// Copyright 2015 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.ImmutableMap;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.cmdline.RepositoryName;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.NullEventHandler;
import com.google.devtools.build.lib.packages.TargetDefinitionContext.NameConflictException;
import com.google.devtools.build.lib.server.FailureDetails;
import com.google.devtools.build.lib.server.FailureDetails.PackageLoading;
import com.google.devtools.build.lib.vfs.Path;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.Nullable;
import net.starlark.java.eval.Dict;
import net.starlark.java.eval.EvalException;
import net.starlark.java.eval.Module;
import net.starlark.java.eval.Mutability;
import net.starlark.java.eval.Printer;
import net.starlark.java.eval.Starlark;
import net.starlark.java.eval.StarlarkCallable;
import net.starlark.java.eval.StarlarkSemantics;
import net.starlark.java.eval.StarlarkThread;
import net.starlark.java.eval.Tuple;
import net.starlark.java.syntax.Program;
import net.starlark.java.syntax.StarlarkFile;
import net.starlark.java.syntax.SyntaxError;

/** Parser for WORKSPACE files. Fills in an ExternalPackage.Builder */
public class WorkspaceFactory {

  private final Package.Builder builder;

  private final Path installDir;
  private final Path workspaceDir;
  private final Path defaultSystemJavabaseDir;
  private final Mutability mutability;

  private final StarlarkSemantics starlarkSemantics;
  private final StarlarkGlobals starlarkGlobals;
  private final ImmutableMap<String, Object> workspaceFunctions;

  // Values accumulated from all previous WORKSPACE file parts.
  private final Map<String, Module> loadedModules = new HashMap<>();
  private final Map<String, Object> bindings = new HashMap<>();

  // TODO(bazel-team): document installDir
  /**
   * @param builder a builder for the Workspace
   * @param ruleClassProvider a provider for known rule classes
   * @param mutability the Mutability for the current evaluation context
   * @param installDir the install directory
   * @param workspaceDir the workspace directory
   * @param defaultSystemJavabaseDir the local JDK directory
   */
  public WorkspaceFactory(
      Package.Builder builder,
      RuleClassProvider ruleClassProvider,
      Mutability mutability,
      boolean allowOverride,
      boolean allowWorkspaceFunction,
      @Nullable Path installDir,
      @Nullable Path workspaceDir,
      @Nullable Path defaultSystemJavabaseDir,
      StarlarkSemantics starlarkSemantics) {
    this.builder = builder;
    this.mutability = mutability;
    this.installDir = installDir;
    this.workspaceDir = workspaceDir;
    this.defaultSystemJavabaseDir = defaultSystemJavabaseDir;
    this.starlarkSemantics = starlarkSemantics;
    this.starlarkGlobals = ruleClassProvider.getBazelStarlarkEnvironment().getStarlarkGlobals();
    this.workspaceFunctions =
        createWorkspaceFunctions(
            allowOverride,
            ruleClassProvider.getRuleClassMap(),
            new WorkspaceGlobals(allowWorkspaceFunction, ruleClassProvider.getRuleClassMap()),
            starlarkSemantics);
  }

  /**
   * Actually runs through the AST, calling the functions in the WORKSPACE file and adding rules to
   * the //external package.
   */
  public void execute(
      StarlarkFile file, // becomes resolved as a side effect
      Map<String, Module> additionalLoadedModules)
      throws InterruptedException {
    loadedModules.putAll(additionalLoadedModules);

    // set up predeclared environment
    HashMap<String, Object> predeclared = new HashMap<>();
    predeclared.putAll(getDefaultEnvironment());
    predeclared.putAll(bindings); // (may shadow bindings in default environment)
    Module module = Module.withPredeclared(starlarkSemantics, predeclared);

    try {
      // compile
      new DotBazelFileSyntaxChecker("WORKSPACE files", /* canLoadBzl= */ true).check(file);
      Program prog = Program.compileFile(file, module);

      // create thread
      StarlarkThread thread =
          StarlarkThread.create(
              mutability,
              starlarkSemantics,
              /* contextDescription= */ "",
              builder.getSymbolGenerator());
      thread.setLoader(loadedModules::get);
      thread.setPrintHandler(Event.makeDebugPrintHandler(builder.getLocalEventHandler()));
      builder.storeInThread(thread);

      try {
        Starlark.execFileProgram(prog, module, thread);
      } catch (EvalException ex) {
        builder
            .getLocalEventHandler()
            .handle(
                Package.error(
                    null, ex.getMessageWithStack(), PackageLoading.Code.STARLARK_EVAL_ERROR));
      }

      // Accumulate the global bindings created by this chunk of the WORKSPACE file,
      // for use in the next chunk. This set does not include the bindings
      // added by getDefaultEnvironment; but it does include bindings created by load,
      // so we will need to set the legacy load-binds-globally flag for this file in due course.
      this.bindings.putAll(module.getGlobals());

    } catch (SyntaxError.Exception ex) {
      // compilation failed
      Event.replayEventsOn(builder.getLocalEventHandler(), ex.errors());
      builder.setFailureDetailOverride(
          FailureDetails.FailureDetail.newBuilder()
              .setMessage(ex.getMessage())
              .setPackageLoading(
                  FailureDetails.PackageLoading.newBuilder()
                      .setCode(PackageLoading.Code.SYNTAX_ERROR))
              .build());
    }

    // cleanup (success or failure)
    // TODO(bazel-team): Package.Builder should manage its own containsErrors bit based on whether
    // its handler has errors, without our telling it to.
    if (builder.getLocalEventHandler().hasErrors()) {
      builder.setContainsErrors();
    }
  }

  /**
   * Adds the various values returned by the parsing of the previous workspace file parts. {@code
   * aPackage} is the package returned by the parent WorkspaceFileFunction, {@code loadedModules} is
   * the set of modules loaded by load statements in the parent WorkspaceFileFunction and {@code
   * variableBindings} the list of top level variable bindings of that same call.
   */
  public void setParent(
      Package aPackage, Map<String, Module> loadedModules, Map<String, Object> bindings)
      throws NameConflictException, InterruptedException {
    this.bindings.putAll(bindings);
    this.loadedModules.putAll(loadedModules);
    builder.setWorkspaceName(aPackage.getWorkspaceName());
    // Transmit the content of the parent package to the new package builder.
    if (aPackage.containsErrors()) {
      builder.setContainsErrors();
    }
    if (aPackage.getFailureDetail() != null) {
      builder.setFailureDetailOverride(aPackage.getFailureDetail());
    }
    builder.addRegisteredExecutionPlatforms(aPackage.getRegisteredExecutionPlatforms());
    builder.addRegisteredToolchains(
        aPackage.getRegisteredToolchains(), /* forWorkspaceSuffix= */ false);
    builder.setFirstWorkspaceSuffixRegisteredToolchain(
        aPackage.getFirstWorkspaceSuffixRegisteredToolchain());
    builder.addRepositoryMappings(aPackage);
    for (Rule rule : aPackage.getTargets(Rule.class)) {
      try {
        // The old rule references another Package instance, and we want to keep the invariant that
        // every Rule references the Package it is contained within.
        Rule newRule =
            builder.createRule(
                rule.getLabel(),
                rule.getRuleClassObject(),
                rule.getLocation(),
                rule.getInteriorCallStack());
        newRule.copyAttributesFrom(rule);
        newRule.populateOutputFiles(NullEventHandler.INSTANCE, builder.getPackageIdentifier());
        if (rule.containsErrors()) {
          newRule.setContainsErrors();
        }
        builder.addRule(newRule);
      } catch (LabelSyntaxException e) {
        // This rule has already been created once, so it should have worked the second time, too
        throw new IllegalStateException(e);
      }
    }
  }

  /**
   * Returns a callable Starlark value that implements the build or workspace rule "ruleClass" (e.g.
   * cc_library) in the specified package context.
   */
  private static StarlarkCallable newRuleFunction(
      final ImmutableMap<String, RuleClass> ruleClassMap,
      final String ruleClassName,
      final boolean allowOverride) {
    return new StarlarkCallable() {
      @Override
      public String getName() {
        return ruleClassName;
      }

      @Override
      public String toString() {
        return getName() + "(...)";
      }

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

      @Override
      public void repr(Printer printer) {
        printer.append("<built-in function " + getName() + ">");
      }

      @Override
      public Object call(StarlarkThread thread, Tuple args, Dict<String, Object> kwargs)
          throws EvalException, InterruptedException {
        if (!args.isEmpty()) {
          throw new EvalException("unexpected positional arguments");
        }
        try {
          Package.Builder builder =
              Package.Builder.fromOrFailDisallowingSymbolicMacros(thread, "repository rules");
          // TODO(adonovan): this cast doesn't look safe!
          String externalRepoName = (String) kwargs.get("name");
          if (!allowOverride
              && externalRepoName != null
              && builder.getTarget(externalRepoName) != null) {
            throw Starlark.errorf(
                "Cannot redefine repository after any load statement in the WORKSPACE file (for"
                    + " repository '%s')",
                externalRepoName);
          }
          // Add an entry in every repository from @<mainRepoName> to "@" to avoid treating
          // @<mainRepoName> as a separate repository. This will be overridden if the main
          // repository has a repo_mapping entry from <mainRepoName> to something.
          WorkspaceFactoryHelper.addMainRepoEntry(builder, externalRepoName);
          WorkspaceFactoryHelper.addRepoMappings(builder, kwargs, externalRepoName);
          RuleClass ruleClass = ruleClassMap.get(ruleClassName);
          RuleClass bindRuleClass = ruleClassMap.get("bind");
          Rule rule =
              WorkspaceFactoryHelper.createAndAddRepositoryRule(
                  builder,
                  ruleClass,
                  bindRuleClass,
                  WorkspaceFactoryHelper.getFinalKwargs(kwargs),
                  thread.getCallStack());
          RepositoryName.validateUserProvidedRepoName(rule.getName());
        } catch (RuleFactory.InvalidRuleException
            | NameConflictException
            | LabelSyntaxException e) {
          throw new EvalException(e);
        }
        return Starlark.NONE;
      }
    };
  }

  private static ImmutableMap<String, Object> createWorkspaceFunctions(
      boolean allowOverride,
      ImmutableMap<String, RuleClass> ruleClassMap,
      WorkspaceGlobals workspaceGlobals,
      StarlarkSemantics starlarkSemantics) {
    ImmutableMap.Builder<String, Object> env = ImmutableMap.builder();
    Starlark.addMethods(env, workspaceGlobals, starlarkSemantics);

    for (String ruleClass : ruleClassMap.keySet()) {
      // There is both a "bind" WORKSPACE function and a "bind" rule. In workspace files,
      // the non-rule function takes precedence.
      // TODO(cparsons): Rule functions should not be added to WORKSPACE files.
      if (!ruleClass.equals("bind")) {
        StarlarkCallable ruleFunction = newRuleFunction(ruleClassMap, ruleClass, allowOverride);
        env.put(ruleClass, ruleFunction);
      }
    }

    return env.buildOrThrow();
  }

  // TODO(b/280446865): Ideally the WORKSPACE environment would be determined by a method in
  // BazelStarlarkEnvironment. The method would accept the values of `__embedded_dir__`, etc., as
  // arguments, and defer to StarlarkGlobals to get the fixed environment (COMMON, select(), etc.).
  // But WORKSPACE logic won't live forever so it's probably not worth migrating.
  private ImmutableMap<String, Object> getDefaultEnvironment() {
    ImmutableMap.Builder<String, Object> env = ImmutableMap.builder();
    env.putAll(starlarkGlobals.getUtilToplevels());
    env.putAll(workspaceFunctions);
    if (installDir != null) {
      env.put("__embedded_dir__", installDir.getPathString());
    }
    if (workspaceDir != null) {
      env.put("__workspace_dir__", workspaceDir.getPathString());
    }
    env.put("DEFAULT_SYSTEM_JAVABASE", getDefaultSystemJavabase());
    return env.buildOrThrow();
  }

  private String getDefaultSystemJavabase() {
    // --javabase is empty if there's no locally installed JDK
    return defaultSystemJavabaseDir != null
        ? defaultSystemJavabaseDir.toString()
        : installDir.getRelative("embedded_tools/tools/jdk/nosystemjdk").getPathString();
  }

  /** Returns the entries to populate the "native" module with, for WORKSPACE-loaded .bzl files. */
  public static ImmutableMap<String, Object> createNativeModuleBindings(
      ImmutableMap<String, RuleClass> ruleClassMap, String bazelVersion) {
    // Machinery to build the collection of workspace functions.
    WorkspaceGlobals workspaceGlobals =
        new WorkspaceGlobals(/* allowWorkspaceFunction= */ false, ruleClassMap);
    // TODO(bazel-team): StarlarkSemantics should be a parameter here, as native module can be
    // configured by flags. [brandjon: This should be possible now that we create the native module
    // in StarlarkBuiltinsFunction. We could defer creation until the StarlarkSemantics are known.
    // But mind that some code may depend on being able to enumerate all possible entries regardless
    // of the particular semantics.]
    ImmutableMap<String, Object> workspaceFunctions =
        createWorkspaceFunctions(
            /* allowOverride= */ false, ruleClassMap, workspaceGlobals, StarlarkSemantics.DEFAULT);

    // Determine the contents for native.
    ImmutableMap.Builder<String, Object> bindings = new ImmutableMap.Builder<>();
    Starlark.addMethods(bindings, new StarlarkNativeModule());
    for (Map.Entry<String, Object> entry : workspaceFunctions.entrySet()) {
      String name = entry.getKey();
      if (name.startsWith("$")) {
        // Skip "abstract" rules like "$go_rule".
        continue;
      }
      // "workspace" is explicitly omitted from the native module,
      // as it must only occur at the top of a WORKSPACE file.
      // TODO(cparsons): Clean up separation between environments.
      if (name.equals("workspace")) {
        continue;
      }
      bindings.put(entry);
    }
    bindings.put("bazel_version", bazelVersion);

    return bindings.buildOrThrow();
  }

  public Map<String, Module> getLoadedModules() {
    return loadedModules;
  }

  public Map<String, Object> getVariableBindings() {
    return ImmutableMap.copyOf(bindings);
  }
}