import { sys } from 'cc';
import { IStorage, MemoryStorage } from './IStorage';

/**
 * The one file in the save module that touches the engine.
 *
 * `sys.localStorage` is backed by the browser store on web and by a native file
 * on Android and iOS, so one implementation covers every target. It can still
 * fail — private browsing, a full quota, a locked profile — so every call is
 * guarded and falls back to an in-memory store, which keeps the session
 * consistent even when nothing can be persisted.
 */
export class CocosStorage implements IStorage {
    private readonly _fallback = new MemoryStorage();
    private _usingFallback = false;

    /** True once a storage call has failed and the session went in-memory. */
    get degraded(): boolean {
        return this._usingFallback;
    }

    getItem(key: string): string | null {
        if (this._usingFallback) {
            return this._fallback.getItem(key);
        }
        try {
            return sys.localStorage.getItem(key);
        } catch (error) {
            this._degrade(error);
            return this._fallback.getItem(key);
        }
    }

    setItem(key: string, value: string): void {
        if (!this._usingFallback) {
            try {
                sys.localStorage.setItem(key, value);
                return;
            } catch (error) {
                this._degrade(error);
            }
        }
        this._fallback.setItem(key, value);
    }

    removeItem(key: string): void {
        if (!this._usingFallback) {
            try {
                sys.localStorage.removeItem(key);
                return;
            } catch (error) {
                this._degrade(error);
            }
        }
        this._fallback.removeItem(key);
    }

    private _degrade(error: unknown): void {
        if (this._usingFallback) return;
        this._usingFallback = true;
        const message = error instanceof Error ? error.message : String(error);
        console.warn(`[save] device storage is unavailable, progress will not persist: ${message}`);
    }
}