import Toybox.Application;
import Toybox.Lang;
import Toybox.Time;

// Persists events in Application.Storage as an array of dictionaries,
// ordered oldest → newest. Prunes entries older than Config.RETENTION_SEC
// whenever loaded.
module EventStore {

    const KEY = "events";

    function getAll() as Array<Event> {
        var raw = Application.Storage.getValue(KEY);
        if (raw == null || !(raw instanceof Array)) {
            return [];
        }
        var out = [];
        for (var i = 0; i < raw.size(); i++) {
            out.add(Event.fromDict(raw[i] as Dictionary));
        }
        return out;
    }

    function add(event as Event) as Void {
        var raw = Application.Storage.getValue(KEY);
        var arr = (raw instanceof Array) ? raw : [];
        arr.add(event.toDict());
        Application.Storage.setValue(KEY, arr);
    }

    function deleteLast() as Boolean {
        var raw = Application.Storage.getValue(KEY);
        if (!(raw instanceof Array) || raw.size() == 0) {
            return false;
        }
        raw = raw.slice(0, raw.size() - 1);
        Application.Storage.setValue(KEY, raw);
        return true;
    }

    function count() as Number {
        var raw = Application.Storage.getValue(KEY);
        return (raw instanceof Array) ? raw.size() : 0;
    }

    function latest() as Event or Null {
        var raw = Application.Storage.getValue(KEY);
        if (!(raw instanceof Array) || raw.size() == 0) {
            return null;
        }
        return Event.fromDict(raw[raw.size() - 1] as Dictionary);
    }

    // Drops events with timestamp < (now - retention).
    function pruneOld() as Void {
        var raw = Application.Storage.getValue(KEY);
        if (!(raw instanceof Array) || raw.size() == 0) {
            return;
        }
        var cutoff = Time.now().value() - Config.RETENTION_SEC;
        var kept = [];
        for (var i = 0; i < raw.size(); i++) {
            var d = raw[i] as Dictionary;
            var ts = d["ts"];
            if (ts != null && (ts as Number) >= cutoff) {
                kept.add(d);
            }
        }
        if (kept.size() != raw.size()) {
            Application.Storage.setValue(KEY, kept);
        }
    }
}