purchases-ios/Sources/Support/PurchasesDiagnostics.swift

//
//  Copyright RevenueCat Inc. 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
//
//  PurchasesDiagnostics.swift
//
//  Created by Nacho Soto on 9/21/22.

import Foundation

/// `PurchasesDiagnostics` allows you to ensure that the SDK is set up correctly by diagnosing configuration errors.
/// To run the test, simply call ``PurchasesDiagnostics/testSDKHealth()``.
///
/// #### Example:
/// ```swift
/// let diagnostics = PurchasesDiagnostics.default
/// do {
///     try await diagnostics.testSDKHealth()
/// } catch {
///     print("Diagnostics failed: \(error.localizedDescription)")
/// }
/// ```
@objc(RCPurchasesDiagnostics)
public final class PurchasesDiagnostics: NSObject {

    typealias SDK = PurchasesType & InternalPurchasesType

    private let purchases: SDK

    init(purchases: SDK) {
        self.purchases = purchases
    }

    /// Default instance of `PurchasesDiagnostics`.
    /// Note: you must call ``Purchases/configure(with:)-6oipy`` before using this.
    @objc
    public static let `default`: PurchasesDiagnostics = .init(purchases: Purchases.shared)
}

extension PurchasesDiagnostics {

    /// An error that represents a failing step in ``PurchasesDiagnostics``
    public enum Error: Swift.Error {

        /// Connection to the API failed
        case failedConnectingToAPI(Swift.Error)

        /// API key is invalid
        case invalidAPIKey

        /// Fetching offerings failed due to the underlying error
        case failedFetchingOfferings(Swift.Error)

        /// Failure performing a signed request
        case failedMakingSignedRequest(Swift.Error)

        /// Any other not identifier error. You can check the undelying error for details.
        case unknown(Swift.Error)

    }

}

// MARK: - Implementation

extension PurchasesDiagnostics {

    /// Perform tests to ensure SDK is configured correctly.
    /// - `Throws`: ``PurchasesDiagnostics/Error`` if any step fails
    @objc(testSDKHealthWithCompletion:)
    public func testSDKHealth() async throws {
        do {
            try await self.unauthenticatedRequest()
            #if !ENABLE_CUSTOM_ENTITLEMENT_COMPUTATION
            try await self.authenticatedRequest()
            #endif
            try await self.offeringsRequest()
            try await self.signatureVerification()
        } catch let error as Error {
            throw error
        } catch let error {
            // Catch every other error to ensure that we only throw `Error`s from here.
            throw Error.unknown(error)
        }
    }

}

// MARK: - Private

private extension PurchasesDiagnostics {

    /// Makes a request to the backend, to verify connectivity, firewalls, or anything blocking network traffic.
    func unauthenticatedRequest() async throws {
        do {
            try await self.purchases.healthRequest(signatureVerification: false)
        } catch {
            throw Error.failedConnectingToAPI(error)
        }
    }

    #if !ENABLE_CUSTOM_ENTITLEMENT_COMPUTATION
    func authenticatedRequest() async throws {
        do {
            _ = try await self.purchases.customerInfo()
        } catch let error as ErrorCode {
            throw self.convert(error)
        } catch {
            throw Error.unknown(error)
        }
    }
    #endif

    func offeringsRequest() async throws {
        do {
            _ = try await self.purchases.offerings(fetchPolicy: .failIfProductsAreMissing)
        } catch {
            throw Error.failedFetchingOfferings(error)
        }
    }

    func signatureVerification() async throws {
        guard self.purchases.responseVerificationMode.isEnabled else { return }

        do {
            try await self.purchases.healthRequest(signatureVerification: true)
        } catch {
            throw Error.failedMakingSignedRequest(error)
        }
    }

    func convert(_ error: ErrorCode) -> Error {
        switch error {
        case .unknownError:
            return Error.unknown(error)

        case .offlineConnectionError:
            return Error.failedConnectingToAPI(error)

        case .invalidCredentialsError:
            return Error.invalidAPIKey

        case .signatureVerificationFailed:
            return Error.failedMakingSignedRequest(error)

        default:
            return Error.unknown(error)
        }
    }

}

extension PurchasesDiagnostics.Error: CustomNSError {

    // swiftlint:disable:next missing_docs
    public var errorUserInfo: [String: Any] {
        return [
            NSUnderlyingErrorKey: self.underlyingError as NSError? ?? NSNull(),
            NSLocalizedDescriptionKey: self.localizedDescription
        ]
    }

    var localizedDescription: String {
        switch self {
        case let .unknown(error): return "Unknown error: \(error.localizedDescription)"
        case let .failedConnectingToAPI(error): return "Error connecting to API: \(error.localizedDescription)"
        case let .failedFetchingOfferings(error): return "Failed fetching offerings: \(error.localizedDescription)"
        case let .failedMakingSignedRequest(error): return "Failed making signed request: \(error.localizedDescription)"
        case .invalidAPIKey: return "API key is not valid"
        }
    }

    private var underlyingError: Swift.Error? {
        switch self {
        case let .unknown(error): return error
        case let .failedConnectingToAPI(error): return error
        case let .failedFetchingOfferings(error): return error
        case let .failedMakingSignedRequest(error): return error
        case .invalidAPIKey: return nil
        }
    }

}