import type { RxCleanupPolicy, RxCollection } from '../../types/index.d.ts';
import { PROMISE_RESOLVE_TRUE } from '../../plugins/utils/index.ts';
import { REPLICATION_STATE_BY_COLLECTION } from '../replication/index.ts';
import { DEFAULT_CLEANUP_POLICY } from './cleanup-helper.ts';
import { runAsyncPluginHooks } from '../../hooks.ts';

/**
 * Even on multiple databases,
 * the calls to RxStorage().cleanup()
 * must never run in parallel.
 * The cleanup is a background task which should
 * not affect the performance of other, more important tasks.
 */
let RXSTORAGE_CLEANUP_QUEUE: Promise<boolean> = PROMISE_RESOLVE_TRUE;

export async function startCleanupForRxCollection(
    rxCollection: RxCollection
) {
    const rxDatabase = rxCollection.database;
    const cleanupPolicy = Object.assign(
        {},
        DEFAULT_CLEANUP_POLICY,
        rxDatabase.cleanupPolicy ? rxDatabase.cleanupPolicy : {}
    );


    await initialCleanupWait(rxCollection, cleanupPolicy);
    if (rxCollection.destroyed) {
        return;
    }

    // initially cleanup the collection
    await cleanupRxCollection(rxCollection, cleanupPolicy);

    /**
     * Afterwards we listen to deletes
     * and only re-run the cleanup after
     * minimumDeletedTime is reached.
     */
    await runCleanupAfterDelete(rxCollection, cleanupPolicy);
}


export async function initialCleanupWait(collection: RxCollection, cleanupPolicy: RxCleanupPolicy) {
    /**
     * Wait until minimumDatabaseInstanceAge is reached
     * or collection is destroyed.
     */
    await collection.promiseWait(cleanupPolicy.minimumCollectionAge);
    if (collection.destroyed) {
        return;
    }

    if (cleanupPolicy.waitForLeadership) {
        await collection.database.waitForLeadership();
    }
}

/**
 * Runs the cleanup for a single RxCollection
 */
export async function cleanupRxCollection(
    rxCollection: RxCollection,
    cleanupPolicy: RxCleanupPolicy
) {
    const rxDatabase = rxCollection.database;
    const storageInstance = rxCollection.storageInstance;

    // run cleanup() until it returns true
    let isDone = false;
    while (!isDone && !rxCollection.destroyed) {
        if (cleanupPolicy.awaitReplicationsInSync) {
            const replicationStates = REPLICATION_STATE_BY_COLLECTION.get(rxCollection);
            if (replicationStates) {
                await Promise.all(
                    replicationStates.map(replicationState => {
                        if (!replicationState.isStopped()) {
                            return replicationState.awaitInSync();
                        }
                    })
                );
            }
        }
        if (rxCollection.destroyed) {
            return;
        }
        RXSTORAGE_CLEANUP_QUEUE = RXSTORAGE_CLEANUP_QUEUE
            .then(async () => {
                if (rxCollection.destroyed) {
                    return true;
                }
                await rxDatabase.requestIdlePromise();
                return storageInstance.cleanup(cleanupPolicy.minimumDeletedTime);
            });
        isDone = await RXSTORAGE_CLEANUP_QUEUE;
    }
    await runAsyncPluginHooks('postCleanup', {
        collectionName: rxCollection.name,
        databaseName: rxDatabase.name
    });
}

/**
 * TODO this is not waiting for deletes!
 * it just runs on interval.
 */
export async function runCleanupAfterDelete(
    rxCollection: RxCollection,
    cleanupPolicy: RxCleanupPolicy
) {
    while (!rxCollection.destroyed) {
        await rxCollection.promiseWait(cleanupPolicy.runEach);
        if (rxCollection.destroyed) {
            return;
        }
        await cleanupRxCollection(rxCollection, cleanupPolicy);
    }
}