"""
Bell flag polling and unseen_count tracking for the tmux-web coordinator.

Based on spike findings: reading the tmux window_bell_flag does NOT clear it.
The flag persists until the window is made active inside tmux.

In-memory state:
    _bell_seen  — tracks whether the bell flag was '1' on the last poll,
                  keyed by session_name. Used to detect 0→1 transitions.

Public API:
    poll_bell_flag(session_name)             → bool
    process_bell_flags(session_names, state) → bool
    should_clear_bell(session_name, state)   → bool
    apply_bell_clear_rule(state)             → list[str]
"""

import time

from coordinator.sessions import run_tmux
from coordinator.state import empty_bell

# ---------------------------------------------------------------------------
# In-memory tracking: session_name → bool (was flag set on last poll?)
# ---------------------------------------------------------------------------

_bell_seen: dict[str, bool] = {}


# ---------------------------------------------------------------------------
# poll_bell_flag
# ---------------------------------------------------------------------------


async def poll_bell_flag(session_name: str) -> bool:
    """Poll the tmux window_bell_flag for session_name.

    Calls: tmux display-message -t <name> -p #{window_bell_flag}

    Returns True if the output is '1', False otherwise (including on errors).
    Note: reading does NOT clear the tmux bell flag.
    """
    try:
        output = await run_tmux(
            "display-message", "-t", session_name, "-p", "#{window_bell_flag}"
        )
        return output.strip() == "1"
    except RuntimeError:
        return False


# ---------------------------------------------------------------------------
# process_bell_flags
# ---------------------------------------------------------------------------


async def process_bell_flags(session_names: list[str], state: dict) -> bool:
    """Poll bell flags for all sessions and update state accordingly.

    NOTE: The tmux alert-bell hook (POST /api/sessions/{name}/bell) is the
    primary bell detection mechanism. window_bell_flag is only set when NO
    tmux client is watching the window — with an SSH/WezTerm session attached,
    the flag is never set even though the bell fires. This function serves as
    a fallback for sessions that fired before the coordinator registered the hook.

    Detects 0→1 transitions using _bell_seen and increments unseen_count.
    Persistent '1' flags (1→1) are not double-counted.
    When flag clears (1→0), _bell_seen is reset so the next '1' counts as
    a new, separate bell event.

    Ensures the bell sub-dict exists for each session in state.

    Args:
        session_names: List of session names to poll.
        state:         Mutable state dict (modified in-place).

    Returns:
        True if any bell state changed (new bell detected), False otherwise.
    """
    changed = False

    for name in session_names:
        # Ensure session entry and bell sub-dict exist
        if name not in state["sessions"]:
            state["sessions"][name] = {}
        if "bell" not in state["sessions"][name]:
            state["sessions"][name]["bell"] = empty_bell()

        bell = state["sessions"][name]["bell"]
        flag_set = await poll_bell_flag(name)
        previously_seen = _bell_seen.get(name, False)

        if flag_set and not previously_seen:
            # 0→1 transition: new bell event
            bell["unseen_count"] += 1
            bell["last_fired_at"] = time.time()
            _bell_seen[name] = True
            changed = True
        elif not flag_set and previously_seen:
            # 1→0: flag cleared — reset tracking so next '1' is a new bell
            # Do NOT decrement unseen_count
            _bell_seen[name] = False

    return changed


# ---------------------------------------------------------------------------
# Bell clear rule constants
# ---------------------------------------------------------------------------

_INTERACTION_WINDOW_SECONDS: float = 60.0


# ---------------------------------------------------------------------------
# should_clear_bell
# ---------------------------------------------------------------------------


def should_clear_bell(session_name: str, state: dict) -> bool:
    """Return True if any connected device qualifies to globally acknowledge bells.

    A session's bells should be cleared when ANY device satisfies ALL of:
        - viewing_session == session_name
        - view_mode == 'fullscreen'
        - last_interaction_at > now - _INTERACTION_WINDOW_SECONDS

    Args:
        session_name: Name of the tmux session to check.
        state:        Current application state dict.

    Returns:
        True if at least one device meets all conditions, False otherwise.
    """
    cutoff = time.time() - _INTERACTION_WINDOW_SECONDS
    for device in state["devices"].values():
        if (
            device["viewing_session"] == session_name
            and device["view_mode"] == "fullscreen"
            and device["last_interaction_at"] > cutoff
        ):
            return True
    return False


# ---------------------------------------------------------------------------
# apply_bell_clear_rule
# ---------------------------------------------------------------------------


def apply_bell_clear_rule(state: dict) -> list[str]:
    """Check every session with unseen_count > 0 against the active-device gate.

    For each qualifying session (unseen_count > 0 AND should_clear_bell):
        - Resets unseen_count to 0
        - Sets seen_at to now
        - Resets _bell_seen[name] = False

    Args:
        state: Mutable application state dict (modified in-place).

    Returns:
        List of session names whose bells were cleared.
    """
    cleared: list[str] = []
    now = time.time()

    for name, session in state["sessions"].items():
        bell = session.get("bell")
        if bell is None or bell.get("unseen_count", 0) == 0:
            continue
        if should_clear_bell(name, state):
            bell["unseen_count"] = 0
            bell["seen_at"] = now
            _bell_seen[name] = False
            cleared.append(name)

    return cleared