From d527c7b1b2ecfb51e8034f79d141fa1acc41fd52 Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Sat, 29 Nov 2025 23:00:09 -0800
Subject: [PATCH] Refactor `Buffer` to use `Line` abstraction and improve
 handling of row operations.

This uses either a GapBuffer or PieceTable depending on the compilation.
---
 .idea/workspace.xml |  40 ++++++--------
 Buffer.cc           |  80 ++++++++++++++--------------
 Buffer.h            | 124 ++++++++++++++++++++++++++++++++++++++++++--
 Command.cc          |   8 +--
 4 files changed, 184 insertions(+), 68 deletions(-)

diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 7414c9f..e133240 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -33,31 +33,11 @@
     </configurations>
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="e1fe3ab0-3650-4fca-8664-a247d5dfa457" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/UndoNode.cc" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/UndoNode.h" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/UndoTree.cc" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/UndoTree.h" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/kte-cloc" afterDir="false" />
+    <list default="true" id="e1fe3ab0-3650-4fca-8664-a247d5dfa457" name="Changes" comment="Add undo/redo infrastructure and buffer management additions.">
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/Buffer.cc" beforeDir="false" afterPath="$PROJECT_DIR$/Buffer.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/CMakeLists.txt" beforeDir="false" afterPath="$PROJECT_DIR$/CMakeLists.txt" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/Buffer.h" beforeDir="false" afterPath="$PROJECT_DIR$/Buffer.h" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/Command.cc" beforeDir="false" afterPath="$PROJECT_DIR$/Command.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/Command.h" beforeDir="false" afterPath="$PROJECT_DIR$/Command.h" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/Editor.cc" beforeDir="false" afterPath="$PROJECT_DIR$/Editor.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/Editor.h" beforeDir="false" afterPath="$PROJECT_DIR$/Editor.h" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/GUIFrontend.cc" beforeDir="false" afterPath="$PROJECT_DIR$/GUIFrontend.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/GUIInputHandler.cc" beforeDir="false" afterPath="$PROJECT_DIR$/GUIInputHandler.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/GUIInputHandler.h" beforeDir="false" afterPath="$PROJECT_DIR$/GUIInputHandler.h" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/GUIRenderer.cc" beforeDir="false" afterPath="$PROJECT_DIR$/GUIRenderer.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/GapBuffer.cc" beforeDir="false" afterPath="$PROJECT_DIR$/GapBuffer.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/KKeymap.cc" beforeDir="false" afterPath="$PROJECT_DIR$/KKeymap.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/PieceTable.cc" beforeDir="false" afterPath="$PROJECT_DIR$/PieceTable.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/TerminalFrontend.cc" beforeDir="false" afterPath="$PROJECT_DIR$/TerminalFrontend.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/TerminalFrontend.h" beforeDir="false" afterPath="$PROJECT_DIR$/TerminalFrontend.h" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/TerminalInputHandler.cc" beforeDir="false" afterPath="$PROJECT_DIR$/TerminalInputHandler.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/TerminalRenderer.cc" beforeDir="false" afterPath="$PROJECT_DIR$/TerminalRenderer.cc" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/main.cc" beforeDir="false" afterPath="$PROJECT_DIR$/main.cc" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -164,8 +144,17 @@
       <option name="number" value="Default" />
       <option name="presentableId" value="Default" />
       <updated>1764457173148</updated>
-      <workItem from="1764457174208" duration="26658000" />
+      <workItem from="1764457174208" duration="27302000" />
     </task>
+    <task id="LOCAL-00001" summary="Add undo/redo infrastructure and buffer management additions.">
+      <option name="closed" value="true" />
+      <created>1764485311566</created>
+      <option name="number" value="00001" />
+      <option name="presentableId" value="LOCAL-00001" />
+      <option name="project" value="LOCAL" />
+      <updated>1764485311566</updated>
+    </task>
+    <option name="localTasksCounter" value="2" />
     <servers />
   </component>
   <component name="TypeScriptGeneratedFilesManager">
@@ -176,6 +165,11 @@
     <isAutomaticFoundErrors value="true" />
     <isAutomaticReloadCMake value="true" />
   </component>
+  <component name="VcsManagerConfiguration">
+    <MESSAGE value="Refactoring" />
+    <MESSAGE value="Add undo/redo infrastructure and buffer management additions." />
+    <option name="LAST_COMMIT_MESSAGE" value="Add undo/redo infrastructure and buffer management additions." />
+  </component>
   <component name="XSLT-Support.FileAssociations.UIState">
     <expand />
     <select />
diff --git a/Buffer.cc b/Buffer.cc
index b2fec81..16c96b3 100644
--- a/Buffer.cc
+++ b/Buffer.cc
@@ -20,21 +20,21 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 {
 	// If the file doesn't exist, initialize an empty, non-file-backed buffer
 	// with the provided filename. Do not touch the filesystem until Save/SaveAs.
-	if (!std::filesystem::exists(path)) {
-		rows_.clear();
-		nrows_          = 0;
-		filename_       = path;
-		is_file_backed_ = false;
-		dirty_          = false;
+ if (!std::filesystem::exists(path)) {
+        rows_.clear();
+        nrows_          = 0;
+        filename_       = path;
+        is_file_backed_ = false;
+        dirty_          = false;
 
-		// Reset cursor/viewport state
-		curx_      = cury_    = rx_ = 0;
-		rowoffs_   = coloffs_ = 0;
-		mark_set_  = false;
-		mark_curx_ = mark_cury_ = 0;
+        // Reset cursor/viewport state
+        curx_      = cury_    = rx_ = 0;
+        rowoffs_   = coloffs_ = 0;
+        mark_set_  = false;
+        mark_curx_ = mark_cury_ = 0;
 
-		return true;
-	}
+        return true;
+    }
 
 	std::ifstream in(path, std::ios::in | std::ios::binary);
 	if (!in) {
@@ -42,19 +42,19 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 		return false;
 	}
 
-	rows_.clear();
-	std::string line;
-	while (std::getline(in, line)) {
-		// std::getline strips the '\n', keep raw line
-		if (!line.empty() && !in.good()) {
-			// fallthrough
-		}
-		// Handle potential Windows CRLF: strip trailing '\r'
-		if (!line.empty() && line.back() == '\r') {
-			line.pop_back();
-		}
-		rows_.push_back(line);
-	}
+ rows_.clear();
+ std::string line;
+ while (std::getline(in, line)) {
+     // std::getline strips the '\n', keep raw line
+     if (!line.empty() && !in.good()) {
+         // fallthrough
+     }
+     // Handle potential Windows CRLF: strip trailing '\r'
+     if (!line.empty() && line.back() == '\r') {
+         line.pop_back();
+     }
+     rows_.emplace_back(line);
+ }
 
 	// If file ends with a trailing newline, getline will have produced an empty
 	// last line already. If the file is empty and no lines were read, keep rows_ empty.
@@ -86,12 +86,14 @@ Buffer::Save(std::string &err) const
 		err = "Failed to open for write: " + filename_;
 		return false;
 	}
-	for (std::size_t i = 0; i < rows_.size(); ++i) {
-		out.write(rows_[i].data(), static_cast<std::streamsize>(rows_[i].size()));
-		if (i + 1 < rows_.size()) {
-			out.put('\n');
-		}
-	}
+ for (std::size_t i = 0; i < rows_.size(); ++i) {
+        const char *d = rows_[i].Data();
+        std::size_t n = rows_[i].Size();
+        if (d && n) out.write(d, static_cast<std::streamsize>(n));
+        if (i + 1 < rows_.size()) {
+            out.put('\n');
+        }
+    }
 	if (!out.good()) {
 		err = "Write error";
 		return false;
@@ -111,12 +113,14 @@ Buffer::SaveAs(const std::string &path, std::string &err)
 		err = "Failed to open for write: " + path;
 		return false;
 	}
-	for (std::size_t i = 0; i < rows_.size(); ++i) {
-		out.write(rows_[i].data(), static_cast<std::streamsize>(rows_[i].size()));
-		if (i + 1 < rows_.size()) {
-			out.put('\n');
-		}
-	}
+ for (std::size_t i = 0; i < rows_.size(); ++i) {
+        const char *d = rows_[i].Data();
+        std::size_t n = rows_[i].Size();
+        if (d && n) out.write(d, static_cast<std::streamsize>(n));
+        if (i + 1 < rows_.size()) {
+            out.put('\n');
+        }
+    }
 	if (!out.good()) {
 		err = "Write error";
 		return false;
diff --git a/Buffer.h b/Buffer.h
index 4d43efb..d8b917b 100644
--- a/Buffer.h
+++ b/Buffer.h
@@ -8,6 +8,8 @@
 #include <string>
 #include <vector>
 
+#include "AppendBuffer.h"
+
 class Buffer {
 public:
 	Buffer();
@@ -57,13 +59,129 @@ public:
 	}
 
 
-	[[nodiscard]] const std::vector<std::string> &Rows() const
+	// Line wrapper backed by AppendBuffer (GapBuffer/PieceTable)
+	class Line {
+	public:
+		Line() = default;
+
+		Line(const char *s)
+		{
+			assign_from(s ? std::string(s) : std::string());
+		}
+
+		Line(const std::string &s)
+		{
+			assign_from(s);
+		}
+
+		Line(const Line &other) = default;
+		Line &operator=(const Line &other) = default;
+		Line(Line &&other) noexcept = default;
+		Line &operator=(Line &&other) noexcept = default;
+
+		// capacity helpers
+		void Clear() { buf_.Clear(); }
+
+		// size/access
+		[[nodiscard]] std::size_t size() const { return buf_.Size(); }
+		[[nodiscard]] bool empty() const { return size() == 0; }
+
+		// read-only raw view
+		[[nodiscard]] const char *Data() const { return buf_.Data(); }
+		[[nodiscard]] std::size_t Size() const { return buf_.Size(); }
+
+		// element access (read-only)
+		[[nodiscard]] char operator[](std::size_t i) const
+		{
+			const char *d = buf_.Data();
+			return (i < buf_.Size() && d) ? d[i] : '\0';
+		}
+
+		// conversions
+		operator std::string() const { return std::string(buf_.Data() ? buf_.Data() : "", buf_.Size()); }
+
+		// string-like API used by command/renderer layers (implemented via materialization for now)
+		std::string substr(std::size_t pos) const
+		{
+			const std::size_t n = buf_.Size();
+			if (pos >= n) return std::string();
+			return std::string(buf_.Data() + pos, n - pos);
+		}
+
+		std::string substr(std::size_t pos, std::size_t len) const
+		{
+			const std::size_t n = buf_.Size();
+			if (pos >= n) return std::string();
+			const std::size_t take = (pos + len > n) ? (n - pos) : len;
+			return std::string(buf_.Data() + pos, take);
+		}
+
+		void erase(std::size_t pos)
+		{
+			// erase to end
+			material_edit([&](std::string &s) {
+				if (pos < s.size()) s.erase(pos);
+			});
+		}
+
+		void erase(std::size_t pos, std::size_t len)
+		{
+			material_edit([&](std::string &s) {
+				if (pos < s.size()) s.erase(pos, len);
+			});
+		}
+
+		void insert(std::size_t pos, const std::string &seg)
+		{
+			material_edit([&](std::string &s) {
+				if (pos > s.size()) pos = s.size();
+				s.insert(pos, seg);
+			});
+		}
+
+		Line &operator+=(const Line &other)
+		{
+			buf_.Append(other.buf_.Data(), other.buf_.Size());
+			return *this;
+		}
+
+		Line &operator+=(const std::string &s)
+		{
+			buf_.Append(s.data(), s.size());
+			return *this;
+		}
+
+		Line &operator=(const std::string &s)
+		{
+			assign_from(s);
+			return *this;
+		}
+
+	private:
+		void assign_from(const std::string &s)
+		{
+			buf_.Clear();
+			if (!s.empty()) buf_.Append(s.data(), s.size());
+		}
+
+		template <typename F>
+		void material_edit(F fn)
+		{
+			std::string tmp = static_cast<std::string>(*this);
+			fn(tmp);
+			assign_from(tmp);
+		}
+
+		AppendBuffer buf_;
+	};
+
+	[[nodiscard]] const std::vector<Line> &Rows() const
 	{
 		return rows_;
 	}
 
 
-	[[nodiscard]] std::vector<std::string> &Rows()
+	[[nodiscard]] std::vector<Line> &Rows()
 	{
 		return rows_;
 	}
@@ -154,7 +272,7 @@ private:
 	std::size_t rx_      = 0; // render x (tabs expanded)
 	std::size_t nrows_   = 0; // number of rows
 	std::size_t rowoffs_ = 0, coloffs_ = 0; // viewport offsets
-	std::vector<std::string> rows_; // buffer rows (without trailing newlines)
+	std::vector<Line> rows_; // buffer rows (without trailing newlines)
 	std::string filename_;
 	bool is_file_backed_   = false;
 	bool dirty_            = false;
diff --git a/Command.cc b/Command.cc
index 1868c00..91e860c 100644
--- a/Command.cc
+++ b/Command.cc
@@ -922,9 +922,9 @@ cmd_newline(CommandContext &ctx)
 	std::size_t x = buf->Curx();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	for (int i = 0; i < repeat; ++i) {
-		if (y >= rows.size())
-			rows.resize(y + 1);
-		std::string &line = rows[y];
+  if (y >= rows.size())
+            rows.resize(y + 1);
+        auto &line = rows[y];
 		std::string tail;
 		if (x < line.size()) {
 			tail = line.substr(x);
@@ -1103,7 +1103,7 @@ cmd_kill_line(CommandContext &ctx)
 		if (rows.size() == 1) {
 			// last remaining line: clear its contents
 			killed_total += rows[0];
-			rows[0].clear();
+   rows[0].Clear();
 			y = 0;
 		} else if (y < rows.size()) {
 			// erase current line; keep y pointing at the next line