Initial release of Discourse

lib/content_buffer.rb

@@ -0,0 +1,64 @@
+# this class is used to track changes to an arbirary buffer
+
+class ContentBuffer
+
+  def initialize(initial_content)
+    @initial_content = initial_content
+    @lines = @initial_content.split("\n")
+  end
+
+  def apply_transform!(transform)
+    start_row = transform[:start][:row]
+    start_col = transform[:start][:col]
+    finish_row = transform[:finish][:row] if transform[:finish]
+    finish_col = transform[:finish][:col] if transform[:finish]
+    text = transform[:text]
+
+    if transform[:operation] == :delete
+      
+      # fix first line 
+      
+      l = @lines[start_row] 
+      l = l[0...start_col]
+      
+      if (finish_row == start_row)
+        l << @lines[start_row][finish_col..-1]
+        @lines[start_row] = l
+        return
+      end
+
+      @lines[start_row] = l
+
+      # remove middle lines 
+      (finish_row - start_row).times do 
+        l = @lines.delete_at start_row + 1
+      end
+
+      # fix last line 
+      @lines[start_row] << @lines[finish_row][finish_col-1..-1]
+    end
+
+    if transform[:operation] == :insert
+        
+      @lines[start_row].insert(start_col, text)
+      
+      split = @lines[start_row].split("\n")
+      
+      if split.length > 1
+        @lines[start_row] = split[0]
+        i = 1
+        split[1..-2].each do |line|
+          @lines.insert(start_row + i, line)
+          i += 1
+        end
+        @lines.insert(i, "") unless @lines.length > i
+        @lines[i] = split[-1] + @lines[i]
+      end
+
+    end
+  end
+
+  def to_s
+    @lines.join("\n")
+  end
+end