ExploreDatabaseConnection.swift

//
//  Created by Pavel Tikhonenko
//  Copyright © 2022 Dash Core Group. All rights reserved.
//
//  Licensed under the MIT License (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//  https://opensource.org/licenses/MIT
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

import Foundation
import SQLite

// MARK: - ExploreDatabaseConnectionError

enum ExploreDatabaseConnectionError: Error {
    case fileNotFound
}

// MARK: - ExploreDatabaseConnection

let kExploreDashDatabaseName = "explore.db"

// MARK: - ExploreDatabaseConnection

class ExploreDatabaseConnection {
    private var db: Connection!

    init() {
        NotificationCenter.default.addObserver(forName: ExploreDatabaseSyncManager.databaseHasBeenUpdatedNotification,
                                               object: nil, queue: .main) { [weak self] _ in
            try? self?.connect()
        }
    }

    func connect() throws {
        db = nil

        guard let dbPath = dbPath() else { throw ExploreDatabaseConnectionError.fileNotFound }

        do {
            db = try Connection(dbPath)
        } catch {
            print(error)
        }
    }

    private func dbPath() -> String? {
        let downloadedPath = FileManager.documentsDirectoryURL.appendingPathComponent(kExploreDashDatabaseName).path

        return FileManager.default.fileExists(atPath: downloadedPath) ? downloadedPath : nil
    }

    func execute<Item: RowDecodable>(query: QueryType) throws -> [Item] {
        let items = try db.prepare(query)

        var resultItems: [Item] = []

        for item in items {
            resultItems.append(Item(row: item))
        }

        return resultItems
    }

    func execute<Item: RowDecodable>(query: String) throws -> [Item] {
        try db.prepareRowIterator(query).map { Item(row: $0) }
    }
}