import uuid from '../../uuid';
import Setting from '../../models/Setting';
import EncryptionService from '../e2ee/EncryptionService';
import { MasterKeyEntity } from '../e2ee/types';
import { localSyncInfo, saveLocalSyncInfo } from '../synchronizer/syncInfoUtils';

export interface DecryptedNoteLockKey {
	id: string;
	plainText: string;
}

// Importers that predate note lock skip this file, since they only read .md files.
export const noteLockKeyFileName = 'note_lock_key.json';

export default class NoteLockKey {

	public static instance_: NoteLockKey = null;

	private constructor(private encryptionService_: EncryptionService = EncryptionService.instance()) {}

	public static instance() {
		if (!this.instance_) {
			this.instance_ = new NoteLockKey();
		}
		return this.instance_;
	}

	public static destroyInstance() {
		this.instance_ = null;
	}

	public load(): MasterKeyEntity {
		return localSyncInfo().noteLockKey;
	}

	public save(o: MasterKeyEntity): MasterKeyEntity {
		const key = { ...o };
		if (!key.id) {
			key.id = uuid.create();
			key.created_time = Date.now();
		}
		key.updated_time = Date.now();

		const syncInfo = localSyncInfo();
		syncInfo.noteLockKey = key;
		// Only a key migration replaces the sync migration id, so a reset keeps the lineage it belongs to.
		if (!syncInfo.syncMigrationId) syncInfo.syncMigrationId = uuid.create();
		saveLocalSyncInfo(syncInfo);

		return key;
	}

	public async create(password: string) {
		if (this.load()) throw new Error('Note lock key already exists');
		const key = await this.encryptionService_.generateMasterKey(password);
		// A key may have arrived through sync while the new one was being generated - keep it,
		// since notes may already be locked with it on another device.
		if (this.load()) throw new Error('Note lock key already exists');
		return this.save(key);
	}

	// Rotate through NoteLockSession.reset() rather than calling this directly, so the session locks
	// and drops the old key as part of the rotation.
	public async reset(password: string) {
		const generated = await this.encryptionService_.generateMasterKey(password);
		// Read once the key is ready, so a sync that finished meanwhile counts; a second reset before that sync keeps the first backup.
		if (!Setting.value('noteLock.keyIdToReset')) Setting.setValue('noteLock.keyIdToReset', this.load()?.id ?? '');
		const key = this.save(generated);
		// Lets the next sync push the new key to the target instead of adopting the old one back.
		Setting.setValue('noteLock.passwordReset', true);
		return key;
	}

	public async changePassword(currentPassword: string, newPassword: string) {
		const key = this.load();
		if (!key) throw new Error('Note lock key has not been created');
		return this.save(await this.encryptionService_.reencryptMasterKey(key, currentPassword, newPassword));
	}

	public needsUpgrade() {
		const key = this.load();
		return !!key && !!this.encryptionService_.masterKeysThatNeedUpgrading([key]).length;
	}

	public async upgrade(password: string) {
		const key = this.load();
		if (!key) throw new Error('Note lock key has not been created');
		if (!this.needsUpgrade()) return key;
		return this.changePassword(password, password);
	}

	public async decrypt(password: string, key: MasterKeyEntity = null): Promise<DecryptedNoteLockKey> {
		if (!key) key = this.load();
		if (!key) throw new Error('Note lock key has not been created');
		if (!key.id) throw new Error('Note lock key does not have an ID');

		const plainText = await this.encryptionService_.decryptMasterKeyContent(key, password);
		return { id: key.id, plainText };
	}
}