Add programmer documentation

DOC.md

@@ -0,0 +1,108 @@
+# How Ze works on the inside
+
+## Terminal viewing
+
+Viewing is done by remembering a file offset for the window.
+For example a window viewing 60 lines on file offset 2 would show lines from 2 to 61.
+Then we have a cursor, which just represents a row-position and a column-position.
+With those two, we can interact with lines, where we have cursor, jump to certain lines and generally move the cursor.
+
+## Overview
+
+Ze represents the file as a *treap*.
+A treap is a randomized search tree, which is a binary search tree for its keys and a max-heap for their *priorities*.
+Internally, the treap operation do not based on node keys, but the sizes of their subtrees - this applies for the b.s.t. attributes.
+Nodes of this treap contain lines from the file.
+The treap is *semi-persistent*, which means it remembers all of its versions and can modify the last one.
+On a higher level, the editor repeatedly takes user input and does corresponding actions.
+Those actions are divided into three modes: *normal*, *insert* and *select*.
+It uses `ncurses` c library for handling terminal input/output.
+
+## Treap Semi-persistence
+
+Ze uses a semi-persistence technique of remembering paths from root to a leaf.
+
+The main idea is that whenever an editation step changes the treap, only nodes on such a path are changed.
+This means that it is sufficient only to remember those paths.
+
+With this method, the version of the treap is represented by the latest root node.
+The root then remembers its son, which is on the change-path and so on.
+Roll-back is done simply by following the latest path and erasing nodes it contains.
+
+## Treap meta-operations
+
+The core of all editation steps are three operations: *insert*, *remove* and *update*.
+Every other operation can wrap something around these three.
+
+Sometimes that includes using more of them - for that scenario the treap also remembers how many of these meta-operations were used.
+Undo is then just erasing as many versions as the editation step used.
+As an added bonus, it also remembers the line changed, which makes it possible to jump on the line, where the change occured.
+
+### Insert
+
+For insert, we need two modes - with and without version-change.
+That is because of treap build - because of it we can just do as many inserts as there are lines of the loaded file and take it as an initial version.
+
+The new-version-remembering mode works recursivelly - starting with root, it decides whether the left sons subtree has higher or the same size as is the desired index where a new line should be inserted.
+If yes, then it calls itself on the left son, otherwise on the right son but with an index, that has the size of the left subtree + 1 subtracted from it.
+When it is called on a non-existent node, it creates a new node and returns it.
+
+With each return, a new node is created with the appropriate son pointer and it's remembered as the next node on its version path.
+But that alone wouldn't suffice, because the treap also acts as a heap.
+Here come node rotations in play.
+If a returned node has higher priority than the original node, they are rotated to suit the heap rules.
+
+At last, the treap remembers a new root, representing a new version.
+
+The version-not-remembering mode works almost the same, but not creating new nodes, but instead modifying the treap.
+
+### Remove
+
+Remove doesn't need the option not to remember a new version, but it's a little more complicated.
+If we're still chasing the node to remove, we simply follow the path to it, same as with insert.
+
+But when we find the node, then comes the fun.
+If any one of the removed nodes sons are non-existent, the removed node is replaced by one that exists, if there is one.
+But if both sons are real, we pick the one with higher priority to replace the removed node.
+We do this with a handy rotation, which keeps b.s.t. rules, but gets the higher-priority son higher.
+Then, when we have the desired son where we want him, we call the remove recursively on the node, we put lower.
+Internally, this is done by making a permanent copy of the son and a temporary copy of the removed node, so we can rotate them and not affect the previous versions.
+
+Each return then creates a new node, just as with an insert.
+
+### Update
+
+With the knowledge of insert and delete, update is pretty simple.
+
+We find the desired point to update by following sizes of subtrees just as with the previous two operations.
+Then, when we find it, we create a new, identical node with the new text and return that.
+Then with each return, we create our trail of breadcrumbs.
+
+## Other editation actions
+
+Everything else, which changes the treap in any way, can be done by using these three meta-operations.
+
+### Select mode and selection
+
+Operations on selected text are generalized by a function called `apply_on_selection()`.
+It just takes a function to apply to the lines selected in the file and applies it on them.
+
+It can remove the selected text from the file - that is done with treap removes and updates on the edges.
+It can copy the selected text into the selectoin.
+
+The selection is just a vector of lines.
+We can paste them into the file afterwards.
+
+### Insert mode
+
+One write on one line should create only one version.
+That is accomplished by buffering changes to one line and applying them afterwards.
+Other than that, we are just updating specific lines.
+
+### Find and replace
+
+We iterate through the file, finding incremental indexes.
+We go through each of these lines and search the desired substring.
+
+Then a find just moves the cursor there.
+A replace does an update on this line, changing the substring to something else.

Makefile

@@ -0,0 +1,11 @@
+CPP_FILES = \
+	main.cpp \
+	treap.cpp \
+	selection.cpp \
+	editor.cpp
+
+HPP_FILES = \
+	everything.hpp
+
+all: $(CPP_FILES) $(HPP_FILES)
+	g++ $(CPP_FILES) -lncurses -o ze

README.md

@@ -1,3 +1,61 @@
-# editor
+# Ze ed
 
-Deez
+Like deez, but backwards.
+
+Ze is a terminal [vim](https://www.vim.org/)-like text editor.
+
+It uses a *treap* data structure to represent file by lines and remembers versions with added *semi-persistence*.
+
+## Dependencies
+
+* `ncurses` c library
+
+## Build
+
+Described in the `Makefile`
+
+## Usage
+
+`ze <filename>`
+
+## Modes
+
+Ze has three modes within which you can edit a file - *normal*, *insert* and *select*.
+Those represent what the user is currently doing:
+* *insert* mode: Writing text
+* *select* mode: Operations on a selection
+* *normal* mode: Everything else
+
+## Default keybinds
+
+`<char>` - Action
+
+### Normal mode
+* `h`,`j`,`k`,`l` - Vim-like movement
+* `g` - Goto a specified line
+* `G` - Goto the last line
+* `d` - Remove current line
+* `x` - Remove character under cursor
+* `o` - Insert empty line before the current
+* `q` - Quit
+* `w` - Save
+* `u` - Undo latest editation action
+* `f` - Find next appearance a specified string
+* `n` - Repeat last find
+* `s` - Find-and-replace
+* `r` - Repeat last find-and-replace
+* `p` - Paste selection
+* `i` - Change into insert mode
+* `v` - Change into select mode
+
+### Insert mode
+* `<ESC>` - Change into normal mode
+* Anything else is written under the cursor
+
+### Select mode
+* `h`,`j`,`k`,`l` - Vim-like movement
+* `g` - Goto a specified line
+* `G` - Goto the last line
+* `v` - Copy selected text
+* `x` - Remove selected text
+* `<ESC>` - Change into normal mode

editor.cpp

@@ -9,7 +9,7 @@ void Editor::save() {
 	}
 
 	for(count_type i = 0; i < file.size(); ++i)
-		outfile << file.get_line(i, 0) << std::endl;
+		outfile << file.get_line(i, false) << '\n';
 }
 
 // Clear line
@@ -39,8 +39,10 @@ string Editor::get_input(string prompt, F func) {
 	string s = "";
 	char ch = getch();
 	while((ch != ENTER && func(ch)) || ch == BS) {
-		if(ch == BS)
-			s.pop_back();
+		if(ch == BS) {
+			if(s.size())
+				s.pop_back();
+		}
 		else
 			s += ch;
 		print_text(cur.r, prompt+": " + s);
@@ -55,13 +57,14 @@ string Editor::get_string(string prompt) {
 }
 // Taking user input - number
 count_type Editor::get_number(string prompt) {
-	return stoi(get_input(prompt, [](char ch) { return ch >= '0' && ch <= '9'; }));
+	string inp = get_input(prompt, [](char ch) { return ch >= '0' && ch <= '9'; });
+	if(inp.size() > 0)
+		return stoi(inp);
+	else
+		return 0;
 }
 
 
-// TODO undo
-
-
 // Jump to end of line
 void Editor::jump_line_end() {
 	count_type line_size = file.get_line(file_offset+cur.r).size();
@@ -79,7 +82,8 @@ void Editor::move_cursor(char ch) {
 			break;
 
 		case 'j':
-			if(file_offset + cur.r >= file.size()-1) break;
+			if(file_offset + cur.r >= file.size()-1)
+				break;
 			if(cur.r < LINES-1) {
 				cur.r += 1;
 				move(cur);
@@ -129,7 +133,7 @@ void Editor::jump(count_type r) {
 }
 
 // Find next string appearance
-std::pair<bool, position> Editor::find(string text) {
+find_result Editor::find(string text) {
 	count_type len = text.size();
 	count_type file_size = file.size();
 
@@ -139,10 +143,16 @@ std::pair<bool, position> Editor::find(string text) {
 		count_type start = ((_r == 0) ? (cur.c+1) : 0);
 		count_type pos = file.get_line(r, 1).find(text, start);
 		if(pos != string::npos)
-			return {true,{r, pos}};
+			return {true, {r, pos}};
 	}
 	return {false, position()};
 }
+void Editor::replace(position p, count_type length, string text) {
+	string line_text = file.get_line(p.r);
+	line_text.erase(p.c, length);
+	line_text.insert(p.c, text);
+	file.update(p.r, line_text);
+}
 
 bool Editor::take_action() {
 	move(cur);
@@ -183,9 +193,15 @@ bool Editor::take_action() {
 				case 'w':
 					save();
 					break;
+				case 'u':
+					if(file.version() > 0) {
+						jump({file.undo(), 0});
+						print_file(file_offset);
+					}
+					break;
 				case 'i':
 					mode = INSERT;
-					current_insert = file.get_line(file_offset + cur.r, 0);
+					current_insert = file.get_line(file_offset + cur.r, false);
 					break;
 				case 'v':
 					mode = SELECT;
@@ -196,9 +212,9 @@ bool Editor::take_action() {
 				case 'n':
 					{
 						auto result = find(last_find);
-						if(!result.first)
+						if(!result.found)
 							break;
-						jump(result.second);
+						jump(result.pos);
 					}
 					print_file(file_offset);
 					break;
@@ -208,18 +224,19 @@ bool Editor::take_action() {
 				case 'r':
 					{
 						auto result = find(last_find);
-						if(!result.first)
+						if(!result.found)
 							break;
-						jump(result.second);
+						jump(result.pos);
 						replace(cur + file_offset, last_find.size(), last_replace);
 					}
 					print_file(file_offset);
 					break;
 				case 'p':
-					selection.paste_selection(cur + file_offset);
+					file.compress_versions(selection.paste_selection(cur + file_offset));
 					print_file(file_offset);
 					break;
 				default:
+					//print_text(cur.r, "Unknown operation.");
 					break;
 			}
 			break;
@@ -227,19 +244,23 @@ bool Editor::take_action() {
 			switch(ch) {
 				case ESC:
 					mode = NORMAL;
-					file.set_line(cur.r, current_insert);
+					file.update(cur.r, current_insert);
 					print_text(cur.r, substitute_tabs(current_insert));
 					current_insert = "";
 					break;
 				case BS:
 					if(cur.c > 0) {
-						cur.c -= 1;
-						current_insert.erase(cur.c - get_tab_offset(cur.c, current_insert), 1);
+						count_type new_c = cur.c;
+						do new_c--;
+							while(new_c > 0 && get_tab_offset(new_c, current_insert) > get_tab_offset(new_c-1, current_insert));
+
+						current_insert.erase(cur.c-1 - get_tab_offset(cur.c-1, current_insert), 1);
+						cur.c = new_c;
 					}
 					print_text(cur.r, substitute_tabs(current_insert));
 					break;
 				case ENTER:
-					file.set_line(cur.r, current_insert);
+					file.update(cur.r, current_insert);
 					file.split_line(cur + file_offset);
 					cur.r++; cur.c = 0; move(cur);
 					current_insert = file.get_line(cur.r);
@@ -267,12 +288,16 @@ bool Editor::take_action() {
 					jump(get_number("line number"));
 					print_file(file_offset);
 					break;
+				case 'G':
+					jump(file.size());
+					print_file(file_offset);
+					break;
 				case 'v':
 					selection.copy_selection(cur + file_offset);
 					mode = NORMAL;
 					break;
 				case 'x':
-					selection.remove_selection(cur + file_offset);
+					file.compress_versions(selection.remove_selection(cur + file_offset)+1);
 					if(file_offset + cur.r >= file.size())
 						jump(cur + file_offset);
 					print_file(file_offset);

everything.hpp

@@ -1,13 +1,16 @@
 #pragma once
 #include <ncurses.h>
 #include <vector>
+#include <stack>
 #include <fstream>
 #include <iostream>
 
 #define TAB_SIZE 8
+constexpr int RANDOM_SEED = 666;
 
 using std::string;
 using std::vector;
+using std::stack;
 typedef unsigned long long count_type;
 
 // Position
@@ -28,43 +31,75 @@ struct line {
 	count_type priority, size; // Treap innards
 	string text; // Content
 	line *left, *right; // Sons
+	line *next_in_version;
+
+	void set_left(line *_left) {
+		left = _left;
+		update_size();
+	}
+	void set_right(line *_right) {
+		right = _right;
+		update_size();
+	}
+
+	void update_size() { size = 1 + (left == nullptr ? 0 : left->size) + (right == nullptr ? 0 : right->size); }
 
 	line(count_type _p, string _t) :
-		priority(_p), text(_t), size(1), left(nullptr), right(nullptr) {}
+		priority(_p), text(_t), size(1), left(nullptr), right(nullptr), next_in_version(nullptr) {}
+
+	line(count_type _p, string _t, line *_left, line *_right, line *_next) :
+		priority(_p), text(_t), left(_left), right(_right), next_in_version(_next) {
+		update_size();
+	}
+
+	line(line *l) :
+		priority(l->priority), text(l->text), left(l->left), right(l->right), next_in_version(nullptr) {
+		update_size();
+	}
 };
-typedef std::pair<line*, line*> two_lines;
+struct change { count_type row, count; };
 
 // Treap data structure
 class Treap {
-	line *root;
+	stack<change> changes;
+	stack<line*> root;
+	line* get_root() { return root.top(); };
 
-	two_lines split(line *l, count_type k);
-	line* join(line *a, line *b);
-	line* join(two_lines two) { return join(two.first, two.second); }
+	line* insert(line *l, count_type k, string s, bool new_version);
+	line* remove(line *l, count_type k);
+	line* update(line *l, count_type k, string s);
 
+	line* pick_higher(line *l);
+	void delete_version(line *l);
 	count_type get_size(line *l);
+	count_type get_priority(line *l);
 	line* find(line *l, count_type k);
-	line* find(count_type k);
 	count_type bulk_find(vector<string> *vec, line *l, count_type k, count_type count);
-public:
 
+public:
 	// General operations
-	Treap() { srand(120); root = nullptr; }
-	count_type size() { return get_size(root); }
+	Treap() { srand(RANDOM_SEED); root.push(nullptr); }
+	count_type size() { return get_size(get_root()); }
 	void clear();
 
-	// Line get operations
-	string get_line(count_type r, bool substitute_tab = 1);
+	// Versioning
+	count_type undo();
+	count_type version() { return root.size()-1; }
+	void compress_versions(count_type count);
+
+	// Line getters
+	string get_line(count_type r, bool substitute_tab = true);
 	vector<string> bulk_get_line(count_type r, count_type count);
 	count_type get_tab_offset(position p) { return ::get_tab_offset(p.c, get_line(p.r, 0)); }
 
-	// Line set operations
-	void split_line(position p);
-	void insert(count_type k, string s);
+	// Line meta-operations
+	void insert(count_type k, string s, bool new_version = true);
 	void remove(count_type k);
-	void set_line(count_type k, string s) { find(k)->text = s; }
+	void update(count_type k, string s);
 
-	// Substring operations
+	// Other line operations
+	void split_line(position p, bool should_compress = true);
+	void merge_line(count_type k, bool should_compress = true);
 	void insert(position p, string t);
 	void remove(position p, count_type len = 1);
 };
@@ -72,18 +107,20 @@ public:
 //// Selection
 class Selection {
 	Treap *file;
-	Treap content;
+	vector<string> content;
 
 	template <typename F, typename G>
 	void apply_on_selection(position p, F func, G func2);
 public:
 	Selection() {}
 	Selection(Treap *_file) { file = _file; }
-	position pos; // last selection position
+	position pos;
+
+	count_type size() { return file->size(); }
 
-	void remove_selection(position p);
 	void copy_selection(position p);
-	void paste_selection(position p);
+	count_type remove_selection(position p);
+	count_type paste_selection(position p);
 };
 
 
@@ -93,6 +130,7 @@ public:
 #define BS 127
 #define adds(s) addstr(s.c_str())
 enum mode_type { INSERT, NORMAL, SELECT };
+struct find_result { bool found; position pos; };
 
 class Editor{
 	// Editor state
@@ -132,8 +170,8 @@ class Editor{
 	void jump(position p) { jump(p.r); cur.c = p.c; }
 	
 	// Find and replace
-	std::pair<bool, position> find(string text);
-	void replace(position p, count_type length, string text) { file.remove(p, length); file.insert(p, text); }
+	find_result find(string text);
+	void replace(position p, count_type length, string text);
 
 public:
 	Editor(string _filename, Treap &_file) {

main.cpp

@@ -49,9 +49,10 @@ int main(int argc, const char *argv[]) {
 
 	// Load file
 	Treap file;
+
 	string line;
 	while (std::getline(infile, line))
-		file.insert(file.size(), line);
+		file.insert(file.size(), line, false);
 
 	// Init
 	initscr();

selection.cpp

@@ -24,34 +24,55 @@ void Selection::apply_on_selection(position p, F func, G func2) {
 	count_type size = ((start.r == end.r) ? end.c+1 : start_line.size()) - start.c;
 	func2(start.r, start.c, size, file, &content);
 }
-// Removing selection
-void Selection::remove_selection(position p) {
-	apply_on_selection(p,
-		[](count_type r, Treap *file, Treap *sel){ file->remove(r); },
-		[](count_type r, count_type start_c, count_type size, Treap *file, Treap *sel) { file->remove({r, start_c-file->get_tab_offset({r, start_c})}, size); }
-	);
-}
 // Copying selection
 void Selection::copy_selection(position p) {
+	// Insert in the wrong order
 	apply_on_selection(p,
-		[](count_type r, Treap *file, Treap *sel){ sel->insert(0, file->get_line(r, false)); },
-		[](count_type r, count_type start_c, count_type size, Treap *file, Treap *sel) { sel->insert(0, file->get_line(r, false).substr(start_c - file->get_tab_offset({r, start_c}), size)); }
+		[](count_type r, Treap *file, vector<string> *sel){ sel->push_back(file->get_line(r, false)); },
+		[](count_type r, count_type start_c, count_type size, Treap *file, vector<string> *sel) { sel->push_back(file->get_line(r, false).substr(start_c - file->get_tab_offset({r, start_c}), size)); }
 	);
+
+	// Reverse order of the vector
+	for(count_type i = 0; i < content.size()/2; ++i) {
+		string tmp = content[content.size()-1 - i];
+		content[content.size()-1 - i] = content[i];
+		content[i] = tmp;
+	}
+}
+// Removing selection
+count_type Selection::remove_selection(position p) {
+	apply_on_selection(p,
+		[](count_type r, Treap *file, vector<string> *sel){ file->remove(r); },
+		[](count_type r, count_type start_c, count_type size, Treap *file, vector<string> *sel) { file->remove({r, start_c-file->get_tab_offset({r, start_c})}, size); }
+	);
+
+	count_type min = p.r, max = pos.r;
+	if(min > max)
+		min = pos.r, max = p.r;
+
+	if(max > min) {
+		file->merge_line(min+1, false);
+		return max - min + 2;
+	}
+	else
+		return 1;
 }
 // Pasting selection
-void Selection::paste_selection(position p) {
-	if(content.size() == 0) return;
+count_type Selection::paste_selection(position p) {
+	if(content.size() == 0) return 0;
 
 	// Insert last line inside of this
-	file->insert(p, content.get_line(content.size()-1, false));
-	if(content.size() == 1) return;
+	file->insert(p, content.back());
+	if(content.size() == 1) return 1;
 
 	// Insert first line in front and split
-	file->split_line(p);
-	file->insert(p, content.get_line(0, false));
-	if(content.size() == 2) return;
+	file->split_line(p, false);
+	file->insert(p, content.front());
+	if(content.size() == 2) return 4;
 
 	// Insert lines
 	for(count_type i = content.size()-2; i > 0; --i)
-		file->insert(p.r, content.get_line(i, false));
+		file->insert(p.r+1, content[i]);
+
+	return content.size()+2;
 }

treap.cpp

@@ -2,99 +2,249 @@
 
 // Get size uf a subtreap
 count_type Treap::get_size(line *l) {
-	if(l == nullptr) return 0;
+	if(l == nullptr)
+		return 0;
 	return l->size;
 }
-
-// Split treap by k-th element
-two_lines Treap::split(line *l, count_type k) {
-	if(l == nullptr) return {nullptr, nullptr};
-
-	if(get_size(l->left) >= k) {
-		// In the left subtree
-		auto two = split(l->left, k);
-		l->left = two.second;
-		l->size -= get_size(two.first);
-		return {two.first, l};
-	}
-	else {
-		// In the right subtree
-		auto two = split(l->right, k - (1+get_size(l->left)));
-		l->right = two.first;
-		l->size -= get_size(two.second);
-		return {l, two.second};
-	}
+count_type Treap::get_priority(line *l) {
+	if(l == nullptr)
+		return 0;
+	return l->priority;
 }
 
-// Join two treaps
-line* Treap::join(line *a, line *b) {
-	if(a == nullptr) return b;
-	if(b == nullptr) return a;
+// Treap node rotations
+line *rotate_left(line *l) {
+	line *r = l->right, *mid = r->left;
 
-	if(a->priority < b->priority) {
-		a->size += get_size(b);
-		a->right = join(a->right, b);
-		return a;
+	// Switch
+	l->set_right(mid);
+	r->set_left(l);
+
+	return r;
+}
+line *rotate_right(line *r) {
+	line *l = r->left,  *mid = l->right;
+
+	// Switch
+	r->set_left(mid);
+	l->set_right(r);
+
+	return l;
+}
+
+// Meta-operations
+line* Treap::insert(line *l, count_type k, string s, bool new_version) {
+	if(l == nullptr)
+		return new line(rand(), s);
+
+	// Insert into left subtree
+	if(k <= get_size(l->left)) {
+		line *son = insert(l->left, k, s, new_version);
+
+		// Update the node
+		if(new_version)
+			l = new line(l->priority, l->text, son, l->right, son);
+		else
+			l->set_left(son);
+
+		// Balance heap-like structure
+		if(get_priority(l->left) > get_priority(l))
+			l = rotate_right(l);
 	}
+
+	// Insert into right subtree
 	else {
-		b->size += get_size(a);
-		b->left = join(a, b->left);
-		return b;
+		line *son = insert(l->right, k - (get_size(l->left)+1), s, new_version);
+
+		// Update the node
+		if(new_version)
+			l = new line(l->priority, l->text, l->left, son, son);
+		else
+			l->set_right(son);
+
+		// Balance heap-like structure
+		if(get_priority(l->right) > get_priority(l))
+			l = rotate_left(l);
+	}
+	return l;
+}
+line* Treap::remove(line *l, count_type k) {
+	line *lson = l->left, *rson = l->right;
+
+	// Remove from left subtree
+	if(k < get_size(lson)) {
+		line *son = remove(lson, k);
+		return new line(l->priority, l->text, son, rson, son);
+	}
+	// Remove this line
+	else if(k == get_size(l->left)) {
+		// Picking the son we can (the easy cases)
+		if(lson == nullptr && rson == nullptr)
+			return nullptr;
+		else if(lson == nullptr)
+			return new line(l->priority, rson->text, rson->left, rson->right, nullptr);
+		else if(rson == nullptr)
+			return new line(l->priority, lson->text, lson->left, lson->right, nullptr);
+
+		// Picking the son with higher priority
+		else if(get_priority(lson) >= get_priority(rson)) {
+			line *son = new line(lson);
+			line l_copy = line(l->priority, l->text, son, l->right, nullptr);
+
+			// Rotate to get the son higher
+			rotate_right(&l_copy);
+			
+			// Remove under
+			son->right = remove(&l_copy, get_size(l_copy.left));
+			son->next_in_version = son->right;
+			son->update_size();
+
+			return son;
+		}
+		else {
+			line *son = new line(rson);
+			line l_copy = line(l->priority, l->text, l->left, son, nullptr);
+
+			// Rotate to get the son higher
+			rotate_left(&l_copy);
+
+			// Remove under
+			son->left = remove(&l_copy, get_size(l_copy.left));
+			son->next_in_version = son->left;
+			son->update_size();
+
+			return son;
+		}
+	}
+	// Remove from right subtree
+	else {
+		line *son = remove(rson, k - (get_size(lson)+1) );
+		return new line(l->priority, l->text, lson, son, son);
+	}
+}
+line* Treap::update(line *l, count_type k, string s) {
+	if(k < get_size(l->left)) {
+		line *son = update(l->left, k, s);
+		return new line(l->priority, l->text, son, l->right, son);
+	}
+	else if(k == get_size(l->left))
+		return new line(l->priority, s, l->left, l->right, nullptr);
+	else {
+		line *son = update(l->right, k - (1+get_size(l->left)), s);
+		return new line(l->priority, l->text, l->left, son, son);
 	}
 }
 
 // Find k-th line of file
 line* Treap::find(line *l, count_type k) {
-	if(l == nullptr) return nullptr;
+	if(l == nullptr)
+		return nullptr;
 
-	if(k <= get_size(l->left))
+	if(k < get_size(l->left))
 		return find(l->left, k);
-	else if(k == get_size(l->left)+1)
+	else if(k == get_size(l->left))
 		return l;
 	else
 		return find(l->right, k - (1+get_size(l->left)) );
 }
-line* Treap::find(count_type k) {
-	if(k >= root->size)
-		return nullptr;
-	// Don't find index k, but k-th line -> +1
-	return find(root, k+1);
+
+// Version control
+void Treap::delete_version(line *l) {
+	if(l == nullptr)
+		return;
+
+	line *next = l->next_in_version;
+	delete l;
+	delete_version(next);
+}
+count_type Treap::undo() {
+	if(changes.size() == 0)
+		return 0;
+
+	// Get number of changes
+	change last = changes.top();
+	changes.pop();
+
+	// Delete all treap versions within the change
+	for(count_type i = 0; i < last.count; i++) {
+		line *last_root = root.top();
+		root.pop();
+		delete_version(last_root);
+	}
+	return last.row;
+}
+void Treap::compress_versions(count_type count) {
+	// Remove all compressed change info
+	for(count_type i = 1; i < count; ++i)
+		changes.pop();
+
+	// Convert them into one grand-info
+	if(count > 0)
+		changes.top().count = count;
 }
 
 // File access
 void Treap::clear() {
-	while(size() > 0) {
-		auto two = split(root, 1);
-		root = two.second;
-		delete two.first;
-	}
+	// Clear all versions
+	while(root.size() > 1)
+		undo();
+
+	// Clear original file
+	while(size() > 0)
+		remove(0);
 }
 
 // Line insert
-void Treap::insert(count_type k, string s) {
-	line *l = new line(rand(), s);
-
-	if(root == nullptr) {
-		root = l;
+void Treap::insert(count_type k, string s, bool new_version) {
+	if(k > size()) {
+		std::cerr << "Inserting out of file range\n";
 		return;
 	}
 
-	auto two = split(root, k);
-	two.first = join(two.first, l);
-	root = join(two);
+	line* new_root = insert(get_root(), k, s, new_version);
+
+	if(new_version) {
+		root.push(new_root);
+		changes.push({k, 1});
+	}
+	else
+		root.top() = new_root;
 }
 // Line removal
 void Treap::remove(count_type k) {
-	auto two = split(root, k+1);
-	auto first_split = split(two.first, k);
-	delete first_split.second;
-	two.first = first_split.first;
-	root = join(two);
+	if(k >= size()) {
+		std::cerr << "Removing out of file range\n";
+		return;
+	}
+
+	if(size() == 1)
+		update(0, "");
+	else {
+		root.push(remove(get_root(), k));
+		changes.push({k, 1});
+	}
+}
+
+// Line text update
+void Treap::update(count_type k, string s) {
+	if(k >= size()) {
+		std::cerr << "Updating out of file range\n";
+		return;
+	}
+
+	if(s == find(get_root(), k)->text)
+		return;
+
+	line *new_root = update(get_root(), k, s);
+
+	root.push(new_root);
+	changes.push({k, 1});
 }
 
 // Accessing the file
 string Treap::get_line(count_type r, bool substitute_tab) {
-	string line = find(r)->text;
+	string line = find(get_root(), r)->text;
+
 	if(substitute_tab)
 		return substitute_tabs(line);
 	else
@@ -104,7 +254,7 @@ string Treap::get_line(count_type r, bool substitute_tab) {
 count_type Treap::bulk_find(vector<string> *vec, line *l, count_type k, count_type count) {
 	if(l == nullptr) return count;
 
-	// Wanted vertex is on the left
+	// Wanted vertex is on the left (this may be wanted afterwards)
 	if(k <= get_size(l->left)) {
 		count_type r = bulk_find(vec, l->left, k, count);
 		if(r > 0)
@@ -115,7 +265,7 @@ count_type Treap::bulk_find(vector<string> *vec, line *l, count_type k, count_ty
 			return 0;
 	}
 
-	// This is the wanted vertex
+	// This is a wanted vertex
 	else if(k == get_size(l->left)+1) {
 		vec->push_back(substitute_tabs(l->text));
 		if(count > 1)
@@ -123,26 +273,53 @@ count_type Treap::bulk_find(vector<string> *vec, line *l, count_type k, count_ty
 		else
 			return 0;
 	}
+
+	// Wanted vertex is on the right (this is never wanted)
 	else
 		return bulk_find(vec, l->right, k - (1+get_size(l->left)), count);
 }
 // Access multiple adjacent vertices
 vector<string> Treap::bulk_get_line(count_type r, count_type count) {
 	vector<string> ret(0);
-	bulk_find(&ret, root, r+1, count);
+	bulk_find(&ret, get_root(), r+1, count);
 	return ret;
 }
 
 void Treap::insert(position p, string t) {
-	find(p.r)->text.insert(p.c-get_tab_offset(p), t);
+	string text = get_line(p.r, false);
+	text.insert(p.c-get_tab_offset(p), t);
+
+	if(text != get_line(p.r, false))
+		update(p.r, text);
 }
 void Treap::remove(position p, count_type len) {
-	find(p.r)->text.erase(p.c-get_tab_offset(p),len);
+	string text = get_line(p.r, false);
+	text.erase(p.c-get_tab_offset(p),len);
+
+	if(text != get_line(p.r, false))
+		update(p.r, text);
 }
 // Split line
-void Treap::split_line(position p) {
-	string line = get_line(p.r);
-	string newline = line.substr(p.c, line.size());
-	remove(p, line.size()-p.c);
+void Treap::split_line(position p, bool should_compress) {
+	string line = get_line(p.r, false);
+	count_type real_c = p.c - get_tab_offset(p);
+	string newline = line.substr(real_c, line.size());
+
+	if(line.size()-real_c > 0)
+		remove(p, line.size()-real_c);
 	insert(p.r+1, newline);
+
+	if(should_compress)
+		compress_versions(2);
+}
+void Treap::merge_line(count_type k, bool should_compress) {
+	if(k == 0)
+		return;
+
+	string text = get_line(k, false);
+	remove(k);
+	update(k-1, get_line(k-1, false) + text);
+
+	if(should_compress)
+		compress_versions(2);
 }