FirefoxFaviconsReader.swift

//
//  FirefoxFaviconsReader.swift
//
//  Copyright © 2022 DuckDuckGo. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
//  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 AppKit
import Foundation
import GRDB
import BrowserServicesKit

final class FirefoxFaviconsReader {

    enum Constants {
        static let faviconsDatabaseName = "favicons.sqlite"
    }

    struct ImportError: DataImportError {
        enum OperationType: Int {
            case copyTemporaryFile
            case dbOpen
            case fetchAllFavicons
        }

        var action: DataImportAction { .favicons }
        let type: OperationType
        let underlyingError: Error?

        var errorType: DataImport.ErrorType { .other }
    }

    final class FirefoxFavicon: FetchableRecord {
        let pageURL: String
        let iconURL: String
        let size: Int
        let imageData: Data

        var image: NSImage? {
            NSImage(data: imageData)
        }

        init(row: Row) throws {
            pageURL = try row["page_url"] ?? { throw FetchableRecordError<FirefoxFavicon>(column: 0) }()
            iconURL = try row["icon_url"] ?? { throw FetchableRecordError<FirefoxFavicon>(column: 1) }()
            size = try row["width"] ?? { throw FetchableRecordError<FirefoxFavicon>(column: 2) }()
            imageData = try row["data"] ?? { throw FetchableRecordError<FirefoxFavicon>(column: 3) }()
        }
    }

    private let firefoxFaviconsDatabaseURL: URL
    private var currentOperationType: ImportError.OperationType = .copyTemporaryFile

    init(firefoxDataDirectoryURL: URL) {
        self.firefoxFaviconsDatabaseURL = firefoxDataDirectoryURL.appendingPathComponent(Constants.faviconsDatabaseName)
    }

    func readFavicons() -> DataImportResult<[String: [FirefoxFavicon]]> {
        do {
            currentOperationType = .copyTemporaryFile
            return try firefoxFaviconsDatabaseURL.withTemporaryFile { temporaryDatabaseURL in
                let favicons = try readFavicons(fromDatabaseURL: temporaryDatabaseURL)
                return .success(favicons)
            }
        } catch let error as ImportError {
            return .failure(error)
        } catch {
            return .failure(ImportError(type: currentOperationType, underlyingError: error))
        }
    }

    // MARK: - Private

    private func readFavicons(fromDatabaseURL databaseURL: URL) throws -> [String: [FirefoxFavicon]] {
        currentOperationType = .dbOpen

        let queue = try DatabaseQueue(path: databaseURL.path)

        currentOperationType = .fetchAllFavicons
        let favicons: [FirefoxFavicon] = try queue.read { database in
            try FirefoxFavicon.fetchAll(database, sql: allFaviconsQuery())
        }

        let faviconsByURL = Dictionary(grouping: favicons, by: { $0.pageURL })

        return faviconsByURL
    }

    // MARK: - Database Queries

    func allFaviconsQuery() -> String {
        return """
        SELECT
            moz_pages_w_icons.page_url, moz_icons.icon_url, moz_icons.width, moz_icons.data
        FROM
            moz_pages_w_icons
        JOIN
            moz_icons_to_pages ON moz_pages_w_icons.id = moz_icons_to_pages.page_id
        JOIN
            moz_icons ON moz_icons.id = moz_icons_to_pages.icon_id;
        """
    }

}