Decouple configuration parsing

components/proxy/src/main/java/com/hotels/styx/StyxConfig.java

@@ -1,5 +1,5 @@
 /**
- * Copyright (C) 2013-2017 Expedia Inc.
+ * Copyright (C) 2013-2018 Expedia Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,7 +21,9 @@
 import com.hotels.styx.api.configuration.Configuration;
 import com.hotels.styx.api.io.ResourceFactory;
 import com.hotels.styx.client.StyxHeaderConfig;
-import com.hotels.styx.infrastructure.configuration.yaml.YamlConfig;
+import com.hotels.styx.infrastructure.configuration.ConfigurationParser;
+import com.hotels.styx.infrastructure.configuration.ConfigurationSource;
+import com.hotels.styx.infrastructure.configuration.yaml.YamlConfiguration;
 import com.hotels.styx.proxy.ProxyServerConfig;
 
 import java.nio.file.Path;
@@ -30,6 +32,7 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.hotels.styx.StartupConfig.defaultStartupConfig;
+import static com.hotels.styx.infrastructure.configuration.yaml.YamlConfigurationFormat.YAML;
 import static java.util.stream.Collectors.toList;
 import static java.util.stream.StreamSupport.stream;
 
@@ -55,7 +58,7 @@ public StyxConfig(Configuration configuration) {
     }
 
     public StyxConfig(String yaml) {
-        this(new YamlConfig(yaml));
+        this(loadYamlConfiguration(yaml));
     }
 
     public StyxConfig(StartupConfig startupConfig, Configuration configuration) {
@@ -67,6 +70,13 @@ public StyxConfig(StartupConfig startupConfig, Configuration configuration) {
         this.styxHeaderConfig = get("styxHeaders", StyxHeaderConfig.class).orElseGet(StyxHeaderConfig::new);
     }
 
+    private static Configuration loadYamlConfiguration(String yaml) {
+        return new ConfigurationParser.Builder<YamlConfiguration>()
+                .format(YAML)
+                .build()
+                .parse(ConfigurationSource.from(yaml));
+    }
+
     @Override
     public <T> Optional<T> get(String key, Class<T> tClass) {
         return configuration.get(key, tClass);

components/proxy/src/main/java/com/hotels/styx/StyxServer.java

@@ -30,11 +30,14 @@
 import com.hotels.styx.admin.AdminServerBuilder;
 import com.hotels.styx.api.HttpHandler2;
 import com.hotels.styx.api.HttpInterceptor;
+import com.hotels.styx.api.configuration.Configuration;
 import com.hotels.styx.api.metrics.MetricRegistry;
 import com.hotels.styx.api.service.spi.StyxService;
 import com.hotels.styx.client.applications.BackendService;
 import com.hotels.styx.infrastructure.Registry;
-import com.hotels.styx.infrastructure.configuration.yaml.YamlConfig;
+import com.hotels.styx.infrastructure.configuration.ConfigurationParser;
+import com.hotels.styx.infrastructure.configuration.ConfigurationSource;
+import com.hotels.styx.infrastructure.configuration.yaml.YamlConfiguration;
 import com.hotels.styx.metrics.reporting.sets.NettyAllocatorMetricSet;
 import com.hotels.styx.proxy.ProxyServerBuilder;
 import com.hotels.styx.proxy.StyxBackendServiceClientFactory;
@@ -77,6 +80,7 @@
 
 import static com.google.common.util.concurrent.MoreExecutors.sameThreadExecutor;
 import static com.hotels.styx.api.configuration.ConfigurationContextResolver.EMPTY_CONFIGURATION_CONTEXT_RESOLVER;
+import static com.hotels.styx.infrastructure.configuration.yaml.YamlConfigurationFormat.YAML;
 import static com.hotels.styx.infrastructure.logging.LOGBackConfigurer.shutdownLogging;
 import static com.hotels.styx.serviceproviders.ServiceProvision.loadServices;
 import static io.netty.util.ResourceLeakDetector.Level.DISABLED;
@@ -126,9 +130,14 @@ private static StyxServer createStyxServer(String[] args) {
             LOG.info("Styx configFileLocation={}", startupConfig.configFileLocation());
             LOG.info("Styx logConfigLocation={}", startupConfig.logConfigLocation());
 
-            YamlConfig yamlConfig = new YamlConfig(startupConfig.configFileLocation(), System.getProperties());
+            Configuration configFromFile =
+                    new ConfigurationParser.Builder<YamlConfiguration>()
+                            .format(YAML)
+                            .overrides(System.getProperties())
+                            .build()
+                            .parse(ConfigurationSource.from(startupConfig.configFileLocation()));
 
-            StyxConfig styxConfig = new StyxConfig(startupConfig, yamlConfig);
+            StyxConfig styxConfig = new StyxConfig(startupConfig, configFromFile);
 
             return new StyxServerBuilder(styxConfig)
                     .logConfigLocationFromEnvironment()

components/proxy/src/main/java/com/hotels/styx/infrastructure/YamlReader.java

@@ -1,5 +1,5 @@
 /**
- * Copyright (C) 2013-2017 Expedia Inc.
+ * Copyright (C) 2013-2018 Expedia Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 import com.hotels.styx.api.Resource;
+import com.hotels.styx.infrastructure.configuration.UnresolvedPlaceholder;
 import com.hotels.styx.infrastructure.configuration.yaml.NodePath;
 import com.hotels.styx.infrastructure.configuration.yaml.PlaceholderResolver;
 
@@ -71,7 +72,7 @@ public T read(byte[] content, TypeReference<T> typeReference) throws Exception {
         JsonNode rootNode = MAPPER.readTree(content);
         List<String> includePaths = includedPaths(rootNode);
 
-        Collection<PlaceholderResolver.UnresolvedPlaceholder> unresolvedPlaceholders = resolvePlaceholders(rootNode, overrides);
+        Collection<UnresolvedPlaceholder> unresolvedPlaceholders = resolvePlaceholders(rootNode, overrides);
 
         checkState(unresolvedPlaceholders.isEmpty(), "Unresolved placeholders: %s", unresolvedPlaceholders);
 

components/proxy/src/main/java/com/hotels/styx/infrastructure/configuration/ConfigurationFormat.java

@@ -0,0 +1,53 @@
+/**
+ * Copyright (C) 2013-2018 Expedia Inc.
+ *
+ * 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.
+ */
+package com.hotels.styx.infrastructure.configuration;
+
+import com.hotels.styx.api.Resource;
+
+import java.util.Map;
+
+/**
+ * Format for configuration, e.g. JSON, YAML.
+ *
+ * @param <C> configuration type
+ */
+public interface ConfigurationFormat<C extends ExtensibleConfiguration<C>> {
+    /**
+     * Deserialise configuration from a literal string. This is primarily intended for tests,
+     * but could be used whenever the configuration has already been loaded.
+     *
+     * @param string string
+     * @return configuration
+     */
+    C deserialise(String string);
+
+    /**
+     * Deserialise configuration from a resource.
+     *
+     * @param resource resource
+     * @return configuration
+     */
+    C deserialise(Resource resource);
+
+    /**
+     * Resolves placeholders in a piece of text, using only overrides, not loaded configuration.
+     *
+     * @param text text
+     * @param overrides overrides
+     * @return text with resolved placeholders
+     */
+    String resolvePlaceholdersInText(String text, Map<String, String> overrides);
+}

components/proxy/src/main/java/com/hotels/styx/infrastructure/configuration/ConfigurationParser.java

@@ -0,0 +1,122 @@
+/**
+ * Copyright (C) 2013-2018 Expedia Inc.
+ *
+ * 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.
+ */
+package com.hotels.styx.infrastructure.configuration;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.hotels.styx.infrastructure.configuration.ExtensibleConfiguration.PlaceholderResolutionResult;
+import org.slf4j.Logger;
+
+import java.util.Map;
+import java.util.Optional;
+import java.util.Properties;
+import java.util.function.Function;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.hotels.styx.api.io.ResourceFactory.newResource;
+import static com.hotels.styx.common.Logging.sanitise;
+import static java.util.Collections.emptyMap;
+import static java.util.Objects.requireNonNull;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Configuration parser.
+ *
+ * @param <C> configuration type
+ */
+public final class ConfigurationParser<C extends ExtensibleConfiguration<C>> {
+    private static final Logger LOGGER = getLogger(ConfigurationParser.class);
+
+    private final ConfigurationFormat<C> format;
+    private final Map<String, String> overrides;
+    private final Function<String, ConfigurationSource> sourceFromIncludeFunction;
+
+    private ConfigurationParser(Builder<C> builder) {
+        this.format = requireNonNull(builder.format);
+        this.overrides = requireNonNull(builder.overrides);
+        this.sourceFromIncludeFunction = builder.sourceFromIncludeFunction != null
+                ? builder.sourceFromIncludeFunction
+                : ConfigurationParser::sourceFromInclude;
+    }
+
+    public C parse(ConfigurationSource provider) {
+        LOGGER.debug("Parsing configuration in format={} from source={}", format, provider);
+
+        C configuration = doParse(provider);
+
+        PlaceholderResolutionResult<C> resolved = configuration.resolvePlaceholders(overrides);
+
+        checkState(resolved.unresolvedPlaceholders().isEmpty(), "Unresolved placeholders: %s", resolved.unresolvedPlaceholders());
+
+        return resolved.resolvedConfiguration();
+    }
+
+    private C doParse(ConfigurationSource provider) {
+        C main = provider.deserialise(format);
+
+        C withInclude = includedParentConfig(main)
+                .map(main::withParent)
+                .orElse(main);
+
+        return withInclude.withOverrides(overrides);
+    }
+
+    private Optional<C> includedParentConfig(C main) {
+        return main.get("include")
+                .map(include -> format.resolvePlaceholdersInText(include, overrides))
+                .map(sourceFromIncludeFunction)
+                .map(this::doParse);
+    }
+
+    private static ConfigurationSource sourceFromInclude(String includePath) {
+        LOGGER.info("Including config file: path={}", sanitise(includePath));
+        return ConfigurationSource.from(newResource(includePath));
+    }
+
+    /**
+     * Builder.
+     *
+     * @param <C> configuration type
+     */
+    public static final class Builder<C extends ExtensibleConfiguration<C>> {
+        private ConfigurationFormat<C> format;
+        private Map<String, String> overrides = emptyMap();
+        private Function<String, ConfigurationSource> sourceFromIncludeFunction;
+
+        public Builder<C> format(ConfigurationFormat<C> format) {
+            this.format = requireNonNull(format);
+            return this;
+        }
+
+        public Builder<C> overrides(Map<String, String> overrides) {
+            this.overrides = requireNonNull(overrides);
+            return this;
+        }
+
+        public Builder<C> overrides(Properties properties) {
+            return overrides((Map) properties);
+        }
+
+        @VisibleForTesting
+        Builder<C> sourceFromIncludeFunction(Function<String, ConfigurationSource> sourceFromIncludeFunction) {
+            this.sourceFromIncludeFunction = requireNonNull(sourceFromIncludeFunction);
+            return this;
+        }
+
+        public ConfigurationParser<C> build() {
+            return new ConfigurationParser<>(this);
+        }
+    }
+}

components/proxy/src/main/java/com/hotels/styx/infrastructure/configuration/ConfigurationSource.java

@@ -0,0 +1,72 @@
+/**
+ * Copyright (C) 2013-2018 Expedia Inc.
+ *
+ * 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.
+ */
+package com.hotels.styx.infrastructure.configuration;
+
+import com.hotels.styx.api.Resource;
+
+/**
+ * Provider of configuration, e.g. file, in-memory string.
+ */
+public interface ConfigurationSource {
+    /**
+     * Deserialise configuration that is in a given format.
+     *
+     * @param format format
+     * @param <C> configuration type
+     * @return configuration
+     */
+    <C extends ExtensibleConfiguration<C>> C deserialise(ConfigurationFormat<C> format);
+
+    /**
+     * Configuration taken from a string in memory.
+     *
+     * @param string a string
+     * @return configuration provider
+     */
+    static ConfigurationSource from(String string) {
+        return new ConfigurationSource() {
+            @Override
+            public <C extends ExtensibleConfiguration<C>> C deserialise(ConfigurationFormat<C> format) {
+                return format.deserialise(string);
+            }
+
+            @Override
+            public String toString() {
+                return "\"" + string + "\"";
+            }
+        };
+    }
+
+    /**
+     * Configuration from a resource.
+     *
+     * @param resource resource
+     * @return configuration provider
+     */
+    static ConfigurationSource from(Resource resource) {
+        return new ConfigurationSource() {
+            @Override
+            public <C extends ExtensibleConfiguration<C>> C deserialise(ConfigurationFormat<C> format) {
+                return format.deserialise(resource);
+            }
+
+            @Override
+            public String toString() {
+                return resource.toString();
+            }
+        };
+    }
+}