/*
    * This file is part of dependency-check-core.
    *
    * 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.
   *
   * Copyright (c) 2015 Institute for Defense Analyses. All Rights Reserved.
   */
  package org.owasp.dependencycheck.analyzer;
  
  import com.github.packageurl.MalformedPackageURLException;
  import com.github.packageurl.PackageURL;
  import com.github.packageurl.PackageURLBuilder;
  import org.apache.commons.io.filefilter.NameFileFilter;
  import org.apache.commons.io.filefilter.SuffixFileFilter;
  import org.owasp.dependencycheck.Engine;
  import org.owasp.dependencycheck.analyzer.exception.AnalysisException;
  import org.owasp.dependencycheck.data.nvd.ecosystem.Ecosystem;
  import org.owasp.dependencycheck.dependency.Confidence;
  import org.owasp.dependencycheck.dependency.Dependency;
  import org.owasp.dependencycheck.dependency.EvidenceType;
  import org.owasp.dependencycheck.dependency.naming.GenericIdentifier;
  import org.owasp.dependencycheck.dependency.naming.PurlIdentifier;
  import org.owasp.dependencycheck.exception.InitializationException;
  import org.owasp.dependencycheck.utils.FileFilterBuilder;
  import org.owasp.dependencycheck.utils.Settings;
  import org.owasp.dependencycheck.utils.UrlStringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.annotation.concurrent.ThreadSafe;
  import java.io.File;
  import java.io.FileFilter;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Used to analyze a Python package, and collect information that can be used to
   * determine the associated CPE.
   *
   * @author Dale Visser
   */
  @Experimental
  @ThreadSafe
  public class PythonPackageAnalyzer extends AbstractFileTypeAnalyzer {
  
      /**
       * The logger.
       */
      private static final Logger LOGGER = LoggerFactory.getLogger(PythonPackageAnalyzer.class);
  
      /**
       * A descriptor for the type of dependencies processed or added by this
       * analyzer.
       */
      public static final String DEPENDENCY_ECOSYSTEM = Ecosystem.PYTHON;
  
      /**
       * Used when compiling file scanning regex patterns.
       */
      private static final int REGEX_OPTIONS = Pattern.DOTALL | Pattern.CASE_INSENSITIVE;
  
      /**
       * Filename extensions for files to be analyzed.
       */
      private static final String EXTENSIONS = "py";
  
      /**
       * Pattern for matching the module doc string in a source file.
       */
      private static final Pattern MODULE_DOCSTRING = Pattern.compile("^(['\\\"]{3})(.*?)\\1", REGEX_OPTIONS);
  
      /**
       * Matches assignments to version variables in Python source code.
       */
      private static final Pattern VERSION_PATTERN = Pattern.compile("\\b(__)?version(__)? *= *(['\"]+)(\\d+\\.\\d+.*?)\\3",
              REGEX_OPTIONS);
  
      /**
       * Matches assignments to title variables in Python source code.
       */
      private static final Pattern TITLE_PATTERN = compileAssignPattern("title");
  
      /**
       * Matches assignments to summary variables in Python source code.
       */
      private static final Pattern SUMMARY_PATTERN = compileAssignPattern("summary");
 
     /**
      * Matches assignments to URL/URL variables in Python source code.
      */
     private static final Pattern URI_PATTERN = compileAssignPattern("ur[il]");
 
     /**
      * Matches assignments to home page variables in Python source code.
      */
     private static final Pattern HOMEPAGE_PATTERN = compileAssignPattern("home_?page");
 
     /**
      * Matches assignments to author variables in Python source code.
      */
     private static final Pattern AUTHOR_PATTERN = compileAssignPattern("author");
 
     /**
      * Filter that detects files named "__init__.py".
      */
     private static final FileFilter INIT_PY_FILTER = new NameFileFilter("__init__.py");
 
     /**
      * The file filter for python files.
      */
     private static final FileFilter PY_FILTER = new SuffixFileFilter(".py");
 
     /**
      * The file filter used to determine which files this analyzer supports.
      */
     private static final FileFilter FILTER = FileFilterBuilder.newInstance().addExtensions(EXTENSIONS).build();
 
     /**
      * Returns the name of the Python Package Analyzer.
      *
      * @return the name of the analyzer
      */
     @Override
     public String getName() {
         return "Python Package Analyzer";
     }
 
     /**
      * Tell that we are used for information collection.
      *
      * @return INFORMATION_COLLECTION
      */
     @Override
     public AnalysisPhase getAnalysisPhase() {
         return AnalysisPhase.INFORMATION_COLLECTION;
     }
 
     /**
      * Returns the key name for the analyzers enabled setting.
      *
      * @return the key name for the analyzers enabled setting
      */
     @Override
     protected String getAnalyzerEnabledSettingKey() {
         return Settings.KEYS.ANALYZER_PYTHON_PACKAGE_ENABLED;
     }
 
     /**
      * Returns the FileFilter
      *
      * @return the FileFilter
      */
     @Override
     protected FileFilter getFileFilter() {
         return FILTER;
     }
 
     /**
      * No-op initializer implementation.
      *
      * @param engine a reference to the dependency-check engine
      * @throws InitializationException never thrown
      */
     @Override
     protected void prepareFileTypeAnalyzer(Engine engine) throws InitializationException {
         // Nothing to do here.
     }
 
     /**
      * Utility function to create a regex pattern matcher.
      *
      * @param name the value to use when constructing the assignment pattern
      * @return the compiled Pattern
      */
     private static Pattern compileAssignPattern(String name) {
         return Pattern.compile(
                 String.format("\\b(__)?%s(__)?\\b *= *(['\"]+)(.*?)\\3", name),
                 REGEX_OPTIONS);
     }
 
     /**
      * Analyzes python packages and adds evidence to the dependency.
      *
      * @param dependency the dependency being analyzed
      * @param engine the engine being used to perform the scan
      * @throws AnalysisException thrown if there is an unrecoverable error
      * analyzing the dependency
      */
     @Override
     protected void analyzeDependency(Dependency dependency, Engine engine)
             throws AnalysisException {
         dependency.setEcosystem(DEPENDENCY_ECOSYSTEM);
         final File file = dependency.getActualFile();
         final File parent = file.getParentFile();
         final String parentName = parent.getName();
         if (INIT_PY_FILTER.accept(file)) {
             //by definition, the containing folder of __init__.py is considered the package, even the file is empty:
             //"The __init__.py files are required to make Python treat the directories as containing packages"
             //see section "6.4 Packages" from https://docs.python.org/2/tutorial/modules.html;
             dependency.addEvidence(EvidenceType.PRODUCT, file.getName(), "PackageName", parentName, Confidence.HIGHEST);
             dependency.setName(parentName);
 
             final File[] fileList = parent.listFiles(PY_FILTER);
             if (fileList != null) {
                 for (final File sourceFile : fileList) {
                     analyzeFileContents(dependency, sourceFile);
                 }
             }
         } else {
             engine.removeDependency(dependency);
         }
     }
 
     /**
      * This should gather information from leading docstrings, file comments,
      * and assignments to __version__, __title__, __summary__, __uri__, __url__,
      * __home*page__, __author__, and their all caps equivalents.
      *
      * @param dependency the dependency being analyzed
      * @param file the file name to analyze
      * @throws AnalysisException thrown if there is an unrecoverable error
      */
     private void analyzeFileContents(Dependency dependency, File file)
             throws AnalysisException {
         final String contents;
         try {
             contents = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8).trim();
         } catch (IOException e) {
             throw new AnalysisException("Problem occurred while reading dependency file.", e);
         }
         if (!contents.isEmpty()) {
             final String source = file.getName();
             gatherEvidence(dependency, EvidenceType.VERSION, VERSION_PATTERN, contents,
                     source, "SourceVersion", Confidence.MEDIUM);
             addSummaryInfo(dependency, SUMMARY_PATTERN, 4, contents,
                     source, "summary");
             if (INIT_PY_FILTER.accept(file)) {
                 addSummaryInfo(dependency, MODULE_DOCSTRING, 2,
                         contents, source, "docstring");
             }
             gatherEvidence(dependency, EvidenceType.PRODUCT, TITLE_PATTERN, contents,
                     source, "SourceTitle", Confidence.LOW);
 
             gatherEvidence(dependency, EvidenceType.VENDOR, AUTHOR_PATTERN, contents,
                     source, "SourceAuthor", Confidence.MEDIUM);
             gatherHomePageEvidence(dependency, EvidenceType.VENDOR, URI_PATTERN,
                     source, "URL", contents);
             gatherHomePageEvidence(dependency, EvidenceType.VENDOR, HOMEPAGE_PATTERN,
                     source, "HomePage", contents);
 
             try {
                 final PackageURLBuilder builder = PackageURLBuilder.aPackageURL().withType("pypi").withName(dependency.getName());
                 if (dependency.getVersion() != null) {
                     builder.withVersion(dependency.getVersion());
                 }
                 final PackageURL purl = builder.build();
                 dependency.addSoftwareIdentifier(new PurlIdentifier(purl, Confidence.HIGHEST));
             } catch (MalformedPackageURLException ex) {
                 LOGGER.debug("Unable to build package url for python", ex);
                 final GenericIdentifier id;
                 if (dependency.getVersion() != null) {
                     id = new GenericIdentifier("generic:" + dependency.getName() + "@" + dependency.getVersion(), Confidence.HIGHEST);
                 } else {
                     id = new GenericIdentifier("generic:" + dependency.getName(), Confidence.HIGHEST);
                 }
                 dependency.addSoftwareIdentifier(id);
             }
         }
     }
 
     /**
      * Adds summary information to the dependency
      *
      * @param dependency the dependency being analyzed
      * @param pattern the pattern used to perform analysis
      * @param group the group from the pattern that indicates the data to use
      * @param contents the data being analyzed
      * @param source the source name to use when recording the evidence
      * @param key the key name to use when recording the evidence
      */
     private void addSummaryInfo(Dependency dependency, Pattern pattern,
                                 int group, String contents, String source, String key) {
         final Matcher matcher = pattern.matcher(contents);
         final boolean found = matcher.find();
         if (found) {
             JarAnalyzer.addDescription(dependency, matcher.group(group),
                     source, key);
         }
     }
 
     /**
      * Collects evidence from the home page URL.
      *
      * @param dependency the dependency that is being analyzed
      * @param type the type of evidence
      * @param pattern the pattern to match
      * @param source the source of the evidence
      * @param name the name of the evidence
      * @param contents the home page URL
      */
     private void gatherHomePageEvidence(Dependency dependency, EvidenceType type, Pattern pattern,
                                         String source, String name, String contents) {
         final Matcher matcher = pattern.matcher(contents);
         if (matcher.find()) {
             final String url = matcher.group(4);
             if (UrlStringUtils.isUrl(url)) {
                 dependency.addEvidence(type, source, name, url, Confidence.MEDIUM);
             }
         }
     }
 
     /**
      * Gather evidence from a Python source file using the given string
      * assignment regex pattern.
      *
      * @param dependency the dependency that is being analyzed
      * @param type the type of evidence
      * @param pattern to scan contents with
      * @param contents of Python source file
      * @param source for storing evidence
      * @param name of evidence
      * @param confidence in evidence
      */
     private void gatherEvidence(Dependency dependency, EvidenceType type, Pattern pattern, String contents,
                                 String source, String name, Confidence confidence) {
         final Matcher matcher = pattern.matcher(contents);
         final boolean found = matcher.find();
         if (found) {
             dependency.addEvidence(type, source, name, matcher.group(4), confidence);
             if (type == EvidenceType.VERSION) {
                 //TODO - this seems broken as we are cycling over py files and could be grabbing versions from multiple?
                 dependency.setVersion(matcher.group(4));
                 final String dispName = String.format("%s:%s", dependency.getName(), dependency.getVersion());
                 dependency.setDisplayFileName(dispName);
             }
         }
     }
 }