Fossil

    db_step(&q);
    blob_reset(&current);
  }
  db_finalize(&q);
}

/*
** Undo or redo changes to the filesystem.  Undo the changes in the
** same order that they were originally carried out - undo the oldest
** change first and undo the most recent change last.
*/
static void undo_all_filesystem(int redoFlag){
  Stmt q;


  db_prepare(&q,
     "SELECT pathname FROM undo"
     " WHERE redoflag=%d"
     " ORDER BY rowid",
     redoFlag
  );
  while( db_step(&q)==SQLITE_ROW ){
    const char *zPathname = db_column_text(&q, 0);
    undo_one(zPathname, redoFlag);
  }
  db_finalize(&q);
}

/*
** Undo or redo all undoable or redoable changes.
*/
static void undo_all(int redoFlag){
  int ucid;
  int ncid;
  undo_all_filesystem(redoFlag);
  db_multi_exec(
    "CREATE TEMP TABLE undo_vfile_2 AS SELECT * FROM vfile;"
    "DELETE FROM vfile;"
    "INSERT INTO vfile SELECT * FROM undo_vfile;"
    "DELETE FROM undo_vfile;"
    "INSERT INTO undo_vfile SELECT * FROM undo_vfile_2;"
    "DROP TABLE undo_vfile_2;"

** Reset the the undo memory.
*/
void undo_reset(void){
  static const char zSql[] =
    @ DROP TABLE IF EXISTS undo;
    @ DROP TABLE IF EXISTS undo_vfile;
    @ DROP TABLE IF EXISTS undo_vmerge;
    @ DROP TABLE IF EXISTS undo_pending;
    ;
  db_multi_exec(zSql);
  db_lset_int("undo_available", 0);
  db_lset_int("undo_checkout", 0);
}

/*
** This flag is true if we are in the process of collecting file changes
** for undo.  When this flag is false, undo_save() is a no-op.
*/
static int undoActive = 0;

/*
** Begin capturing a snapshot that can be undone.
*/
void undo_begin(void){
  int cid;
  static const char zSql[] = 
    @ CREATE TABLE undo(
    @   pathname TEXT UNIQUE,             -- Name of the file
    @   redoflag BOOLEAN,                 -- 0 for undoable.  1 for redoable
    @   existsflag BOOLEAN,               -- True if the file exists
    @   content BLOB                      -- Saved content
    @ );
    @ CREATE TABLE undo_vfile AS SELECT * FROM vfile;
    @ CREATE TABLE undo_vmerge AS SELECT * FROM vmerge;
    @ CREATE TABLE undo_pending(undoId INTEGER PRIMARY KEY);
  ;
  undo_reset();
  db_multi_exec(zSql);
  cid = db_lget_int("checkout", 0);
  db_lset_int("undo_checkout", cid);
  db_lset_int("undo_available", 1);
  undoActive = 1;
}

/*
** This flag is true if one or more files have changed and have been
** recorded in the undo log but the undo log has not yet been committed.
**
** If a fatal error occurs and this flag is set, that means we should
** rollback all the filesystem changes.
*/
static int undoNeedRollback = 0;

/*
** Save the current content of the file zPathname so that it
** will be undoable.  The name is relative to the root of the
** tree.
*/
void undo_save(const char *zPathname){
  char *zFullname;
  Blob content;
  int existsFlag;
  Stmt q;

  if( !undoActive ) return;
  zFullname = mprintf("%s/%s", g.zLocalRoot, zPathname);
  existsFlag = file_size(zFullname)>=0;
  db_prepare(&q,
    "REPLACE INTO undo(pathname,redoflag,existsflag,content)"
    " VALUES(%Q,0,%d,:c)",
    zPathname, existsFlag
  );
  if( existsFlag ){
    blob_read_from_file(&content, zFullname);
    db_bind_blob(&q, ":c", &content);
  }
  free(zFullname);
  db_step(&q);
  db_finalize(&q);
  if( existsFlag ){
    blob_reset(&content);
  }
  undoNeedRollback = 1;
}

/*
** Complete the undo process is one is currently in process.
*/
void undo_finish(void){
  if( undoActive ){
    undoActive = 0;
    undoNeedRollback = 0;
  }
}

/*
** This routine is called when the process aborts due to an error.
** If an undo was being accumulated but was not finished, attempt
** to rollback all of the filesystem changes.
**
** This rollback occurs, for example, if an "update" or "merge" operation
** could not run to completion because a file that needed to be written
** was locked or had permissions turned off.
*/
void undo_rollback(void){
  if( !undoNeedRollback ) return;
  assert( undoActive );
  undoNeedRollback = 0;
  undoActive = 0;
  printf("Rolling back prior filesystem changes...\n");
  undo_all_filesystem(0);
}

/*
** COMMAND: undo
**
** Usage: %fossil undo ?FILENAME...?
**