// copyright (C) 2002, 2003 graydon hoare <graydon@pobox.com>
// all rights reserved.
// licensed to the public under the terms of the GNU GPL (>= 2)
// see the file COPYING for details

#include <algorithm>
#include <iterator>
#include <vector>
#include <string>
#include <iostream>

#include "config.h"
#include "diff_patch.hh"
#include "interner.hh"
#include "lcs.hh"
#include "manifest.hh"
#include "packet.hh"
#include "sanity.hh"
#include "transforms.hh"
#include "vocab.hh"

using namespace std;

bool guess_binary(string const & s)
{
  // these do not occur in ASCII text files
  // FIXME: this heuristic is (a) crap and (b) hardcoded. fix both these.
  if (s.find_first_of("\x00\x01\x02\x03\x04\x05\x06\x0e\x0f"
                      "\x10\x11\x12\x13\x14\x15\x16\x17\x18"
                      "\x19\x1a\x1c\x1d\x1e\x1f") != string::npos)
    return true;
  return false;
}

//
// a 3-way merge works like this:
//
//            /---->   right
//    ancestor
//            \---->   left
//
// first you compute the edit list "EDITS(ancestor,left)".
// 
// then you make an offset table "leftpos" which describes positions in
// "ancestor" as they map to "left"; that is, for 0 < apos <
// ancestor.size(), we have
//
//  left[leftpos[apos]] == ancestor[apos]
//
// you do this by walking through the edit list and either jumping the
// current index ahead an extra position, on an insert, or remaining still,
// on a delete. on an insert *or* a delete, you push the current index back
// onto the leftpos array.
//
// next you compute the edit list "EDITS(ancestor,right)".
//
// you then go through this edit list applying the edits to left, rather
// than ancestor, and using the table leftpos to map the position of each
// edit to an appropriate spot in left. this means you walk a "curr_left" 
// index through the edits, and for each edit e:
//
// - if e is a delete (and e.pos is a position in ancestor)
//   - increment curr_left without copying anything to "merged"
//
// - if e is an insert (and e.pos is a position in right)
//   - copy right[e.pos] to "merged"
//   - leave curr_left alone
//
// - when advancing to apos (and apos is a position in ancestor)
//   - copy left[curr_left] to merged while curr_left < leftpos[apos]
//
//
// the practical upshot is that you apply the delta from ancestor->right
// to the adjusted contexts in left, producing something vaguely like
// the concatenation of delta(ancestor,left) :: delta(ancestor,right).
//
// NB: this is, as far as I can tell, what diff3 does. I don't think I'm
// infringing on anyone's fancy patents here.
//

typedef enum { preserved = 0, deleted = 1, changed = 2 } edit_t;
static char *etab[3] = 
  {
    "preserved",
    "deleted",
    "changed"
  };

struct extent
{
  extent(size_t p, size_t l, edit_t t) 
    : pos(p), len(l), type(t)
  {}
  size_t pos;
  size_t len;
  edit_t type;
};

void calculate_extents(vector<long> const & a_b_edits,
                       vector<long> const & b,
                       vector<long> & prefix,
                       vector<extent> & extents,
                       vector<long> & suffix,
                       size_t const a_len,
                       interner<long> & intern)
{
  extents.reserve(a_len * 2);

  size_t a_pos = 0, b_pos = 0;

  for (vector<long>::const_iterator i = a_b_edits.begin(); 
       i != a_b_edits.end(); ++i)
    {
      // L(F("edit: %d") % *i);
      if (*i < 0)
        {
          // negative elements code the negation of the one-based index into A
          // of the element to be deleted
          size_t a_deleted = (-1 - *i);

          // fill positions out to the deletion point
          while (a_pos < a_deleted)
            {
              a_pos++;
              extents.push_back(extent(b_pos++, 1, preserved));
            }

          // L(F(" -- delete at A-pos %d (B-pos = %d)\n") % a_deleted % b_pos);

          // skip the deleted line
          a_pos++;
          extents.push_back(extent(b_pos, 0, deleted));
        }
      else
        {
          // positive elements code the one-based index into B of the element to
          // be inserted
          size_t b_inserted = (*i - 1);

          // fill positions out to the insertion point
          while (b_pos < b_inserted)
            {
              a_pos++;
              extents.push_back(extent(b_pos++, 1, preserved));
            }

          // L(F(" -- insert at B-pos %d (A-pos = %d) : '%s'\n") 
          //   % b_inserted % a_pos % intern.lookup(b.at(b_inserted)));
          
          // record that there was an insertion, but a_pos did not move.
          if ((b_pos == 0 && extents.empty())
              || (b_pos == prefix.size()))
            {
              prefix.push_back(b.at(b_pos));
            }
          else if (a_len == a_pos)
            {
              suffix.push_back(b.at(b_pos));
            }
          else
            {
              // make the insertion
              extents.back().type = changed;
              extents.back().len++;
            }
          b_pos++;
        }
    }

  while (extents.size() < a_len)
    extents.push_back(extent(b_pos++, 1, preserved));
}

void normalize_extents(vector<extent> & a_b_map,
                       vector<long> const & a,
                       vector<long> const & b)
{
  for (size_t i = 0; i < a_b_map.size(); ++i)
    {
      if (i > 0)
      { 
        size_t j = i;
        while (j > 0
               && (a_b_map.at(j-1).type == preserved)
               && (a_b_map.at(j).type == changed)
               && (a.at(j) == a.at(j-1))
               && (b.at(a_b_map.at(j-1).pos) == 
                   b.at(a_b_map.at(j).pos + a_b_map.at(j).len - 1)))
          {

            //
            // Coming into this loop, we've identified this situation:
            //
            //       A                               B
            //   --------                    ----------------
            //   j-1: foo   --preserved-->   mapped[j-1]: foo
            //     j: foo   --changed---->   mapped[  j]: bar 
            //                                            foo
            //
            // The normalization we want to perform is to move all
            // "changed" extents to the earliest possible position which
            // still causes the same B image to be produced.
            // 
            //       A                               B
            //   --------                    ----------------
            //   j-1: foo   --changed---->   mapped[j-1]: foo
            //                                            bar
            //     j: foo   --preserved-->   mapped[  j]: foo
            //

            // This code is almost untested, because we've only been able to
            // find one test case that exercises it!  Maybe this text will
            // make us look bad when/if someone discovers it, but better to
            // have a bad reputation and good software than vice-versa.
            W(F("You've found files that trigger a strange edge-case of the merge logic.\n"));
            W(F("We believe it works, but don't have many tests; so, if you could send us\n"));
            W(F("a note, and, if possible, the files that triggered it for inclusion in our\n"));
            W(F("test suite, we'd appreciate it.  Address: " PACKAGE_BUGREPORT ".  Thanks!\n"));

            L(F("exchanging preserved extent [%d+%d] with changed extent [%d+%d]\n")
              % a_b_map.at(j-1).pos
              % a_b_map.at(j-1).len
              % a_b_map.at(j).pos
              % a_b_map.at(j).len);

            swap(a_b_map.at(j-1).len, a_b_map.at(j).len);
            swap(a_b_map.at(j-1).type, a_b_map.at(j).type);
            --j;
          }
      }
    }

  for (size_t i = 0; i < a_b_map.size(); ++i)
    {
      if (i > 0)
      { 
        size_t j = i;
        while (j > 0
               && a_b_map.at(j).type == changed
               && a_b_map.at(j-1).type == changed
               && a_b_map.at(j).len > 1
               && a_b_map.at(j-1).pos + a_b_map.at(j-1).len == a_b_map.at(j).pos)
          {
            // step 1: move a chunk from this insert extent to its
            // predecessor
            size_t piece = a_b_map.at(j).len - 1;
            //      L(F("moving change piece of len %d from pos %d to pos %d\n")
            //        % piece
            //        % a_b_map.at(j).pos
            //        % a_b_map.at(j-1).pos);
            a_b_map.at(j).len = 1;
            a_b_map.at(j).pos += piece;
            a_b_map.at(j-1).len += piece;
            
            // step 2: if this extent (now of length 1) has become a "changed" 
            // extent identical to its previous state, switch it to a "preserved"
            // extent.
            if (b.at(a_b_map.at(j).pos) == a.at(j))
              {
                //              L(F("changing normalized 'changed' extent at %d to 'preserved'\n")
                //                % a_b_map.at(j).pos);
                a_b_map.at(j).type = preserved;
              }
            --j;
          }
      }
    }
}


void merge_extents(vector<extent> const & a_b_map,
                   vector<extent> const & a_c_map,
                   vector<long> const & b,
                   vector<long> const & c,
                   interner<long> const & in,
                   vector<long> & merged)
{
  I(a_b_map.size() == a_c_map.size());

  vector<extent>::const_iterator i = a_b_map.begin();
  vector<extent>::const_iterator j = a_c_map.begin();
  merged.reserve(a_b_map.size() * 2);

  //   for (; i != a_b_map.end(); ++i, ++j)
  //     {
  
  //       L(F("trying to merge: [%s %d %d] vs. [%s %d %d] \n")
  //            % etab[i->type] % i->pos % i->len 
  //            % etab[j->type] % j->pos % j->len);
  //     }
  
  //   i = a_b_map.begin();
  //   j = a_c_map.begin();

  for (; i != a_b_map.end(); ++i, ++j)
    {

      //       L(F("trying to merge: [%s %d %d] vs. [%s %d %d] \n")
      //                % etab[i->type] % i->pos % i->len 
      //                % etab[j->type] % j->pos % j->len);
      
      // mutual, identical preserves / inserts / changes
      if (((i->type == changed && j->type == changed)
           || (i->type == preserved && j->type == preserved))
          && i->len == j->len)
        {
          for (size_t k = 0; k < i->len; ++k)
            {
              if (b.at(i->pos + k) != c.at(j->pos + k))
                {
                  L(F("conflicting edits: %s %d[%d] '%s' vs. %s %d[%d] '%s'\n")
                    % etab[i->type] % i->pos % k % in.lookup(b.at(i->pos + k)) 
                    % etab[j->type] % j->pos % k % in.lookup(c.at(j->pos + k)));
                  throw conflict();
                }
              merged.push_back(b.at(i->pos + k));
            }
        }

      // mutual or single-edge deletes
      else if ((i->type == deleted && j->len == deleted)
               || (i->type == deleted && j->type == preserved)
               || (i->type == preserved && j->type == deleted))
        { 
          // do nothing
        }

      // single-edge insert / changes 
      else if (i->type == changed && j->type == preserved)
        for (size_t k = 0; k < i->len; ++k)
          merged.push_back(b.at(i->pos + k));
      
      else if (i->type == preserved && j->type == changed)
        for (size_t k = 0; k < j->len; ++k)
          merged.push_back(c.at(j->pos + k));
      
      else
        {
          L(F("conflicting edits: [%s %d %d] vs. [%s %d %d]\n")
            % etab[i->type] % i->pos % i->len 
            % etab[j->type] % j->pos % j->len);
          throw conflict();       
        }      
      
      //       if (merged.empty())
      //        L(F(" --> EMPTY\n"));
      //       else
      //                L(F(" --> [%d]: %s\n") % (merged.size() - 1) % in.lookup(merged.back()));
    }
}


void merge_via_edit_scripts(vector<string> const & ancestor,
                            vector<string> const & left,                            
                            vector<string> const & right,
                            vector<string> & merged)
{
  vector<long> anc_interned;  
  vector<long> left_interned, right_interned;  
  vector<long> left_edits, right_edits;  
  vector<long> left_prefix, right_prefix;  
  vector<long> left_suffix, right_suffix;  
  vector<extent> left_extents, right_extents;
  vector<long> merged_interned;
  interner<long> in;

  //   for (int i = 0; i < std::min(std::min(left.size(), right.size()), ancestor.size()); ++i)
  //     {
  //       std::cerr << "[" << i << "] " << left[i] << " " << ancestor[i] <<  " " << right[i] << endl;
  //     }

  anc_interned.reserve(ancestor.size());
  for (vector<string>::const_iterator i = ancestor.begin();
       i != ancestor.end(); ++i)
    anc_interned.push_back(in.intern(*i));

  left_interned.reserve(left.size());
  for (vector<string>::const_iterator i = left.begin();
       i != left.end(); ++i)
    left_interned.push_back(in.intern(*i));

  right_interned.reserve(right.size());
  for (vector<string>::const_iterator i = right.begin();
       i != right.end(); ++i)
    right_interned.push_back(in.intern(*i));

  L(F("calculating left edit script on %d -> %d lines\n")
    % anc_interned.size() % left_interned.size());

  edit_script(anc_interned.begin(), anc_interned.end(),
              left_interned.begin(), left_interned.end(),
              std::min(ancestor.size(), left.size()),
              left_edits);
  
  L(F("calculating right edit script on %d -> %d lines\n")
    % anc_interned.size() % right_interned.size());

  edit_script(anc_interned.begin(), anc_interned.end(),
              right_interned.begin(), right_interned.end(),
              std::min(ancestor.size(), right.size()),
              right_edits);

  L(F("calculating left extents on %d edits\n") % left_edits.size());
  calculate_extents(left_edits, left_interned, 
                    left_prefix, left_extents, left_suffix, 
                    anc_interned.size(), in);

  L(F("calculating right extents on %d edits\n") % right_edits.size());
  calculate_extents(right_edits, right_interned, 
                    right_prefix, right_extents, right_suffix, 
                    anc_interned.size(), in);

  L(F("normalizing %d right extents\n") % right_extents.size());
  normalize_extents(right_extents, anc_interned, right_interned);

  L(F("normalizing %d left extents\n") % left_extents.size());
  normalize_extents(left_extents, anc_interned, left_interned);


  if ((!right_prefix.empty()) && (!left_prefix.empty()))
    {
      L(F("conflicting prefixes\n"));
      throw conflict();
    }

  if ((!right_suffix.empty()) && (!left_suffix.empty()))
    {
      L(F("conflicting suffixes\n"));
      throw conflict();
    }

  L(F("merging %d left, %d right extents\n") 
    % left_extents.size() % right_extents.size());

  copy(left_prefix.begin(), left_prefix.end(), back_inserter(merged_interned));
  copy(right_prefix.begin(), right_prefix.end(), back_inserter(merged_interned));

  merge_extents(left_extents, right_extents,
                left_interned, right_interned, 
                in, merged_interned);

  copy(left_suffix.begin(), left_suffix.end(), back_inserter(merged_interned));
  copy(right_suffix.begin(), right_suffix.end(), back_inserter(merged_interned));

  merged.reserve(merged_interned.size());
  for (vector<long>::const_iterator i = merged_interned.begin();
       i != merged_interned.end(); ++i)
    merged.push_back(in.lookup(*i));
}


bool merge3(vector<string> const & ancestor,
            vector<string> const & left,
            vector<string> const & right,
            vector<string> & merged)
{
  try 
   { 
      merge_via_edit_scripts(ancestor, left, right, merged);
    }
  catch(conflict & c)
    {
      L(F("conflict detected. no merge.\n"));
      return false;
    }
  return true;
}


merge_provider::merge_provider(app_state & app, 
                               manifest_map const & anc_man,
                               manifest_map const & left_man, 
                               manifest_map const & right_man)
  : app(app), anc_man(anc_man), left_man(left_man), right_man(right_man)
{}

void merge_provider::record_merge(file_id const & left_ident, 
                                         file_id const & right_ident, 
                                         file_id const & merged_ident,
                                         file_data const & left_data, 
                                         file_data const & merged_data)
{  
  L(F("recording successful merge of %s <-> %s into %s\n")
    % left_ident % right_ident % merged_ident);

  base64< gzip<delta> > merge_delta;
  transaction_guard guard(app.db);

  diff(left_data.inner(), merged_data.inner(), merge_delta);  
  packet_db_writer dbw(app);
  dbw.consume_file_delta (left_ident, merged_ident, file_delta(merge_delta));
  guard.commit();
}

void merge_provider::get_version(file_path const & path,
                                 file_id const & ident,
                                 file_data & dat)
{
  app.db.get_file_version(ident, dat);
}

std::string merge_provider::get_file_encoding(file_path const & path,
                                              manifest_map const & man)
{
  std::string enc;
  if (get_attribute_from_db(path, encoding_attribute, man, enc, app))
    return enc;
  else
    return default_encoding;
}

bool merge_provider::try_to_merge_files(file_path const & anc_path,
                                        file_path const & left_path,
                                        file_path const & right_path,
                                        file_path const & merged_path,
                                        file_id const & ancestor_id,                                    
                                        file_id const & left_id,
                                        file_id const & right_id,
                                        file_id & merged_id)
{
  // This version of try_to_merge_files should only be called when there is a
  // real merge3 to perform.
  I(!null_id(ancestor_id));
  I(!null_id(left_id));
  I(!null_id(right_id));
  
  L(F("trying to merge %s <-> %s (ancestor: %s)\n")
    % left_id % right_id % ancestor_id);

  if (left_id == right_id)
    {
      L(F("files are identical\n"));
      merged_id = left_id;
      return true;      
    }  

  file_data left_data, right_data, ancestor_data;
  data left_unpacked, ancestor_unpacked, right_unpacked, merged_unpacked;
  string left_encoding, anc_encoding, right_encoding;
  vector<string> left_lines, ancestor_lines, right_lines, merged_lines;

  this->get_version(left_path, left_id, left_data);
  this->get_version(anc_path, ancestor_id, ancestor_data);
  this->get_version(right_path, right_id, right_data);

  left_encoding = this->get_file_encoding(left_path, left_man);
  anc_encoding = this->get_file_encoding(anc_path, anc_man);
  right_encoding = this->get_file_encoding(right_path, right_man);
    
  unpack(left_data.inner(), left_unpacked);
  unpack(ancestor_data.inner(), ancestor_unpacked);
  unpack(right_data.inner(), right_unpacked);

  split_into_lines(left_unpacked(), left_encoding, left_lines);
  split_into_lines(ancestor_unpacked(), anc_encoding, ancestor_lines);
  split_into_lines(right_unpacked(), right_encoding, right_lines);
    
  if (merge3(ancestor_lines, 
             left_lines, 
             right_lines, 
             merged_lines))
    {
      hexenc<id> tmp_id;
      base64< gzip<data> > packed_merge;
      string tmp;
      
      L(F("internal 3-way merged ok\n"));
      join_lines(merged_lines, tmp);
      calculate_ident(data(tmp), tmp_id);
      file_id merged_fid(tmp_id);
      pack(data(tmp), packed_merge);

      merged_id = merged_fid;
      record_merge(left_id, right_id, merged_fid, 
                   left_data, packed_merge);

      return true;
    }

  P(F("help required for 3-way merge\n"));
  P(F("[ancestor] %s\n") % anc_path);
  P(F("[    left] %s\n") % left_path);
  P(F("[   right] %s\n") % right_path);
  P(F("[  merged] %s\n") % merged_path);

  if (app.lua.hook_merge3(anc_path, left_path, right_path, merged_path,
                          ancestor_unpacked, left_unpacked, 
                          right_unpacked, merged_unpacked))
    {
      hexenc<id> tmp_id;
      base64< gzip<data> > packed_merge;

      L(F("lua merge3 hook merged ok\n"));
      calculate_ident(merged_unpacked, tmp_id);
      file_id merged_fid(tmp_id);
      pack(merged_unpacked, packed_merge);

      merged_id = merged_fid;
      record_merge(left_id, right_id, merged_fid, 
                   left_data, packed_merge);
      return true;
    }

  return false;
}

bool merge_provider::try_to_merge_files(file_path const & left_path,
                                        file_path const & right_path,
                                        file_path const & merged_path,
                                        file_id const & left_id,
                                        file_id const & right_id,
                                        file_id & merged_id)
{
  I(!null_id(left_id));
  I(!null_id(right_id));

  file_data left_data, right_data;
  data left_unpacked, right_unpacked, merged_unpacked;

  L(F("trying to merge %s <-> %s\n")
    % left_id % right_id);

  if (left_id == right_id)
    {
      L(F("files are identical\n"));
      merged_id = left_id;
      return true;      
    }  

  this->get_version(left_path, left_id, left_data);
  this->get_version(right_path, right_id, right_data);
    
  unpack(left_data.inner(), left_unpacked);
  unpack(right_data.inner(), right_unpacked);

  P(F("help required for 2-way merge\n"));
  P(F("[    left] %s\n") % left_path);
  P(F("[   right] %s\n") % right_path);
  P(F("[  merged] %s\n") % merged_path);

  if (app.lua.hook_merge2(left_path, right_path, merged_path, 
                          left_unpacked, right_unpacked, merged_unpacked))
    {
      hexenc<id> tmp_id;
      base64< gzip<data> > packed_merge;
      
      L(F("lua merge2 hook merged ok\n"));
      calculate_ident(merged_unpacked, tmp_id);
      file_id merged_fid(tmp_id);
      pack(merged_unpacked, packed_merge);
      
      merged_id = merged_fid;
      record_merge(left_id, right_id, merged_fid, 
                   left_data, packed_merge);
      return true;
    }
  
  return false;
}


// during the "update" command, the only real differences from merging
// are that we take our right versions from the filesystem, not the db,
// and we only record the merges in a transient, in-memory table.

update_merge_provider::update_merge_provider(app_state & app,
                                             manifest_map const & anc_man,
                                             manifest_map const & left_man, 
                                             manifest_map const & right_man) 
  : merge_provider(app, anc_man, left_man, right_man) {}

void update_merge_provider::record_merge(file_id const & left_id, 
                                         file_id const & right_id,
                                         file_id const & merged_id,
                                         file_data const & left_data, 
                                         file_data const & merged_data)
{  
  L(F("temporarily recording merge of %s <-> %s into %s\n")
    % left_id % right_id % merged_id);
  I(temporary_store.find(merged_id) == temporary_store.end());
  temporary_store.insert(make_pair(merged_id, merged_data));
}

void update_merge_provider::get_version(file_path const & path,
                                        file_id const & ident, 
                                        file_data & dat)
{
  if (app.db.file_version_exists(ident))
    app.db.get_file_version(ident, dat);
  else
    {
      base64< gzip<data> > tmp;
      file_id fid;
      N(file_exists (path),
        F("file %s does not exist in working copy") % path);
      read_localized_data(path, tmp, app.lua);
      calculate_ident(tmp, fid);
      N(fid == ident,
        F("file %s in working copy has id %s, wanted %s")
        % path % fid % ident);
      dat = tmp;
    }
}

std::string update_merge_provider::get_file_encoding(file_path const & path,
                                                     manifest_map const & man)
{
  std::string enc;
  if (get_attribute_from_working_copy(path, encoding_attribute, enc))
    return enc;
  else if (get_attribute_from_db(path, encoding_attribute, man, enc, app))
    return enc;
  else
    return default_encoding;
}



// the remaining part of this file just handles printing out various
// diff formats for the case where someone wants to *read* a diff
// rather than apply it.

struct hunk_consumer
{
  virtual void flush_hunk(size_t pos) = 0;
  virtual void advance_to(size_t newpos) = 0;
  virtual void insert_at(size_t b_pos) = 0;
  virtual void delete_at(size_t a_pos) = 0;
  virtual ~hunk_consumer() {}
};

void walk_hunk_consumer(vector<long> const & lcs,
                        vector<long> const & lines1,
                        vector<long> const & lines2,                    
                        hunk_consumer & cons)
{

  size_t a = 0, b = 0;
  if (lcs.begin() == lcs.end())
    {
      // degenerate case: files have nothing in common
      cons.advance_to(0);
      while (a < lines1.size())
        cons.delete_at(a++);
      while (b < lines2.size())
        cons.insert_at(b++);
      cons.flush_hunk(a);
    }
  else
    {
      // normal case: files have something in common
      for (vector<long>::const_iterator i = lcs.begin();
           i != lcs.end(); ++i, ++a, ++b)
        {         
          if (idx(lines1, a) == *i && idx(lines2, b) == *i)
            continue;

          cons.advance_to(a);
          while (idx(lines1,a) != *i)
              cons.delete_at(a++);
          while (idx(lines2,b) != *i)
            cons.insert_at(b++);
        }
      if (b < lines2.size())
        {
          cons.advance_to(a);
          while(b < lines2.size())
            cons.insert_at(b++);
        }
      if (a < lines1.size())
        {
          cons.advance_to(a);
          while(a < lines1.size())
            cons.delete_at(a++);
        }
      cons.flush_hunk(a);
    }
}

struct unidiff_hunk_writer : public hunk_consumer
{
  vector<string> const & a;
  vector<string> const & b;
  size_t ctx;
  ostream & ost;
  size_t a_begin, b_begin, a_len, b_len;
  long skew;
  vector<string> hunk;
  unidiff_hunk_writer(vector<string> const & a,
                      vector<string> const & b,
                      size_t ctx,
                      ostream & ost);
  virtual void flush_hunk(size_t pos);
  virtual void advance_to(size_t newpos);
  virtual void insert_at(size_t b_pos);
  virtual void delete_at(size_t a_pos);
  virtual ~unidiff_hunk_writer() {}
};

unidiff_hunk_writer::unidiff_hunk_writer(vector<string> const & a,
                                         vector<string> const & b,
                                         size_t ctx,
                                         ostream & ost)
: a(a), b(b), ctx(ctx), ost(ost),
  a_begin(0), b_begin(0),
  a_len(0), b_len(0), skew(0)
{}

void unidiff_hunk_writer::insert_at(size_t b_pos)
{
  b_len++;
  hunk.push_back(string("+") + b[b_pos]);
}

void unidiff_hunk_writer::delete_at(size_t a_pos)
{
  a_len++;
  hunk.push_back(string("-") + a[a_pos]);  
}

void unidiff_hunk_writer::flush_hunk(size_t pos)
{
  if (hunk.size() > 0)
    {
      // insert trailing context
      size_t a_pos = a_begin + a_len;
      for (size_t i = 0; (i < ctx) && (a_pos + i < a.size()); ++i)
        {         
          hunk.push_back(string(" ") + a[a_pos + i]);
          a_len++;
          b_len++;
        }
      
      // write hunk to stream
      ost << "@@ -" << a_begin+1;
      if (a_len > 1)
        ost << "," << a_len;
      
      ost << " +" << b_begin+1;
      if (b_len > 1)
    ost << "," << b_len;
      ost << " @@" << endl;
      
      copy(hunk.begin(), hunk.end(), ostream_iterator<string>(ost, "\n"));
    }
  
  // reset hunk
  hunk.clear();
  skew += b_len - a_len;
  a_begin = pos;
  b_begin = pos + skew;
  a_len = 0;
  b_len = 0;
}

void unidiff_hunk_writer::advance_to(size_t newpos)
{
  if (a_begin + a_len + (2 * ctx) < newpos)
    {
      flush_hunk(newpos);

      // insert new leading context
      if (newpos - ctx < a.size())
        {
          for (int i = ctx; i > 0; --i)
            {
              if (newpos - i < 0)
                continue;
              hunk.push_back(string(" ") + a[newpos - i]);
              a_begin--; a_len++;
              b_begin--; b_len++;
            }
        }
    }
  else
    {
      // pad intermediate context
      while(a_begin + a_len < newpos)
        {
          hunk.push_back(string(" ") + a[a_begin + a_len]);
          a_len++;
          b_len++;        
        }
    }
}

struct cxtdiff_hunk_writer : public hunk_consumer
{
  vector<string> const & a;
  vector<string> const & b;
  size_t ctx;
  ostream & ost;
  size_t a_begin, b_begin, a_len, b_len;
  long skew;
  vector<size_t> inserts;
  vector<size_t> deletes;
  vector<string> from_file;
  vector<string> to_file;
  bool have_insertions;
  bool have_deletions;
  cxtdiff_hunk_writer(vector<string> const & a,
                      vector<string> const & b,
                      size_t ctx,
                      ostream & ost);
  virtual void flush_hunk(size_t pos);
  virtual void advance_to(size_t newpos);
  virtual void insert_at(size_t b_pos);
  virtual void delete_at(size_t a_pos);
  void flush_pending_mods();
  virtual ~cxtdiff_hunk_writer() {}
};
  
cxtdiff_hunk_writer::cxtdiff_hunk_writer(vector<string> const & a,
                                         vector<string> const & b,
                                         size_t ctx,
                                         ostream & ost)
    : a(a), b(b), ctx(ctx), ost(ost),
      a_begin(0), b_begin(0),
      a_len(0), b_len(0), skew(0),
      have_insertions(false), have_deletions(false)
{}

void cxtdiff_hunk_writer::insert_at(size_t b_pos)
{
  inserts.push_back(b_pos);
  have_insertions = true;
}
  
void cxtdiff_hunk_writer::delete_at(size_t a_pos)
{
  deletes.push_back(a_pos);
  have_deletions = true;
}

void cxtdiff_hunk_writer::flush_hunk(size_t pos)
{
  flush_pending_mods();

  if (have_deletions || have_insertions)
    {
      // insert trailing context
      size_t ctx_start = a_begin + a_len;
      for (size_t i = 0; (i < ctx) && (ctx_start + i < a.size()); ++i)
        {
          from_file.push_back(string("  ") + a[ctx_start + i]);
          a_len++;
        }

      ctx_start = b_begin + b_len;
      for (size_t i = 0; (i < ctx) && (ctx_start + i < b.size()); ++i)
        {
          to_file.push_back(string("  ") + b[ctx_start + i]);
          b_len++;
        }

      ost << "***************" << endl;

      ost << "*** " << (a_begin + 1) << "," << (a_begin + a_len) << " ****" << endl;
      if (have_deletions)
        copy(from_file.begin(), from_file.end(), ostream_iterator<string>(ost, "\n"));

      ost << "--- " << (b_begin + 1) << "," << (b_begin + b_len) << " ----" << endl;
      if (have_insertions)
        copy(to_file.begin(), to_file.end(), ostream_iterator<string>(ost, "\n"));
    }

  // reset hunk
  to_file.clear();
  from_file.clear();
  have_insertions = false;
  have_deletions = false;
  skew += b_len - a_len;
  a_begin = pos;
  b_begin = pos + skew;
  a_len = 0;
  b_len = 0;
}

void cxtdiff_hunk_writer::flush_pending_mods()
{
  // nothing to flush?
  if (inserts.empty() && deletes.empty())
    return;

  string prefix;

  // if we have just insertions to flush, prefix them with "+"; if
  // just deletions, prefix with "-"; if both, prefix with "!"
  if (inserts.empty() && !deletes.empty())
    prefix = "-";
  else if (deletes.empty() && !inserts.empty())
    prefix = "+";
  else
    prefix = "!";

  for (vector<size_t>::const_iterator i = deletes.begin();
       i != deletes.end(); ++i)
    {
      from_file.push_back(prefix + string(" ") + a[*i]);
      a_len++;
    }
  for (vector<size_t>::const_iterator i = inserts.begin();
       i != inserts.end(); ++i)
    {
      to_file.push_back(prefix + string(" ") + b[*i]);
      b_len++;
    }

  // clear pending mods
  inserts.clear();
  deletes.clear();
}

void cxtdiff_hunk_writer::advance_to(size_t newpos)
{
  if (a_begin + a_len + (2 * ctx) < newpos)
    {
      flush_hunk(newpos);

      // insert new leading context
      if (newpos - ctx < a.size())
        {
          for (int i = ctx; i > 0; --i)
            {
              if (newpos - i < 0)
                continue;

              // note that context diffs prefix common text with two
              // spaces, whereas unified diffs use a single space
              from_file.push_back(string("  ") + a[newpos - i]);
              to_file.push_back(string("  ") + a[newpos - i]);
              a_begin--; a_len++;
              b_begin--; b_len++;
            }
        }
    }
  else
    {
      flush_pending_mods();
      // pad intermediate context
      while (a_begin + a_len < newpos)
        {
          from_file.push_back(string("  ") + a[a_begin + a_len]);
          to_file.push_back(string("  ") + a[a_begin + a_len]);
          a_len++;
          b_len++;        
        }
    }
}

void make_diff(string const & filename1,
               string const & filename2,
               vector<string> const & lines1,
               vector<string> const & lines2,
               ostream & ost,
               diff_type type)
{
  vector<long> left_interned;  
  vector<long> right_interned;  
  vector<long> lcs;  

  interner<long> in;

  left_interned.reserve(lines1.size());
  for (vector<string>::const_iterator i = lines1.begin();
       i != lines1.end(); ++i)
    left_interned.push_back(in.intern(*i));

  right_interned.reserve(lines2.size());
  for (vector<string>::const_iterator i = lines2.begin();
       i != lines2.end(); ++i)
    right_interned.push_back(in.intern(*i));

  lcs.reserve(std::min(lines1.size(),lines2.size()));
  longest_common_subsequence(left_interned.begin(), left_interned.end(),
                             right_interned.begin(), right_interned.end(),
                             std::min(lines1.size(), lines2.size()),
                             back_inserter(lcs));

  switch (type)
    {
      case unified_diff:
      {
        ost << "--- " << filename1 << endl;
        ost << "+++ " << filename2 << endl;

        unidiff_hunk_writer hunks(lines1, lines2, 3, ost);
        walk_hunk_consumer(lcs, left_interned, right_interned, hunks);
        break;
      }
      case context_diff:
      {
        ost << "*** " << filename1 << endl;
        ost << "--- " << filename2 << endl;

        cxtdiff_hunk_writer hunks(lines1, lines2, 3, ost);
        walk_hunk_consumer(lcs, left_interned, right_interned, hunks);
        break;
      }
    }
}

#ifdef BUILD_UNIT_TESTS
#include "unit_tests.hh"
#include "transforms.hh"
#include <boost/lexical_cast.hpp>
#include "randomfile.hh"

using boost::lexical_cast;

static void dump_incorrect_merge(vector<string> const & expected,
                                 vector<string> const & got,
                                 string const & prefix)
{
  size_t mx = expected.size();
  if (mx < got.size())
    mx = got.size();
  for (size_t i = 0; i < mx; ++i)
    {
      cerr << "bad merge: " << i << " [" << prefix << "]\t";
      
      if (i < expected.size())
        cerr << "[" << expected[i] << "]\t";
      else
        cerr << "[--nil--]\t";
      
      if (i < got.size())
        cerr << "[" << got[i] << "]\t";
      else
        cerr << "[--nil--]\t";
      
      cerr << endl;
    }
}

// regression blockers go here
static void unidiff_append_test()
{
  string src(string("#include \"hello.h\"\n")
             + "\n"
             + "void say_hello()\n"
             + "{\n"
             + "        printf(\"hello, world\\n\");\n"
             + "}\n"
             + "\n"
             + "int main()\n"
             + "{\n"
             + "        say_hello();\n"
             + "}\n");
  
  string dst(string("#include \"hello.h\"\n")
             + "\n"
             + "void say_hello()\n"
             + "{\n"
             + "        printf(\"hello, world\\n\");\n"
             + "}\n"
             + "\n"
             + "int main()\n"
             + "{\n"
             + "        say_hello();\n"
             + "}\n"
             + "\n"
             + "void say_goodbye()\n"
             + "{\n"
             + "        printf(\"goodbye\\n\");\n"
             + "}\n"
             + "\n");
  
  string ud(string("--- hello.c\n")
            + "+++ hello.c\n"
            + "@@ -9,3 +9,9 @@\n"
            + " {\n"
            + "         say_hello();\n"
            + " }\n"
            + "+\n"
            + "+void say_goodbye()\n"
            + "+{\n"
            + "+        printf(\"goodbye\\n\");\n"
            + "+}\n"
            + "+\n");

  vector<string> src_lines, dst_lines;
  split_into_lines(src, src_lines);
  split_into_lines(dst, dst_lines);
  stringstream sst;
  make_diff("hello.c", "hello.c", src_lines, dst_lines, sst, unified_diff);
  BOOST_CHECK(sst.str() == ud);
}


// high tech randomizing test

static void randomizing_merge_test()
{
  for (int i = 0; i < 30; ++i)
    {
      vector<string> anc, d1, d2, m1, m2, gm;

      file_randomizer::build_random_fork(anc, d1, d2, gm,
                                         i * 1023, (10 + 2 * i));      

      BOOST_CHECK(merge3(anc, d1, d2, m1));
      if (gm != m1)
        dump_incorrect_merge (gm, m1, "random_merge 1");
      BOOST_CHECK(gm == m1);

      BOOST_CHECK(merge3(anc, d2, d1, m2));
      if (gm != m2)
        dump_incorrect_merge (gm, m2, "random_merge 2");
      BOOST_CHECK(gm == m2);
    }
}


// old boring tests

static void merge_prepend_test()
{
  BOOST_CHECKPOINT("prepend test");
  vector<string> anc, d1, d2, m1, m2, gm;
  for (int i = 10; i < 20; ++i)
    {
      d2.push_back(lexical_cast<string>(i));
      gm.push_back(lexical_cast<string>(i));
    }

  for (int i = 0; i < 10; ++i)
    {
      anc.push_back(lexical_cast<string>(i));
      d1.push_back(lexical_cast<string>(i));
      d2.push_back(lexical_cast<string>(i));
      gm.push_back(lexical_cast<string>(i));
    }

  BOOST_CHECK(merge3(anc, d1, d2, m1));
  if (gm != m1)
    dump_incorrect_merge (gm, m1, "merge_prepend 1");
  BOOST_CHECK(gm == m1);


  BOOST_CHECK(merge3(anc, d2, d1, m2));
  if (gm != m2)
    dump_incorrect_merge (gm, m2, "merge_prepend 2");
  BOOST_CHECK(gm == m2);
}


static void merge_append_test()
{
  BOOST_CHECKPOINT("append test");
  vector<string> anc, d1, d2, m1, m2, gm;
  for (int i = 0; i < 10; ++i)
      anc.push_back(lexical_cast<string>(i));

  d1 = anc;
  d2 = anc;
  gm = anc;

  for (int i = 10; i < 20; ++i)
    {
      d2.push_back(lexical_cast<string>(i));
      gm.push_back(lexical_cast<string>(i));
    }

  BOOST_CHECK(merge3(anc, d1, d2, m1));
  if (gm != m1)
    dump_incorrect_merge (gm, m1, "merge_append 1");
  BOOST_CHECK(gm == m1);

  BOOST_CHECK(merge3(anc, d2, d1, m2));
  if (gm != m2)
    dump_incorrect_merge (gm, m2, "merge_append 2");
  BOOST_CHECK(gm == m2);


}

static void merge_additions_test()
{
  BOOST_CHECKPOINT("additions test");
  string ancestor("I like oatmeal\nI like orange juice\nI like toast");
  string desc1("I like oatmeal\nI don't like spam\nI like orange juice\nI like toast");
  string confl("I like oatmeal\nI don't like tuna\nI like orange juice\nI like toast");
  string desc2("I like oatmeal\nI like orange juice\nI don't like tuna\nI like toast");
  string good_merge("I like oatmeal\nI don't like spam\nI like orange juice\nI don't like tuna\nI like toast");
  vector<string> anc, d1, cf, d2, m1, m2, gm;

  split_into_lines(ancestor, anc);
  split_into_lines(desc1, d1);
  split_into_lines(confl, cf);
  split_into_lines(desc2, d2);
  split_into_lines(good_merge, gm);
  
  BOOST_CHECK(merge3(anc, d1, d2, m1));
  if (gm != m1)
    dump_incorrect_merge (gm, m1, "merge_addition 1");
  BOOST_CHECK(gm == m1);

  BOOST_CHECK(merge3(anc, d2, d1, m2));
  if (gm != m2)
    dump_incorrect_merge (gm, m2, "merge_addition 2");
  BOOST_CHECK(gm == m2);

  BOOST_CHECK(!merge3(anc, d1, cf, m1));
}

static void merge_deletions_test()
{
  string ancestor("I like oatmeal\nI like orange juice\nI like toast");
  string desc2("I like oatmeal\nI like toast");

  vector<string> anc, d1, d2, m1, m2, gm;

  split_into_lines(ancestor, anc);
  split_into_lines(desc2, d2);
  d1 = anc;
  gm = d2;

  BOOST_CHECK(merge3(anc, d1, d2, m1));
  if (gm != m1)
    dump_incorrect_merge (gm, m1, "merge_deletion 1");
  BOOST_CHECK(gm == m1);

  BOOST_CHECK(merge3(anc, d2, d1, m2));
  if (gm != m2)
    dump_incorrect_merge (gm, m2, "merge_deletion 2");
  BOOST_CHECK(gm == m2);
}


void add_diff_patch_tests(test_suite * suite)
{
  I(suite);
  suite->add(BOOST_TEST_CASE(&unidiff_append_test));
  suite->add(BOOST_TEST_CASE(&merge_prepend_test));
  suite->add(BOOST_TEST_CASE(&merge_append_test));
  suite->add(BOOST_TEST_CASE(&merge_additions_test));
  suite->add(BOOST_TEST_CASE(&merge_deletions_test));
  suite->add(BOOST_TEST_CASE(&randomizing_merge_test));
}


#endif // BUILD_UNIT_TESTS