From 23507d0e705efe533a4728385f7f2c5db31d2f10 Mon Sep 17 00:00:00 2001
From: Jared Miller <jared@smell.flowers>
Date: Sat, 7 Feb 2026 22:55:53 -0500
Subject: [PATCH] Add editor class with buffer, commands, and undo

---
 src/mudlib/editor.py | 373 +++++++++++++++++++++++++++++++++++++++++++
 tests/test_editor.py | 346 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 719 insertions(+)
 create mode 100644 src/mudlib/editor.py
 create mode 100644 tests/test_editor.py

diff --git a/src/mudlib/editor.py b/src/mudlib/editor.py
new file mode 100644
index 0000000..f90d1ae
--- /dev/null
+++ b/src/mudlib/editor.py
@@ -0,0 +1,373 @@
+"""Text editor for in-game content editing."""
+
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass, field
+
+
+@dataclass
+class EditorResponse:
+    """Response from editor input handling."""
+
+    output: str  # text to send back to the player
+    done: bool  # True if editor should be closed (quit/save-and-quit)
+    saved: bool = False  # True if save was performed
+
+
+@dataclass
+class Editor:
+    """Line-based text editor for in-game content.
+
+    Doesn't know about telnet — takes string input, returns string output.
+    Will be integrated into the shell loop in a later step.
+    """
+
+    buffer: list[str] = field(default_factory=list)
+    cursor: int = 0  # current line (0-indexed internally)
+    undo_stack: list[list[str]] = field(default_factory=list)
+    save_callback: Callable[[str], Awaitable[None]] | None = None
+    content_type: str = "text"  # hint for syntax highlighting later
+    dirty: bool = False
+
+    def __init__(
+        self,
+        initial_content: str = "",
+        save_callback: Callable[[str], Awaitable[None]] | None = None,
+        content_type: str = "text",
+    ):
+        """Initialize editor with optional content."""
+        self.save_callback = save_callback
+        self.content_type = content_type
+        self.cursor = 0
+        self.undo_stack = []
+        self.dirty = False
+
+        if initial_content:
+            self.buffer = initial_content.split("\n")
+        else:
+            self.buffer = []
+
+    def _save_undo_state(self) -> None:
+        """Save current buffer state to undo stack."""
+        self.undo_stack.append(self.buffer.copy())
+        # Cap undo stack at 50 entries
+        if len(self.undo_stack) > 50:
+            self.undo_stack.pop(0)
+
+    def _mark_dirty(self) -> None:
+        """Mark buffer as modified."""
+        self.dirty = True
+
+    def _view_buffer(self) -> str:
+        """Return formatted view of entire buffer."""
+        if not self.buffer:
+            return "(empty buffer)"
+
+        # Calculate padding for line numbers
+        max_line_num = len(self.buffer)
+        padding = len(str(max_line_num))
+
+        lines = []
+        for i, line in enumerate(self.buffer, 1):
+            lines.append(f"{i:>{padding}}  {line}")
+        return "\n".join(lines)
+
+    def _view_line(self, line_num: int) -> str:
+        """Return formatted view of specific line with context."""
+        if line_num < 1 or line_num > len(self.buffer):
+            return f"Error: Line {line_num} does not exist"
+
+        # Show 3 lines of context on each side
+        context = 3
+        start = max(0, line_num - 1 - context)
+        end = min(len(self.buffer), line_num + context)
+
+        # Calculate padding for line numbers
+        max_line_num = end
+        padding = len(str(max_line_num))
+
+        lines = []
+        for i in range(start, end):
+            display_num = i + 1
+            lines.append(f"{display_num:>{padding}}  {self.buffer[i]}")
+        return "\n".join(lines)
+
+    def _insert_line(self, line_num: int, text: str) -> str:
+        """Insert text at specified line number."""
+        if line_num < 1:
+            return "Error: Line number must be >= 1"
+
+        self._save_undo_state()
+
+        # Insert at end if line_num is beyond buffer
+        if line_num > len(self.buffer):
+            self.buffer.append(text)
+        else:
+            self.buffer.insert(line_num - 1, text)
+
+        self._mark_dirty()
+        return f"Inserted at line {line_num}"
+
+    def _delete_line(self, start: int, end: int | None = None) -> str:
+        """Delete line(s) at specified range."""
+        if start < 1 or start > len(self.buffer):
+            return f"Error: Line {start} does not exist"
+
+        self._save_undo_state()
+
+        if end is None:
+            # Delete single line
+            self.buffer.pop(start - 1)
+            self._mark_dirty()
+            return f"Deleted line {start}"
+        else:
+            # Delete range
+            if end < start or end > len(self.buffer):
+                return f"Error: Invalid range {start}-{end}"
+
+            # Delete from start to end (inclusive)
+            del self.buffer[start - 1 : end]
+            self._mark_dirty()
+            return f"Deleted lines {start}-{end}"
+
+    def _replace_line(self, line_num: int, text: str) -> str:
+        """Replace line at specified number with new text."""
+        if line_num < 1 or line_num > len(self.buffer):
+            return f"Error: Line {line_num} does not exist"
+
+        self._save_undo_state()
+        self.buffer[line_num - 1] = text
+        self._mark_dirty()
+        return f"Replaced line {line_num}"
+
+    def _search_replace(self, old: str, new: str, replace_all: bool = False) -> str:
+        """Search and replace text in buffer."""
+        self._save_undo_state()
+        count = 0
+
+        for i, line in enumerate(self.buffer):
+            if old in line:
+                if replace_all:
+                    self.buffer[i] = line.replace(old, new)
+                    count += line.count(old)
+                else:
+                    self.buffer[i] = line.replace(old, new, 1)
+                    count = 1
+                    self._mark_dirty()
+                    return f"Replaced '{old}' with '{new}' on line {i + 1}"
+
+        if count > 0:
+            self._mark_dirty()
+            return f"Replaced {count} occurrence(s) of '{old}' with '{new}'"
+        else:
+            # Restore undo state since nothing changed
+            self.undo_stack.pop()
+            return f"Not found: '{old}'"
+
+    def _undo(self) -> str:
+        """Undo last buffer change."""
+        if not self.undo_stack:
+            return "Nothing to undo"
+
+        self.buffer = self.undo_stack.pop()
+        # Undo might restore clean state, but we'll keep dirty flag
+        # (conservative approach - user can save to clear it)
+        return "Undone last change"
+
+    async def _save(self) -> str:
+        """Save buffer content via callback."""
+        if self.save_callback is None:
+            return "Error: Cannot save (no save callback configured)"
+
+        content = "\n".join(self.buffer)
+        await self.save_callback(content)
+        self.dirty = False
+        return "Saved"
+
+    def _help(self) -> str:
+        """Return help text."""
+        return """Editor Commands:
+:           - view entire buffer with line numbers
+:N          - view line N with context
+:h          - show this help
+:i N text   - insert 'text' at line N
+:d N        - delete line N
+:d N M      - delete lines N through M
+:r N text   - replace line N with 'text'
+:s old new  - search and replace first occurrence
+:sa old new - search and replace all occurrences
+:w          - save
+:wq         - save and quit
+:q          - quit (warns if unsaved changes)
+:q!         - force quit without saving
+:u          - undo last change
+.           - save and quit (MOO convention)
+
+Any line not starting with : is appended to the buffer."""
+
+    async def handle_input(self, line: str) -> EditorResponse:
+        """Handle editor input and return response."""
+        # Special case: dot on its own saves and quits
+        if line == ".":
+            if self.save_callback is None:
+                return EditorResponse(
+                    output="Error: Cannot save (no save callback configured)",
+                    done=False,
+                )
+            save_msg = await self._save()
+            return EditorResponse(output=save_msg, done=True, saved=True)
+
+        # Check if it's a command
+        if not line.startswith(":"):
+            # Append to buffer
+            self._save_undo_state()
+            self.buffer.append(line)
+            self._mark_dirty()
+            return EditorResponse(output="", done=False)
+
+        # Parse command
+        cmd = line[1:].strip()
+
+        # Empty command - view buffer
+        if not cmd:
+            output = self._view_buffer()
+            return EditorResponse(output=output, done=False)
+
+        # Check for numeric line view
+        if cmd.isdigit():
+            line_num = int(cmd)
+            output = self._view_line(line_num)
+            return EditorResponse(output=output, done=False)
+
+        # Parse command parts
+        parts = cmd.split(None, 1)
+        command = parts[0]
+        args = parts[1] if len(parts) > 1 else ""
+
+        # Help
+        if command == "h":
+            output = self._help()
+            return EditorResponse(output=output, done=False)
+
+        # Insert
+        if command == "i":
+            if not args:
+                return EditorResponse(
+                    output="Error: :i requires line number and text", done=False
+                )
+            parts = args.split(None, 1)
+            if len(parts) < 2:
+                return EditorResponse(
+                    output="Error: :i requires line number and text", done=False
+                )
+            try:
+                line_num = int(parts[0])
+                text = parts[1]
+                output = self._insert_line(line_num, text)
+                return EditorResponse(output=output, done=False)
+            except ValueError:
+                return EditorResponse(output="Error: Invalid line number", done=False)
+
+        # Delete
+        if command == "d":
+            if not args:
+                return EditorResponse(
+                    output="Error: :d requires line number(s)", done=False
+                )
+            parts = args.split()
+            try:
+                start = int(parts[0])
+                end = int(parts[1]) if len(parts) > 1 else None
+                output = self._delete_line(start, end)
+                return EditorResponse(output=output, done=False)
+            except (ValueError, IndexError):
+                return EditorResponse(
+                    output="Error: Invalid line number(s)", done=False
+                )
+
+        # Replace
+        if command == "r":
+            if not args:
+                return EditorResponse(
+                    output="Error: :r requires line number and text", done=False
+                )
+            parts = args.split(None, 1)
+            if len(parts) < 2:
+                return EditorResponse(
+                    output="Error: :r requires line number and text", done=False
+                )
+            try:
+                line_num = int(parts[0])
+                text = parts[1]
+                output = self._replace_line(line_num, text)
+                return EditorResponse(output=output, done=False)
+            except ValueError:
+                return EditorResponse(output="Error: Invalid line number", done=False)
+
+        # Search and replace
+        if command == "s":
+            parts = args.split(None, 1)
+            if len(parts) < 2:
+                return EditorResponse(
+                    output="Error: :s requires old and new text", done=False
+                )
+            old_new = parts[1].split(None, 1) if len(parts) > 1 else []
+            if len(old_new) < 2:
+                # Try parsing the whole args as "old new"
+                split_args = args.split(None, 1)
+                if len(split_args) < 2:
+                    return EditorResponse(
+                        output="Error: :s requires old and new text", done=False
+                    )
+                old = split_args[0]
+                new = split_args[1]
+            else:
+                old = parts[0]
+                new = old_new[1] if len(old_new) > 1 else old_new[0]
+            output = self._search_replace(old, new, replace_all=False)
+            return EditorResponse(output=output, done=False)
+
+        # Search and replace all
+        if command == "sa":
+            parts = args.split(None, 1)
+            if len(parts) < 2:
+                return EditorResponse(
+                    output="Error: :sa requires old and new text", done=False
+                )
+            old = parts[0]
+            new = parts[1]
+            output = self._search_replace(old, new, replace_all=True)
+            return EditorResponse(output=output, done=False)
+
+        # Undo
+        if command == "u":
+            output = self._undo()
+            return EditorResponse(output=output, done=False)
+
+        # Save
+        if command == "w":
+            output = await self._save()
+            return EditorResponse(output=output, done=False, saved=True)
+
+        # Save and quit
+        if command == "wq":
+            output = await self._save()
+            return EditorResponse(output=output, done=True, saved=True)
+
+        # Quit
+        if command == "q":
+            if self.dirty:
+                return EditorResponse(
+                    output=(
+                        "Unsaved changes! Use :wq to save and quit, "
+                        "or :q! to force quit"
+                    ),
+                    done=False,
+                )
+            return EditorResponse(output="", done=True)
+
+        # Force quit
+        if command == "q!":
+            return EditorResponse(output="", done=True)
+
+        # Unknown command
+        return EditorResponse(output=f"Unknown command: :{command}", done=False)
diff --git a/tests/test_editor.py b/tests/test_editor.py
new file mode 100644
index 0000000..17b446e
--- /dev/null
+++ b/tests/test_editor.py
@@ -0,0 +1,346 @@
+"""Tests for the text editor."""
+
+import pytest
+
+from mudlib.editor import Editor
+
+
+@pytest.mark.asyncio
+async def test_create_editor_with_empty_buffer():
+    """Editor starts with empty buffer."""
+    editor = Editor()
+    assert editor.buffer == []
+    assert editor.cursor == 0
+    assert editor.dirty is False
+
+
+@pytest.mark.asyncio
+async def test_create_editor_with_initial_content():
+    """Editor can be initialized with content."""
+    editor = Editor(initial_content="line 1\nline 2\nline 3")
+    assert editor.buffer == ["line 1", "line 2", "line 3"]
+    assert editor.dirty is False
+
+
+@pytest.mark.asyncio
+async def test_append_line():
+    """Typing text that isn't a command appends to buffer."""
+    editor = Editor()
+    response = await editor.handle_input("hello world")
+    assert response.output == ""
+    assert response.done is False
+    assert editor.buffer == ["hello world"]
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_append_multiple_lines():
+    """Multiple lines can be appended."""
+    editor = Editor()
+    await editor.handle_input("line 1")
+    await editor.handle_input("line 2")
+    await editor.handle_input("line 3")
+    assert editor.buffer == ["line 1", "line 2", "line 3"]
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_view_buffer():
+    """':' shows the entire buffer with line numbers."""
+    editor = Editor(initial_content="line 1\nline 2\nline 3")
+    response = await editor.handle_input(":")
+    assert "1  line 1" in response.output
+    assert "2  line 2" in response.output
+    assert "3  line 3" in response.output
+
+
+@pytest.mark.asyncio
+async def test_view_empty_buffer():
+    """':' on empty buffer shows appropriate message."""
+    editor = Editor()
+    response = await editor.handle_input(":")
+    assert "empty" in response.output.lower() or response.output == ""
+
+
+@pytest.mark.asyncio
+async def test_view_specific_line():
+    """':5' shows line 5 with context."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 11)]))
+    response = await editor.handle_input(":5")
+    # Should show lines 2-8 (3 lines of context on each side)
+    assert "5  line 5" in response.output
+    assert "2  line 2" in response.output
+    assert "8  line 8" in response.output
+
+
+@pytest.mark.asyncio
+async def test_view_specific_line_at_start():
+    """Viewing line near start shows available context."""
+    editor = Editor(initial_content="line 1\nline 2\nline 3")
+    response = await editor.handle_input(":1")
+    assert "1  line 1" in response.output
+
+
+@pytest.mark.asyncio
+async def test_insert_at_line():
+    """':i 5 text' inserts 'text' at line 5."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 6)]))
+    await editor.handle_input(":i 3 inserted text")
+    assert editor.buffer[2] == "inserted text"
+    assert editor.buffer[3] == "line 3"
+    assert len(editor.buffer) == 6
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_insert_at_end():
+    """':i' can insert at end of buffer."""
+    editor = Editor(initial_content="line 1\nline 2")
+    await editor.handle_input(":i 3 line 3")
+    assert editor.buffer[2] == "line 3"
+
+
+@pytest.mark.asyncio
+async def test_delete_single_line():
+    """':d 5' deletes line 5."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 6)]))
+    await editor.handle_input(":d 3")
+    assert editor.buffer == ["line 1", "line 2", "line 4", "line 5"]
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_delete_range():
+    """':d 5 8' deletes lines 5 through 8."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 11)]))
+    await editor.handle_input(":d 3 6")
+    expected = ["line 1", "line 2", "line 7", "line 8", "line 9", "line 10"]
+    assert editor.buffer == expected
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_delete_invalid_line():
+    """Deleting invalid line shows error."""
+    editor = Editor(initial_content="line 1\nline 2")
+    response = await editor.handle_input(":d 10")
+    assert "error" in response.output.lower() or "invalid" in response.output.lower()
+    assert editor.buffer == ["line 1", "line 2"]
+
+
+@pytest.mark.asyncio
+async def test_replace_line():
+    """':r 5 text' replaces line 5 with 'text'."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 6)]))
+    await editor.handle_input(":r 3 replaced text")
+    assert editor.buffer[2] == "replaced text"
+    assert len(editor.buffer) == 5
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_search_and_replace_first():
+    """':s old new' replaces first occurrence."""
+    editor = Editor(initial_content="hello world\nhello again\nhello there")
+    await editor.handle_input(":s hello hi")
+    assert editor.buffer[0] == "hi world"
+    assert editor.buffer[1] == "hello again"
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_search_and_replace_all():
+    """':sa old new' replaces all occurrences."""
+    editor = Editor(initial_content="hello world\nhello again\nhello there")
+    await editor.handle_input(":sa hello hi")
+    assert editor.buffer[0] == "hi world"
+    assert editor.buffer[1] == "hi again"
+    assert editor.buffer[2] == "hi there"
+    assert editor.dirty is True
+
+
+@pytest.mark.asyncio
+async def test_search_replace_no_match():
+    """Search/replace with no match shows message."""
+    editor = Editor(initial_content="hello world")
+    response = await editor.handle_input(":s foo bar")
+    assert (
+        "not found" in response.output.lower() or "no match" in response.output.lower()
+    )
+
+
+@pytest.mark.asyncio
+async def test_undo():
+    """':u' undoes last buffer change."""
+    editor = Editor(initial_content="line 1\nline 2")
+    await editor.handle_input("line 3")
+    assert len(editor.buffer) == 3
+    response = await editor.handle_input(":u")
+    assert editor.buffer == ["line 1", "line 2"]
+    assert "undo" in response.output.lower()
+
+
+@pytest.mark.asyncio
+async def test_undo_multiple_times():
+    """Undo can be called multiple times."""
+    editor = Editor(initial_content="line 1")
+    await editor.handle_input("line 2")
+    await editor.handle_input("line 3")
+    await editor.handle_input(":u")
+    await editor.handle_input(":u")
+    assert editor.buffer == ["line 1"]
+
+
+@pytest.mark.asyncio
+async def test_undo_when_empty():
+    """Undo with no history shows message."""
+    editor = Editor()
+    response = await editor.handle_input(":u")
+    assert (
+        "nothing to undo" in response.output.lower()
+        or "no undo" in response.output.lower()
+    )
+
+
+@pytest.mark.asyncio
+async def test_save():
+    """':w' calls save callback."""
+    saved_content = None
+
+    async def save_callback(content: str):
+        nonlocal saved_content
+        saved_content = content
+
+    editor = Editor(initial_content="line 1\nline 2", save_callback=save_callback)
+    await editor.handle_input("line 3")
+    response = await editor.handle_input(":w")
+    assert response.saved is True
+    assert response.done is False
+    assert saved_content == "line 1\nline 2\nline 3"
+    assert editor.dirty is False
+
+
+@pytest.mark.asyncio
+async def test_save_without_callback():
+    """':w' without callback shows error."""
+    editor = Editor(initial_content="line 1")
+    response = await editor.handle_input(":w")
+    assert (
+        "cannot save" in response.output.lower() or "no save" in response.output.lower()
+    )
+
+
+@pytest.mark.asyncio
+async def test_save_and_quit():
+    """':wq' saves and quits."""
+    saved_content = None
+
+    async def save_callback(content: str):
+        nonlocal saved_content
+        saved_content = content
+
+    editor = Editor(initial_content="line 1", save_callback=save_callback)
+    response = await editor.handle_input(":wq")
+    assert response.saved is True
+    assert response.done is True
+    assert saved_content == "line 1"
+
+
+@pytest.mark.asyncio
+async def test_quit_when_dirty_warns():
+    """':q' when dirty warns and doesn't quit."""
+    editor = Editor(initial_content="line 1")
+    await editor.handle_input("line 2")
+    response = await editor.handle_input(":q")
+    assert response.done is False
+    assert "unsaved" in response.output.lower() or "save" in response.output.lower()
+
+
+@pytest.mark.asyncio
+async def test_quit_when_clean():
+    """':q' when clean quits successfully."""
+    editor = Editor(initial_content="line 1")
+    response = await editor.handle_input(":q")
+    assert response.done is True
+
+
+@pytest.mark.asyncio
+async def test_force_quit():
+    """':q!' quits without saving."""
+    editor = Editor(initial_content="line 1")
+    await editor.handle_input("line 2")
+    response = await editor.handle_input(":q!")
+    assert response.done is True
+    assert response.saved is False
+
+
+@pytest.mark.asyncio
+async def test_dot_saves_and_quits():
+    """'.' on its own line saves and quits (MOO convention)."""
+    saved_content = None
+
+    async def save_callback(content: str):
+        nonlocal saved_content
+        saved_content = content
+
+    editor = Editor(initial_content="line 1", save_callback=save_callback)
+    await editor.handle_input("line 2")
+    response = await editor.handle_input(".")
+    assert response.done is True
+    assert response.saved is True
+    assert saved_content == "line 1\nline 2"
+
+
+@pytest.mark.asyncio
+async def test_dirty_flag_tracking():
+    """Dirty flag is properly tracked."""
+    editor = Editor(initial_content="line 1")
+    assert editor.dirty is False
+
+    await editor.handle_input("line 2")
+    assert editor.dirty is True
+
+    # Mock save
+    saved_content = None
+
+    async def save_callback(content: str):
+        nonlocal saved_content
+        saved_content = content
+
+    editor.save_callback = save_callback
+    await editor.handle_input(":w")
+    assert editor.dirty is False
+
+
+@pytest.mark.asyncio
+async def test_help():
+    """':h' shows help."""
+    editor = Editor()
+    response = await editor.handle_input(":h")
+    assert ":w" in response.output
+    assert ":q" in response.output
+    assert ":i" in response.output
+    assert ":d" in response.output
+
+
+@pytest.mark.asyncio
+async def test_undo_stack_size_limit():
+    """Undo stack is capped at 50 entries."""
+    editor = Editor()
+    # Add 60 lines
+    for i in range(60):
+        await editor.handle_input(f"line {i}")
+    # Undo stack should be capped
+    assert len(editor.undo_stack) <= 50
+
+
+@pytest.mark.asyncio
+async def test_line_numbers_padded():
+    """Line numbers in view are left-padded."""
+    editor = Editor(initial_content="\n".join([f"line {i}" for i in range(1, 12)]))
+    response = await editor.handle_input(":")
+    # Line 1 should have padding, line 11 should not have extra padding
+    lines = response.output.split("\n")
+    # Find lines with numbers
+    assert any(" 1  line 1" in line for line in lines)
+    assert any("11  line 11" in line for line in lines)