// 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.docgen;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.LinkedListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Ordering;
import com.google.common.collect.Sets;
import com.google.devtools.build.docgen.DocgenConsts.RuleType;
import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
import com.google.devtools.build.lib.packages.RuleClass;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * A class to assemble documentation for the Build Encyclopedia. This class uses
 * {@link BuildDocCollector} to extract documentation fragments from rule classes.
 */
public class BuildEncyclopediaProcessor {
  private static final Predicate<String> RULE_WORTH_DOCUMENTING = new Predicate<String>() {
    @Override
    public boolean apply(String name) {
      return !name.contains("$");
    }
  };

  private ConfiguredRuleClassProvider ruleClassProvider;

  /**
   * Creates the BuildEncyclopediaProcessor instance. The ruleClassProvider parameter
   * is used for rule class hierarchy and attribute checking.
   *
   */
  public BuildEncyclopediaProcessor(ConfiguredRuleClassProvider ruleClassProvider) {
    this.ruleClassProvider = Preconditions.checkNotNull(ruleClassProvider);
  }

  /**
   * Collects and processes all the rule and attribute documentation in inputDirs and
   * generates the Build Encyclopedia into the outputDir.
   *
   * @param inputDirs list of directory to scan for document in the source code
   * @param outputRootDir output directory where to write the build encyclopedia
   * @param blackList optional path to a file listing rules to not document
   */
  public void generateDocumentation(String[] inputDirs, String outputDir, String blackList)
      throws BuildEncyclopediaDocException, IOException {
    writeStaticPage(outputDir, "make-variables");
    writeStaticPage(outputDir, "predefined-python-variables");
    writeStaticPage(outputDir, "functions");
    writeCommonDefinitionsPage(outputDir);

    BuildDocCollector collector = new BuildDocCollector(ruleClassProvider, false);
    Map<String, RuleDocumentation> ruleDocEntries = collector.collect(inputDirs, blackList);
    warnAboutUndocumentedRules(
        Sets.difference(ruleClassProvider.getRuleClassMap().keySet(), ruleDocEntries.keySet()));

    writeRuleDocs(outputDir, ruleDocEntries.values());
  }

  private void writeStaticPage(String outputDir, String name) throws IOException {
    File file = new File(outputDir + "/" + name + ".html");
    Page page = TemplateEngine.newPage(
        "com/google/devtools/build/docgen/templates/be/" + name + ".vm");
    page.write(file);
  }

  private void writeCommonDefinitionsPage(String outputDir) throws IOException {
    File file = new File(outputDir + "/common-definitions.html");
    Page page = TemplateEngine.newPage(DocgenConsts.COMMON_DEFINITIONS_TEMPLATE);
    page.add("commonAttributes", PredefinedAttributes.COMMON_ATTRIBUTES);
    page.add("testAttributes", PredefinedAttributes.TEST_ATTRIBUTES);
    page.add("binaryAttributes", PredefinedAttributes.BINARY_ATTRIBUTES);
    page.write(file);
  }

  private List<RuleFamily> assembleRuleFamilies(
      Map<String, ListMultimap<RuleType, RuleDocumentation>> ruleMapping,
      Set<String> ruleFamilyNames) {
    List<RuleFamily> ruleFamilies = new ArrayList<>(ruleFamilyNames.size());
    for (String name : ruleFamilyNames) {
      ListMultimap<RuleType, RuleDocumentation> ruleTypeMap = ruleMapping.get(name);
      ruleFamilies.add(new RuleFamily(ruleTypeMap, name));
    }
    return ruleFamilies;
  }

  private void writeRuleDocs(String outputDir, Iterable<RuleDocumentation> docEntries)
      throws BuildEncyclopediaDocException, IOException {
    // Separate rule families into language-specific and generic ones.
    Set<String> langSpecificRuleFamilyNames = new TreeSet<>();
    Set<String> genericRuleFamilyNames = new TreeSet<>();
    separateRuleFamilies(docEntries, langSpecificRuleFamilyNames, genericRuleFamilyNames);

    // Create a mapping of rules based on rule type and family.
    Map<String, ListMultimap<RuleType, RuleDocumentation>> ruleMapping = new HashMap<>();
    createRuleMapping(docEntries, ruleMapping);

    // Create lists of RuleFamily objects that will be used to generate the documentation.
    // The separate language-specific and general rule families will be used to generate
    // the Overview page while the list containing all rule families will be used to
    // generate all other documentation.
    List<RuleFamily> langSpecificRuleFamilies =
        assembleRuleFamilies(ruleMapping, langSpecificRuleFamilyNames);
    List<RuleFamily> genericRuleFamilies =
        assembleRuleFamilies(ruleMapping, genericRuleFamilyNames);
    List<RuleFamily> allRuleFamilies = new ArrayList<>(langSpecificRuleFamilies);
    allRuleFamilies.addAll(genericRuleFamilies);

    // Generate documentation.
    writeOverviewPage(outputDir, langSpecificRuleFamilies, genericRuleFamilies);
    writeBeNav(outputDir, allRuleFamilies);
    for (RuleFamily ruleFamily : allRuleFamilies) {
      if (ruleFamily.size() > 0) {
        writeRuleDoc(outputDir, ruleFamily);
      }
    }
  }

  private void writeOverviewPage(String outputDir,
      List<RuleFamily> langSpecificRuleFamilies,
      List<RuleFamily> genericRuleFamilies)
      throws BuildEncyclopediaDocException, IOException {
    File file = new File(outputDir + "/overview.html");
    Page page = TemplateEngine.newPage(DocgenConsts.OVERVIEW_TEMPLATE);
    page.add("langSpecificRuleFamilies", langSpecificRuleFamilies);
    page.add("genericRuleFamilies", genericRuleFamilies);
    page.write(file);
  }

  private void writeRuleDoc(String outputDir, RuleFamily ruleFamily)
      throws BuildEncyclopediaDocException, IOException {
    File file = new File(outputDir + "/" + ruleFamily.getId() + ".html");
    Page page = TemplateEngine.newPage(DocgenConsts.RULES_TEMPLATE);
    page.add("ruleFamily", ruleFamily);
    page.write(file);
  }

  private void writeBeNav(String outputDir, List<RuleFamily> ruleFamilies) throws IOException {
    File file = new File(outputDir + "/be-nav.html");
    Page page = TemplateEngine.newPage(DocgenConsts.BE_NAV_TEMPLATE);
    page.add("ruleFamilies", ruleFamilies);
    page.write(file);
  }

  /**
   * Create a mapping of rules based on rule type and family.
   */
  private void createRuleMapping(Iterable<RuleDocumentation> docEntries,
      Map<String, ListMultimap<RuleType, RuleDocumentation>> ruleMapping)
      throws BuildEncyclopediaDocException {
    for (RuleDocumentation ruleDoc : docEntries) {
      RuleClass ruleClass = ruleClassProvider.getRuleClassMap().get(ruleDoc.getRuleName());
      if (ruleClass != null) {
        String ruleFamily = ruleDoc.getRuleFamily();
        if (!ruleMapping.containsKey(ruleFamily)) {
          ruleMapping.put(ruleFamily, LinkedListMultimap.<RuleType, RuleDocumentation>create());
        }
        if (ruleClass.isDocumented()) {
          ruleMapping.get(ruleFamily).put(ruleDoc.getRuleType(), ruleDoc);
        }
      } else {
        throw ruleDoc.createException("Can't find RuleClass for " + ruleDoc.getRuleName());
      }
    }
  }

  /**
   * Separates all rule families in docEntries into language-specific rules and generic rules.
   */
  private void separateRuleFamilies(Iterable<RuleDocumentation> docEntries,
      Set<String> langSpecific, Set<String> generic)
      throws BuildEncyclopediaDocException {
    for (RuleDocumentation ruleDoc : docEntries) {
      if (ruleDoc.isLanguageSpecific()) {
        if (generic.contains(ruleDoc.getRuleFamily())) {
          throw ruleDoc.createException("The rule is marked as being language-specific, but other "
              + "rules of the same family have already been marked as being not.");
        }
        langSpecific.add(ruleDoc.getRuleFamily());
      } else {
        if (langSpecific.contains(ruleDoc.getRuleFamily())) {
          throw ruleDoc.createException("The rule is marked as being generic, but other rules of "
              + "the same family have already been marked as being language-specific.");
        }
        generic.add(ruleDoc.getRuleFamily());
      }
    }
  }

  private static void warnAboutUndocumentedRules(Iterable<String> rulesWithoutDocumentation) {
      Iterable<String> undocumentedRules = Iterables.filter(rulesWithoutDocumentation,
          RULE_WORTH_DOCUMENTING);
      System.err.printf("WARNING: The following rules are undocumented: [%s]\n",
          Joiner.on(", ").join(Ordering.<String>natural().immutableSortedCopy(undocumentedRules)));
  }
}