"""Talking to sway.

Shared by classroom-window, which moves windows around, and by
classroom-dvd-session, which needs to know when VLC has actually taken
the screen.
"""

import json
import re
import subprocess

HIDDEN_WORKSPACE = "__ekklesia_hidden"

# sway parks scratchpad windows on a workspace of its own. Nothing here
# puts them there, but treating it as hidden means a window left in the
# scratchpad by an older classroom build can still be restored.
HIDDEN_WORKSPACES = {HIDDEN_WORKSPACE, "__i3_scratch"}


def swaymsg(*arguments):
    """Run swaymsg, returning stdout or None when sway is unavailable."""
    try:
        result = subprocess.run(
            ["swaymsg", *arguments],
            capture_output=True,
            text=True,
        )
    except (OSError, subprocess.SubprocessError):
        return None

    if result.returncode != 0:
        return None

    return result.stdout


def command(argument):
    """Run a sway command, ignoring criteria that match nothing."""
    swaymsg("--", argument)


def query(kind):
    output = swaymsg("-t", kind, "-r")

    if not output:
        return None

    try:
        return json.loads(output)
    except ValueError:
        return None


def collect(node, workspace, found, floating=False):
    """Flatten the sway tree into the windows the classroom cares about."""
    if node.get("type") == "workspace":
        workspace = node.get("name")

    is_window = node.get("pid") is not None and not node.get("nodes")

    if is_window:
        properties = node.get("window_properties") or {}

        found.append(
            {
                "id": node.get("id"),
                "app_id": node.get("app_id") or "",
                "name": node.get("name") or "",
                "class": properties.get("class") or "",
                "instance": properties.get("instance") or "",
                "focused": bool(node.get("focused")),
                "fullscreen": bool(node.get("fullscreen_mode")),
                "workspace": workspace,
                "hidden": workspace in HIDDEN_WORKSPACES,
                "floating": floating,
            }
        )

    for child in node.get("nodes", []):
        collect(child, workspace, found, floating)

    for child in node.get("floating_nodes", []):
        collect(child, workspace, found, True)

    return found


def windows():
    tree = query("get_tree")

    if tree is None:
        return []

    return collect(tree, None, [])


def matches(window, patterns):
    """Match a window against app_id / X11 class / X11 instance."""
    identities = [
        window["app_id"],
        window["class"],
        window["instance"],
    ]

    for pattern in patterns:
        expression = re.compile(pattern, re.IGNORECASE)

        for identity in identities:
            if identity and expression.fullmatch(identity):
                return True

    return False


def visible_workspace():
    """The workspace a restored window should come back to."""
    workspaces = query("get_workspaces") or []

    for workspace in workspaces:
        if workspace.get("focused") and workspace.get("name") not in HIDDEN_WORKSPACES:
            return workspace.get("name")

    for workspace in workspaces:
        if workspace.get("visible") and workspace.get("name") not in HIDDEN_WORKSPACES:
            return workspace.get("name")

    return "1"