// 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.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.docgen.skylark.SkylarkDocUtils;
import com.google.devtools.build.docgen.skylark.SkylarkMethodDoc;
import com.google.devtools.build.docgen.skylark.SkylarkModuleDoc;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
import com.google.devtools.build.lib.util.Classpath;
import com.google.devtools.build.lib.util.Classpath.ClassPathException;
import java.io.File;
import java.io.IOException;
import java.text.Collator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

/**
 * A class to assemble documentation for Skylark.
 */
public final class SkylarkDocumentationProcessor {

  private static final ImmutableList<SkylarkModuleCategory> GLOBAL_CATEGORIES =
      ImmutableList.<SkylarkModuleCategory>of(
          SkylarkModuleCategory.NONE, SkylarkModuleCategory.TOP_LEVEL_TYPE);

  // Common prefix of packages that may contain Skylark modules.
  @VisibleForTesting static final String MODULES_PACKAGE_PREFIX = "com/google/devtools/build";

  private SkylarkDocumentationProcessor() {}

  /**
   * Generates the Skylark documentation to the given output directory.
   */
  public static void generateDocumentation(String outputDir, String... args)
      throws IOException, ClassPathException {
    parseOptions(args);

    Map<String, SkylarkModuleDoc> modules =
        SkylarkDocumentationCollector.collectModules(Classpath.findClasses(MODULES_PACKAGE_PREFIX));

    // Generate the top level module first in the doc
    SkylarkModuleDoc topLevelModule = modules.remove(
        SkylarkDocumentationCollector.getTopLevelModule().name());
    writePage(outputDir, topLevelModule);

    // Use a LinkedHashMap to preserve ordering of categories, as the output iterates over
    // this map's entry set to determine category ordering.
    Map<SkylarkModuleCategory, List<SkylarkModuleDoc>> modulesByCategory = new LinkedHashMap<>();
    for (SkylarkModuleCategory c : SkylarkModuleCategory.values()) {
      modulesByCategory.put(c, new ArrayList<SkylarkModuleDoc>());
    }

    modulesByCategory.get(topLevelModule.getAnnotation().category()).add(topLevelModule);

    for (SkylarkModuleDoc module : modules.values()) {
      if (module.getAnnotation().documented()) {
        writePage(outputDir, module);
        modulesByCategory.get(module.getAnnotation().category()).add(module);
      }
    }
    Collator us = Collator.getInstance(Locale.US);
    for (List<SkylarkModuleDoc> module : modulesByCategory.values()) {
      Collections.sort(module, (doc1, doc2) -> us.compare(doc1.getTitle(), doc2.getTitle()));
    }
    writeCategoryPage(SkylarkModuleCategory.CONFIGURATION_FRAGMENT, outputDir, modulesByCategory);
    writeCategoryPage(SkylarkModuleCategory.BUILTIN, outputDir, modulesByCategory);
    writeCategoryPage(SkylarkModuleCategory.PROVIDER, outputDir, modulesByCategory);
    writeNavPage(outputDir, modulesByCategory.get(SkylarkModuleCategory.TOP_LEVEL_TYPE));

    // In the code, there are two SkylarkModuleCategory instances that have no heading:
    // TOP_LEVEL_TYPE and NONE.

    // TOP_LEVEL_TYPE also contains the "global" module.
    // We remove both categories and the "global" module from the map and display them manually:
    // - Methods in the "global" module are displayed under "Global Methods and Constants".
    // - Modules in both categories are displayed under "Global Modules" (except for the global
    // module itself).
    List<String> globalFunctions = new ArrayList<>();
    SkylarkModuleDoc globalModule = findGlobalModule(modulesByCategory);
    for (SkylarkMethodDoc method : globalModule.getMethods()) {
      if (method.documented()) {
        globalFunctions.add(method.getName());
      }
    }

    List<String> globalModules = new ArrayList<>();
    for (SkylarkModuleCategory globalCategory : GLOBAL_CATEGORIES) {
      List<SkylarkModuleDoc> allGlobalModules = modulesByCategory.remove(globalCategory);
      for (SkylarkModuleDoc module : allGlobalModules) {
        if (!module.getName().equals(globalModule.getName())) {
          globalModules.add(module.getName());
        }
      }
    }

    Collections.sort(globalModules, us);
    writeOverviewPage(
        outputDir, globalModule.getName(), globalFunctions, globalModules, modulesByCategory);
  }

  private static SkylarkModuleDoc findGlobalModule(
      Map<SkylarkModuleCategory, List<SkylarkModuleDoc>> modulesByCategory) {
    List<SkylarkModuleDoc> topLevelModules =
        modulesByCategory.get(SkylarkModuleCategory.TOP_LEVEL_TYPE);
    String globalModuleName = SkylarkDocumentationCollector.getTopLevelModule().name();
    for (SkylarkModuleDoc module : topLevelModules) {
      if (module.getName().equals(globalModuleName)) {
        return module;
      }
    }

    throw new IllegalStateException("No globals module in the top level category.");
  }

  private static void writePage(String outputDir, SkylarkModuleDoc module) throws IOException {
    File skylarkDocPath = new File(outputDir + "/" + module.getName() + ".html");
    Page page = TemplateEngine.newPage(DocgenConsts.SKYLARK_LIBRARY_TEMPLATE);
    page.add("module", module);
    page.write(skylarkDocPath);
  }

  private static void writeCategoryPage(
      SkylarkModuleCategory category,
      String outputDir,
      Map<SkylarkModuleCategory, List<SkylarkModuleDoc>> modules) throws IOException {
    File skylarkDocPath = new File(String.format("%s/skylark-%s.html",
        outputDir, category.getTemplateIdentifier()));
    Page page = TemplateEngine.newPage(DocgenConsts.SKYLARK_MODULE_CATEGORY_TEMPLATE);
    page.add("category", category);
    page.add("modules", modules.get(category));
    page.add("description", SkylarkDocUtils.substituteVariables(category.getDescription()));
    page.write(skylarkDocPath);
  }

  private static void writeNavPage(String outputDir, List<SkylarkModuleDoc> navModules)
      throws IOException {
    File navFile = new File(outputDir + "/skylark-nav.html");
    Page page = TemplateEngine.newPage(DocgenConsts.SKYLARK_NAV_TEMPLATE);
    page.add("modules", navModules);
    page.write(navFile);
  }

  private static void writeOverviewPage(
      String outputDir,
      String globalModuleName,
      List<String> globalFunctions,
      List<String> globalModules,
      Map<SkylarkModuleCategory, List<SkylarkModuleDoc>> modulesPerCategory)
      throws IOException {
    File skylarkDocPath = new File(outputDir + "/skylark-overview.html");
    Page page = TemplateEngine.newPage(DocgenConsts.SKYLARK_OVERVIEW_TEMPLATE);
    page.add("global_name", globalModuleName);
    page.add("global_functions", globalFunctions);
    page.add("global_modules", globalModules);
    page.add("modules", modulesPerCategory);
    page.write(skylarkDocPath);
  }

  private static void parseOptions(String... args) {
    for (String arg : args) {
      if (arg.startsWith("--be_root=")) {
        DocgenConsts.BeDocsRoot = arg.split("--be_root=", 2)[1];
      }
      if (arg.startsWith("--doc_extension=")) {
        DocgenConsts.documentationExtension = arg.split("--doc_extension=", 2)[1];
      }
    }
  }
}