WebCacheManager.swift

//
//  WebCacheManager.swift
//  DuckDuckGo
//
//  Copyright © 2017 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 Common
import WebKit
import GRDB

public protocol WebCacheManagerCookieStore {
    
    func getAllCookies(_ completionHandler: @escaping ([HTTPCookie]) -> Void)

    func setCookie(_ cookie: HTTPCookie, completionHandler: (() -> Void)?)

    func delete(_ cookie: HTTPCookie, completionHandler: (() -> Void)?)
    
}

public protocol WebCacheManagerDataStore {
    
    var cookieStore: WebCacheManagerCookieStore? { get }
    
    func removeAllDataExceptCookies(completion: @escaping () -> Void)
    
}

public class WebCacheManager {

    private struct Constants {
        static let cookieDomainsToPreserve = ["duckduckgo.com", "surveys.duckduckgo.com"]
    }
    
    public static var shared = WebCacheManager()
    
    private init() { }

    /// This function is used to extract cookies stored in CookieStorage and restore them to WKWebView's HTTP cookie store during the Fire button operation.
    /// The Fire button no longer persists and restores cookies, but this function remains in the event that cookies have been stored and not yet restored.
    public func consumeCookies(cookieStorage: CookieStorage = CookieStorage(),
                               httpCookieStore: WebCacheManagerCookieStore? = WKWebsiteDataStore.default().cookieStore,
                               completion: @escaping () -> Void) {
        
        guard let httpCookieStore = httpCookieStore else {
            completion()
            return
        }
        
        let cookies = cookieStorage.cookies
        
        guard !cookies.isEmpty else {
            completion()
            return
        }
        
        let group = DispatchGroup()
        
        var consumedCookiesCount = 0
        
        for cookie in cookies {
            group.enter()
            consumedCookiesCount += 1
            httpCookieStore.setCookie(cookie) {
                group.leave()
            }
        }
        
        Pixel.fire(pixel: .legacyCookieMigration, withAdditionalParameters: [
            PixelParameters.count: "\(consumedCookiesCount)"
        ])
        
        DispatchQueue.global(qos: .userInitiated).async {
            group.wait()
            
            DispatchQueue.main.async {
                cookieStorage.clear()
                completion()
                
                if cookieStorage.cookies.count > 0 {
                    os_log("Error removing cookies: %d cookies left in legacy CookieStorage",
                           log: .generalLog, type: .debug, cookieStorage.cookies.count)
                    
                    Pixel.fire(pixel: .legacyCookieCleanupError, withAdditionalParameters: [
                        PixelParameters.count: "\(cookieStorage.cookies.count)"
                    ])
                }
            }
        }
    }

    public func removeCookies(forDomains domains: [String],
                              dataStore: WebCacheManagerDataStore = WKWebsiteDataStore.default(),
                              completion: @escaping () -> Void) {

        guard let cookieStore = dataStore.cookieStore else {
            completion()
            return
        }

        cookieStore.getAllCookies { cookies in
            let group = DispatchGroup()
            cookies.forEach { cookie in
                if domains.contains(where: { self.isCookie(cookie, matchingDomain: $0) }) {
                    group.enter()
                    cookieStore.delete(cookie) {
                        group.leave()
                    }
                }
            }

            DispatchQueue.global(qos: .userInitiated).async {
                let result = group.wait(timeout: .now() + 5)

                if result == .timedOut {
                    Pixel.fire(pixel: .cookieDeletionTimedOut, withAdditionalParameters: [
                        PixelParameters.removeCookiesTimedOut: "1"
                    ])
                }

                DispatchQueue.main.async {
                    completion()
                }
            }
        }

    }

    public func clear(dataStore: WebCacheManagerDataStore = WKWebsiteDataStore.default(),
                      logins: PreserveLogins = PreserveLogins.shared,
                      tabCountInfo: TabCountInfo? = nil,
                      completion: @escaping () -> Void) {

        dataStore.removeAllDataExceptCookies {
            guard let cookieStore = dataStore.cookieStore else {
                completion()
                return
            }
            
            let cookieClearingSummary = WebStoreCookieClearingSummary()

            cookieStore.getAllCookies { cookies in
                let group = DispatchGroup()
                let cookiesToRemove = cookies.filter {
                    !logins.isAllowed(cookieDomain: $0.domain) &&
                    !Constants.cookieDomainsToPreserve.contains($0.domain)
                }
                let protectedCookiesCount = cookies.count - cookiesToRemove.count
                
                cookieClearingSummary.storeInitialCount = cookies.count
                cookieClearingSummary.storeProtectedCount = protectedCookiesCount
                
                for cookie in cookiesToRemove {
                    group.enter()
                    cookieStore.delete(cookie) {
                        group.leave()
                    }
                }

                DispatchQueue.global(qos: .userInitiated).async {
                    let result = group.wait(timeout: .now() + 5)

                    if result == .timedOut {
                        cookieClearingSummary.didStoreDeletionTimeOut = true
                        Pixel.fire(pixel: .cookieDeletionTimedOut, withAdditionalParameters: [
                            PixelParameters.clearWebDataTimedOut: "1"
                        ])
                    }
                    
                    // Remove legacy HTTPCookieStorage cookies
                    let storageCookies = HTTPCookieStorage.shared.cookies ?? []
                    let storageCookiesToRemove = storageCookies.filter {
                        !logins.isAllowed(cookieDomain: $0.domain) && !Constants.cookieDomainsToPreserve.contains($0.domain)
                    }
                    
                    let protectedStorageCookiesCount = storageCookies.count - storageCookiesToRemove.count
                    
                    cookieClearingSummary.storageInitialCount = storageCookies.count
                    cookieClearingSummary.storageProtectedCount = protectedStorageCookiesCount
                    
                    for storageCookie in storageCookiesToRemove {
                        HTTPCookieStorage.shared.deleteCookie(storageCookie)
                    }

                    self.removeObservationsData()

                    self.performSanityCheck(for: cookieStore, summary: cookieClearingSummary, tabCountInfo: tabCountInfo)
                    
                    DispatchQueue.main.async {
                        completion()
                    }
                }
            }
        }
    }
    
    private func performSanityCheck(for cookieStore: WebCacheManagerCookieStore, summary: WebStoreCookieClearingSummary, tabCountInfo: TabCountInfo?) {
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            cookieStore.getAllCookies { cookiesAfterCleaning in
                let storageCookiesAfterCleaning = HTTPCookieStorage.shared.cookies ?? []
                
                summary.storeAfterDeletionCount = cookiesAfterCleaning.count
                summary.storageAfterDeletionCount = storageCookiesAfterCleaning.count
                
                let cookieStoreDiff = cookiesAfterCleaning.count - summary.storeProtectedCount
                let cookieStorageDiff = storageCookiesAfterCleaning.count - summary.storageProtectedCount
                
                summary.storeAfterDeletionDiffCount = cookieStoreDiff
                summary.storageAfterDeletionDiffCount = cookieStorageDiff
                
                if cookieStoreDiff + cookieStorageDiff > 0 {
                    os_log("Error removing cookies: %d cookies left in WKHTTPCookieStore, %d cookies left in HTTPCookieStorage",
                           log: .generalLog, type: .debug, cookieStoreDiff, cookieStorageDiff)
                    
                    var parameters = summary.makeDictionaryRepresentation()
                    
                    if let tabCountInfo = tabCountInfo {
                        parameters.merge(tabCountInfo.makeDictionaryRepresentation(), uniquingKeysWith: { _, new in new })
                    }
                    
                    Pixel.fire(pixel: .cookieDeletionLeftovers,
                               withAdditionalParameters: parameters)
                }
            }
        }
    }

    /// The Fire Button does not delete the user's DuckDuckGo search settings, which are saved as cookies. Removing these cookies would reset them and have undesired consequences, i.e. changing the theme, default language, etc.
    /// The Fire Button also does not delete temporary cookies associated with 'surveys.duckduckgo.com'. When we launch surveys to help us understand issues that impact users over time, we use this cookie to temporarily store anonymous survey answers, before deleting the cookie. Cookie storage duration is communicated to users before they opt to submit survey answers.
    /// These cookies are not stored in a personally identifiable way. For example, the large size setting is stored as 's=l.' More info in https://duckduckgo.com/privacy
    public func isCookie(_ cookie: HTTPCookie, matchingDomain domain: String) -> Bool {
        return cookie.domain == domain || (cookie.domain.hasPrefix(".") && domain.hasSuffix(cookie.domain))
    }

    private func removeObservationsData() {
        if let pool = getValidDatabasePool() {
            removeObservationsData(from: pool)
        } else {
            os_log("Could not find valid pool to clear observations data", log: .generalLog, type: .debug)
        }
    }

    func getValidDatabasePool() -> DatabasePool? {
        let bundleID = Bundle.main.bundleIdentifier ?? ""

        let databaseURLs = [
            FileManager.default.urls(for: .libraryDirectory, in: .userDomainMask)[0]
                       .appendingPathComponent("WebKit/WebsiteData/ResourceLoadStatistics/observations.db"),
            FileManager.default.urls(for: .libraryDirectory, in: .userDomainMask)[0]
                       .appendingPathComponent("WebKit/\(bundleID)/WebsiteData/ResourceLoadStatistics/observations.db")
        ]

        guard let validURL = databaseURLs.first(where: { FileManager.default.fileExists(atPath: $0.path) }),
              let pool = try? DatabasePool(path: validURL.absoluteString) else {
            return nil
        }

        return pool
    }


    private func removeObservationsData(from pool: DatabasePool) {
         do {
             try pool.write { database in
                 try database.execute(sql: "PRAGMA wal_checkpoint(TRUNCATE);")

                 let tables = try String.fetchAll(database, sql: "SELECT name FROM sqlite_master WHERE type='table'")

                 for table in tables {
                     try database.execute(sql: "DELETE FROM \(table)")
                 }
             }
         } catch {
             Pixel.fire(pixel: .debugCannotClearObservationsDatabase, error: error)
         }
     }

}

extension WKHTTPCookieStore: WebCacheManagerCookieStore {
        
}

extension WKWebsiteDataStore: WebCacheManagerDataStore {

    public var cookieStore: WebCacheManagerCookieStore? {
        return self.httpCookieStore
    }

    public func removeAllDataExceptCookies(completion: @escaping () -> Void) {
        var types = WKWebsiteDataStore.allWebsiteDataTypes()

        // Force the HSTS, Media and Alt services cache to clear when using the Fire button.
        // https://github.com/WebKit/WebKit/blob/0f73b4d4350c707763146ff0501ab62425c902d6/Source/WebKit/UIProcess/API/Cocoa/WKWebsiteDataRecord.mm#L47
        types.insert("_WKWebsiteDataTypeHSTSCache")
        types.insert("_WKWebsiteDataTypeMediaKeys")
        types.insert("_WKWebsiteDataTypeAlternativeServices")
        types.insert("_WKWebsiteDataTypeSearchFieldRecentSearches")
        types.insert("_WKWebsiteDataTypeResourceLoadStatistics")
        types.insert("_WKWebsiteDataTypeCredentials")
        types.insert("_WKWebsiteDataTypeAdClickAttributions")
        types.insert("_WKWebsiteDataTypePrivateClickMeasurements")

        types.remove(WKWebsiteDataTypeCookies)

        removeData(ofTypes: types,
                   modifiedSince: Date.distantPast,
                   completionHandler: completion)
    }
    
}

final class WebStoreCookieClearingSummary {
    var storeInitialCount: Int = 0
    var storeProtectedCount: Int = 0
    var didStoreDeletionTimeOut: Bool = false
    var storageInitialCount: Int = 0
    var storageProtectedCount: Int = 0
    
    var storeAfterDeletionCount: Int = 0
    var storageAfterDeletionCount: Int = 0
    var storeAfterDeletionDiffCount: Int = 0
    var storageAfterDeletionDiffCount: Int = 0
    
    func makeDictionaryRepresentation() -> [String: String] {
        [PixelParameters.storeInitialCount: "\(storeInitialCount)",
         PixelParameters.storeProtectedCount: "\(storeProtectedCount)",
         PixelParameters.didStoreDeletionTimeOut: didStoreDeletionTimeOut ? "true" : "false",
         PixelParameters.storageInitialCount: "\(storageInitialCount)",
         PixelParameters.storageProtectedCount: "\(storageProtectedCount)",
         PixelParameters.storeAfterDeletionCount: "\(storeAfterDeletionCount)",
         PixelParameters.storageAfterDeletionCount: "\(storageAfterDeletionCount)",
         PixelParameters.storeAfterDeletionDiffCount: "\(storeAfterDeletionDiffCount)",
         PixelParameters.storageAfterDeletionDiffCount: "\(storageAfterDeletionDiffCount)"]
    }
}

public final class TabCountInfo {
    var tabsModelCount: Int = 0
    var tabControllerCacheCount: Int = 0
    
    public init() { }
        
    public init(tabsModelCount: Int, tabControllerCacheCount: Int) {
        self.tabsModelCount = tabsModelCount
        self.tabControllerCacheCount = tabControllerCacheCount
    }
    
    func makeDictionaryRepresentation() -> [String: String] {
        [PixelParameters.tabsModelCount: "\(tabsModelCount)",
         PixelParameters.tabControllerCacheCount: "\(tabControllerCacheCount)"]
    }
}