session-ios/SessionUtilitiesKit/Networking/BatchResponse.swift

// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import Foundation
import Combine

public extension HTTP {
    // MARK: - BatchResponse
    
    struct BatchResponse {
        public let info: ResponseInfoType
        public let responses: [Decodable]
        
        public static func decodingResponses(
            from data: Data?,
            as types: [Decodable.Type],
            requireAllResults: Bool,
            using dependencies: Dependencies = Dependencies()
        ) throws -> [Decodable] {
            // Need to split the data into an array of data so each item can be Decoded correctly
            guard let data: Data = data else { throw HTTPError.parsingFailed }
            guard let jsonObject: Any = try? JSONSerialization.jsonObject(with: data, options: [.fragmentsAllowed]) else {
                throw HTTPError.parsingFailed
            }
            
            let dataArray: [Data]
            
            switch jsonObject {
                case let anyArray as [Any]:
                    dataArray = anyArray.compactMap { try? JSONSerialization.data(withJSONObject: $0) }
                    
                    guard !requireAllResults || dataArray.count == types.count else {
                        throw HTTPError.parsingFailed
                    }
                    
                case let anyDict as [String: Any]:
                    guard
                        let resultsArray: [Data] = (anyDict["results"] as? [Any])?
                            .compactMap({ try? JSONSerialization.data(withJSONObject: $0) }),
                        (
                            !requireAllResults ||
                            resultsArray.count == types.count
                        )
                    else { throw HTTPError.parsingFailed }
                    
                    dataArray = resultsArray
                    
                default: throw HTTPError.parsingFailed
            }
            
            return try zip(dataArray, types)
                .map { data, type in try type.decoded(from: data, using: dependencies) }
        }
    }
    
    // MARK: - BatchSubResponse<T>
    
    struct BatchSubResponse<T: Decodable>: BatchSubResponseType {
        public enum CodingKeys: String, CodingKey {
            case code
            case headers
            case body
        }
        
        /// The numeric http response code (e.g. 200 for success)
        public let code: Int
        
        /// Any headers returned by the request
        public let headers: [String: String]
        
        /// The body of the request; will be plain json if content-type is `application/json`, otherwise it will be base64 encoded data
        public let body: T?
        
        /// A flag to indicate that there was a body but it failed to parse
        public let failedToParseBody: Bool
        
        public init(
            code: Int,
            headers: [String: String] = [:],
            body: T? = nil,
            failedToParseBody: Bool = false
        ) {
            self.code = code
            self.headers = headers
            self.body = body
            self.failedToParseBody = failedToParseBody
        }
    }
}

public protocol BatchSubResponseType: Decodable {
    var code: Int { get }
    var headers: [String: String] { get }
    var failedToParseBody: Bool { get }
}

extension BatchSubResponseType {
    public var responseInfo: ResponseInfoType { HTTP.ResponseInfo(code: code, headers: headers) }
}

extension HTTP.BatchSubResponse: Encodable where T: Encodable {}

public extension HTTP.BatchSubResponse {
    init(from decoder: Decoder) throws {
        let container: KeyedDecodingContainer<CodingKeys> = try decoder.container(keyedBy: CodingKeys.self)
        let body: T? = try? container.decode(T.self, forKey: .body)
        
        self = HTTP.BatchSubResponse(
            code: try container.decode(Int.self, forKey: .code),
            headers: ((try? container.decode([String: String].self, forKey: .headers)) ?? [:]),
            body: body,
            failedToParseBody: (
                body == nil &&
                T.self != NoResponse.self &&
                !(T.self is ExpressibleByNilLiteral.Type)
            )
        )
    }
}

// MARK: - Convenience

public extension Decodable {
    static func decoded(from data: Data, using dependencies: Dependencies = Dependencies()) throws -> Self {
        return try data.decoded(as: Self.self, using: dependencies)
    }
}

public extension Publisher where Output == (ResponseInfoType, Data?), Failure == Error {
    func decoded(
        as types: [Decodable.Type],
        requireAllResults: Bool = true,
        using dependencies: Dependencies = Dependencies()
    ) -> AnyPublisher<HTTP.BatchResponse, Error> {
        self
            .tryMap { responseInfo, maybeData -> HTTP.BatchResponse in
                HTTP.BatchResponse(
                    info: responseInfo,
                    responses: try HTTP.BatchResponse.decodingResponses(
                        from: maybeData,
                        as: types,
                        requireAllResults: requireAllResults,
                        using: dependencies
                    )
                )
            }
            .eraseToAnyPublisher()
    }
}