// Copyright 2017 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.packages;

import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.syntax.EvalException;
import com.google.devtools.build.lib.syntax.FuncallExpression;
import com.google.devtools.build.lib.syntax.FuncallExpression.MethodDescriptor;
import java.util.Map;

/** Base class for native implementations of {@link Info}. */
// todo(vladmos,dslomov): make abstract once DefaultInfo stops instantiating it.
public class NativeInfo extends Info {
  protected final ImmutableMap<String, Object> values;

  // Initialized lazily.
  private ImmutableSet<String> fieldNames;

  @Override
  public Object getValue(String name) throws EvalException {
    if (values.containsKey(name)) {
      return values.get(name);
    } else if (hasField(name)) {
      MethodDescriptor methodDescriptor = FuncallExpression.getStructField(this.getClass(), name);
      try {
        return FuncallExpression.invokeStructField(methodDescriptor, name, this);
      } catch (InterruptedException exception) {
        // Struct fields on NativeInfo objects are supposed to behave well and not throw
        // exceptions, as they should be logicless field accessors. If this occurs, it's
        // indicative of a bad NativeInfo implementation.
        throw new IllegalStateException(
            String.format("Access of field %s was unexpectedly interrupted, but should be "
                + "uninterruptible. This is indicative of a bad provider implementation.", name));
      }
    } else {
      return null;
    }
  }

  @Override
  public boolean hasField(String name) {
    return getFieldNames().contains(name);
  }

  @Override
  public ImmutableCollection<String> getFieldNames() {
    if (fieldNames == null) {
      fieldNames = ImmutableSet.<String>builder()
          .addAll(values.keySet())
          .addAll(FuncallExpression.getStructFieldNames(this.getClass()))
          .build();
    }
    return fieldNames;
  }

  public NativeInfo(Provider provider) {
    this(provider, Location.BUILTIN);
  }

  public NativeInfo(Provider provider, Location loc) {
    this(provider, ImmutableMap.of(), loc);
  }

  // TODO(cparsons): Remove this constructor once DefaultInfo and ToolchainInfo stop using it.
  @Deprecated
  public NativeInfo(Provider provider, Map<String, Object> values, Location loc) {
    super(provider, loc);
    this.values = copyValues(values);
  }
}