// Reads the per-session state files written by the Claude Code hook and keeps
// them in sync with the filesystem.
//
// The hook only writes on an actual state change, so a directory monitor is
// enough and there is nothing to poll. The timer here exists for two other
// reasons: displayed ages go stale on their own, and a session whose terminal
// was killed never sends SessionEnd, so liveness has to be rechecked.

import GObject from 'gi://GObject';
import Gio from 'gi://Gio';
import GLib from 'gi://GLib';

Gio._promisify(Gio.File.prototype, 'enumerate_children_async');
Gio._promisify(Gio.FileEnumerator.prototype, 'next_files_async');
Gio._promisify(Gio.File.prototype, 'load_contents_async');

// Aggregation order: a session blocked on a permission prompt is the only one
// that is actually stuck, so it outranks one that merely finished its turn.
export const STATES = ['blocked', 'waiting', 'busy', 'idle'];

const KNOWN = new Set(STATES);
const LIVENESS_INTERVAL = 20; // seconds

// Fallback for sessions whose process could not be identified (pid 0): there is
// nothing to test for liveness, so age is the only signal left. Long enough
// that a session genuinely left waiting overnight is still listed in the
// morning, which is exactly the case this indicator exists for.
const UNKNOWN_PID_MAX_AGE = 36 * 3600; // seconds

export function stateRank(state) {
    const i = STATES.indexOf(state);
    return i < 0 ? STATES.length : i;
}

export function stateDir() {
    const base = GLib.getenv('XDG_STATE_HOME') ||
        GLib.build_filenamev([GLib.get_home_dir(), '.local', 'state']);
    return GLib.build_filenamev([base, 'claude-code-status']);
}

export const SessionStore = GObject.registerClass({
    Signals: { 'changed': {} },
}, class SessionStore extends GObject.Object {
    _init() {
        super._init();
        this._dir = Gio.File.new_for_path(stateDir());
        this._sessions = [];
        this._monitor = null;
        this._debounceId = 0;
        this._timerId = 0;
        this._cancellable = new Gio.Cancellable();
        this._loading = false;
        this._loadAgain = false;
    }

    get sessions() {
        return this._sessions;
    }

    start() {
        // The directory is created by the first hook run, which may not have
        // happened yet; monitoring a missing directory still reports its
        // creation, so there is nothing to wait for.
        try {
            this._monitor = this._dir.monitor_directory(Gio.FileMonitorFlags.WATCH_MOVES, null);
            this._monitor.connect('changed', () => this._scheduleLoad());
        } catch (e) {
            logError(e, 'claude-code-status: cannot monitor state directory');
        }

        this._timerId = GLib.timeout_add_seconds(GLib.PRIORITY_DEFAULT, LIVENESS_INTERVAL, () => {
            // Ages advance and processes die without any file changing, so this
            // tick is what makes a killed terminal disappear from the panel.
            this._load();
            return GLib.SOURCE_CONTINUE;
        });

        this._load();
    }

    // One atomic write lands as several monitor events (created, moved, changed).
    // Collapsing them keeps a burst of five sessions from causing five reloads.
    _scheduleLoad() {
        if (this._debounceId)
            GLib.Source.remove(this._debounceId);
        this._debounceId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, 120, () => {
            this._debounceId = 0;
            this._load();
            return GLib.SOURCE_REMOVE;
        });
    }

    async _load() {
        if (this._loading) {
            this._loadAgain = true;
            return;
        }
        this._loading = true;
        const cancellable = this._cancellable;
        try {
            const sessions = await this._readAll(cancellable);
            if (cancellable.is_cancelled())
                return;
            sessions.sort((a, b) => {
                const byState = stateRank(a.state) - stateRank(b.state);
                // Oldest first within a state: the session you forgot about is
                // the one that has been waiting longest, not the latest one.
                return byState !== 0 ? byState : a.since - b.since;
            });
            this._sessions = sessions;
            // Emitted unconditionally: even with no structural change the
            // displayed ages have advanced, and redrawing a handful of labels
            // is cheaper than tracking what moved.
            this.emit('changed');
        } catch (e) {
            if (!cancellable.is_cancelled())
                logError(e, 'claude-code-status: failed to read session state');
        } finally {
            this._loading = false;
            if (this._loadAgain) {
                this._loadAgain = false;
                this._load();
            }
        }
    }

    async _readAll(cancellable) {
        let enumerator;
        try {
            enumerator = await this._dir.enumerate_children_async(
                'standard::name', Gio.FileQueryInfoFlags.NONE,
                GLib.PRIORITY_DEFAULT, cancellable);
        } catch (e) {
            // No directory yet means no sessions have ever run; not an error.
            if (e.matches?.(Gio.IOErrorEnum, Gio.IOErrorEnum.NOT_FOUND))
                return [];
            throw e;
        }

        const names = [];
        for (;;) {
            const batch = await enumerator.next_files_async(
                32, GLib.PRIORITY_DEFAULT, cancellable);
            if (!batch.length)
                break;
            for (const info of batch) {
                const name = info.get_name();
                // ".tmp" files are half-written state; "debug" is the hook's
                // opt-in event log and is not a session.
                if (name.endsWith('.json'))
                    names.push(name);
            }
        }

        const sessions = [];
        for (const name of names) {
            const session = await this._readOne(name, cancellable);
            if (session)
                sessions.push(session);
        }
        return sessions;
    }

    async _readOne(name, cancellable) {
        const file = this._dir.get_child(name);
        let raw;
        try {
            const [contents] = await file.load_contents_async(cancellable);
            raw = JSON.parse(new TextDecoder().decode(contents));
        } catch (e) {
            // A file replaced mid-read, or truncated by a crash: skip it and
            // let the next monitor event pick up the good version.
            return null;
        }
        if (!raw || typeof raw !== 'object')
            return null;

        const pid = Number(raw.pid) || 0;
        const eventTs = Number(raw.event_ts) || 0;
        const age = GLib.get_real_time() / 1e6 - eventTs;
        // pid 0 is "the hook could not tell", not "dead": treating it as dead
        // would hide a perfectly live session, so those fall back to an age
        // cutoff instead.
        const gone = pid > 0 ? !isAlive(pid) : age > UNKNOWN_PID_MAX_AGE;
        if (gone) {
            // The terminal was killed without a SessionEnd hook. Removing the
            // file here (rather than only hiding it) keeps the directory from
            // growing forever across reboots.
            // The hook's lock file goes with it; dropping only the state file
            // would leave one empty ".lock" behind per session, forever.
            for (const victim of [file, this._dir.get_child(`${name}.lock`)]) {
                victim.delete_async(GLib.PRIORITY_LOW, null, (obj, res) => {
                    try {
                        obj.delete_finish(res);
                    } catch (e) {
                        // Already gone: the hook's own sweep got there first.
                    }
                });
            }
            return null;
        }

        const state = KNOWN.has(raw.state) ? raw.state : 'idle';
        return {
            sessionId: String(raw.session_id ?? name.replace(/\.json$/, '')),
            state,
            cwd: String(raw.cwd ?? ''),
            since: Number(raw.since) || 0,
            pid,
            message: String(raw.message ?? ''),
            notificationType: String(raw.notification_type ?? ''),
            zellijSession: String(raw.zellij_session ?? ''),
            zellijPane: String(raw.zellij_pane ?? ''),
        };
    }

    destroy() {
        this._cancellable.cancel();
        if (this._debounceId) {
            GLib.Source.remove(this._debounceId);
            this._debounceId = 0;
        }
        if (this._timerId) {
            GLib.Source.remove(this._timerId);
            this._timerId = 0;
        }
        this._monitor?.cancel();
        this._monitor = null;
        this._sessions = [];
    }
});

function isAlive(pid) {
    return pid > 0 && GLib.file_test(`/proc/${pid}`, GLib.FileTest.EXISTS);
}