# -*- coding: utf-8 -*-
"""
Vollbild-Overlay zur Bereichswahl fuer Snapshot in der Empfang-Desktop-WebView.

- Nur nach expliziter Nutzeraktion (Klick auf Snapshot) gestartet.
- Keine Netz-/Log-Ausgabe von Bildinhalten oder Praxisdaten.
- Windows: virtuelle Bildschirmflaeche; PIL ImageGrab fuer den gewaehlten Bereich.
"""

from __future__ import annotations

import base64
import io
import sys
import threading
import tkinter as tk
from typing import Callable

_LOCK = threading.Lock()
_ACTIVE = False

# Sehr kleine Auswahlen ignorieren (Klicks ohne Zieh-Bewegung).
_MIN_SIDE_PX = 6


def _virtual_screen_win32() -> tuple[int, int, int, int] | None:
    if sys.platform != "win32":
        return None
    try:
        import ctypes

        user32 = ctypes.windll.user32
        SM_XVIRTUALSCREEN = 76
        SM_YVIRTUALSCREEN = 77
        SM_CXVIRTUALSCREEN = 78
        SM_CYVIRTUALSCREEN = 79
        x = int(user32.GetSystemMetrics(SM_XVIRTUALSCREEN))
        y = int(user32.GetSystemMetrics(SM_YVIRTUALSCREEN))
        w = int(user32.GetSystemMetrics(SM_CXVIRTUALSCREEN))
        h = int(user32.GetSystemMetrics(SM_CYVIRTUALSCREEN))
        if w <= 0 or h <= 0:
            return None
        return (x, y, w, h)
    except Exception:
        return None


def _grab_bbox_to_png_data_url(left: int, top: int, right: int, bottom: int) -> str | None:
    """Liefert data:image/png;base64,... oder None bei Fehler."""
    try:
        from PIL import ImageGrab
    except Exception:
        return None
    L = min(left, right)
    T = min(top, bottom)
    R = max(left, right)
    B = max(top, bottom)
    if R - L < _MIN_SIDE_PX or B - T < _MIN_SIDE_PX:
        return None
    try:
        try:
            img = ImageGrab.grab(bbox=(L, T, R, B), all_screens=True)  # type: ignore[call-arg]
        except TypeError:
            img = ImageGrab.grab(bbox=(L, T, R, B))
    except Exception:
        return None
    try:
        buf = io.BytesIO()
        img.save(buf, format="PNG", optimize=True)
        raw = buf.getvalue()
        if not raw or len(raw) < 32:
            return None
        b64 = base64.b64encode(raw).decode("ascii")
        return f"data:image/png;base64,{b64}"
    except Exception:
        return None


def _run_overlay(on_done: Callable[[str | None], None]) -> None:
    global _ACTIVE
    root = tk.Tk()
    root.title("")
    root.configure(cursor="crosshair", bg="#101820")
    try:
        root.attributes("-alpha", 0.28)
    except Exception:
        pass
    try:
        root.attributes("-topmost", True)
    except Exception:
        pass
    root.overrideredirect(True)

    box = _virtual_screen_win32()
    if box:
        vx, vy, vw, vh = box
        root.geometry(f"{vw}x{vh}+{vx}+{vy}")
    else:
        try:
            root.attributes("-fullscreen", True)
        except Exception:
            root.state("zoomed")

    canvas = tk.Canvas(root, highlightthickness=0, bg="#000010", cursor="crosshair")
    canvas.pack(fill=tk.BOTH, expand=True)

    hint = tk.Label(
        root,
        text="Bereich mit der Maus aufziehen. Esc oder Rechtsklick: Abbrechen.",
        fg="#e8eef4",
        bg="#1a2530",
        font=("Segoe UI", 10),
        padx=10,
        pady=6,
    )
    hint.place(x=8, y=8)

    sel: dict[str, int | None] = {"x0": None, "y0": None, "rid": None}

    def finish(data_url: str | None) -> None:
        global _ACTIVE
        try:
            root.destroy()
        except Exception:
            pass
        with _LOCK:
            _ACTIVE = False
        try:
            on_done(data_url)
        except Exception:
            pass

    def on_press(event: tk.Event) -> None:  # type: ignore[name-defined]
        if int(getattr(event, "num", 1) or 1) == 3:
            finish(None)
            return
        sel["x0"] = int(event.x_root)
        sel["y0"] = int(event.y_root)
        if sel["rid"] is not None:
            try:
                canvas.delete(sel["rid"])
            except Exception:
                pass
            sel["rid"] = None

    def _scr_to_cv(sx: int, sy: int) -> tuple[int, int]:
        return int(sx - canvas.winfo_rootx()), int(sy - canvas.winfo_rooty())

    def on_motion(event: tk.Event) -> None:  # type: ignore[name-defined]
        x0, y0 = sel["x0"], sel["y0"]
        if x0 is None or y0 is None:
            return
        x1, y1 = int(event.x_root), int(event.y_root)
        if sel["rid"] is not None:
            try:
                canvas.delete(sel["rid"])
            except Exception:
                pass
        cx0, cy0 = _scr_to_cv(int(x0), int(y0))
        cx1, cy1 = _scr_to_cv(x1, y1)
        sel["rid"] = canvas.create_rectangle(
            cx0,
            cy0,
            cx1,
            cy1,
            outline="#4af",
            width=2,
            dash=(4, 4),
        )

    def on_release(event: tk.Event) -> None:  # type: ignore[name-defined]
        x0, y0 = sel["x0"], sel["y0"]
        if x0 is None or y0 is None:
            return
        x1, y1 = int(event.x_root), int(event.y_root)
        data = _grab_bbox_to_png_data_url(x0, y0, x1, y1)
        finish(data)

    def on_esc(_event: tk.Event | None = None) -> None:  # type: ignore[name-defined]
        finish(None)

    canvas.bind("<ButtonPress-1>", on_press)
    canvas.bind("<B1-Motion>", on_motion)
    canvas.bind("<ButtonRelease-1>", on_release)
    canvas.bind("<ButtonPress-3>", lambda e: finish(None))
    root.bind("<Escape>", on_esc)
    try:
        root.focus_force()
    except Exception:
        pass

    try:
        root.mainloop()
    except Exception:
        with _LOCK:
            _ACTIVE = False
        try:
            on_done(None)
        except Exception:
            pass


def start_region_snapshot_capture(
    on_done: Callable[[str | None], None],
) -> str:
    """
    Startet die Bereichswahl in einem eigenen Thread (eigenes Tk-Fenster).

    Returns:
        "started" | "busy"
    """
    global _ACTIVE
    with _LOCK:
        if _ACTIVE:
            return "busy"
        _ACTIVE = True

    def _thread_main() -> None:
        global _ACTIVE
        try:
            _run_overlay(on_done)
        except Exception:
            with _LOCK:
                _ACTIVE = False
            try:
                on_done(None)
            except Exception:
                pass

    try:
        threading.Thread(target=_thread_main, daemon=True).start()
    except Exception:
        with _LOCK:
            _ACTIVE = False
        return "busy"
    return "started"