/*
    * 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 org.basepom.mojo.propertyhelper;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkState;
  import static java.lang.String.format;
  
  import org.basepom.mojo.propertyhelper.ValueProvider.MapValueProvider;
  import org.basepom.mojo.propertyhelper.beans.AbstractDefinition;
  import org.basepom.mojo.propertyhelper.beans.IgnoreWarnFailCreate;
  import org.basepom.mojo.propertyhelper.util.Log;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.file.Files;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Properties;
  import java.util.StringJoiner;
  import javax.annotation.Nonnull;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.collect.ForwardingMap;
  import com.google.common.collect.Maps;
  
  public final class ValueCache {
  
      private static final Log LOG = Log.findLog();
      private final Map<String, String> ephemeralValues = Maps.newHashMap();
      /**
       * Cache for values files loaded from disk
       */
      private final Map<File, ValueCacheEntry> valueFiles = Maps.newHashMap();
  
      @VisibleForTesting
      static ValueProvider findCurrentValueProvider(final Map<String, String> values,
              final AbstractDefinition<?> definition) {
          checkNotNull(values, "values is null");
          final String name = definition.getPropertyName();
          final boolean hasValue = values.containsKey(name);
  
          final boolean createProperty = IgnoreWarnFailCreate.checkState(
                  definition.getOnMissingProperty(), hasValue, name);
  
          if (hasValue) {
              return new MapValueProvider(values, name);
          } else if (createProperty) {
              if (definition.getInitialValue().isPresent()) {
                  values.put(name, definition.getInitialValue().get());
              }
              return new MapValueProvider(values, name);
          } else {
              return ValueProvider.NULL_PROVIDER;
          }
      }
  
      public ValueProvider getValueProvider(final AbstractDefinition<?> definition)
              throws IOException {
          final Optional<Map<String, String>> values = getValues(definition);
          if (values.isEmpty()) {
              final String name = definition.getPropertyName();
              final Optional<String> value = definition.getInitialValue();
              value.ifPresent(s -> ephemeralValues.put(name, s));
              return new MapValueProvider(ephemeralValues, name);
          } else {
              return ValueCache.findCurrentValueProvider(values.get(), definition);
          }
      }
  
      @VisibleForTesting
      Optional<Map<String, String>> getValues(final AbstractDefinition<?> definition)
              throws IOException {
          final Optional<File> definitionFile = definition.getPropertyFile();
  
          // Ephemeral, so return null.
          if (definitionFile.isEmpty()) {
              return Optional.empty();
          }
  
          ValueCacheEntry cacheEntry;
          final File canonicalFile = definitionFile.get().getCanonicalFile();
  
         // Throws an exception if the file must exist and does not.
         final boolean createFile = IgnoreWarnFailCreate.checkState(definition.getOnMissingFile(),
                 canonicalFile.exists(),
                 definitionFile.get().getCanonicalPath());
 
         cacheEntry = valueFiles.get(canonicalFile);
 
         if (cacheEntry != null) {
             // If there is a cache hit, something either has loaded the file
             // or another property has already put in a creation order.
             // Make sure that if this number has a creation order it is obeyed.
             if (createFile) {
                 cacheEntry.doCreate();
             }
         } else {
             // Try loading or creating properties.
             final Properties props = new Properties();
 
             if (!canonicalFile.exists()) {
                 cacheEntry = new ValueCacheEntry(props, false, createFile); // does not exist
                 valueFiles.put(canonicalFile, cacheEntry);
             } else {
                 if (canonicalFile.isFile() && canonicalFile.canRead()) {
                     try (InputStream stream = Files.newInputStream(canonicalFile.toPath())) {
                         props.load(stream);
                         cacheEntry = new ValueCacheEntry(props, true, createFile);
                         valueFiles.put(canonicalFile, cacheEntry);
                     }
                 } else {
                     throw new IllegalStateException(
                             format("Can not load %s, not a file!", definitionFile.get().getCanonicalPath()));
                 }
             }
         }
 
         return Optional.of(cacheEntry.getValues());
     }
 
     public void persist()
             throws IOException {
         for (final Entry<File, ValueCacheEntry> entries : valueFiles.entrySet()) {
             final ValueCacheEntry entry = entries.getValue();
             if (!entry.isDirty()) {
                 continue;
             }
             final File file = entries.getKey();
             if (entry.isExists() || entry.isCreate()) {
                 checkNotNull(file, "no file defined, can not persist!");
                 final File oldFile = new File(file.getCanonicalPath() + ".bak");
 
                 if (entry.isExists()) {
                     checkState(file.exists(), "'%s' should exist!", file.getCanonicalPath());
                     // unlink an old file if necessary
                     if (oldFile.exists()) {
                         checkState(oldFile.delete(), "Could not delete '%s'", file.getCanonicalPath());
                     }
                 }
 
                 final File folder = file.getParentFile();
                 if (!folder.exists()) {
                     checkState(folder.mkdirs(), "Could not create folder '%s'", folder.getCanonicalPath());
                 }
 
                 final File newFile = new File(file.getCanonicalPath() + ".new");
                 try (OutputStream stream = Files.newOutputStream(newFile.toPath())) {
                     entry.store(stream, "created by property-helper-maven-plugin");
                 }
 
                 if (file.exists()) {
                     if (!file.renameTo(oldFile)) {
                         LOG.warn("Could not rename '%s' to '%s'!", file, oldFile);
                     }
                 }
 
                 if (!file.exists()) {
                     if (!newFile.renameTo(file)) {
                         LOG.warn("Could not rename '%s' to '%s'!", newFile, file);
                     }
                 }
             }
         }
     }
 
     public static class ValueCacheEntry {
 
         private final Map<String, String> values = Maps.newHashMap();
 
         private final boolean exists;
 
         private boolean create;
 
         private boolean dirty = false;
 
         ValueCacheEntry(@Nonnull final Properties props,
                 final boolean exists,
                 final boolean create) {
             checkNotNull(props, "props is null");
 
             values.putAll(Maps.fromProperties(props));
 
             this.exists = exists;
             this.create = create;
         }
 
         public void store(final OutputStream out, final String comment)
                 throws IOException {
             final Properties p = new Properties();
             for (Entry<String, String> entry : values.entrySet()) {
                 p.setProperty(entry.getKey(), entry.getValue());
             }
             p.store(out, comment);
         }
 
         public boolean isDirty() {
             return dirty;
         }
 
         public void dirty() {
             this.dirty = true;
         }
 
         public Map<String, String> getValues() {
             return new ForwardingMap<>() {
                 @Override
                 protected Map<String, String> delegate() {
                     return values;
                 }
 
                 @Override
                 public String remove(Object object) {
                     dirty();
                     return super.remove(object);
                 }
 
                 @Override
                 public void clear() {
                     dirty();
                     super.clear();
                 }
 
                 @Override
                 public String put(String key, String value) {
                     final String oldValue = super.put(key, value);
                     if (!Objects.equals(value, oldValue)) {
                         dirty();
                     }
                     return oldValue;
                 }
 
                 @Override
                 public void putAll(Map<? extends String, ? extends String> map) {
                     dirty();
                     super.putAll(map);
                 }
             };
         }
 
         public boolean isExists() {
             return exists;
         }
 
         public boolean isCreate() {
             return create;
         }
 
         public void doCreate() {
             this.create = true;
             dirty();
         }
 
         @Override
         public String toString() {
             return new StringJoiner(", ", ValueCacheEntry.class.getSimpleName() + "[", "]")
                     .add("values=" + values)
                     .add("exists=" + exists)
                     .add("create=" + create)
                     .add("dirty=" + dirty)
                     .toString();
         }
 
         @Override
         public boolean equals(Object o) {
             if (this == o) {
                 return true;
             }
             if (o == null || getClass() != o.getClass()) {
                 return false;
             }
             ValueCacheEntry that = (ValueCacheEntry) o;
             return exists == that.exists && create == that.create && dirty == that.dirty
                     && Objects.equals(values, that.values);
         }
 
         @Override
         public int hashCode() {
             return Objects.hash(values, exists, create, dirty);
         }
     }
 }