const DB_NAME = 'SpreadsheetDB'
const STORE_NAME = 'sheets'
const LOG_STORE_NAME = 'op_logs' // Table for operation records
const DB_VERSION = 2 // Increment version to trigger upgrade

const openDB = () => {
    return new Promise((resolve, reject) => {
        const request = indexedDB.open(DB_NAME, DB_VERSION)

        request.onupgradeneeded = (event) => {
            const db = event.target.result
            // Main sheet store
            if (!db.objectStoreNames.contains(STORE_NAME)) {
                db.createObjectStore(STORE_NAME)
            }
            // Operation log store
            if (!db.objectStoreNames.contains(LOG_STORE_NAME)) {
                const store = db.createObjectStore(LOG_STORE_NAME, { keyPath: 'id', autoIncrement: true })
                store.createIndex('timestamp', 'timestamp')
            }
        }

        request.onsuccess = () => resolve(request.result)
        request.onerror = () => reject(request.error)
    })
}

export const db = {
    async get(key) {
        const db = await openDB()
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(STORE_NAME, 'readonly')
            const store = transaction.objectStore(STORE_NAME)
            const request = store.get(key)
            request.onsuccess = () => resolve(request.result)
            request.onerror = () => reject(request.error)
        })
    },

    async set(key, value) {
        const db = await openDB()
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(STORE_NAME, 'readwrite')
            const store = transaction.objectStore(STORE_NAME)
            const rawValue = JSON.parse(JSON.stringify(value))
            const request = store.put(rawValue, key)
            request.onsuccess = () => resolve()
            request.onerror = () => reject(request.error)
        })
    },

    // New: Add operation record
    async addLog(type, details) {
        const db = await openDB()
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(LOG_STORE_NAME, 'readwrite')
            const store = transaction.objectStore(LOG_STORE_NAME)
            const record = {
                type,
                details: JSON.parse(JSON.stringify(details)), // Ensure plain object
                timestamp: Date.now()
            }
            const request = store.add(record)
            request.onsuccess = () => resolve(request.result)
            request.onerror = () => reject(request.error)
        })
    },

    // New: Get recent logs (for restoring history if needed)
    async getLogs(limit = 50) {
        const db = await openDB()
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(LOG_STORE_NAME, 'readonly')
            const store = transaction.objectStore(LOG_STORE_NAME)
            const index = store.index('timestamp')
            const request = index.openCursor(null, 'prev') // Newest first
            const results = []

            request.onsuccess = (event) => {
                const cursor = event.target.result
                if (cursor && results.length < limit) {
                    results.push(cursor.value)
                    cursor.continue()
                } else {
                    resolve(results.reverse())
                }
            }
            request.onerror = () => reject(request.error)
        })
    }
}