/*
 * diff.c :  routines for doing diffs
 *
 * ====================================================================
 *    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.
 * ====================================================================
 */


#include <apr.h>
#include <apr_pools.h>
#include <apr_general.h>

#include "svn_pools.h"
#include "svn_error.h"
#include "svn_diff.h"
#include "svn_types.h"

#include "diff.h"


svn_diff__token_index_t*
svn_diff__get_token_counts(svn_diff__position_t *loop_start,
                           svn_diff__token_index_t num_tokens,
                           apr_pool_t *pool)
{
  svn_diff__token_index_t *token_counts;
  svn_diff__token_index_t token_index;
  svn_diff__position_t *current;

  token_counts = apr_palloc(pool, num_tokens * sizeof(*token_counts));
  for (token_index = 0; token_index < num_tokens; token_index++)
    token_counts[token_index] = 0;

  current = loop_start;
  if (current != NULL)
    {
      do
        {
          token_counts[current->token_index]++;
          current = current->next;
        }
      while (current != loop_start);
    }

  return token_counts;
}


svn_diff_t *
svn_diff__diff(svn_diff__lcs_t *lcs,
               apr_off_t original_start, apr_off_t modified_start,
               svn_boolean_t want_common,
               apr_pool_t *pool)
{
  svn_diff_t *diff;
  svn_diff_t **diff_ref = &diff;

  while (1)
    {
      if (original_start < lcs->position[0]->offset
          || modified_start < lcs->position[1]->offset)
      {
          (*diff_ref) = apr_palloc(pool, sizeof(**diff_ref));

          (*diff_ref)->type = svn_diff__type_diff_modified;
          (*diff_ref)->original_start = original_start - 1;
          (*diff_ref)->original_length =
            lcs->position[0]->offset - original_start;
          (*diff_ref)->modified_start = modified_start - 1;
          (*diff_ref)->modified_length =
            lcs->position[1]->offset - modified_start;
          (*diff_ref)->latest_start = 0;
          (*diff_ref)->latest_length = 0;

          diff_ref = &(*diff_ref)->next;
      }

      /* Detect the EOF */
      if (lcs->length == 0)
          break;

      original_start = lcs->position[0]->offset;
      modified_start = lcs->position[1]->offset;

      if (want_common)
        {
          (*diff_ref) = apr_palloc(pool, sizeof(**diff_ref));

          (*diff_ref)->type = svn_diff__type_common;
          (*diff_ref)->original_start = original_start - 1;
          (*diff_ref)->original_length = lcs->length;
          (*diff_ref)->modified_start = modified_start - 1;
          (*diff_ref)->modified_length = lcs->length;
          (*diff_ref)->latest_start = 0;
          (*diff_ref)->latest_length = 0;

          diff_ref = &(*diff_ref)->next;
        }

      original_start += lcs->length;
      modified_start += lcs->length;

      lcs = lcs->next;
    }

  *diff_ref = NULL;

  return diff;
}


svn_error_t *
svn_diff_diff_2(svn_diff_t **diff,
                void *diff_baton,
                const svn_diff_fns2_t *vtable,
                apr_pool_t *pool)
{
  svn_diff__tree_t *tree;
  svn_diff__position_t *position_list[2];
  svn_diff__token_index_t num_tokens;
  svn_diff__token_index_t *token_counts[2];
  svn_diff_datasource_e datasource[] = {svn_diff_datasource_original,
                                        svn_diff_datasource_modified};
  svn_diff__lcs_t *lcs;
  apr_pool_t *subpool;
  apr_pool_t *treepool;
  apr_off_t prefix_lines = 0;
  apr_off_t suffix_lines = 0;

  *diff = NULL;

  subpool = svn_pool_create(pool);
  treepool = svn_pool_create(pool);

  svn_diff__tree_create(&tree, treepool);

  SVN_ERR(vtable->datasources_open(diff_baton, &prefix_lines, &suffix_lines,
                                   datasource, 2));

  /* Insert the data into the tree */
  SVN_ERR(svn_diff__get_tokens(&position_list[0],
                               tree,
                               diff_baton, vtable,
                               svn_diff_datasource_original,
                               prefix_lines,
                               subpool));

  SVN_ERR(svn_diff__get_tokens(&position_list[1],
                               tree,
                               diff_baton, vtable,
                               svn_diff_datasource_modified,
                               prefix_lines,
                               subpool));

  num_tokens = svn_diff__get_node_count(tree);

  /* The cool part is that we don't need the tokens anymore.
   * Allow the app to clean them up if it wants to.
   */
  if (vtable->token_discard_all != NULL)
    vtable->token_discard_all(diff_baton);

  /* We don't need the nodes in the tree either anymore, nor the tree itself */
  svn_pool_destroy(treepool);

  token_counts[0] = svn_diff__get_token_counts(position_list[0], num_tokens,
                                               subpool);
  token_counts[1] = svn_diff__get_token_counts(position_list[1], num_tokens,
                                               subpool);

  /* Get the lcs */
  lcs = svn_diff__lcs(position_list[0], position_list[1], token_counts[0],
                      token_counts[1], num_tokens, prefix_lines,
                      suffix_lines, subpool);

  /* Produce the diff */
  *diff = svn_diff__diff(lcs, 1, 1, TRUE, pool);

  /* Get rid of all the data we don't have a use for anymore */
  svn_pool_destroy(subpool);

  return SVN_NO_ERROR;
}