/*
 * Copyright 2012-2020 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.boot.jdbc;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;
import java.util.function.Function;

import javax.sql.DataSource;

import org.springframework.beans.BeanUtils;
import org.springframework.boot.context.properties.bind.Bindable;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
import org.springframework.boot.context.properties.source.ConfigurationPropertyNameAliases;
import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;
import org.springframework.util.ClassUtils;

Convenience class for building a DataSource with common implementations and properties. If HikariCP, Tomcat, Commons DBCP or Oracle UCP are on the classpath one of them will be selected (in that order with Hikari first). In the interest of a uniform interface, and so that there can be a fallback to an embedded database if one can be detected on the classpath, only a small set of common configuration properties are supported. To inject additional properties into the result you can downcast it, or use @ConfigurationProperties. 
Author:
Dave Syer, Madhura Bhave, Fabio Grassi
Type parameters:
<T> – type of DataSource produced by the builder
Since:
2.0.0/**
 * Convenience class for building a {@link DataSource} with common implementations and
 * properties. If HikariCP, Tomcat, Commons DBCP or Oracle UCP are on the classpath one of
 * them will be selected (in that order with Hikari first). In the interest of a uniform
 * interface, and so that there can be a fallback to an embedded database if one can be
 * detected on the classpath, only a small set of common configuration properties are
 * supported. To inject additional properties into the result you can downcast it, or use
 * {@code @ConfigurationProperties}.
 *
 * @param <T> type of DataSource produced by the builder
 * @author Dave Syer
 * @author Madhura Bhave
 * @author Fabio Grassi
 * @since 2.0.0
 */
public final class DataSourceBuilder<T extends DataSource> {

	private Class<? extends DataSource> type;

	private final DataSourceSettingsResolver settingsResolver;

	private final Map<String, String> properties = new HashMap<>();

	public static DataSourceBuilder<?> create() {
		return new DataSourceBuilder<>(null);
	}

	public static DataSourceBuilder<?> create(ClassLoader classLoader) {
		return new DataSourceBuilder<>(classLoader);
	}

	private DataSourceBuilder(ClassLoader classLoader) {
		this.settingsResolver = new DataSourceSettingsResolver(classLoader);
	}

	@SuppressWarnings("unchecked")
	public T build() {
		Class<? extends DataSource> type = getType();
		DataSource result = BeanUtils.instantiateClass(type);
		maybeGetDriverClassName();
		bind(result);
		return (T) result;
	}

	private void maybeGetDriverClassName() {
		if (!this.properties.containsKey("driverClassName") && this.properties.containsKey("url")) {
			String url = this.properties.get("url");
			String driverClass = DatabaseDriver.fromJdbcUrl(url).getDriverClassName();
			this.properties.put("driverClassName", driverClass);
		}
	}

	private void bind(DataSource result) {
		ConfigurationPropertySource source = new MapConfigurationPropertySource(this.properties);
		ConfigurationPropertyNameAliases aliases = new ConfigurationPropertyNameAliases();
		this.settingsResolver.registerAliases(result, aliases);
		Binder binder = new Binder(source.withAliases(aliases));
		binder.bind(ConfigurationPropertyName.EMPTY, Bindable.ofInstance(result));
	}

	@SuppressWarnings("unchecked")
	public <D extends DataSource> DataSourceBuilder<D> type(Class<D> type) {
		this.type = type;
		return (DataSourceBuilder<D>) this;
	}

	public DataSourceBuilder<T> url(String url) {
		this.properties.put("url", url);
		return this;
	}

	public DataSourceBuilder<T> driverClassName(String driverClassName) {
		this.properties.put("driverClassName", driverClassName);
		return this;
	}

	public DataSourceBuilder<T> username(String username) {
		this.properties.put("username", username);
		return this;
	}

	public DataSourceBuilder<T> password(String password) {
		this.properties.put("password", password);
		return this;
	}

	public static Class<? extends DataSource> findType(ClassLoader classLoader) {
		DataSourceSettings preferredDataSourceSettings = new DataSourceSettingsResolver(classLoader)
				.getPreferredDataSourceSettings();
		return (preferredDataSourceSettings != null) ? preferredDataSourceSettings.getType() : null;
	}

	private Class<? extends DataSource> getType() {
		if (this.type != null) {
			return this.type;
		}
		DataSourceSettings preferredDataSourceSettings = this.settingsResolver.getPreferredDataSourceSettings();
		if (preferredDataSourceSettings != null) {
			return preferredDataSourceSettings.getType();
		}
		throw new IllegalStateException("No supported DataSource type found");
	}

	private static class DataSourceSettings {

		private final Class<? extends DataSource> type;

		private final Consumer<ConfigurationPropertyNameAliases> aliasesCustomizer;

		DataSourceSettings(Class<? extends DataSource> type,
				Consumer<ConfigurationPropertyNameAliases> aliasesCustomizer) {
			this.type = type;
			this.aliasesCustomizer = aliasesCustomizer;
		}

		DataSourceSettings(Class<? extends DataSource> type) {
			this(type, (aliases) -> {
			});
		}

		Class<? extends DataSource> getType() {
			return this.type;
		}

		void registerAliases(DataSource candidate, ConfigurationPropertyNameAliases aliases) {
			if (this.type != null && this.type.isInstance(candidate)) {
				this.aliasesCustomizer.accept(aliases);
			}
		}

	}

	private static class OracleDataSourceSettings extends DataSourceSettings {

		OracleDataSourceSettings(Class<? extends DataSource> type) {
			super(type, (aliases) -> aliases.addAliases("username", "user"));
		}

		@Override
		public Class<? extends DataSource> getType() {
			return null; // Base interface
		}

	}

	private static class DataSourceSettingsResolver {

		private final DataSourceSettings preferredDataSourceSettings;

		private final List<DataSourceSettings> allDataSourceSettings;

		DataSourceSettingsResolver(ClassLoader classLoader) {
			List<DataSourceSettings> supportedProviders = resolveAvailableDataSourceSettings(classLoader);
			this.preferredDataSourceSettings = (!supportedProviders.isEmpty()) ? supportedProviders.get(0) : null;
			this.allDataSourceSettings = new ArrayList<>(supportedProviders);
			addIfAvailable(this.allDataSourceSettings,
					create(classLoader, "org.springframework.jdbc.datasource.SimpleDriverDataSource",
							(type) -> new DataSourceSettings(type,
									(aliases) -> aliases.addAliases("driver-class-name", "driver-class"))));
			addIfAvailable(this.allDataSourceSettings,
					create(classLoader, "oracle.jdbc.datasource.OracleDataSource", OracleDataSourceSettings::new));
		}

		private static List<DataSourceSettings> resolveAvailableDataSourceSettings(ClassLoader classLoader) {
			List<DataSourceSettings> providers = new ArrayList<>();
			addIfAvailable(providers, create(classLoader, "com.zaxxer.hikari.HikariDataSource",
					(type) -> new DataSourceSettings(type, (aliases) -> aliases.addAliases("url", "jdbc-url"))));
			addIfAvailable(providers,
					create(classLoader, "org.apache.tomcat.jdbc.pool.DataSource", DataSourceSettings::new));
			addIfAvailable(providers,
					create(classLoader, "org.apache.commons.dbcp2.BasicDataSource", DataSourceSettings::new));
			addIfAvailable(providers, create(classLoader, "oracle.ucp.jdbc.PoolDataSourceImpl", (type) -> {
				// Unfortunately Oracle UCP has an import on the Oracle driver itself
				if (ClassUtils.isPresent("oracle.jdbc.OracleConnection", classLoader)) {
					return new DataSourceSettings(type, (aliases) -> {
						aliases.addAliases("username", "user");
						aliases.addAliases("driver-class-name", "connection-factory-class-name");
					});
				}
				return null;
			}));
			return providers;
		}

		@SuppressWarnings("unchecked")
		private static DataSourceSettings create(ClassLoader classLoader, String target,
				Function<Class<? extends DataSource>, DataSourceSettings> factory) {
			if (ClassUtils.isPresent(target, classLoader)) {
				try {
					Class<? extends DataSource> type = (Class<? extends DataSource>) ClassUtils.forName(target,
							classLoader);
					return factory.apply(type);
				}
				catch (Exception ex) {
					// Ignore
				}
			}
			return null;
		}

		private static void addIfAvailable(Collection<DataSourceSettings> list, DataSourceSettings dataSourceSettings) {
			if (dataSourceSettings != null) {
				list.add(dataSourceSettings);
			}
		}

		DataSourceSettings getPreferredDataSourceSettings() {
			return this.preferredDataSourceSettings;
		}

		void registerAliases(DataSource result, ConfigurationPropertyNameAliases aliases) {
			this.allDataSourceSettings.forEach((settings) -> settings.registerAliases(result, aliases));
		}

	}

}