package org.kuali.common.jute.project.maven;
   
   import static com.google.common.base.Optional.fromNullable;
   import static com.google.common.base.Preconditions.checkState;
   import static org.kuali.common.jute.reflect.Reflection.checkNoNulls;
   
   import java.util.Properties;
   
   import javax.inject.Inject;
  import javax.inject.Provider;
  
  import org.kuali.common.jute.collect.ImmutableProperties;
  import org.kuali.common.jute.env.Environment;
  import org.kuali.common.jute.project.maven.annotation.EnvPrefix;
  import org.kuali.common.jute.project.maven.annotation.ProjectProperties;
  
  import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
  import com.google.common.base.Optional;
  
  /**
   * Maven resolves property values using system properties, environment variables, and project properties.
   *
   * It looks up environment variables using the prefix 'env'.
   */
  @JsonDeserialize(builder = MavenEnvironment.Builder.class)
  public final class MavenEnvironment implements Environment {
  
      private final Environment env;
      private final ImmutableProperties properties;
      private final String prefix;
  
      @Override
      public Optional<String> getProperty(String key) {
          Optional<String> standard = env.getProperty(key);
          if (standard.isPresent()) {
              return standard;
          }
          Optional<String> prefixed = env.getProperty(prefix + "." + key);
          if (prefixed.isPresent()) {
              return prefixed;
          }
          return fromNullable(properties.getProperty(key));
      }
  
      @Override
      public boolean containsProperty(String key) {
          return getProperty(key).isPresent();
      }
  
      @Override
      public String getProperty(String key, String defaultValue) {
          Optional<String> value = getProperty(key);
          if (value.isPresent()) {
              return value.get();
          } else {
              return defaultValue;
          }
      }
  
      @Override
      public String getRequiredProperty(String key) {
          Optional<String> value = getProperty(key);
          checkState(value.isPresent(), "'%s' is required", key);
          return value.get();
      }
  
      public Environment getEnv() {
          return env;
      }
  
      public Properties getProperties() {
          return properties;
      }
  
      public String getPrefix() {
          return prefix;
      }
  
      private MavenEnvironment(Builder builder) {
          this.env = builder.env;
          this.properties = ImmutableProperties.copyOf(builder.properties);
          this.prefix = builder.prefix;
      }
  
      public static class Builder implements org.apache.commons.lang3.builder.Builder<MavenEnvironment>, Provider<MavenEnvironment> {
  
          private Environment env;
          private Properties properties;
          private String prefix;
  
          @Inject
          public Builder withEnv(Environment env) {
              this.env = env;
              return this;
          }
  
          @Inject
          public Builder withProperties(@ProjectProperties Properties properties) {
              this.properties = properties;
             return this;
         }
 
         @Inject
         public Builder withPrefix(@EnvPrefix String prefix) {
             this.prefix = prefix;
             return this;
         }
 
         @Override
         public MavenEnvironment get() {
             return build();
         }
 
         @Override
         public MavenEnvironment build() {
             return checkNoNulls(new MavenEnvironment(this));
         }
     }
 
 }