// Who else is in the meeting, and what to say about it - derived ONCE and shared by both call
// surfaces.
//
// BOTH OF THIS MODULE'S REASONS FOR EXISTING CAME OUT OF THE FIRST REAL BROWSER CALL
// (Spencer, 2026-08-02):
//
// 1. The patient left and the practitioner was told NOTHING. The presence line lived only on the
// docked `EncounterVideoPane`; `FloatingCallSurface` had none - its own comment said "Task 13
// decides what, if anything, it should say", and Task 13 never decided. The floating surface is
// exactly where a practitioner ends up when they navigate away from the encounter, so the one
// surface that could go silent was the one most likely to be on screen.
//
// 2. "Waiting for the patient to join..." is the WRONG SENTENCE for somebody who has left. Those are
// different events - not arrived yet vs hung up - and they were indistinguishable because the
// observable state is identical: empty roster, no remote tiles. `everRemote` is the only thing
// that separates them, which is why `ChimeCallSession` now tracks it.
//
// Pure on purpose: no React, no SDK. Two surfaces asking the same question must not each answer it -
// that divergence IS defect 1.
import type { CallPhase } from './callMachine';

export type RoomPresence = 'occupied' | 'never-arrived' | 'departed';

export interface RoomFacts {
    phase: CallPhase;
    /** Everyone else on the roster. The PRIMARY signal - an audio-only participant has no tile. */
    remoteAttendees: string[];
    /** A weaker second witness (Task 9): presence tracking is best-effort, and a remote tile only
 * exists on a positive `localTile === false`, so it can reduce a false "waiting" but never
 * create a false "not waiting". */
    remoteTiles: number[];
    /** Has anybody else EVER been in this meeting? The only thing distinguishing "not arrived" from
 * "left", since both look like an empty room. */
    everRemote: boolean;
}

export const roomPresence = (f: RoomFacts): RoomPresence | undefined => {
    // Before `active` there is nobody to be waiting for - the meeting is still being provisioned and
    // the camera is still coming up. Saying "waiting for the patient" then is noise at best.
    if (f.phase !== 'active') return undefined;
    if (f.remoteAttendees.length > 0 || f.remoteTiles.length > 0) return 'occupied';
    return f.everRemote ? 'departed' : 'never-arrived';
};

/** IT DEPENDS ON WHO IS READING IT, not only on the kind of meeting - and getting that wrong is how
 * the PATIENT was told "The patient has left the visit." when their PRACTITIONER left (Spencer,
 * 2026-08-02, the second browser round).
 *
 * That is the SAME defect class as the join banner's "Your provider is waiting" shown to a
 * clinician, which had been fixed hours earlier - and this copy was written straight afterwards with
 * the identical mistake. In a two-party call every sentence about "the other person" has two audiences;
 * a helper that takes only the context can never say the right thing to both.
 *
 * NEVER says "the patient" on a `collabteam#` conference: that is the team conferring ABOUT a
 * patient with the patient deliberately excluded, so naming them there is both wrong and
 * alarming to whoever reads it. Conferences are practitioner-only, so they need no audience split. */
export const roomPresenceCopy = (
    presence: RoomPresence,
    context: string | undefined,
    viewerIsClinician: boolean,
): string | undefined => {
    if (presence === 'occupied') return undefined;
    const clinical = context?.startsWith('encounter#');
    if (!clinical) {
        return presence === 'never-arrived'
            ? 'Waiting for others to join…'
            : 'Everyone else has left the conference.';
    }
    // A 1:1 visit: the OTHER party is the patient if you are the clinician, and the provider if you are
    // the patient.
    const other = viewerIsClinician ? 'the patient' : 'your provider';
    return presence === 'never-arrived'
        ? `Waiting for ${other} to join…`
        : `${viewerIsClinician ? 'The patient' : 'Your provider'} has left the visit.`;
};