"""Display — WebSocket frame streaming + REST app management for GUI apps.

Pattern mirrors terminal.py: WebSocket attaches to a running GUI app,
receives JPEG frames, sends input events. REST endpoints manage app lifecycle.
"""

import logging
import os
import re
import shutil
from pathlib import Path
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Query, WebSocket, WebSocketDisconnect
from pydantic import BaseModel

from backend.auth import get_current_user, ws_authenticate
from backend.display import display_manager, HAS_DISPLAY_DEPS

router = APIRouter(prefix="/api/display", tags=["display"])
log = logging.getLogger("atlus.display.router")


# ---------------------------------------------------------------------------
# Guards
# ---------------------------------------------------------------------------

def _require_deps():
    if not HAS_DISPLAY_DEPS:
        raise HTTPException(503, "Display dependencies not installed (Xvfb, xdotool, ImageMagick)")


# ---------------------------------------------------------------------------
# REST — app lifecycle
# ---------------------------------------------------------------------------

class AppLaunchRequest(BaseModel):
    command: str
    title: str = ""
    args: list[str] = []
    target_fps: int = 10


@router.get("/apps")
async def list_apps(user: str = Depends(get_current_user)):
    """List running GUI apps for the current user."""
    _require_deps()
    return {"apps": display_manager.list_apps(user)}


@router.post("/apps")
async def launch_app(req: AppLaunchRequest, user: str = Depends(get_current_user)):
    """Launch a GUI application on the user's virtual display."""
    _require_deps()

    # Check if this command is already running
    existing = display_manager.get_app_by_command(user, req.command)
    if existing:
        return existing.to_dict()

    try:
        app = await display_manager.launch_app(
            user, req.command, req.title, req.args, req.target_fps,
        )
        return app.to_dict()
    except ValueError as e:
        raise HTTPException(400, str(e))
    except FileNotFoundError as e:
        raise HTTPException(404, str(e))
    except RuntimeError as e:
        raise HTTPException(500, str(e))


@router.delete("/apps/{app_id}")
async def close_app(app_id: str, user: str = Depends(get_current_user)):
    """Stop a running GUI application."""
    _require_deps()
    if not display_manager.close_app(user, app_id):
        raise HTTPException(404, "App not found")
    return {"ok": True}


@router.post("/apps/{app_id}/restart")
async def restart_app(app_id: str, user: str = Depends(get_current_user)):
    """Restart a running GUI application (stop + relaunch)."""
    _require_deps()
    app = display_manager.get_app(user, app_id)
    if not app:
        raise HTTPException(404, "App not found")

    # Save launch params before killing
    command = app.command
    title = app.title
    target_fps = app.target_fps

    # Stop the old instance
    display_manager.close_app(user, app_id)

    # Brief pause to let the process fully exit
    import asyncio
    await asyncio.sleep(1)

    # Relaunch
    try:
        new_app = await display_manager.launch_app(
            user, command, title, target_fps=target_fps,
        )
        return new_app.to_dict()
    except Exception as e:
        raise HTTPException(500, f"Restart failed: {e}")


@router.get("/status")
async def display_status(user: str = Depends(get_current_user)):
    """Check display system availability."""
    return {
        "available": HAS_DISPLAY_DEPS,
        "apps": display_manager.list_apps(user),
    }


# ---------------------------------------------------------------------------
# Desktop file discovery — find installed GUI apps
# ---------------------------------------------------------------------------

_DESKTOP_DIRS = [
    Path("/usr/share/applications"),
    Path("/usr/local/share/applications"),
    Path(os.path.expanduser("~/.local/share/applications")),
    Path("/var/lib/flatpak/exports/share/applications"),
    Path(os.path.expanduser("~/.local/share/flatpak/exports/share/applications")),
    Path("/snap/applications"),
]

# Categories that indicate a docked/GUI application
_GUI_CATEGORIES = {
    "network", "webbrowser", "email", "office", "graphics", "audio", "video",
    "chat", "instantmessaging", "filetransfer", "p2p", "remoteaccess",
    "viewer", "player", "game", "utility", "system", "settings",
    "monitor", "filesystem", "security", "accessibility",
}

# Commands to exclude (system utilities, terminals, etc.)
_EXCLUDED_CMDS = {
    "bash", "sh", "zsh", "fish", "xterm", "xfce4-terminal", "gnome-terminal",
    "lxterminal", "urxvt", "alacritty", "kitty", "foot",
    "true", "false", "update-manager", "software-properties-gtk",
}


def _parse_desktop_file(path: Path) -> Optional[dict]:
    """Parse a .desktop file and return app info, or None if not a GUI app."""
    try:
        content = path.read_text(errors="replace")
    except Exception:
        return None

    entry = {}
    in_desktop_entry = False

    for line in content.splitlines():
        line = line.strip()
        if line == "[Desktop Entry]":
            in_desktop_entry = True
            continue
        if line.startswith("[") and line.endswith("]"):
            if in_desktop_entry:
                break  # End of [Desktop Entry] section
            continue
        if not in_desktop_entry or "=" not in line:
            continue
        key, _, value = line.partition("=")
        key = key.strip()
        value = value.strip()
        if key in ("Name", "Exec", "Icon", "Type", "NoDisplay", "Hidden",
                    "Categories", "Terminal", "Comment"):
            entry[key] = value

    # Must be Type=Application
    if entry.get("Type") != "Application":
        return None
    # Skip hidden/no-display
    if entry.get("NoDisplay", "").lower() == "true":
        return None
    if entry.get("Hidden", "").lower() == "true":
        return None
    # Skip terminal apps
    if entry.get("Terminal", "").lower() == "true":
        return None

    exec_line = entry.get("Exec", "")
    if not exec_line:
        return None

    # Extract command: remove field codes (%u, %U, %f, %F, etc.)
    exec_clean = re.sub(r"%[a-zA-Z]", "", exec_line).strip()
    # Get first token as command, strip path
    parts = exec_clean.split()
    if not parts:
        return None
    command = os.path.basename(parts[0])

    if command in _EXCLUDED_CMDS or not command:
        return None

    # Check the command actually exists
    if not shutil.which(command):
        return None

    # Parse categories
    categories = set()
    if entry.get("Categories"):
        categories = {c.strip().lower() for c in entry["Categories"].split(";")}

    name = entry.get("Name", command)
    icon = entry.get("Icon", "🖥")
    comment = entry.get("Comment", "")

    return {
        "name": name,
        "command": command,
        "icon": icon,
        "comment": comment,
        "categories": sorted(categories - {""}),
        "desktop_file": path.name,
    }


@router.get("/discover-apps")
async def discover_apps(_user: str = Depends(get_current_user)):
    """Scan .desktop files for installed GUI applications."""
    apps = {}

    for d in _DESKTOP_DIRS:
        if not d.is_dir():
            continue
        for f in d.glob("*.desktop"):
            app = _parse_desktop_file(f)
            if app and app["command"] not in apps:
                apps[app["command"]] = app

    # Sort alphabetically
    result = sorted(apps.values(), key=lambda a: a["name"].lower())
    return result


# ---------------------------------------------------------------------------
# WebSocket — frame streaming + input
# ---------------------------------------------------------------------------

@router.websocket("/ws")
async def display_ws(
    websocket: WebSocket,
    app_id: str = Query(default=None),
):
    """Attach to a GUI app's window — receive JPEG frames, send input.

    Query params:
      - app_id: required — the GUI app to stream
      - token: auth token (handled by ws_authenticate)

    Server sends:
      - Binary: raw JPEG frame bytes
      - {"type": "meta", "app_id": "...", "title": "...", "command": "..."}
      - {"type": "closed", "data": "Application exited"}
      - {"type": "error", "data": "..."}

    Client sends:
      - {"type": "mouse", "action": "click|dblclick|move|scroll",
         "x": N, "y": N, "button": 1, "delta": N}
      - {"type": "key", "action": "press|release",
         "key": "a", "code": "KeyA", "modifiers": ["ctrl"]}
      - {"type": "set_fps", "fps": 15}
    """
    username = await ws_authenticate(websocket)
    await websocket.accept()

    if not app_id:
        await websocket.send_json({"type": "error", "data": "app_id required"})
        await websocket.close(code=4000)
        return

    app = display_manager.get_app(username, app_id)
    if not app:
        await websocket.send_json({"type": "error", "data": "App not found"})
        await websocket.close(code=4004)
        return

    # Send metadata
    await websocket.send_json({
        "type": "meta",
        "app_id": app.app_id,
        "title": app.title,
        "command": app.command,
    })

    # Send last captured frame for instant display on reconnect
    if app.last_frame:
        await websocket.send_bytes(app.last_frame)

    app.attach_ws(websocket)
    log.info("WebSocket attached to app %s (%s) for %s", app_id, app.command, username)

    _input_count = 0
    try:
        while True:
            msg = await websocket.receive_json()
            msg_type = msg.get("type")

            if msg_type in ("mouse", "key"):
                _input_count += 1
                if _input_count <= 5:
                    log.info("Input #%d from %s: %s %s", _input_count, username,
                             msg_type, msg.get("action", msg.get("key", "")))
                await app.send_input(msg)
            elif msg_type == "set_fps":
                fps = msg.get("fps", 10)
                app.target_fps = max(1, min(30, fps))
    except WebSocketDisconnect:
        pass
    except Exception:
        log.exception("Display WS error for %s/%s", username, app_id)
    finally:
        app.detach_ws(websocket)
        log.info("WebSocket detached from app %s for %s", app_id, username)