"""Device configuration for the Ekklesia Classroom shell.

Everything that has to agree about /etc/ekklesia-classroom/device.conf
reads it through here, so the dock, the notification daemon and the DVD
commands cannot drift apart over what a setting means.
"""

import math
from pathlib import Path

CONFIG_FILE = Path("/etc/ekklesia-classroom/device.conf")

TRUTHY = {"1", "true", "yes", "on", "enabled"}

# The dock is tuned for a 1080p classroom TV at 1.0. Smaller rooms with a
# 32" panel sit near the bottom of this range, a 65" set near the top.
UI_SCALE_DEFAULT = 1.0
UI_SCALE_MIN = 0.8
UI_SCALE_MAX = 1.5


DEVICE_CONFIG_TEMPLATE = """# Ekklesia Classroom device configuration

UPDATE_URL=https://updates.riverofglorymn.org
CHANNEL=stable

# Show the Sanctuary LIVE placeholder in the dock. Live viewing is not
# implemented yet; this only controls whether the current placeholder appears.
LIVE_ENABLED=false

# Which output the room plays through.
#
#   auto    prefer a connected HDMI or DisplayPort television, and fall
#           back to the analog jack. This is right for almost every room.
#   hdmi    always the television, even if it does not report itself.
#   analog  always the jack.
#
# auto re-decides whenever the hardware changes, so a television switched
# on after the computer is picked up without anybody touching anything,
# and sound that is already playing is moved across to it.
AUDIO_OUTPUT=auto

# Size of the dock, clock and notifications, 0.8 to 1.5.
# Larger rooms and larger TVs want a larger number.
UI_SCALE=1.0

# Church message broker. The room is this machine's hostname unless ROOM
# is set. Leave MQTT_ENABLED=false until a broker exists.
MQTT_ENABLED=false
MQTT_HOST=
MQTT_PORT=1883
MQTT_USERNAME=
MQTT_PASSWORD=
"""


# Sections added after the first classroom release. Keeping them separate lets
# an upgrade make a setting discoverable without replacing anything an
# administrator has already put in device.conf.
DEVICE_CONFIG_SECTIONS = (
    (
        "LIVE_ENABLED",
        """# Show the Sanctuary LIVE placeholder in the dock. Live viewing is not
# implemented yet; this only controls whether the current placeholder appears.
LIVE_ENABLED=false
""",
    ),
    (
        "AUDIO_OUTPUT",
        """# Which output the room plays through.
#
#   auto    prefer a connected HDMI or DisplayPort television, and fall
#           back to the analog jack. This is right for almost every room.
#   hdmi    always the television, even if it does not report itself.
#   analog  always the jack.
#
# auto re-decides whenever the hardware changes, so a television switched
# on after the computer is picked up without anybody touching anything,
# and sound that is already playing is moved across to it.
AUDIO_OUTPUT=auto
""",
    ),
    (
        "UI_SCALE",
        """# Size of the dock, clock and notifications, 0.8 to 1.5.
# Larger rooms and larger TVs want a larger number.
UI_SCALE=1.0
""",
    ),
    (
        "MQTT_ENABLED",
        """# Church message broker. The room is this machine's hostname unless ROOM
# is set. Leave MQTT_ENABLED=false until a broker exists.
MQTT_ENABLED=false
MQTT_HOST=
MQTT_PORT=1883
MQTT_USERNAME=
MQTT_PASSWORD=
""",
    ),
)


def read_device_config(path=None):
    config = {}
    path = Path(path) if path is not None else CONFIG_FILE

    if not path.exists():
        return config

    for raw_line in path.read_text().splitlines():
        line = raw_line.strip()

        if not line or line.startswith("#") or "=" not in line:
            continue

        key, value = line.split("=", 1)
        config[key.strip()] = value.strip()

    return config


def enabled(config, key, default=False):
    if key not in config:
        return default

    return config[key].lower() in TRUTHY


def ensure_device_config(path=None):
    """Create device.conf or append any missing settings exactly once.

    Existing bytes are otherwise left alone: per-room settings, comments and
    even keys this release does not know about all survive an upgrade.
    """
    path = Path(path) if path is not None else CONFIG_FILE

    if not path.exists():
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_text(DEVICE_CONFIG_TEMPLATE)
        return

    text = path.read_text()
    config = read_device_config(path)
    additions = []

    for key, section in DEVICE_CONFIG_SECTIONS:
        if key not in config:
            additions.append(section.rstrip("\n"))

    if not additions:
        return

    separator = "" if not text or text.endswith("\n") else "\n"
    path.write_text(text + separator + "\n\n".join(additions) + "\n")


def ui_scale(config):
    """UI_SCALE, clamped to something a classroom can actually use."""
    raw = config.get("UI_SCALE", "")

    try:
        value = float(raw)
    except (TypeError, ValueError):
        return UI_SCALE_DEFAULT

    if not math.isfinite(value):
        return UI_SCALE_DEFAULT

    return min(max(value, UI_SCALE_MIN), UI_SCALE_MAX)


# The scale the classroom's own GTK surfaces render at.
#
# UI_SCALE is applied to the whole output (see classroom-scale),
# which scales Chrome, VLC and every other application along with the
# panel. Our surfaces are measured in the same logical pixels the
# compositor is
# already scaling, so scaling them here as well would apply UI_SCALE
# twice and the dock would come out half again too big.
#
# This is the seam: if compositor scaling ever has to be abandoned,
# changing this back to ui_scale(config) restores per-surface scaling
# without touching the templates.
SHELL_SCALE = 1.0


def scaled(value, scale):
    """A pixel measurement at the given scale, never smaller than 1."""
    return max(1, int(round(value * scale)))