/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.maven.scm.provider.git.gitexe.command.changelog;
  
  import java.util.ArrayList;
  import java.util.Calendar;
  import java.util.Date;
  import java.util.List;
  import java.util.Locale;
  import java.util.TimeZone;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.maven.scm.ChangeFile;
  import org.apache.maven.scm.ChangeSet;
  import org.apache.maven.scm.ScmFileStatus;
  import org.apache.maven.scm.util.AbstractConsumer;
  
  /**
   * @author <a href="mailto:struberg@yahoo.de">Mark Struberg</a>
   * @author Olivier Lamy
   */
  public class GitChangeLogConsumer extends AbstractConsumer {
      /**
       * Date formatter for git timestamp
       * we use iso format cli git log --date=iso sample : 2008-08-06 01:37:18 +0200.
       */
      private static final String GIT_TIMESTAMP_PATTERN = "yyyy-MM-dd HH:mm:ss Z";
  
      /**
       * State machine constant: expecting header.
       */
      private static final int STATUS_GET_HEADER = 1;
  
      /**
       * State machine constant: expecting author information.
       */
      private static final int STATUS_GET_AUTHOR = 2;
  
      /**
       * State machine constant: expecting parent hash information.
       */
      private static final int STATUS_RAW_TREE = 21;
  
      /**
       * State machine constant: expecting parent hash information.
       */
      private static final int STATUS_RAW_PARENT = 22;
  
      /**
       * State machine constant: expecting author name, email and timestamp information.
       */
      private static final int STATUS_RAW_AUTHOR = 23;
  
      /**
       * State machine constant: expecting committer name, email and timestamp information.
       */
      private static final int STATUS_RAW_COMMITTER = 24;
  
      /**
       * State machine constant: expecting date information.
       */
      private static final int STATUS_GET_DATE = 3;
  
      /**
       * State machine constant: expecting file information.
       */
      private static final int STATUS_GET_FILE = 4;
  
      /**
       * State machine constant: expecting comments.
       */
      private static final int STATUS_GET_COMMENT = 5;
  
      /**
       * The pattern used to match git header lines.
       */
      private static final Pattern HEADER_PATTERN = Pattern.compile("^commit ([A-Fa-f0-9]+)(?: \\((.*)\\))?$");
  
      /**
       * The pattern used to match git author lines.
       */
      private static final Pattern AUTHOR_PATTERN = Pattern.compile("^Author: (.*)");
 
     /**
      * The pattern used to match git tree hash lines (raw mode)
      */
     private static final Pattern RAW_TREE_PATTERN = Pattern.compile("^tree ([A-Fa-f0-9]+)");
 
     /**
      * The pattern used to match git parent hash lines (raw mode)
      */
     private static final Pattern RAW_PARENT_PATTERN = Pattern.compile("^parent ([A-Fa-f0-9]+)");
 
     /**
      * The pattern used to match git author lines (raw mode)
      */
     private static final Pattern RAW_AUTHOR_PATTERN = Pattern.compile("^author (.+ <.+>) ([0-9]+) (.*)");
 
     /**
      * The pattern used to match git author lines (raw mode)
      */
     private static final Pattern RAW_COMMITTER_PATTERN = Pattern.compile("^committer (.+ <.+>) ([0-9]+) (.*)");
 
     /**
      * The pattern used to match git date lines.
      */
     private static final Pattern DATE_PATTERN = Pattern.compile("^Date:\\s*(.*)");
 
     /**
      * The pattern used to match git file lines.
      */
     private static final Pattern FILE_PATTERN =
             Pattern.compile("^:\\d* \\d* [A-Fa-f0-9]*\\.* [A-Fa-f0-9]*\\.* ([A-Z])[0-9]*\\t([^\\t]*)(\\t(.*))?");
 
     /**
      * Current status of the parser.
      */
     private int status = STATUS_GET_HEADER;
 
     /**
      * List of change log entries.
      */
     private final List<ChangeSet> entries = new ArrayList<>();
 
     /**
      * The current log entry being processed by the parser.
      */
     private ChangeSet currentChange;
 
     /**
      * The current revision of the entry being processed by the parser.
      */
     private String currentRevision;
 
     /**
      * The current comment of the entry being processed by the parser.
      */
     private StringBuilder currentComment;
 
     private final String userDateFormat;
 
     /**
      * Default constructor.
      */
     public GitChangeLogConsumer(String userDateFormat) {
         this.userDateFormat = userDateFormat;
     }
 
     public List<ChangeSet> getModifications() {
         // this is needed since the processFile does not always get a the end-sequence correctly.
         processGetFile("");
 
         return entries;
     }
 
     // ----------------------------------------------------------------------
     // StreamConsumer Implementation
     // ----------------------------------------------------------------------
 
     /**
      * {@inheritDoc}
      */
     public void consumeLine(String line) {
         switch (status) {
             case STATUS_GET_HEADER:
                 processGetHeader(line);
                 break;
             case STATUS_GET_AUTHOR:
                 processGetAuthor(line);
                 break;
             case STATUS_GET_DATE:
                 processGetDate(line, null);
                 break;
             case STATUS_GET_COMMENT:
                 processGetComment(line);
                 break;
             case STATUS_GET_FILE:
                 processGetFile(line);
                 break;
             case STATUS_RAW_TREE:
                 processGetRawTree(line);
                 break;
             case STATUS_RAW_PARENT:
                 processGetRawParent(line);
                 break;
             case STATUS_RAW_AUTHOR:
                 processGetRawAuthor(line);
                 break;
             case STATUS_RAW_COMMITTER:
                 processGetRawCommitter(line);
                 break;
             default:
                 throw new IllegalStateException("Unknown state: " + status);
         }
     }
 
     // ----------------------------------------------------------------------
     //
     // ----------------------------------------------------------------------
 
     /**
      * Process the current input line in the GET_HEADER state.  The
      * author, date, and the revision of the entry are gathered.  Note,
      * Git does not have per-file revisions, instead, the entire
      * branch is given a single revision number, which is also used for
      * the revision number of each file.
      *
      * @param line a line of text from the git log output
      */
     private void processGetHeader(String line) {
         Matcher matcher = HEADER_PATTERN.matcher(line);
         if (!matcher.matches()) {
             return;
         }
 
         currentRevision = matcher.group(1);
 
         currentChange = new ChangeSet();
 
         currentChange.setRevision(currentRevision);
 
         // Extract the tags (if present)
         String tagList = matcher.group(2);
         if (tagList != null) {
             String[] rawTags = tagList.split(",");
             for (String rawTag : rawTags) {
                 String[] tagParts = rawTag.trim().split(":");
                 if (tagParts.length == 2 && "tag".equals(tagParts[0])) {
                     currentChange.addTag(tagParts[1].trim());
                 }
             }
         }
 
         status = STATUS_GET_AUTHOR;
     }
 
     /**
      * Process the current input line in the STATUS_GET_AUTHOR state.  This
      * state gathers all of the author information that are part of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetAuthor(String line) {
         // this autodetects 'raw' format
         if (RAW_TREE_PATTERN.matcher(line).matches()) {
             status = STATUS_RAW_TREE;
             processGetRawTree(line);
             return;
         }
 
         Matcher matcher = AUTHOR_PATTERN.matcher(line);
         if (!matcher.matches()) {
             return;
         }
         String author = matcher.group(1);
 
         currentChange.setAuthor(author);
 
         status = STATUS_GET_DATE;
     }
 
     /**
      * Process the current input line in the STATUS_RAW_TREE state.  This
      * state gathers tree hash part of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetRawTree(String line) {
         if (!RAW_TREE_PATTERN.matcher(line).matches()) {
             return;
         }
         // here we could set treeHash if it appears in the model: currentChange.setTreeHash( matcher.group( 1 ) );
         status = STATUS_RAW_PARENT;
     }
 
     /**
      * Process the current input line in the STATUS_RAW_PARENT state.  This
      * state gathers parent revisions of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetRawParent(String line) {
         Matcher matcher = RAW_PARENT_PATTERN.matcher(line);
         if (!matcher.matches()) {
             status = STATUS_RAW_AUTHOR;
             processGetRawAuthor(line);
             return;
         }
         String parentHash = matcher.group(1);
 
         addParentRevision(parentHash);
     }
 
     /**
      * In git log, both parent and merged revisions are called parent. Fortunately, the real parent comes first in the
      * log. This method takes care of the difference.
      *
      * @param hash -
      */
     private void addParentRevision(String hash) {
         if (currentChange.getParentRevision() == null) {
             currentChange.setParentRevision(hash);
         } else {
             currentChange.addMergedRevision(hash);
         }
     }
 
     /**
      * Process the current input line in the STATUS_RAW_AUTHOR state.  This
      * state gathers all the author information of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetRawAuthor(String line) {
         Matcher matcher = RAW_AUTHOR_PATTERN.matcher(line);
         if (!matcher.matches()) {
             return;
         }
         String author = matcher.group(1);
         currentChange.setAuthor(author);
 
         String datestring = matcher.group(2);
         String tz = matcher.group(3);
 
         // with --format=raw option (which gets us to this methods), date is always in seconds since beginning of time
         // even explicit --date=iso is ignored, so we ignore both userDateFormat and GIT_TIMESTAMP_PATTERN here
         Calendar c = Calendar.getInstance(TimeZone.getTimeZone(tz));
         c.setTimeInMillis(Long.parseLong(datestring) * 1000);
         currentChange.setDate(c.getTime());
 
         status = STATUS_RAW_COMMITTER;
     }
 
     /**
      * Process the current input line in the STATUS_RAW_AUTHOR state.  This
      * state gathers all the committer information of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetRawCommitter(String line) {
         if (!RAW_COMMITTER_PATTERN.matcher(line).matches()) {
             return;
         }
         // here we could set committer and committerDate, the same way as in processGetRawAuthor
         status = STATUS_GET_COMMENT;
     }
 
     /**
      * Process the current input line in the STATUS_GET_DATE state.  This
      * state gathers all of the date information that are part of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetDate(String line, Locale locale) {
         Matcher matcher = DATE_PATTERN.matcher(line);
         if (!matcher.matches()) {
             return;
         }
 
         String datestring = matcher.group(1);
 
         Date date = parseDate(datestring.trim(), userDateFormat, GIT_TIMESTAMP_PATTERN, locale);
 
         currentChange.setDate(date);
 
         status = STATUS_GET_COMMENT;
     }
 
     /**
      * Process the current input line in the GET_COMMENT state.  This
      * state gathers all of the comments that are part of a log entry.
      *
      * @param line a line of text from the git log output
      */
     private void processGetComment(String line) {
         if (line.length() < 4) {
             if (currentComment == null) {
                 currentComment = new StringBuilder();
             } else {
                 currentChange.setComment(currentComment.toString());
                 status = STATUS_GET_FILE;
             }
         } else {
             if (currentComment.length() > 0) {
                 currentComment.append('\n');
             }
 
             currentComment.append(line.substring(4));
         }
     }
 
     /**
      * Process the current input line in the GET_FILE state.  This state
      * adds each file entry line to the current change log entry.  Note,
      * the revision number for the entire entry is used for the revision
      * number of each file.
      *
      * @param line a line of text from the git log output
      */
     private void processGetFile(String line) {
         if (line.length() == 0) {
             if (currentChange != null) {
                 entries.add(currentChange);
             }
 
             resetChangeLog();
 
             status = STATUS_GET_HEADER;
         } else {
             Matcher matcher = FILE_PATTERN.matcher(line);
             if (!matcher.matches()) {
                 return;
             }
             final String actionChar = matcher.group(1);
             // action is currently not used
             final ScmFileStatus action;
             String name = matcher.group(2);
             String originalName = null;
             String originalRevision = null;
             if ("A".equals(actionChar)) {
                 action = ScmFileStatus.ADDED;
             } else if ("M".equals(actionChar)) {
                 action = ScmFileStatus.MODIFIED;
             } else if ("D".equals(actionChar)) {
                 action = ScmFileStatus.DELETED;
             } else if ("R".equals(actionChar)) {
                 action = ScmFileStatus.RENAMED;
                 originalName = name;
                 name = matcher.group(4);
                 originalRevision = currentChange.getParentRevision();
             } else if ("C".equals(actionChar)) {
                 action = ScmFileStatus.COPIED;
                 originalName = name;
                 name = matcher.group(4);
                 originalRevision = currentChange.getParentRevision();
             } else {
                 action = ScmFileStatus.UNKNOWN;
             }
 
             final ChangeFile changeFile = new ChangeFile(name, currentRevision);
             changeFile.setAction(action);
             changeFile.setOriginalName(originalName);
             changeFile.setOriginalRevision(originalRevision);
             currentChange.addFile(changeFile);
         }
     }
 
     private void resetChangeLog() {
         currentComment = null;
         currentChange = null;
     }
 }