refactor: Convert AppState to pure dataclass with functional state management

gtm

@@ -5,6 +5,8 @@ import os
 import subprocess
 import sys
 import argparse
+from dataclasses import dataclass, field, replace
+from typing import List, Optional, Tuple
 
 VERSION = "2025-06-07.3"
 
@@ -91,121 +93,129 @@ def get_diff_info(current_commit, prev_commit, filename):
         i += 1
     return added_lines, deleted_lines
 
-# --- Application State Class ---
+@dataclass
-
 class AppState:
-    def __init__(self, filename, width, height, show_diff, show_add, show_del, mouse):
+    filename: str
-        self.filename = filename
+    width: int
-        self.width = width
+    height: int
-        self.height = height
+    show_whole_diff: bool
-        self.show_whole_diff = show_diff
+    show_additions: bool
-        self.show_additions = show_add
+    show_deletions: bool
-        self.show_deletions = show_del
+    enable_mouse: bool
-        self.enable_mouse = mouse
-        self.show_sidebar = True
     
-        self.commits = get_commits(filename)
+    show_sidebar: bool = True
-        self.file_lines = []
+    commits: List[str] = field(default_factory=list)
-        self.added_lines = []
+    file_lines: List[str] = field(default_factory=list)
-        self.deleted_lines = []
+    added_lines: List[Tuple[int, str]] = field(default_factory=list)
+    deleted_lines: List[Tuple[int, str]] = field(default_factory=list)
 
-        self.focus = "left"
+    focus: str = "left"
-        self.divider_col = 40
+    divider_col: int = 40
     
-        self.selected_commit_idx = 0
+    selected_commit_idx: int = 0
-        self.left_scroll_offset = 0
+    left_scroll_offset: int = 0
-        self.right_scroll_offset = 0
+    right_scroll_offset: int = 0
 
-        self.dragging_divider = False
+    dragging_divider: bool = False
-        self.should_exit = False
+    should_exit: bool = False
 
-        self.is_selecting = False
+    is_selecting: bool = False
-        self.selection_start_coord = None
+    selection_start_coord: Optional[Tuple[int, int]] = None
-        self.selection_end_coord = None
+    selection_end_coord: Optional[Tuple[int, int]] = None
-        self.click_position = None  # Store click position to detect clicks vs. drags
+    click_position: Optional[Tuple[int, int]] = None
-        self.last_bstate = 0
+    last_bstate: int = 0
-        self.mouse_x = -1
+    mouse_x: int = -1
-        self.mouse_y = -1
+    mouse_y: int = -1
 
-    def update_dimensions(self, height, width):
+# --- Actions (Controller) ---
-        self.height = height
-        self.width = width
 
-    def toggle_mouse(self):
+def load_commit_content(state: AppState) -> AppState:
-        self.enable_mouse = not self.enable_mouse
+    if not state.commits:
-        if self.enable_mouse:
+        return state
-            curses.mousemask(curses.ALL_MOUSE_EVENTS | curses.REPORT_MOUSE_POSITION)
-        else:
-            curses.mousemask(0)
-            
-    def toggle_sidebar(self):
-        self.show_sidebar = not self.show_sidebar
-        # When hiding sidebar, focus should be on right pane
-        if not self.show_sidebar:
-            self.focus = "right"
-
-    def move_commit_selection(self, delta):
-        new_idx = self.selected_commit_idx + delta
-        if 0 <= new_idx < len(self.commits):
-            self.selected_commit_idx = new_idx
-            self.load_commit_content()
-
-    def page_commit_selection(self, direction):
-        page_size = self.height - 1
-        delta = page_size * direction
-        self.move_commit_selection(delta)
-
-    def scroll_right_pane(self, delta):
-        max_scroll = max(0, len(self.file_lines) - (self.height - 1))
-        new_offset = self.right_scroll_offset + delta
-        self.right_scroll_offset = max(0, min(new_offset, max_scroll))
-
-    def page_right_pane(self, direction):
-        page_size = self.height - 1
-        delta = page_size * direction
-        self.scroll_right_pane(delta)
-
-    def update_divider(self, mx):
-        min_col = 10
-        max_col = self.width - 20
-        self.divider_col = max(min_col, min(mx, max_col))
-
-    def load_commit_content(self):
-        if not self.commits:
-            return
     
     reference_line = None
     scroll_percentage = 0
-        if len(self.file_lines) > 0:
+    if len(state.file_lines) > 0:
-            max_scroll_old = max(0, len(self.file_lines) - (self.height - 1))
+        max_scroll_old = max(0, len(state.file_lines) - (state.height - 1))
         if max_scroll_old > 0:
-                scroll_percentage = self.right_scroll_offset / max_scroll_old
+            scroll_percentage = state.right_scroll_offset / max_scroll_old
-            if self.right_scroll_offset < len(self.file_lines):
+        if state.right_scroll_offset < len(state.file_lines):
-                reference_line = self.file_lines[self.right_scroll_offset]
+            reference_line = state.file_lines[state.right_scroll_offset]
     
-        commit_hash = self.commits[self.selected_commit_idx].split()[0]
+    commit_hash = state.commits[state.selected_commit_idx].split()[0]
-        self.file_lines = get_file_at_commit(commit_hash, self.filename)
+    file_lines = get_file_at_commit(commit_hash, state.filename)
 
     prev_commit_hash = None
-        if self.selected_commit_idx < len(self.commits) - 1:
+    if state.selected_commit_idx < len(state.commits) - 1:
-            prev_commit_hash = self.commits[self.selected_commit_idx + 1].split()[0]
+        prev_commit_hash = state.commits[state.selected_commit_idx + 1].split()[0]
 
-        if self.show_whole_diff or self.show_additions or self.show_deletions:
+    if state.show_whole_diff or state.show_additions or state.show_deletions:
-            self.added_lines, self.deleted_lines = get_diff_info(commit_hash, prev_commit_hash, self.filename)
+        added_lines, deleted_lines = get_diff_info(commit_hash, prev_commit_hash, state.filename)
     else:
-            self.added_lines, self.deleted_lines = [], []
+        added_lines, deleted_lines = [], []
     
-        max_scroll_new = max(0, len(self.file_lines) - (self.height - 1))
+    max_scroll_new = max(0, len(file_lines) - (state.height - 1))
+    right_scroll_offset = state.right_scroll_offset
     if reference_line:
-            matching_line_idx = find_best_matching_line(reference_line, self.file_lines, 1000)
+        matching_line_idx = find_best_matching_line(reference_line, file_lines, 1000)
         if matching_line_idx is not None:
-                self.right_scroll_offset = matching_line_idx
+            right_scroll_offset = matching_line_idx
         else:
-                self.right_scroll_offset = int(scroll_percentage * max_scroll_new)
+            right_scroll_offset = int(scroll_percentage * max_scroll_new)
     else:
-            self.right_scroll_offset = int(scroll_percentage * max_scroll_new)
+        right_scroll_offset = int(scroll_percentage * max_scroll_new)
+    
+    right_scroll_offset = max(0, min(right_scroll_offset, max_scroll_new))
+
+    return replace(state,
+        file_lines=file_lines,
+        added_lines=added_lines,
+        deleted_lines=deleted_lines,
+        right_scroll_offset=right_scroll_offset
+    )
+
+def update_dimensions(state: AppState, height: int, width: int) -> AppState:
+    return replace(state, height=height, width=width)
+
+def toggle_mouse(state: AppState) -> AppState:
+    return replace(state, enable_mouse=not state.enable_mouse)
+            
+def toggle_sidebar(state: AppState) -> AppState:
+    new_show_sidebar = not state.show_sidebar
+    new_focus = state.focus
+    if not new_show_sidebar:
+        new_focus = "right"
+    return replace(state, show_sidebar=new_show_sidebar, focus=new_focus)
+
+def move_commit_selection(state: AppState, delta: int) -> AppState:
+    new_idx = state.selected_commit_idx + delta
+    if 0 <= new_idx < len(state.commits):
+        new_state = replace(state, selected_commit_idx=new_idx)
+        return load_commit_content(new_state)
+    return state
+
+def page_commit_selection(state: AppState, direction: int) -> AppState:
+    page_size = state.height - 1
+    delta = page_size * direction
+    return move_commit_selection(state, delta)
+
+def scroll_right_pane(state: AppState, delta: int) -> AppState:
+    max_scroll = max(0, len(state.file_lines) - (state.height - 1))
+    new_offset = state.right_scroll_offset + delta
+    new_offset = max(0, min(new_offset, max_scroll))
+    return replace(state, right_scroll_offset=new_offset)
+
+def page_right_pane(state: AppState, direction: int) -> AppState:
+    page_size = state.height - 1
+    delta = page_size * direction
+    return scroll_right_pane(state, delta)
+
+def update_divider(state: AppState, mx: int) -> AppState:
+    min_col = 10
+    max_col = state.width - 20
+    new_divider_col = max(min_col, min(mx, max_col))
+    return replace(state, divider_col=new_divider_col)
 
-        self.right_scroll_offset = max(0, min(self.right_scroll_offset, max_scroll_new))
 
 # --- Rendering Functions (View) ---
 
@@ -507,42 +517,32 @@ def copy_selection_to_clipboard(stdscr, state):
             except (FileNotFoundError, subprocess.CalledProcessError):
                 pass
 
-def handle_mouse_input(stdscr, state):
+def handle_mouse_input(stdscr, state: AppState) -> AppState:
     try:
         _, mx, my, _, bstate = curses.getmouse()
-        state.last_bstate = bstate
+        state = replace(state, last_bstate=bstate, mouse_x=mx, mouse_y=my)
-        state.mouse_x, state.mouse_y = mx, my
 
         # Handle mouse button press
         if bstate & curses.BUTTON1_PRESSED:
-            # Check if clicking near divider (only if sidebar is visible)
             if state.show_sidebar and abs(mx - state.divider_col) <= 1:
-                state.dragging_divider = True
+                return replace(state, dragging_divider=True)
             else:
-                # Switch panes immediately on click (only if sidebar is visible)
+                focus = "right"
                 if state.show_sidebar:
-                    state.focus = "left" if mx < state.divider_col else "right"
+                    focus = "left" if mx < state.divider_col else "right"
-                else:
-                    state.focus = "right"  # When sidebar is hidden, focus is always right
                 
-                # Also start a potential selection (in case this becomes a drag)
+                return replace(state, 
-                state.is_selecting = True
+                               focus=focus,
-                state.selection_start_coord = (mx, my)
+                               is_selecting=True,
-                state.selection_end_coord = (mx, my)
+                               selection_start_coord=(mx, my),
-                state.click_position = (mx, my)
+                               selection_end_coord=(mx, my),
-                
+                               click_position=(mx, my))
-                # Redraw immediately to show selection highlight and focus change
-                draw_ui(stdscr, state)
-            return
             
         # Handle mouse button release
         if bstate & curses.BUTTON1_RELEASED:
-            # End of divider drag
             if state.dragging_divider:
-                state.dragging_divider = False
+                return replace(state, dragging_divider=False)
-                return
                 
-            # End of selection
             if state.is_selecting:
                 # Check if this was a click (press and release at same position)
                 # or very close to the same position (within 1-2 pixels)
@@ -550,80 +550,77 @@ def handle_mouse_input(stdscr, state):
                     abs(state.click_position[0] - mx) <= 2 and 
                     abs(state.click_position[1] - my) <= 2):
                     # This was a click, so switch panes (only if sidebar is visible)
+                    focus = "right"
                     if state.show_sidebar:
-                        state.focus = "left" if mx < state.divider_col else "right"
+                        focus = "left" if mx < state.divider_col else "right"
-                    else:
+                    
-                        state.focus = "right"  # When sidebar is hidden, focus is always right
+                    new_state = replace(state, focus=focus)
 
                     # If clicking in the left pane on a commit entry, select that commit
                     if state.show_sidebar and mx < state.divider_col and my < min(state.height - 1, len(state.commits) - state.left_scroll_offset):
                         new_commit_idx = my + state.left_scroll_offset
                         if 0 <= new_commit_idx < len(state.commits):
-                            state.selected_commit_idx = new_commit_idx
+                            new_state = replace(new_state, selected_commit_idx=new_commit_idx)
-                            state.load_commit_content()
+                            new_state = load_commit_content(new_state)
+                    
+                    # Reset selection state
+                    return replace(new_state, is_selecting=False, selection_start_coord=None, selection_end_coord=None, click_position=None)
+
                 elif state.selection_start_coord and state.selection_end_coord:
                     # This was a drag selection, copy the text
                     copy_selection_to_clipboard(stdscr, state)
                 
                 # Reset selection state
-                state.is_selecting = False
+                return replace(state, is_selecting=False, selection_start_coord=None, selection_end_coord=None, click_position=None)
-                state.selection_start_coord = None
-                state.selection_end_coord = None
-                state.click_position = None
-                return
         
         # Handle mouse movement during drag operations
         if state.dragging_divider:
-            # Update divider position during drag
+            return update_divider(state, mx)
-            state.update_divider(mx)
         elif state.is_selecting:
-            # Update selection end coordinates during drag
+            return replace(state, selection_end_coord=(mx, my))
-            state.selection_end_coord = (mx, my)
-            # Redraw immediately to show selection highlight during drag
-            draw_ui(stdscr, state)
 
     except curses.error:
         pass
+    return state
 
-def handle_keyboard_input(key, state):
+def handle_keyboard_input(key, state: AppState) -> AppState:
     if key in [ord('q')]:
-        state.should_exit = True
+        return replace(state, should_exit=True)
     elif key == 27:  # Escape key
         if state.is_selecting:
-            state.is_selecting = False
+            return replace(state, is_selecting=False, selection_start_coord=None, selection_end_coord=None)
-            state.selection_start_coord = None
-            state.selection_end_coord = None
         else:
-            state.should_exit = True
+            return replace(state, should_exit=True)
     elif key == ord('m'):
-        state.toggle_mouse()
+        return toggle_mouse(state)
     elif key == ord('s'):
-        state.toggle_sidebar()
+        return toggle_sidebar(state)
     elif key in [curses.KEY_LEFT, ord('h')]:
         if state.show_sidebar:
-            state.focus = "left"
+            return replace(state, focus="left")
     elif key in [curses.KEY_RIGHT, ord('l')]:
-        state.focus = "right"
+        return replace(state, focus="right")
     
     elif state.focus == "left":
         if key in [curses.KEY_DOWN, ord('j')]:
-            state.move_commit_selection(1)
+            return move_commit_selection(state, 1)
         elif key in [curses.KEY_UP, ord('k')]:
-            state.move_commit_selection(-1)
+            return move_commit_selection(state, -1)
         elif key in [curses.KEY_NPAGE, ord(' ')]:
-            state.page_commit_selection(1)
+            return page_commit_selection(state, 1)
         elif key in [curses.KEY_PPAGE, 8, 127, curses.KEY_SR]:
-            state.page_commit_selection(-1)
+            return page_commit_selection(state, -1)
 
     elif state.focus == "right":
         if key in [curses.KEY_DOWN, ord('j')]:
-            state.scroll_right_pane(1)
+            return scroll_right_pane(state, 1)
         elif key in [curses.KEY_UP, ord('k')]:
-            state.scroll_right_pane(-1)
+            return scroll_right_pane(state, -1)
         elif key in [curses.KEY_NPAGE, ord(' ')]:
-            state.page_right_pane(1)
+            return page_right_pane(state, 1)
         elif key in [curses.KEY_PPAGE, 8, 127, curses.KEY_SR]:
-            state.page_right_pane(-1)
+            return page_right_pane(state, -1)
+    return state
 
 # --- Main Application ---
 
@@ -644,7 +641,12 @@ def main(stdscr, filename, show_diff, show_add, show_del, mouse):
         curses.init_pair(4, curses.COLOR_RED, -1)
 
     height, width = stdscr.getmaxyx()
-    state = AppState(filename, width, height, show_diff, show_add, show_del, mouse)
+    state = AppState(
+        filename=filename, width=width, height=height,
+        show_whole_diff=show_diff, show_additions=show_add,
+        show_deletions=show_del, enable_mouse=mouse,
+        commits=get_commits(filename)
+    )
     
     if state.enable_mouse:
         curses.mousemask(curses.ALL_MOUSE_EVENTS | curses.REPORT_MOUSE_POSITION)
@@ -656,7 +658,7 @@ def main(stdscr, filename, show_diff, show_add, show_del, mouse):
             except Exception:
                 pass
     
-    state.load_commit_content()
+    state = load_commit_content(state)
     
     # Initial draw before the main loop starts
     draw_ui(stdscr, state)
@@ -665,16 +667,24 @@ def main(stdscr, filename, show_diff, show_add, show_del, mouse):
         try:
             key = stdscr.getch()
             
+            old_mouse_enabled = state.enable_mouse
+
             # Process input and update the application state
             if key == -1:  # No input available (timeout)
                 pass  # Just redraw the UI and continue
             elif key == curses.KEY_RESIZE:
                 h, w = stdscr.getmaxyx()
-                state.update_dimensions(h, w)
+                state = update_dimensions(state, h, w)
             elif state.enable_mouse and key == curses.KEY_MOUSE:
-                handle_mouse_input(stdscr, state)
+                state = handle_mouse_input(stdscr, state)
             else:
-                handle_keyboard_input(key, state)
+                state = handle_keyboard_input(key, state)
+            
+            if old_mouse_enabled != state.enable_mouse:
+                if state.enable_mouse:
+                    curses.mousemask(curses.ALL_MOUSE_EVENTS | curses.REPORT_MOUSE_POSITION)
+                else:
+                    curses.mousemask(0)
 
             # After every action, redraw the UI to reflect changes immediately.
             # This is crucial for real-time feedback during mouse drags.