// Oldham, Jeffrey D.
// 2000Mar13
// CS1321

// Modified by:
// Massingill, Berna L.
// 2001 March

// Brain-Dead String Editor Class Implementation

// uses our dll class 

#include "dll.h"
#include <iostream>
#include <string>

class buffer {
public:

  // Constructor.
  // Initially the line is empty, and the "cursor" points past 
  //   end-of-line.
  buffer(void) { pos = line.end(); }

  // Move cursor backward.
  // Post:  cursor has been moved left one position (or if already at
  //          start of line, is unchanged).
  void backCursor(void) {
    if (pos != line.begin())
      pos = line.pred(pos);
    return;
  }

  // Move cursor forward.
  // Post:  cursor has been moved right one position (or if already at
  //          end of line, is unchanged).
  void forwardCursor(void) {
    if (pos != line.end())
      pos = line.succ(pos);
  }

  // Delete character.
  // Post:  character at current cursor position has been deleted,
  //          cursor points to next character.
  void deleteChar(void) {
    if (pos != line.end())
      pos = line.erase(pos);
  }

  // Insert characters.
  // Post:  characters in "s" have inserted before the current cursor
  //          position.
  void insertChars(const string & s) {
    if (s.empty())
      return;
    else {
      line.insert(pos, s[0]);
      insertChars(s.substr(1));
      return;
    }
  }

  // Output operator.
  friend ostream& operator<<(ostream& out, const buffer & b) {
    for (dll::link * p = b.line.begin();
         p != b.line.end();
	 p = b.line.succ(p))
      out << p->itm;
    return out;
  }

  // Print a line showing the cursor's position.
  // Post:  prints to output stream "out" a line of spaces and a '^'
  //          showing the cursor's current position.
  //        returns updated "out".
  friend ostream& printCursor(ostream& out, const buffer & b) {
    for (dll::link * p = b.line.begin();
         p != b.pos;
	 p = b.line.succ(p))
      out << ' ';
    return out << '^';
  }

private:
  dll line;			// contents of line
  dll::link * pos;		// position of "cursor" -- where
				//   characters will be inserted/deleted
};