# by ChatGPT

import curses
import subprocess
import sys

def get_commits(filename):
    cmd = ['git', 'log', '--pretty=format:%h %ad %s', '--date=short', '--', filename]
    result = subprocess.run(cmd, capture_output=True, text=True)
    return result.stdout.splitlines()

def get_file_at_commit(commit_hash, filename):
    cmd = ['git', 'show', f'{commit_hash}:{filename}']
    result = subprocess.run(cmd, capture_output=True, text=True)
    return result.stdout.splitlines()

def main(stdscr, filename):
    curses.curs_set(0)
    curses.mousemask(curses.ALL_MOUSE_EVENTS)
    curses.mouseinterval(0)
    stdscr.keypad(True)
    
    # Initialize colors if terminal supports them
    if curses.has_colors():
        curses.use_default_colors()  # Use terminal's default colors
        
    # Initialize key variable
    key = 0

    commits = get_commits(filename)
    selected_commit = 0
    divider_col = 40
    focus = "left"
    scroll_offset = 0

    dragging_divider = False

    # Initialize file content
    commit_hash = commits[selected_commit].split()[0]
    file_lines = get_file_at_commit(commit_hash, filename)
    
    # Enable nodelay for smoother scrolling
    stdscr.nodelay(True)
    
    while True:
        stdscr.erase()  # Use erase instead of clear for less flickering
        height, width = stdscr.getmaxyx()

        # Only fetch file content when commit changes
        if key in [curses.KEY_DOWN, curses.KEY_UP, ord('j'), ord('k')] and focus == "left":
            commit_hash = commits[selected_commit].split()[0]
            file_lines = get_file_at_commit(commit_hash, filename)
            
        max_scroll = max(0, len(file_lines) - (height - 1))
        scroll_offset = min(scroll_offset, max_scroll)
        visible_lines = file_lines[scroll_offset:scroll_offset + height - 1]

        # Draw commit list (left pane)
        for i in range(min(len(commits), height - 1)):
            line = commits[i]
            if i == selected_commit:
                stdscr.attron(curses.A_REVERSE)  # Highlight selected commit
            stdscr.addnstr(i, 0, line, divider_col - 1)
            if i == selected_commit:
                stdscr.attroff(curses.A_REVERSE)

        # Vertical divider
        divider_char = "║" if dragging_divider else "│"
        for y in range(height):
            stdscr.addch(y, divider_col, divider_char)

        # Draw file content (right pane) - more efficiently
        right_width = width - divider_col - 3
        for i, line in enumerate(visible_lines):
            # Only draw what fits in the window
            if i < height - 1:
                stdscr.addnstr(i, divider_col + 2, line, right_width)

        # Status bar for right pane
        visible_height = height - 1  # Reserve 1 line for the status bar
        last_visible_line = scroll_offset + visible_height

        if len(file_lines) > 0:
            percent = int((last_visible_line / len(file_lines)) * 100)
            percent = 100 if last_visible_line >= len(file_lines) else percent
        else:
            percent = 0

        status = f"{percent}%"
        x = width - len(status) - 1
        stdscr.addnstr(height - 1, x, status, len(status), curses.A_REVERSE)

        # Get input with a small timeout for smoother scrolling
        stdscr.timeout(50)  # 50ms timeout
        key = stdscr.getch()
        
        # If no key was pressed, continue the loop
        if key == -1:
            continue

        # Mouse interaction
        if key == curses.KEY_MOUSE:
            try:
                _, mx, my, _, bstate = curses.getmouse()

                # Handle divider dragging
                if bstate & curses.BUTTON1_PRESSED:
                    # Start dragging when clicked near divider
                    if abs(mx - divider_col) <= 1:  # Allow clicking within 1 column of divider
                        dragging_divider = True
                
                # If already dragging, update divider position
                if dragging_divider:
                    # Update divider position while dragging
                    min_col = 10
                    max_col = width - 20  # leave space for right pane
                    divider_col = max(min_col, min(mx, max_col))
                
                # Handle mouse release
                if bstate & curses.BUTTON1_RELEASED:
                    if dragging_divider:
                        dragging_divider = False
                    else:
                        # Change focus on mouse click (when not dragging)
                        focus = "left" if mx < divider_col else "right"
            except curses.error:
                pass

        # Exit on 'q' or ESC
        elif key in [ord('q'), 27]:
            break

        # Left pane movement
        elif focus == "left":
            if key in [curses.KEY_DOWN, ord('j')]:
                if selected_commit < len(commits) - 1:
                    selected_commit += 1
                    scroll_offset = 0
            elif key in [curses.KEY_UP, ord('k')]:
                if selected_commit > 0:
                    selected_commit -= 1
                    scroll_offset = 0

        # Right pane scrolling
        elif focus == "right":
            if key in [curses.KEY_DOWN, ord('j')]:
                if scroll_offset < max_scroll:
                    scroll_offset += 1
            elif key in [curses.KEY_UP, ord('k')]:
                if scroll_offset > 0:
                    scroll_offset -= 1
            elif key in [curses.KEY_NPAGE, ord(' ')]:
                scroll_offset = min(scroll_offset + height - 1, max_scroll)
            elif key in [curses.KEY_PPAGE, 8, 127, curses.KEY_SR]:  # Page Up, Backspace, Delete, or Shift+Up
                scroll_offset = max(0, scroll_offset - (height - 1))
            elif key == curses.KEY_BACKSPACE:  # Another way to detect Shift+Space in some terminals
                scroll_offset = max(0, scroll_offset - (height - 1))

        # Pane switching
        if key in [curses.KEY_LEFT, ord('h')]:
            focus = "left"
        elif key in [curses.KEY_RIGHT, ord('l')]:
            focus = "right"

        stdscr.refresh()

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print("Usage: python git_time_machine.py path/to/file")
        sys.exit(1)
    filename = sys.argv[1]
    curses.wrapper(main, filename)