import curses
import curses.textpad
"""TODOS:
    opening the drawing pad should create a queue to prevent race conditions
    Moving the cursor off the screen should draw it along the edge rather
        than the cursor freezing on the edge
    create_window_mode needs x and y clamped to the anchors to prevent crash
"""
PADY = 1000 # Absolute pad height
PADX = 1000 # Absolute pad width
SCREEN_WIDTH_IDX = None # Must be set after calling `curses.wrapper`
SCREEN_HEIGHT_IDX = None # Must be set after calling `curses.wrapper`
SCROLL_X, SCROLL_Y = 0, 0 # Pad will always be scrolled to top left

def color_pair(fg, bg):
    """`color_pair` is a helper that replaces calls to `curses.color_pair`
    """
    return curses.color_pair(fg + bg * 8)

def refresh_stdscr(stdscr):
    """`refresh_stdscr` is a helper to refresh the pad.
    """
    global SCREEN_WIDTH_IDX, SCREEN_HEIGHT_IDX, SCROLL_X, SCROLL_Y
    stdscr.refresh(
            SCROLL_Y, SCROLL_X,
            0, 0, # Pad is always rendered from top-left side of screen
            SCREEN_HEIGHT_IDX, SCREEN_WIDTH_IDX)

def write_note_mode(stdscr, selected_area_window, fg_color, bg_color):
    """`write_note_mode` is called by `create_window_mode` to allow the user to
    type text into the new window they created.
    It overwrites selected_area_window over stdscr
    """
    selected_area_window.bkgd(" ", color_pair(fg_color, bg_color))
    textbox = curses.textpad.Textbox(selected_area_window)
    textbox.edit()
    selected_area_window.overwrite(stdscr)
    return stdscr

def set_color_mode(stdscr, selected_area_window):
    """`set_color_mode` is called by `create_window_mode` to change stdscr's
    color before passing it to `set_color_mode`
    """
    fg_color, bg_color = 0, 0
    while True:
        selected_area_window.bkgd(
                "X",
                color_pair(fg_color, bg_color))
        selected_area_window.touchwin()
        selected_area_window.refresh()

        # Handle keypresses:
        keypress = stdscr.getch()
        match keypress:
            # Quit
            case 113: # 'q'
                return stdscr, selected_area_window, 0, 0

            # Vim keys (h j k l) for changing color:
            # Down and Up - j and k - change foreground color
            # Left and Right - h and l - change background color
            case 104: # 'h'
                bg_color = (bg_color - 1) % 8
            case 106: # 'j'
                fg_color = (fg_color - 1) % 8
            case 107: # 'k'
                fg_color = (fg_color + 1) % 8
            case 108: # 'l'
                bg_color = (bg_color + 1) % 8

            # Choose currently selected color
            case 10: # 'Enter'
                return stdscr, selected_area_window, fg_color, bg_color
    return stdscr

def create_window_mode(stdscr):
    """`create_window_mode` allows the user to draw a subwindow,
    then it passes control to `style_window_mode`
    """
    # Initialize variables:
    global SCROLL_X, SCROLL_Y
    fg_color, bg_color = 0, 0
    anchor_y, anchor_x = stdscr.getyx() # Coords used as anchor
    y, x = anchor_y, anchor_x
    selected_area_window = curses.newwin(1, 1, anchor_y, anchor_x)

    # Main loop:
    WINDOW_MODE_RUNNING = True
    while WINDOW_MODE_RUNNING:
        # Draw updates:
        selected_area_window.bkgd('*', color_pair(fg_color, bg_color))
        refresh_stdscr(stdscr) # Update pad before derwin
        selected_area_window.touchwin() # Required to update color
        selected_area_window.refresh()
        
        # Handle keypresses:
        keypress = stdscr.getch()
        match keypress:
            # Quit:
            case 113: # 'q'
                return stdscr

            # Move to `write_note_mode`:
            case 10: # 'Enter'
                stdscr = write_note_mode(
                        stdscr,
                        selected_area_window,
                        fg_color,
                        bg_color)
                return stdscr

            # Move to `set_color_mode`:
            case 99:
                stdscr, selected_area_window, fg, bg = \
                    set_color_mode(stdscr, selected_area_window)
                fg_color, bg_color = fg, bg

            # Screen navigation:
            case 104: # 'h'
                x = max(x - 1, anchor_x) # Clamp to left
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 72: # 'H'
                x = max(x - 5, anchor_x) # Clamp to left
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 106: # 'j'
                y = min(y + 1, SCREEN_HEIGHT_IDX) # Clamp to bottom
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 74: # 'J'
                y = min(y + 5, SCREEN_HEIGHT_IDX) # Clamp to bottom
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 107: # 'k'
                y = max(y - 1, 0) # Clamp to top
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 75: # 'K'
                y = max(y - 5, 0) # Clamp to top
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 108: # 'l'
                x = min(x + 1, SCREEN_WIDTH_IDX) # Clamp to right
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)
            case 76: # 'L'
                x = min(x + 5, SCREEN_WIDTH_IDX) # Clamp to right
                selected_area_window.resize(y - anchor_y + 1, x - anchor_x + 1)
                stdscr.move(y, x)

def main():
    curses.wrapper(_main)

def _main(stdscr):
    # Constants:
    global SCREEN_WIDTH_IDX, SCREEN_HEIGHT_IDX, PADY, PADX, SCROLL_X, SCROLL_Y
    SCREEN_WIDTH_IDX = curses.COLS - 1 # Adjusted for index
    SCREEN_HEIGHT_IDX = curses.LINES - 1 # Adjusted for index
    running = True # App state

    # Open old window data:
    try: 
        with open("old.window", "rb") as file:
            file.seek(0, 2) # Seek end of file
            if file.tell():
                file.seek(0) # Return to beginning
                stdscr = curses.getwin(file) # Load window
    except FileNotFoundError: # Ignore missing
        stdscr = curses.newpad(PADY, PADX) # Create new window

    # Initialize screen settings:
    stdscr.keypad(True)
    curses.start_color()
    for fg in range(0, 8): # Initialize all colors as pairs immediately
        for bg in range(0, 8):
            curses.init_pair(fg + bg * 8 + 1, fg, bg)
    y, x = stdscr.getyx()

    # Main loop:
    while running:
        # Draw state:
        refresh_stdscr(stdscr)

        # Handle input:
        keypress = stdscr.getch()
        match keypress:
            case 113: # 'q'
                with open("old.window", "wb+") as file:
                    stdscr.putwin(file)
                    running = False

            case 10: # 'ENTER'
                stdscr = create_window_mode(stdscr)

            # Screen navigation:
            case 104: # 'h'
                x = max(x - 1, 0) # Clamp to left edge of screen
                stdscr.move(y, x)
            case 72: # 'H'
                x = max(x - 5, 0) # Clamp to left edge of screen
                stdscr.move(y, x)
            case 106: # 'j'
                y = min(y + 1, PADX) # Clamp to bottom edge of pad
                stdscr.move(y, x)
            case 74: # 'J'
                y = min(y + 5, PADY) # Clamp to bottom edge of pad
                stdscr.move(y, x)
            case 107: # 'k'
                y = max(y - 1, 0) # Clamp to top edge of screen
                stdscr.move(y, x)
            case 75: # 'K'
                y = max(y - 5, 0) # Clamp to top edge of screen
                stdscr.move(y, x)
            case 108: # 'l'
                x = min(x + 1, PADX) # Clamp to right edge of pad
                stdscr.move(y, x)
            case 76: # 'L'
                x = min(x + 5, PADY) # Clamp to right edge of pad
                stdscr.move(y, x)

            # Scroll pane
            case curses.KEY_UP: # 'ARROW UP'
                SCROLL_Y = max(SCROLL_Y - 1, 0) # Clamp to top
            case curses.KEY_LEFT:# 'ARROW LEFT'
                SCROLL_X = max(SCROLL_X - 1, 0) # Clamp to left
            case curses.KEY_DOWN:# 'ARROW DOWN'
                SCROLL_Y = min(SCROLL_Y + 1, SCREEN_HEIGHT_IDX) # Clamp to bottom
            case curses.KEY_RIGHT: # 'ARROW RIGHT'
                SCROLL_X = min(SCROLL_X + 1, SCREEN_WIDTH_IDX) # Clamp to right

            case _:
                pass

if __name__ == "__main__":
    main()