//
//  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
//
//  ErrorResponse.swift
//
//  Created by Nacho Soto on 6/22/23.

import Foundation

/// The response content of a failed request.
struct ErrorResponse: Equatable {

    var code: BackendErrorCode
    var originalCode: Int
    var message: String?
    var attributeErrors: [String: String] = [:]

}

extension ErrorResponse {

    /// Converts this `ErrorResponse` into an `ErrorCode` backed by the corresponding `BackendErrorCode`.
    func asBackendError(
        with statusCode: HTTPStatusCode,
        file: String = #fileID,
        function: String = #function,
        line: UInt = #line
    ) -> PurchasesError {
        var userInfo: [NSError.UserInfoKey: Any] = [
            .statusCode: statusCode.rawValue
        ]

        if !self.attributeErrors.isEmpty {
            userInfo[.attributeErrors] = self.attributeErrors as NSDictionary
        }

        // If the backend didn't provide a message we default to showing the status code.
        let errorMessage = self.message ?? Strings.network.api_request_failed_status_code(statusCode).description

        let message: String? = self.code != .unknownBackendError
            ? errorMessage
            : [
                errorMessage,
                // Append original error code if we couldn't map it to a value.
                "(\(self.originalCode))"
            ]
            .compactMap { $0 }
            .joined(separator: " ")

        return ErrorUtils.backendError(
            withBackendCode: self.code,
            originalBackendErrorCode: self.originalCode,
            message: self.attributeErrors.isEmpty
                ? nil
                : self.attributeErrors.description,
            backendMessage: message,
            extraUserInfo: userInfo,
            fileName: file, functionName: function, line: line
        )
    }

}

extension ErrorResponse: Decodable {

    private enum CodingKeys: String, CodingKey {

        case code
        case message
        case attributeErrors

    }

    private struct AttributeError: Decodable {

        let keyName: String
        let message: String

    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)

        let codeAsInteger = try? container.decodeIfPresent(Int.self, forKey: .code)
        let codeAsString = try? container.decodeIfPresent(String.self, forKey: .code)

        self.code = BackendErrorCode(code: codeAsInteger ?? codeAsString)
        self.originalCode = codeAsInteger ?? BackendErrorCode.unknownBackendError.rawValue
        self.message = try container.decodeIfPresent(String.self, forKey: .message)

        let attributeErrors = (
            try? container.decodeIfPresent(Array<AttributeError>.self,
                                           forKey: .attributeErrors)
        ) ?? []

        self.attributeErrors = attributeErrors
            .dictionaryAllowingDuplicateKeys { $0.keyName }
            .mapValues { $0.message }
    }

}

extension ErrorResponse {

    /// For some endpoints the backend may return `ErrorResponse` inside of this wrapper.
    private struct Wrapper: Decodable {

        let attributesErrorResponse: ErrorResponse

    }

    private static func parseWrapper(_ data: Data) -> Wrapper? {
        return try? JSONDecoder.default.decode(jsonData: data, logErrors: false)
    }

    /// Creates an `ErrorResponse` with the content of an `HTTPResponse`.
    /// This method supports extracting error information from the root, or from inside `"attributes_error_response"`
    /// - Note: if the error couldn't be decoded, a default error is created.
    /// - Warning: this is "deprecated". Ideally in the future all `ErrorResponses` are created from `Data`.
    static func from(_ dictionary: [String: Any]) -> Self {
        guard let data = try? JSONSerialization.data(withJSONObject: dictionary) else {
            return .defaultResponse
        }

        return Self.from(data)
    }

    /// Creates an `ErrorResponse` with the content of an `HTTPResponse`.
    /// This method supports extracting error information from the root, or from inside `"attributes_error_response"`
    /// - Note: if the error couldn't be decoded, a default error is created.
    static func from(_ data: Data) -> Self {
        do {
            if let wrapper = Self.parseWrapper(data) {
                return wrapper.attributesErrorResponse
            } else {
                return try JSONDecoder.default.decode(jsonData: data)
            }
        } catch {
            ErrorUtils.logDecodingError(error, type: Self.self, data: data)
            return Self.defaultResponse
        }
    }

    static let defaultResponse: Self = .init(code: .unknownError,
                                             originalCode: BackendErrorCode.unknownError.rawValue,
                                             message: nil)

}