import { resolveLogPath, tailLog } from './logs.js';

// Match markers for T5 Plutonium's `logs/games_sp.log`. Verified against a live
// sample: each game session is bracketed by `InitGame:` and `ShutdownGame:`.
// A REAL completed match always emits `ExitLevel: executed` right before
// `ShutdownGame:`. Idle map cycles print `InitGame:` / `ShutdownGame:` at
// 0:00 with no ExitLevel — those don't count as a played match.
//
// So the reliable discriminator is `ExitLevel: executed`: seeing that line
// after `healthy_at` means a game actually ended normally (no crash — a crash
// would kill the container before ExitLevel fires and take RCON with it).
export const MATCH_START = /InitGame:/;
export const MATCH_END = /ExitLevel:\s*executed/;
export const MATCH_SHUTDOWN = /ShutdownGame:/;
// Player join line: `MM:SS J;<guid>;<slot>;<name>`. games_sp.log accumulates
// across restarts and contains many old J; lines; only the ones AFTER the
// latest InitGame belong to the current match cycle.
export const MATCH_JOIN = /\sJ;[^;]*;\d+;/;

/**
 * Poll a server's games_sp.log tail for match markers. Returns whether a
 * completed match end has been observed since `sinceIso` (the server's
 * `healthy_at` timestamp).
 */
export async function scanForMatchEnd(
    serverName: string,
    sinceIso: string
): Promise<{ ended: boolean; started: boolean; reason?: string }> {
    const path = resolveLogPath(serverName, 'games_sp');
    if (!path) return { ended: false, started: false, reason: 'log path resolution failed' };

    const tail = await tailLog(path, 2000);
    if (!tail) return { ended: false, started: false, reason: 'log not written yet' };
    if (tail.mtime < sinceIso) return { ended: false, started: false, reason: 'no log activity since healthy' };

    let started = false;
    let ended = false;
    for (const line of tail.lines) {
        if (MATCH_START.test(line)) started = true;
        if (MATCH_END.test(line)) ended = true;
    }
    return { ended, started };
}

export type MatchScanKind = 'no-signal' | 'idle' | 'in-progress' | 'ended';

export interface MatchScanResult {
    kind: MatchScanKind;
    // Opaque identifier for the currently-observed match cycle. When kind is
    // 'in-progress' or 'ended', this is the first J; line after the latest
    // InitGame. Compare against persisted state to detect a fresh cycle
    // (e.g. game auto-restart with same players — new J; line = new key).
    cycleKey?: string;
}

/**
 * Read the games_sp.log tail and classify the current match state. We do NOT
 * infer any wall-clock timestamps from log content — the caller stamps
 * game_started_at/game_ended_at with the observation time.
 *
 *   - `in-progress`: latest InitGame has at least one J; join line after it
 *     and no ExitLevel/ShutdownGame between that J; and end-of-tail. `cycleKey`
 *     is set to the first J; line after the latest InitGame.
 *   - `ended`: latest InitGame has a J; join line followed by an ExitLevel
 *     or ShutdownGame. `cycleKey` identifies which cycle ended.
 *   - `idle`: no J; line after the latest InitGame — empty map loaded, no
 *     match happening.
 *   - `no-signal`: log missing / unreadable / no InitGame in tail.
 */
export async function scanMatchState(serverName: string): Promise<MatchScanResult> {
    const path = resolveLogPath(serverName, 'games_sp');
    if (!path) return { kind: 'no-signal' };

    const tail = await tailLog(path, 2000);
    if (!tail || tail.lines.length === 0) return { kind: 'no-signal' };

    const lines = tail.lines;
    // Find the LATEST InitGame — everything before it is prior sessions that
    // this log accumulated. Only what comes after is the current cycle.
    let lastInit = -1;
    for (let i = lines.length - 1; i >= 0; i--) {
        if (MATCH_START.test(lines[i])) {
            lastInit = i;
            break;
        }
    }
    if (lastInit === -1) return { kind: 'no-signal' };

    // Scan only the current cycle (everything after the latest InitGame).
    let firstJoinIdx = -1;
    let endIdx = -1;
    for (let i = lastInit + 1; i < lines.length; i++) {
        if (firstJoinIdx === -1 && MATCH_JOIN.test(lines[i])) {
            firstJoinIdx = i;
        }
        if (MATCH_END.test(lines[i]) || MATCH_SHUTDOWN.test(lines[i])) {
            endIdx = i;
            break;
        }
    }

    // No join in the current cycle -> nobody entered this match yet.
    if (firstJoinIdx === -1) return { kind: 'idle' };

    const cycleKey = lines[firstJoinIdx];
    if (endIdx !== -1 && endIdx > firstJoinIdx) {
        return { kind: 'ended', cycleKey };
    }
    return { kind: 'in-progress', cycleKey };
}