1 files changed, 173 insertions, 0 deletions
diff --git a/js/undo.js b/js/undo.js
new file mode 100644
index 0000000..3bdc0a9
--- /dev/null
+++ b/js/undo.js
@@ -0,0 +1,173 @@
+var undo = (function(){
+
+var max_states = 200;
+
+// undotimetotal = 0;
+
+var stack = {undo: [], redo: []};
+var current_undo = null;
+var dom = {undo: undo_el, redo: redo_el};
+dom.undo.is_visible = dom.redo.is_visible = false
+
+var LexState = function(lex){
+  this.fg = lex.fg;
+  this.bg = lex.bg;
+  this.char = lex.char;
+  this.opacity = lex.opacity;
+};
+
+var update_dom_visibility = function(type){
+  var el = dom[type]
+  if (el.is_visible){
+    if (stack[type].length === 0) {
+      el.classList.add('hidden')
+      el.is_visible = false
+    }
+  } else if (stack[type].length > 0){
+    el.classList.remove('hidden')
+    el.is_visible = true
+  }
+}
+var update_dom = function(){
+  update_dom_visibility('undo')
+  update_dom_visibility('redo')
+}
+
+var new_state = function(){
+  var state = {lexs:{}};
+  save_focus(canvas.focus_x, canvas.focus_y, state)
+  return state
+}
+var new_redo = function(){
+  return new_state()
+}
+var new_undo = function(){
+  current_undo = new_state()
+  stack.redo = []
+  stack.undo.push(current_undo)
+  if (stack.undo.length > max_states) stack.undo.shift();
+  update_dom()
+  return current_undo
+}
+
+var save_focus = function(x, y, state){
+  state = state || current_undo
+  state.focus = {x:x, y:y}
+}
+var save_size = function(w, h, state){
+  state = state || current_undo
+  state.size = {w:w, h:h};
+}
+// the reason for stringifying the x y coords is so that each
+// coordinate is saved only once in an undo state.
+// otherwise there would be problems with, eg, a brush stroke 
+// that passed over the same grid cell twice. 
+var save_lex = function(x, y, lex, state){
+  // var start = Date.now()
+  state = state || current_undo
+  var lexs = state.lexs;
+  var xy = x + "," + y;
+  if (xy in lexs) return;
+  lexs[xy] = new LexState(lex)
+  // undotimetotal += Date.now() - start
+}
+var save_focused_lex = function(state){
+  state = state || current_undo
+  var x = canvas.focus_x
+  var y = canvas.focus_y
+  save_lex(x, y, canvas.aa[y][x], state)
+}
+var save_rect = function(xpos, ypos, w, h, state){
+  state = state || current_undo;
+  var aa = canvas.aa;
+  
+  var xlen = xpos + w
+  var ylen = ypos + h
+
+  for (var x = xpos; x < xlen; x++){
+    for (var y = ypos; y < ylen; y++){
+      save_lex(x, y, aa[y][x], state)
+    }
+  }
+}
+
+var restore_state = function(state){
+  // all redo states will have a cached undo state on them
+  // an undo state might have a cached redo state
+  // if it doesn't have one, generate one
+  var make_redo = ! ('redo' in state || 'undo' in state);
+  var aa = canvas.aa
+  var lexs = state.lexs
+
+  if (make_redo){
+    state.redo = new_redo()
+  }
+
+  if ('size' in state){
+    if (make_redo){
+      save_size(canvas.w, canvas.h, state.redo)
+      // note that resizing canvas redo saves the whole canvas instead of
+      // just the changed part which is inefficient...
+      save_rect(0,0, canvas.w, canvas.h, state.redo)
+      make_redo = false // already saved whole canvas, skip lexs below
+    }
+    canvas.resize(state.size.w, state.size.h);
+  }
+
+  for (var key in lexs){
+    var xy = key.split(',');
+    var lex = aa[xy[1]][xy[0]]
+    if (make_redo)
+      save_lex(xy[0], xy[1], lex, state.redo)
+    lex.assign(lexs[key])
+  }
+
+  if ('focus' in state){
+    canvas.focus_x = state.focus.x
+    canvas.focus_y = state.focus.y
+    if (focused_input === canvas) canvas.focus()
+  }
+}
+
+var undo = function(){
+  var state = stack.undo.pop();
+  if (!state) return;
+
+  restore_state(state)
+  
+  // now take the applied undo state and store it on the redo state
+  // and push the redo state to the redo stack
+  state.redo.undo = state
+  stack.redo.push(state.redo)
+  delete state.redo
+
+  update_dom()
+}
+
+var redo = function(){
+  var state = stack.redo.pop();
+  if (!state) return;
+  
+  restore_state(state)
+
+  state.undo.redo = state
+  stack.undo.push(state.undo)
+  delete state.undo
+
+  update_dom()
+}
+
+return {
+  stack: stack,
+  new: new_undo,
+//  new_redo: new_redo,
+  save_focus: save_focus,
+  save_size: save_size,
+  save_lex: save_lex,
+  save_focused_lex: save_focused_lex,
+  save_rect: save_rect,
+  undo: undo,
+  redo: redo
+}
+
+})()