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/* Copyright 2021 Comcast Cable Communications Management, LLC
   Licensed 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.
   SPDX-License-Identifier: Apache-2.0
 */
package com.comcast.dynocon;

import com.comcast.dynocon.sources.EnvironmentVariablesSource;
import com.comcast.dynocon.sources.PollingSystemPropertiesSource;
import com.comcast.dynocon.sources.PollingUrlsPropertiesSource;
import com.comcast.dynocon.sources.SystemPropertiesSource;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public enum SourcesFactory {

    instance;

    public static final String PARAM_SOURCES = "dynocon.sources";
    public static final String SOURCE_ENV = "env";
    public static final String SOURCE_SYS = "sys";
    public static final String SOURCE_POLL_SYS = "poll-sys";
    public static final String SOURCE_POLL_URLS = "poll-urls";

    public static final String DEFAULT_SOURCES = SOURCE_ENV + "," + SOURCE_SYS + "," + SOURCE_POLL_URLS;

    private static final HashMap SOURCES = new HashMap<>();

    public void registerSourceAlias(String alias, PropertiesSource source) {
        if (SOURCES.get(alias) != null) {
            throw new RuntimeException("Source with alias " + alias + " is already registered.");
        }
        SOURCES.put(alias, source);
    }

    public List getSources() {
        List sources = new ArrayList<>();
        String aliases = System.getProperty(PARAM_SOURCES, DEFAULT_SOURCES);
        for (String alias : aliases.split(",")) {
            PropertiesSource source = SOURCES.get(alias);
            if (source == null) {
                switch (alias) {
                    case SOURCE_ENV:
                        registerSourceAlias(SOURCE_ENV, new EnvironmentVariablesSource());
                        break;
                    case SOURCE_SYS:
                        registerSourceAlias(SOURCE_SYS, new SystemPropertiesSource());
                        break;
                    case SOURCE_POLL_URLS:
                        registerSourceAlias(SOURCE_POLL_URLS, new PollingUrlsPropertiesSource());
                        break;
                    case SOURCE_POLL_SYS:
                        registerSourceAlias(SOURCE_POLL_SYS, new PollingSystemPropertiesSource());
                        break;
                }
                source = SOURCES.get(alias);
            }
            if (source != null) {
                sources.add(source);
            }
        }
        return sources;
    }
}