/**
 * Story History Module
 * Stores rendered story blocks in IndexedDB and keeps only a short live window
 * in the page DOM.
 */
import { BaseModule } from './base-module.js';

class StoryHistoryModule extends BaseModule {
    constructor() {
        super('story-history', 'Story History');

        this.dependencies = ['persistence-manager'];
        this.dbName = 'ttsAudioCacheDB';
        this.dbVersion = 2;
        this.historyStore = 'storyHistoryStore';
        this.saveStore = 'storySaveStore';
        this.db = null;
        this.currentGameId = null;
        this.nextBlockId = 1;
        this.visibleLimit = 20;

        this.bindMethods([
            'initialize',
            'openDB',
            'startNewGame',
            'setCurrentGame',
            'recordBlock',
            'saveSlot',
            'loadSlot',
            'hasSaveSlot',
            'getSaveSlots',
            'getBlocks',
            'clearGame',
            'tx'
        ]);
    }

    async initialize() {
        await this.openDB();
        this.reportProgress(100, 'Story history ready');
        return true;
    }

    openDB() {
        if (this.db) return Promise.resolve(this.db);
        return new Promise((resolve, reject) => {
            const request = indexedDB.open(this.dbName, this.dbVersion);
            request.onerror = () => reject(request.error);
            request.onsuccess = () => {
                this.db = request.result;
                resolve(this.db);
            };
            request.onupgradeneeded = () => {
                const db = request.result;
                if (!db.objectStoreNames.contains(this.historyStore)) {
                    const historyStore = db.createObjectStore(this.historyStore, { keyPath: 'key' });
                    historyStore.createIndex('gameId', 'gameId', { unique: false });
                    historyStore.createIndex('gameOrder', ['gameId', 'blockId'], { unique: true });
                }
                if (!db.objectStoreNames.contains(this.saveStore)) {
                    db.createObjectStore(this.saveStore, { keyPath: 'slot' });
                }
            };
        });
    }

    tx(storeName, mode = 'readonly') {
        return this.db.transaction(storeName, mode).objectStore(storeName);
    }

    async startNewGame() {
        const gameId = `game-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
        this.currentGameId = gameId;
        this.nextBlockId = 1;
        const persistenceManager = this.getModule('persistence-manager');
        persistenceManager?.updatePreference?.('app', 'currentGameId', gameId);
        return gameId;
    }

    setCurrentGame(gameId, latestBlockId = 0) {
        this.currentGameId = gameId || this.currentGameId;
        this.nextBlockId = Math.max(1, Number(latestBlockId || 0) + 1);
    }

    recordBlock(block) {
        if (!this.db || !this.currentGameId || !block) return Promise.resolve(null);
        const blockId = this.nextBlockId++;
        const record = {
            ...block,
            key: `${this.currentGameId}:${blockId}`,
            gameId: this.currentGameId,
            blockId,
            createdAt: Date.now()
        };
        return new Promise((resolve, reject) => {
            const request = this.tx(this.historyStore, 'readwrite').put(record);
            request.onsuccess = () => resolve(record);
            request.onerror = () => reject(request.error);
        });
    }

    saveSlot(slot = 1, saveData = {}) {
        if (!this.db) return Promise.resolve(false);
        const record = {
            slot,
            ...saveData,
            gameId: saveData.gameId || this.currentGameId,
            latestBlockId: Math.max(0, this.nextBlockId - 1),
            savedAt: Date.now()
        };
        return new Promise((resolve, reject) => {
            const request = this.tx(this.saveStore, 'readwrite').put(record);
            request.onsuccess = () => resolve(record);
            request.onerror = () => reject(request.error);
        });
    }

    loadSlot(slot = 1) {
        if (!this.db) return Promise.resolve(null);
        return new Promise((resolve, reject) => {
            const request = this.tx(this.saveStore).get(slot);
            request.onsuccess = () => resolve(request.result || null);
            request.onerror = () => reject(request.error);
        });
    }

    async hasSaveSlot(slot = 1) {
        return Boolean(await this.loadSlot(slot));
    }

    getSaveSlots() {
        if (!this.db) return Promise.resolve([]);
        return new Promise((resolve, reject) => {
            const request = this.tx(this.saveStore).getAllKeys();
            request.onsuccess = () => resolve(request.result || []);
            request.onerror = () => reject(request.error);
        });
    }

    getBlocks(gameId = this.currentGameId, limit = this.visibleLimit, beforeBlockId = Infinity) {
        if (!this.db || !gameId) return Promise.resolve([]);
        return new Promise((resolve, reject) => {
            const blocks = [];
            const index = this.tx(this.historyStore).index('gameOrder');
            const upper = Number.isFinite(beforeBlockId) ? beforeBlockId : Number.MAX_SAFE_INTEGER;
            const range = IDBKeyRange.bound([gameId, 0], [gameId, upper], false, true);
            const request = index.openCursor(range, 'prev');
            request.onsuccess = () => {
                const cursor = request.result;
                if (!cursor || blocks.length >= limit) {
                    resolve(blocks.reverse());
                    return;
                }
                blocks.push(cursor.value);
                cursor.continue();
            };
            request.onerror = () => reject(request.error);
        });
    }

    clearGame(gameId = this.currentGameId) {
        if (!this.db || !gameId) return Promise.resolve();
        return new Promise((resolve, reject) => {
            const store = this.tx(this.historyStore, 'readwrite');
            const index = store.index('gameId');
            const request = index.openCursor(IDBKeyRange.only(gameId));
            request.onsuccess = () => {
                const cursor = request.result;
                if (!cursor) {
                    resolve();
                    return;
                }
                cursor.delete();
                cursor.continue();
            };
            request.onerror = () => reject(request.error);
        });
    }
}

const storyHistory = new StoryHistoryModule();

export { storyHistory as StoryHistory };

if (window.moduleRegistry) {
    window.moduleRegistry.register(storyHistory);
}

window.StoryHistory = storyHistory;