> reserved = new HashSet<>(ScriptType.values().length + ScriptContext.Standard.values().length);
        for (ScriptType scriptType : ScriptType.values()) {
            reserved.add(scriptType.toString());
        }
        for (ScriptContext.Standard scriptContext : ScriptContext.Standard.values()) {
            reserved.add(scriptContext.getKey());
        }
        reserved.add("script");
        reserved.add("engine");
        return unmodifiableSet(reserved);
    }
}
