#!/usr/bin/env python3

import curses
import os
import subprocess
import sys
import argparse

VERSION = "2025-06-07"

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 get_diff_info(current_commit, prev_commit, filename):
    """Get diff information between two commits for a file"""
    if not prev_commit:
        # For the first commit, we can't compare with a previous one
        return [], []
    
    # Get additions
    cmd_additions = ['git', 'diff', '--unified=0', prev_commit, current_commit, '--', filename]
    result_additions = subprocess.run(cmd_additions, capture_output=True, text=True)
    
    added_lines = []
    deleted_lines = []
    
    # Initialize variables outside the loop to avoid UnboundLocalError
    start_line = 0
    del_start = 0
    
    for line in result_additions.stdout.splitlines():
        # Parse the diff output to find line numbers of additions and deletions
        if line.startswith('@@'):
            # Parse the hunk header to get line numbers
            parts = line.split()
            if len(parts) >= 3:
                # Format is like @@ -a,b +c,d @@
                # We're interested in the +c,d part for additions
                add_part = parts[2][1:]  # Remove the + sign
                if ',' in add_part:
                    start_line, count = map(int, add_part.split(','))
                else:
                    start_line, count = int(add_part), 1
                
                # For deletions, we look at the -a,b part
                del_part = parts[1][1:]  # Remove the - sign
                if ',' in del_part:
                    del_start, del_count = map(int, del_part.split(','))
                else:
                    del_start, del_count = int(del_part), 1
        elif line.startswith('+') and not line.startswith('+++'):
            # This is an added line
            added_lines.append((start_line, line[1:]))
            start_line += 1
        elif line.startswith('-') and not line.startswith('---'):
            # This is a deleted line
            deleted_lines.append((del_start, line[1:]))
            del_start += 1
        elif not line.startswith('+') and not line.startswith('-') and not line.startswith('@@'):
            # Context line, increment both counters
            start_line += 1
            del_start += 1
    
    return added_lines, deleted_lines

def main(stdscr, filename, show_additions=False, show_deletions=False):
    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
        curses.init_pair(1, 5, 7)  # Focused status bar
        curses.init_pair(2, curses.COLOR_WHITE, 8)   # Unfocused status bar
        curses.init_pair(3, curses.COLOR_GREEN, -1)  # Added lines
        curses.init_pair(4, curses.COLOR_RED, -1)    # Deleted lines
        
    # Initialize key variable
    key = 0

    commits = get_commits(filename)
    selected_commit = 0
    divider_col = 40
    focus = "left"
    scroll_offset = 0
    left_scroll_offset = 0  # Scroll position for left pane

    dragging_divider = False

    # Initialize file content
    commit_hash = commits[selected_commit].split()[0]
    file_lines = get_file_at_commit(commit_hash, filename)
    
    # Get previous commit hash for diff
    prev_commit_hash = None
    if selected_commit < len(commits) - 1:
        prev_commit_hash = commits[selected_commit + 1].split()[0]
    
    # Get diff information if needed
    added_lines = []
    deleted_lines = []
    if show_additions or show_deletions:
        added_lines, deleted_lines = get_diff_info(commit_hash, prev_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)
            
            # Update diff information when commit changes
            prev_commit_hash = None
            if selected_commit < len(commits) - 1:
                prev_commit_hash = commits[selected_commit + 1].split()[0]
            
            if show_additions or show_deletions:
                added_lines, deleted_lines = get_diff_info(commit_hash, prev_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]

        # Calculate visible commits for left pane
        left_max_scroll = max(0, len(commits) - (height - 1))
        left_scroll_offset = min(left_scroll_offset, left_max_scroll)
        
        # Ensure selected commit is visible
        if selected_commit < left_scroll_offset:
            left_scroll_offset = selected_commit
        elif selected_commit >= left_scroll_offset + height - 1:
            left_scroll_offset = selected_commit - (height - 2)
            
        # Draw commit list (left pane)
        visible_commits = commits[left_scroll_offset:left_scroll_offset + height - 1]
        for i, line in enumerate(visible_commits):
            display_index = i + left_scroll_offset
            if display_index == selected_commit:
                stdscr.attron(curses.A_REVERSE)  # Highlight selected commit
            stdscr.addnstr(i, 0, line, divider_col - 1)
            if display_index == selected_commit:
                stdscr.attroff(curses.A_REVERSE)

        # Vertical divider
        divider_char = "║" if dragging_divider else "│"
        for y in range(height):
            try:
                stdscr.addch(y, divider_col, divider_char)
            except curses.error:
                # Avoid errors when drawing at the last column
                pass

        # Draw file content (right pane) - more efficiently
        right_width = width - divider_col - 3
        
        # First, collect all lines to display (regular and deleted)
        display_lines = []
        
        for i, line in enumerate(visible_lines):
            line_num = i + scroll_offset + 1  # 1-based line number
            
            # Check if this is an added line
            is_added = False
            if show_additions:
                for added_line_num, _ in added_lines:
                    if added_line_num == line_num:
                        is_added = True
                        break
            
            # Add the regular line to our display list
            display_lines.append({
                'type': 'added' if is_added else 'regular',
                'content': line,
                'line_num': line_num
            })
            
            # If showing deletions, check if there are deleted lines at this position
            if show_deletions:
                for del_line_num, del_line_content in deleted_lines:
                    if del_line_num == line_num:
                        # Add the deleted line after the current line
                        display_lines.append({
                            'type': 'deleted',
                            'content': del_line_content,
                            'line_num': line_num
                        })
        
        # Now display all lines
        display_row = 0
        for line_info in display_lines:
            # Stop if we've reached the bottom of the screen
            if display_row >= height - 1:
                break
                
            line_type = line_info['type']
            content = line_info['content']
            
            if line_type == 'added':
                # Green with + prefix for added lines
                stdscr.addstr(display_row, divider_col + 2, "+ ", curses.color_pair(3))
                stdscr.addnstr(display_row, divider_col + 4, content, right_width - 2, curses.color_pair(3))
            elif line_type == 'deleted':
                # Red with - prefix for deleted lines
                stdscr.addstr(display_row, divider_col + 2, "- ", curses.color_pair(4))
                stdscr.addnstr(display_row, divider_col + 4, content, right_width - 2, curses.color_pair(4))
            else:
                # Regular line
                stdscr.addnstr(display_row, divider_col + 2, content, right_width)
            
            display_row += 1

        # Status bars for both panes
        visible_height = height - 1  # Reserve 1 line for the status bar
        
        # Right pane status
        last_visible_line = scroll_offset + visible_height
        if len(file_lines) > 0:
            right_percent = int((last_visible_line / len(file_lines)) * 100)
            right_percent = 100 if last_visible_line >= len(file_lines) else right_percent
        else:
            right_percent = 0
        right_status = f"{right_percent}% "
        
        # Left pane status
        last_visible_commit = left_scroll_offset + visible_height
        if len(commits) > 0:
            left_percent = int((last_visible_commit / len(commits)) * 100)
            left_percent = 100 if last_visible_commit >= len(commits) else left_percent
        else:
            left_percent = 0
        left_status = f"{left_percent}%"
        
        # Draw status bars - full width with different colors based on focus
        left_attr = curses.color_pair(1) if focus == "left" else curses.color_pair(2)
        right_attr = curses.color_pair(1) if focus == "right" else curses.color_pair(2)
        
        # Fill the entire bottom row for each pane
        for x in range(divider_col):
            stdscr.addch(height - 1, x, ' ', left_attr)
        for x in range(divider_col + 1, width - 1):  # Avoid the last column
            stdscr.addch(height - 1, x, ' ', right_attr)
            
        # Add the percentage text
        stdscr.addstr(height - 1, 1, left_status, left_attr)
        stdscr.addstr(height - 1, width - len(right_status) - 1, right_status, right_attr)
        
        # Add divider character at the bottom row
        stdscr.addch(height - 1, divider_col, divider_char)

        # 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
            elif key in [curses.KEY_NPAGE, ord(' ')]:
                # Page down in left pane
                new_selected = min(selected_commit + height - 1, len(commits) - 1)
                if new_selected != selected_commit:
                    selected_commit = new_selected
                    scroll_offset = 0
            elif key in [curses.KEY_PPAGE, 8, 127, curses.KEY_SR]:
                # Page up in left pane
                new_selected = max(0, selected_commit - (height - 1))
                if new_selected != selected_commit:
                    selected_commit = new_selected
                    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()

def show_help():
    """Display help information"""
    print("A \"Git Time Machine\" for viewing file history.")
    print()
    print("Usage:")
    print("\tgtm [OPTIONS] FILENAME")
    print()
    print("Options:")
    print("\t--diff-additions\thighlight newly added lines in green")
    print("\t--diff-deletions\tshow deleted lines in red")
    print("\t-v, --version\tshow version number")
    print("\t-h, --help\tshow this help")

if __name__ == "__main__":
    parser = argparse.ArgumentParser(add_help=False, description="A Git Time Machine for viewing file history.")
    parser.add_argument("--diff-additions", action="store_true", help="Highlight newly added lines in green")
    parser.add_argument("--diff-deletions", action="store_true", help="Show deleted lines in red")
    parser.add_argument("-v", "--version", action="store_true", help="Show version number")
    parser.add_argument("-h", "--help", action="store_true", help="Show help information")
    parser.add_argument("filename", nargs="?", help="File to view history for")
    
    args = parser.parse_args()
    
    if args.version:
        print(f"gtm version {VERSION}")
        sys.exit(0)
    elif args.help or not args.filename:
        show_help()
        sys.exit(0 if args.help else 1)
    
    filename = args.filename
    
    # Check if the file exists
    if not os.path.isfile(filename):
        print(f"Error: File '{filename}' does not exist")
        sys.exit(1)
        
    curses.wrapper(main, filename, args.diff_additions, args.diff_deletions)