/*
 * Copyright 2014-present Facebook, 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.facebook.buck.python;

import com.facebook.buck.cxx.CxxPlatform;
import com.facebook.buck.io.ProjectFilesystem;
import com.facebook.buck.model.BuildTarget;
import com.facebook.buck.model.BuildTargets;
import com.facebook.buck.model.Flavor;
import com.facebook.buck.model.FlavorDomain;
import com.facebook.buck.model.FlavorDomainException;
import com.facebook.buck.model.HasSourceUnderTest;
import com.facebook.buck.model.ImmutableFlavor;
import com.facebook.buck.rules.AbstractBuildRule;
import com.facebook.buck.rules.BuildContext;
import com.facebook.buck.rules.BuildRule;
import com.facebook.buck.rules.BuildRuleParams;
import com.facebook.buck.rules.BuildRuleResolver;
import com.facebook.buck.rules.BuildRuleType;
import com.facebook.buck.rules.BuildTargetSourcePath;
import com.facebook.buck.rules.BuildableContext;
import com.facebook.buck.rules.Description;
import com.facebook.buck.rules.ImmutableBuildRuleType;
import com.facebook.buck.rules.Label;
import com.facebook.buck.rules.PathSourcePath;
import com.facebook.buck.rules.RuleKey;
import com.facebook.buck.rules.SourcePath;
import com.facebook.buck.rules.SourcePathResolver;
import com.facebook.buck.step.Step;
import com.facebook.buck.step.fs.MkdirStep;
import com.facebook.buck.step.fs.WriteFileStep;
import com.facebook.buck.util.HumanReadableException;
import com.facebook.infer.annotation.SuppressFieldNotInitialized;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Suppliers;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;

import java.nio.file.Path;
import java.nio.file.Paths;

public class PythonTestDescription implements Description<PythonTestDescription.Arg> {

  private static final BuildRuleType TYPE = ImmutableBuildRuleType.of("python_test");

  private static final Flavor BINARY_FLAVOR = ImmutableFlavor.of("binary");

  private final ProjectFilesystem projectFilesystem;
  private final Path pathToPex;
  private final Optional<Path> pathToPythonTestMain;
  private final PythonEnvironment pythonEnvironment;
  private final CxxPlatform defaultCxxPlatform;
  private final FlavorDomain<CxxPlatform> cxxPlatforms;

  public PythonTestDescription(
      ProjectFilesystem projectFilesystem,
      Path pathToPex,
      Optional<Path> pathToPythonTestMain,
      PythonEnvironment pythonEnvironment,
      CxxPlatform defaultCxxPlatform,
      FlavorDomain<CxxPlatform> cxxPlatforms) {
    this.projectFilesystem = projectFilesystem;
    this.pathToPex = pathToPex;
    this.pathToPythonTestMain = pathToPythonTestMain;
    this.pythonEnvironment = pythonEnvironment;
    this.defaultCxxPlatform = defaultCxxPlatform;
    this.cxxPlatforms = cxxPlatforms;
  }

  @Override
  public BuildRuleType getBuildRuleType() {
    return TYPE;
  }

  @Override
  public Arg createUnpopulatedConstructorArg() {
    return new Arg();
  }

  @VisibleForTesting
  protected Path getTestMainName() {
    return Paths.get("__test_main__.py");
  }

  @VisibleForTesting
  protected Path getTestModulesListName() {
    return Paths.get("__test_modules__.py");
  }

  @VisibleForTesting
  protected Path getTestModulesListPath(BuildTarget buildTarget) {
    return BuildTargets.getGenPath(buildTarget, "%s").resolve(getTestModulesListName());
  }

  @VisibleForTesting
  protected BuildTarget getBinaryBuildTarget(BuildTarget target) {
    return BuildTargets.createFlavoredBuildTarget(target.checkUnflavored(), BINARY_FLAVOR);
  }

  /**
   * Create the contents of a python source file that just contains a list of
   * the given test modules.
   */
  private static String getTestModulesListContents(ImmutableSet<String> modules) {
    String contents = "TEST_MODULES = [\n";
    for (String module : modules) {
      contents += String.format("    \"%s\",\n", module);
    }
    contents += "]";
    return contents;
  }

  /**
   * Return a {@link BuildRule} that constructs the source file which contains the list
   * of test modules this python test rule will run.  Setting up a separate build rule
   * for this allows us to use the existing python binary rule without changes to account
   * for the build-time creation of this file.
   */
  private static BuildRule createTestModulesSourceBuildRule(
      BuildRuleParams params,
      BuildRuleResolver resolver,
      final Path outputPath,
      ImmutableSet<String> testModules) {

    // Modify the build rule params to change the target, type, and remove all deps.
    BuildRuleParams newParams = params.copyWithChanges(
        ImmutableBuildRuleType.of("create_test_modules_list"),
        BuildTargets.createFlavoredBuildTarget(
            params.getBuildTarget().checkUnflavored(),
            ImmutableFlavor.of("test_module")),
        Suppliers.ofInstance(ImmutableSortedSet.<BuildRule>of()),
        Suppliers.ofInstance(ImmutableSortedSet.<BuildRule>of()));

    final String contents = getTestModulesListContents(testModules);

    return new AbstractBuildRule(newParams, new SourcePathResolver(resolver)) {

      @Override
      protected ImmutableCollection<Path> getInputsToCompareToOutput() {
        return ImmutableList.of();
      }

      @Override
      protected RuleKey.Builder appendDetailsToRuleKey(RuleKey.Builder builder) {
        return builder
            .setReflectively("contents", contents)
            .setReflectively("output", outputPath.toString());
      }

      @Override
      public ImmutableList<Step> getBuildSteps(
          BuildContext context, BuildableContext buildableContext) {
        buildableContext.recordArtifact(outputPath);
        return ImmutableList.of(
            new MkdirStep(outputPath.getParent()),
            new WriteFileStep(contents, outputPath));
      }

      @Override
      public Path getPathToOutputFile() {
        return outputPath;
      }

    };
  }

  @Override
  public <A extends Arg> PythonTest createBuildRule(
      BuildRuleParams params,
      BuildRuleResolver resolver,
      A args) {

    if (!pathToPythonTestMain.isPresent()) {
      throw new HumanReadableException(
          "Please configure python -> path_to_python_test_main in your .buckconfig");
    }

    // Extract the platform from the flavor, falling back to the default platform if none are
    // found.
    CxxPlatform cxxPlatform;
    try {
      cxxPlatform = cxxPlatforms
          .getValue(ImmutableSet.copyOf(params.getBuildTarget().getFlavors()))
          .or(defaultCxxPlatform);
    } catch (FlavorDomainException e) {
      throw new HumanReadableException("%s: %s", params.getBuildTarget(), e.getMessage());
    }

    SourcePathResolver pathResolver = new SourcePathResolver(resolver);
    Path baseModule = PythonUtil.getBasePath(params.getBuildTarget(), args.baseModule);

    ImmutableMap<Path, SourcePath> srcs = PythonUtil.toModuleMap(
        params.getBuildTarget(),
        pathResolver,
        "srcs",
        baseModule, args.srcs);

    ImmutableMap<Path, SourcePath> resources = PythonUtil.toModuleMap(
        params.getBuildTarget(),
        pathResolver,
        "resources",
        baseModule, args.resources);

    // Convert the passed in module paths into test module names.
    ImmutableSet.Builder<String> testModulesBuilder = ImmutableSet.builder();
    for (Path name : srcs.keySet()) {
      testModulesBuilder.add(
          PythonUtil.toModuleName(params.getBuildTarget(), name.toString()));
    }
    ImmutableSet<String> testModules = testModulesBuilder.build();

    // Construct a build rule to generate the test modules list source file and
    // add it to the build.
    BuildRule testModulesBuildRule = createTestModulesSourceBuildRule(
        params,
        resolver,
        getTestModulesListPath(params.getBuildTarget()),
        testModules);
    resolver.addToIndex(testModulesBuildRule);

    // Build up the list of everything going into the python test.
    PythonPackageComponents testComponents = ImmutablePythonPackageComponents.of(
        ImmutableMap
            .<Path, SourcePath>builder()
            .put(
                getTestModulesListName(),
                new BuildTargetSourcePath(
                    testModulesBuildRule.getProjectFilesystem(),
                    testModulesBuildRule.getBuildTarget()))
            .put(
                getTestMainName(),
                new PathSourcePath(projectFilesystem, pathToPythonTestMain.get()))
            .putAll(srcs)
            .build(),
        resources,
        ImmutableMap.<Path, SourcePath>of());
    PythonPackageComponents allComponents =
        PythonUtil.getAllComponents(params, testComponents, cxxPlatform);

    // Build the PEX using a python binary rule with the minimum dependencies.
    BuildRuleParams binaryParams = params.copyWithChanges(
        PythonBinaryDescription.TYPE,
        getBinaryBuildTarget(params.getBuildTarget()),
        Suppliers.ofInstance(PythonUtil.getDepsFromComponents(pathResolver, allComponents)),
        Suppliers.ofInstance(ImmutableSortedSet.<BuildRule>of()));
    PythonBinary binary = new PythonBinary(
        binaryParams,
        pathResolver,
        pathToPex,
        pythonEnvironment,
        getTestMainName(),
        allComponents);
    resolver.addToIndex(binary);

    // Generate and return the python test rule, which depends on the python binary rule above.
    return new PythonTest(
        params.copyWithDeps(
            Suppliers.ofInstance(
                ImmutableSortedSet.<BuildRule>naturalOrder()
                    .addAll(params.getDeclaredDeps())
                    .add(binary)
                    .build()),
            Suppliers.ofInstance(params.getExtraDeps())),
        pathResolver,
        binary,
        resolver.getAllRules(args.sourceUnderTest.or(ImmutableSortedSet.<BuildTarget>of())),
        args.labels.or(ImmutableSet.<Label>of()),
        args.contacts.or(ImmutableSet.<String>of()));
  }

  @SuppressFieldNotInitialized
  public static class Arg extends PythonLibraryDescription.Arg implements HasSourceUnderTest {
    public Optional<ImmutableSet<String>> contacts;
    public Optional<ImmutableSet<Label>> labels;
    public Optional<ImmutableSortedSet<BuildTarget>> sourceUnderTest;

    @Override
    public ImmutableSortedSet<BuildTarget> getSourceUnderTest() {
      return sourceUnderTest.get();
    }
  }

}