// Copyright 2014 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.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.packages.Attribute.SkylarkComputedDefaultTemplate.CannotPrecomputeDefaultsException;
import com.google.devtools.build.lib.packages.Package.NameConflictException;
import com.google.devtools.build.lib.packages.PackageFactory.PackageContext;
import com.google.devtools.build.lib.syntax.BaseFunction;
import com.google.devtools.build.lib.syntax.Environment;
import com.google.devtools.build.lib.syntax.FuncallExpression;
import com.google.devtools.build.lib.syntax.UserDefinedFunction;
import com.google.devtools.build.lib.util.Pair;
import com.google.devtools.build.lib.util.Preconditions;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Given a {@link RuleClass} and a set of attribute values, returns a {@link Rule} instance. Also
 * performs a number of checks and associates the {@link Rule} and the owning {@link Package}
 * with each other.
 *
 * <p>Note: the code that actually populates the RuleClass map has been moved to {@link
 * RuleClassProvider}.
 */
public class RuleFactory {

  /**
   * Maps rule class name to the metaclass instance for that rule.
   */
  private final ImmutableMap<String, RuleClass> ruleClassMap;
  private final Function<RuleClass, AttributeContainer> attributeContainerFactory;

  /**
   * Constructs a RuleFactory instance.
   */
  public RuleFactory(
      RuleClassProvider provider,
      Function<RuleClass, AttributeContainer> attributeContainerFactory) {
    this.attributeContainerFactory = attributeContainerFactory;
    this.ruleClassMap = ImmutableMap.copyOf(provider.getRuleClassMap());
  }

  /**
   * Returns the (immutable, unordered) set of names of all the known rule classes.
   */
  public Set<String> getRuleClassNames() {
    return ruleClassMap.keySet();
  }

  /**
   * Returns the RuleClass for the specified rule class name.
   */
  public RuleClass getRuleClass(String ruleClassName) {
    return ruleClassMap.get(ruleClassName);
  }

  AttributeContainer getAttributeContainer(RuleClass ruleClass) {
    return attributeContainerFactory.apply(ruleClass);
  }

  Function<RuleClass, AttributeContainer> getAttributeContainerFactory() {
    return attributeContainerFactory;
  }

  /**
   * Creates and returns a rule instance.
   *
   * <p>It is the caller's responsibility to add the rule to the package (the caller may choose not
   * to do so if, for example, the rule has errors).
   */
  static Rule createRule(
      Package.Builder pkgBuilder,
      RuleClass ruleClass,
      BuildLangTypedAttributeValuesMap attributeValues,
      EventHandler eventHandler,
      @Nullable FuncallExpression ast,
      Location location,
      @Nullable Environment env,
      AttributeContainer attributeContainer)
      throws InvalidRuleException, InterruptedException {
    Preconditions.checkNotNull(ruleClass);
    String ruleClassName = ruleClass.getName();
    Object nameObject = attributeValues.getAttributeValue("name");
    if (nameObject == null) {
      throw new InvalidRuleException(ruleClassName + " rule has no 'name' attribute");
    } else if (!(nameObject instanceof String)) {
      throw new InvalidRuleException(ruleClassName + " 'name' attribute must be a string");
    }
    String name = (String) nameObject;
    Label label;
    try {
      // Test that this would form a valid label name -- in particular, this
      // catches cases where Makefile variables $(foo) appear in "name".
      label = pkgBuilder.createLabel(name);
    } catch (LabelSyntaxException e) {
      throw new InvalidRuleException("illegal rule name: " + name + ": " + e.getMessage());
    }
    boolean inWorkspaceFile = pkgBuilder.isWorkspace();
    if (ruleClass.getWorkspaceOnly() && !inWorkspaceFile) {
      throw new RuleFactory.InvalidRuleException(
          ruleClass + " must be in the WORKSPACE file " + "(used by " + label + ")");
    } else if (!ruleClass.getWorkspaceOnly() && inWorkspaceFile) {
      throw new RuleFactory.InvalidRuleException(
          ruleClass + " cannot be in the WORKSPACE file " + "(used by " + label + ")");
    }

    AttributesAndLocation generator =
        generatorAttributesForMacros(attributeValues, env, location, label);
    try {
      return ruleClass.createRule(
          pkgBuilder,
          label,
          generator.attributes,
          eventHandler,
          ast,
          generator.location,
          attributeContainer);
    } catch (LabelSyntaxException | CannotPrecomputeDefaultsException e) {
      throw new RuleFactory.InvalidRuleException(ruleClass + " " + e.getMessage());
    }
  }

  /**
   * Creates a {@link Rule} instance, adds it to the {@link Package.Builder} and returns it.
   *
   * @param pkgBuilder the under-construction {@link Package.Builder} to which the rule belongs
   * @param ruleClass the {@link RuleClass} of the rule
   * @param attributeValues a {@link BuildLangTypedAttributeValuesMap} mapping attribute names to
   *     attribute values of build-language type. Each attribute must be defined for this class of
   *     rule, and have a build-language-typed value which can be converted to the appropriate
   *     native type of the attribute (i.e. via {@link BuildType#selectableConvert}). There must
   *     be a map entry for each non-optional attribute of this class of rule.
   * @param eventHandler a eventHandler on which errors and warnings are reported during
   *     rule creation
   * @param ast the abstract syntax tree of the rule expression (optional)
   * @param location the location at which this rule was declared
   * @param env the lexical environment of the function call which declared this rule (optional)
   * @param attributeContainer the {@link AttributeContainer} the rule will contain
   * @throws InvalidRuleException if the rule could not be constructed for any
   *     reason (e.g. no {@code name} attribute is defined)
   * @throws NameConflictException if the rule's name or output files conflict with others in this
   *     package
   * @throws InterruptedException if interrupted
   */
  static Rule createAndAddRule(
      Package.Builder pkgBuilder,
      RuleClass ruleClass,
      BuildLangTypedAttributeValuesMap attributeValues,
      EventHandler eventHandler,
      @Nullable FuncallExpression ast,
      Location location,
      @Nullable Environment env,
      AttributeContainer attributeContainer)
      throws InvalidRuleException, NameConflictException, InterruptedException {
    Rule rule =
        createRule(
            pkgBuilder,
            ruleClass,
            attributeValues,
            eventHandler,
            ast,
            location,
            env,
            attributeContainer);
    pkgBuilder.addRule(rule);
    return rule;
  }

  /**
   * Creates a {@link Rule} instance, adds it to the {@link Package.Builder} and returns it.
   *
   * @param context the package-building context in which this rule was declared
   * @param ruleClass the {@link RuleClass} of the rule
   * @param attributeValues a {@link BuildLangTypedAttributeValuesMap} mapping attribute names to
   *     attribute values of build-language type. Each attribute must be defined for this class
   *     of rule, and have a build-language-typed value which can be converted to the appropriate
   *     native type of the attribute (i.e. via {@link BuildType#selectableConvert}). There must
   *     be a map entry for each non-optional attribute of this class of rule.
   * @param ast the abstract syntax tree of the rule expression (mandatory because this looks up a
   *     {@link Location} from the {@code ast})
   * @param env the lexical environment of the function call which declared this rule (optional)
   * @param attributeContainer the {@link AttributeContainer} the rule will contain
   * @throws InvalidRuleException if the rule could not be constructed for any reason (e.g. no
   *     {@code name} attribute is defined)
   * @throws NameConflictException if the rule's name or output files conflict with others in this
   *     package
   * @throws InterruptedException if interrupted
   */
  public static Rule createAndAddRule(
      PackageContext context,
      RuleClass ruleClass,
      BuildLangTypedAttributeValuesMap attributeValues,
      FuncallExpression ast,
      @Nullable Environment env,
      AttributeContainer attributeContainer)
      throws InvalidRuleException, NameConflictException, InterruptedException {
    return createAndAddRule(
        context.pkgBuilder,
        ruleClass,
        attributeValues,
        context.eventHandler,
        ast,
        ast.getLocation(),
        env,
        attributeContainer);
  }

  /**
   * InvalidRuleException is thrown by {@link Rule} creation methods if the {@link Rule} could
   * not be constructed. It contains an error message.
   */
  public static class InvalidRuleException extends Exception {
    private InvalidRuleException(String message) {
      super(message);
    }
  }

  /** A pair of attributes and location. */
  private static final class AttributesAndLocation {
    final BuildLangTypedAttributeValuesMap attributes;
    final Location location;

    AttributesAndLocation(BuildLangTypedAttributeValuesMap attributes, Location location) {
      this.attributes = attributes;
      this.location = location;
    }
  }

  /**
   * A wrapper around an map of named attribute values that specifies whether the map's values
   * are of "build-language" or of "native" types.
   */
  public interface AttributeValues<T> {
    /**
     * Returns {@code true} if all the map's values are "build-language typed", i.e., resulting
     * from the evaluation of an expression in the build language. Returns {@code false} if all
     * the map's values are "natively typed", i.e. of a type returned by {@link
     * BuildType#selectableConvert}.
     */
    boolean valuesAreBuildLanguageTyped();

    Iterable<T> getAttributeAccessors();

    String getName(T attributeAccessor);
    Object getValue(T attributeAccessor);
    boolean isExplicitlySpecified(T attributeAccessor);
  }

  /** A {@link AttributeValues} of explicit "build-language" values. */
  public static final class BuildLangTypedAttributeValuesMap
      implements AttributeValues<Map.Entry<String, Object>> {
    private final Map<String, Object> attributeValues;

    public BuildLangTypedAttributeValuesMap(Map<String, Object> attributeValues) {
      this.attributeValues = attributeValues;
    }

    private boolean containsAttributeNamed(String attributeName) {
      return attributeValues.containsKey(attributeName);
    }

    private Object getAttributeValue(String attributeName) {
      return attributeValues.get(attributeName);
    }

    @Override
    public boolean valuesAreBuildLanguageTyped() {
      return true;
    }

    @Override
    public Iterable<Map.Entry<String, Object>> getAttributeAccessors() {
      return attributeValues.entrySet();
    }

    @Override
    public String getName(Map.Entry<String, Object> attributeAccessor) {
      return attributeAccessor.getKey();
    }

    @Override
    public Object getValue(Map.Entry<String, Object> attributeAccessor) {
      return attributeAccessor.getValue();
    }

    @Override
    public boolean isExplicitlySpecified(Map.Entry<String, Object> attributeAccessor) {
      return true;
    }
  }

  /**
   * If the rule was created by a macro, this method sets the appropriate values for the
   * attributes generator_{name, function, location} and returns all attributes.
   *
   * <p>Otherwise, it returns the given attributes without any changes.
   */
  private static AttributesAndLocation generatorAttributesForMacros(
      BuildLangTypedAttributeValuesMap args,
      @Nullable Environment env,
      Location location,
      Label label) {
    // Returns the original arguments if a) there is only the rule itself on the stack
    // trace (=> no macro) or b) the attributes have already been set by Python pre-processing.
    if (env == null) {
      return new AttributesAndLocation(args, location);
    }
    boolean hasName = args.containsAttributeNamed("generator_name");
    boolean hasFunc = args.containsAttributeNamed("generator_function");
    // TODO(bazel-team): resolve cases in our code where hasName && !hasFunc, or hasFunc && !hasName
    if (hasName || hasFunc) {
      return new AttributesAndLocation(args, location);
    }
    Pair<FuncallExpression, BaseFunction> topCall = env.getTopCall();
    if (topCall == null || !(topCall.second instanceof UserDefinedFunction)) {
      return new AttributesAndLocation(args, location);
    }

    FuncallExpression generator = topCall.first;
    BaseFunction function = topCall.second;
    String name = generator.getNameArg();
    
    ImmutableMap.Builder<String, Object> builder = ImmutableMap.builder();
    for (Map.Entry<String, Object> attributeAccessor : args.getAttributeAccessors()) {
      String attributeName = args.getName(attributeAccessor);
      builder.put(attributeName, args.getValue(attributeAccessor));
    }
    builder.put("generator_name", (name == null) ? args.getAttributeValue("name") : name);
    builder.put("generator_function", function.getName());

    if (generator.getLocation() != null) {
      location = generator.getLocation();
    }
    String relativePath = maybeGetRelativeLocation(location, label);
    if (relativePath != null) {
      builder.put("generator_location", relativePath);
    }

    try {
      return new AttributesAndLocation(
          new BuildLangTypedAttributeValuesMap(builder.build()), location);
    } catch (IllegalArgumentException ex) {
      // We just fall back to the default case and swallow any messages.
      return new AttributesAndLocation(args, location);
    }
  }

  /**
   * Uses the given label to retrieve the workspace-relative path of the given location (including
   * the line number).
   *
   * <p>For example, the location /usr/local/workspace/my/cool/package/BUILD:3:1 and the label
   * //my/cool/package:BUILD would lead to "my/cool/package:BUILD:3".
   *
   * @return The workspace-relative path of the given location, or null if it could not be computed.
   */
  @Nullable
  private static String maybeGetRelativeLocation(@Nullable Location location, Label label) {
    if (location == null) {
      return null;
    }
    // Determining the workspace root only works reliably if both location and label point to files
    // in the same package.
    // It would be preferable to construct the path from the label itself, but this doesn't work for
    // rules created from function calls in a subincluded file, even if both files share a path
    // prefix (for example, when //a/package:BUILD subincludes //a/package/with/a/subpackage:BUILD).
    // We can revert to that approach once subincludes aren't supported anymore.
    String absolutePath = Location.printLocation(location);
    int pos = absolutePath.indexOf(label.getPackageName());
    return (pos < 0) ? null : absolutePath.substring(pos);
  }
}