//
//  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
//
//  HTTPRequestPath.swift
//
//  Created by Nacho Soto on 8/8/23.

// swiftlint:disable file_length

import Foundation

/// Provides endpoint-specific inputs for backend response signature verification.
///
/// Most endpoints use the raw response body and request body. Specialized endpoints can override
/// either input.
protocol ResponseSignatureContextProvider {

    /// Returns the response bytes that should be verified against the backend signature.
    ///
    /// This may throw when deriving the signed payload requires validating response structure first.
    func responsePayloadForSignature(from body: Data?, statusCode: HTTPStatusCode) throws -> Data?

    /// Returns the request body component to include in signature parameters, if any.
    func requestBodyForSignature(for request: HTTPRequest) -> HTTPRequestBody?

}

struct DefaultResponseSignatureContextProvider: ResponseSignatureContextProvider {

    func responsePayloadForSignature(from body: Data?, statusCode: HTTPStatusCode) throws -> Data? {
        return body
    }

    func requestBodyForSignature(for request: HTTPRequest) -> HTTPRequestBody? {
        return request.requestBody
    }

}

extension HTTPRequest {

    struct Path: Hashable {

        // swiftlint:disable:next nesting
        enum ETagBehavior {
            case send
            case ignore
        }

        private static let fallbackServerHostURLs = [
            URL(string: "https://api-production.8-lives-cat.io")
        ]

        static func == (lhs: Self, rhs: Self) -> Bool {
            return lhs.name == rhs.name &&
            lhs.serverHostURL == rhs.serverHostURL &&
            lhs.relativePath == rhs.relativePath
        }

        static var serverHostURL: URL { SystemInfo.apiBaseURL }

        /// The base URL for requests to this path.
        var serverHostURL: URL { self.customServerHostURL ?? Self.serverHostURL }

        private var customServerHostURL: URL?

        /// The fallback URLs to use when the main server is down.
        ///
        /// Not all endpoints have a fallback URL, but some do.
        var fallbackUrls: [URL]

        var supportsFallbackURLs: Bool { !fallbackUrls.isEmpty }

        /// Whether requests to this path are authenticated.
        var authenticated: Bool

        /// Whether requests to this path can be cached using `ETagManager`.
        var etagBehavior: ETagBehavior

        var shouldSendEtag: Bool { etagBehavior == .send }

        /// Whether the endpoint will perform signature verification.
        var supportsSignatureVerification: Bool

        /// Whether endpoint requires a nonce for signature verification.
        var needsNonceForSigning: Bool

        /// The name of the endpoint.
        var name: String

        var pathComponent: String

        /// The full relative path for this endpoint.
        var relativePath: String {
            pathComponent.hasPrefix("/") ? pathComponent : "/v1/\(pathComponent)"
        }

        var iamPathComponent: String

        /// The full relative path for this endpoint when using IAM tokens.
        var relativeIAMPath: String {
            iamPathComponent.hasPrefix("/") ? iamPathComponent : "/v1/\(iamPathComponent)"
        }

        /// The fallback relative path for this endpoint, if any.
        var fallbackRelativePath: String?

        /// Whether this path resolves its base host from the API source provider (the main-API host
        /// list with failover) rather than the static `serverHostURL`.
        var usesAPISources: Bool

        /// Whether this path's `serverHostURL` is a fallback host rather than the main API host.
        ///
        /// Requests to such a path are fallback attempts from the very first try, even though
        /// `HTTPClient`'s own fallback walk never started, so they must not be treated as main-source
        /// requests when picking a timeout or updating the per-host fail-fast memory.
        var isFallbackHostPath: Bool

        /// Additional headers specific to this endpoint.
        var additionalHeaders: HTTPRequest.Headers

        /// Provides endpoint-specific inputs for response signature verification.
        var responseSignatureContextProvider: ResponseSignatureContextProvider

        /// Whether this path corresponds to an IAM request
        var isIAMPath: Bool

        init(name: String,
             serverHostURL: URL? = nil,
             authenticated: Bool = true,
             etagBehavior: ETagBehavior,
             supportsSignatureVerification: Bool,
             needsNonceForSigning: Bool,
             pathComponent: String,
             iamPathComponent: String? = nil,
             fallbackRelativePath: String? = nil,
             fallbackURLs: [URL]? = nil,
             usesAPISources: Bool = true,
             isFallbackHostPath: Bool = false,
             additionalHeaders: HTTPRequest.Headers = [:],
             responseSignatureContextProvider: ResponseSignatureContextProvider? = nil,
             isIAMPath: Bool = false) {

            self.customServerHostURL = serverHostURL
            self.authenticated = authenticated
            self.etagBehavior = etagBehavior
            self.supportsSignatureVerification = supportsSignatureVerification
            self.needsNonceForSigning = needsNonceForSigning
            self.name = name
            self.pathComponent = pathComponent
            self.iamPathComponent = (iamPathComponent ?? pathComponent)
            self.fallbackRelativePath = fallbackRelativePath
            self.usesAPISources = usesAPISources
            self.isFallbackHostPath = isFallbackHostPath
            self.additionalHeaders = additionalHeaders

            let signatureContextProvider = responseSignatureContextProvider ?? DefaultResponseSignatureContextProvider()
            self.responseSignatureContextProvider = signatureContextProvider

            self.isIAMPath = isIAMPath

            if let fallbackURLs {
                self.fallbackUrls = fallbackURLs
            } else if let fallbackRelativePath {
                self.fallbackUrls = Self.fallbackServerHostURLs.compactMap { baseURL in
                    guard let baseURL = baseURL,
                          let fallbackUrl = URL(string: fallbackRelativePath, relativeTo: baseURL) else {
                        let errorMessage = "Invalid fallback URL configuration for path: \(name)"
                        assertionFailure(errorMessage)
                        Logger.error(errorMessage)
                        return nil
                    }
                    return fallbackUrl
                }
            } else {
                self.fallbackUrls = []
            }

            return
        }

        func hash(into hasher: inout Hasher) {
            hasher.combine(name)
            hasher.combine(serverHostURL)
            hasher.combine(relativePath)
        }

        func url(proxyURL: URL? = nil,
                 apiSourceURL: URL? = nil,
                 fallbackUrlIndex: Int? = nil,
                 preferIAMPath: Bool) -> URL? {
            let baseURL: URL
            if let proxyURL {
                // When a Proxy URL is set, we don't support API sources or fallback URLs
                guard fallbackUrlIndex == nil, apiSourceURL == nil else {
                    // This is to safe guard against a potential infinite loop if the caller mistakenly
                    // passes a proxyURL together with an apiSourceURL or a fallbackUrlIndex.
                    return nil
                }
                baseURL = proxyURL
            } else if let fallbackUrlIndex {
                return self.fallbackUrls[safe: fallbackUrlIndex]
            } else if let apiSourceURL {
                baseURL = apiSourceURL
            } else {
                baseURL = self.serverHostURL
            }

            let path = preferIAMPath ? self.relativeIAMPath : self.relativePath
            return URL(string: path, relativeTo: baseURL)
        }

    }

}

extension HTTPRequest.Path {

    // swiftlint:disable:next force_unwrapping
    private static let remoteConfigFallbackHost = URL(string: "https://api-production.8-lives-cat.io")!

    // swiftlint:disable:next force_unwrapping
    private static let apiDiagnosticsHost = URL(string: "https://api-diagnostics.revenuecat.com")!

    // swiftlint:disable:next force_unwrapping
    private static let postFeatureEventsHost = URL(string: "https://api-paywalls.revenuecat.com")!

    // swiftlint:disable:next force_unwrapping
    private static let postAdEventsHost = URL(string: "https://a.revenue.cat")!

    static let logIn = HTTPRequest.Path(name: "log_in",
                                        etagBehavior: .send,
                                        supportsSignatureVerification: true,
                                        needsNonceForSigning: true,
                                        pathComponent: "subscribers/identify")

    static let health = HTTPRequest.Path(name: "post_health",
                                         authenticated: false,
                                         etagBehavior: .ignore,
                                         supportsSignatureVerification: true,
                                         needsNonceForSigning: true,
                                         pathComponent: "health")

    static func getCustomerInfo(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_customer",
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: true,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)",
                         iamPathComponent: "customer")
    }

    static func getOfferings(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_offerings",
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/offerings",
                         iamPathComponent: "customer/offerings",
                         fallbackRelativePath: "/v1/offerings")
    }

    static func getIntroEligibility(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_intro_eligibility",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/intro_eligibility",
                         iamPathComponent: "customer/intro_eligibility")
    }

    static func remoteConfigFallback(domain: String) -> Self {
        HTTPRequest.Path(name: "remote_config_fallback",
                         serverHostURL: remoteConfigFallbackHost,
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: false,
                         pathComponent: "config/\(domain.trimmedAndEscaped)",
                         fallbackRelativePath: nil,
                         usesAPISources: false,
                         isFallbackHostPath: true,
                         responseSignatureContextProvider: FallbackSignatureContextProvider())
    }

    static let postDiagnostics = HTTPRequest.Path(name: "post_diagnostics",
                                                  serverHostURL: apiDiagnosticsHost,
                                                  etagBehavior: .ignore,
                                                  supportsSignatureVerification: false,
                                                  needsNonceForSigning: false,
                                                  pathComponent: "diagnostics",
                                                  usesAPISources: false)

    static let postFeatureEvents = HTTPRequest.Path(name: "post_paywall_events",
                                                    serverHostURL: postFeatureEventsHost,
                                                    etagBehavior: .ignore,
                                                    supportsSignatureVerification: false,
                                                    needsNonceForSigning: false,
                                                    pathComponent: "events",
                                                    usesAPISources: false)

    static let postAdEvents = HTTPRequest.Path(name: "post_ad_events",
                                               serverHostURL: postAdEventsHost,
                                               etagBehavior: .ignore,
                                               supportsSignatureVerification: false,
                                               needsNonceForSigning: false,
                                               pathComponent: "events",
                                               usesAPISources: false)

    static func postAttributionData(appUserID: String) -> Self {
        HTTPRequest.Path(name: "post_attribution",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/attribution",
                         iamPathComponent: "customer/attribution")
    }

    static let postOfferForSigning = HTTPRequest.Path(name: "post_offer_for_signing",
                                                      etagBehavior: .send,
                                                      supportsSignatureVerification: false,
                                                      needsNonceForSigning: false,
                                                      pathComponent: "offers")

    static let postReceiptData = HTTPRequest.Path(name: "post_receipt",
                                                  etagBehavior: .send,
                                                  supportsSignatureVerification: true,
                                                  needsNonceForSigning: true,
                                                  pathComponent: "receipts")

    static func postSubscriberAttributes(appUserID: String) -> Self {
        HTTPRequest.Path(name: "post_attributes",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/attributes",
                         iamPathComponent: "customer/attributes")
    }

    static func postAdServicesToken(appUserID: String) -> Self {
        HTTPRequest.Path(name: "post_adservices_token",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/adservices_attribution",
                         iamPathComponent: "customer/adservices_attribution")
    }

    static func appHealthReport(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_app_health_report",
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: false,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/health_report",
                         iamPathComponent: "customer/health_report")
    }

    static func appHealthReportAvailability(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_app_health_report_availability",
                         authenticated: false,
                         etagBehavior: .ignore,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: true,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/health_report_availability")
    }

    static let getProductEntitlementMapping = HTTPRequest.Path(name: "get_product_entitlement_mapping",
                                                               etagBehavior: .send,
                                                               supportsSignatureVerification: true,
                                                               needsNonceForSigning: false,
                                                               pathComponent: "product_entitlement_mapping",
                                                               fallbackRelativePath: "/v1/product_entitlement_mapping")

    static func getCustomerCenterConfig(appUserID: String) -> Self {
        HTTPRequest.Path(name: "customer_center",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "customercenter/\(appUserID.trimmedAndEscaped)",
                         iamPathComponent: "customer/customercenter")
    }

    static func getVirtualCurrencies(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_virtual_currencies",
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: true,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/virtual_currencies",
                         iamPathComponent: "customer/virtual_currencies")
    }

    static let spendVirtualCurrencies = HTTPRequest.Path(name: "spend_virtual_currencies",
                                                         etagBehavior: .send,
                                                         supportsSignatureVerification: true,
                                                         needsNonceForSigning: true,
                                                         pathComponent: "customer/virtual_currencies/spend")

    static let postRedeemWebPurchase = HTTPRequest.Path(name: "post_redeem_web_purchase",
                                                        etagBehavior: .send,
                                                        supportsSignatureVerification: true,
                                                        needsNonceForSigning: true,
                                                        pathComponent: "subscribers/redeem_purchase")

    static let postExternalPurchaseToken = HTTPRequest.Path(name: "post_external_purchase_token",
                                                            authenticated: true,
                                                            etagBehavior: .ignore,
                                                            supportsSignatureVerification: false,
                                                            needsNonceForSigning: false,
                                                            pathComponent: "external_purchase_tokens")

    static let postCreateTicket = HTTPRequest.Path(name: "post_create_ticket",
                                                   etagBehavior: .send,
                                                   supportsSignatureVerification: false,
                                                   needsNonceForSigning: false,
                                                   pathComponent: "customercenter/support/create-ticket")

    static func isPurchaseAllowedByRestoreBehavior(appUserID: String) -> Self {
        HTTPRequest.Path(name: "post_restore_eligibility",
                         etagBehavior: .send,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: true,
                         pathComponent: "subscribers/\(appUserID.trimmedAndEscaped)/restore/eligibility",
                         iamPathComponent: "customer/restore/eligibility")
    }

    static func rewardVerificationStatus(appUserID: String, clientTransactionID: String, adUnitID: String?) -> Self {
        let txn = clientTransactionID.trimmedAndEscaped
        var path = "subscribers/\(appUserID.trimmedAndEscaped)/ads/reward_verifications/\(txn)"
        if let adUnitID = adUnitID?.notEmptyOrWhitespaces,
           let encodedAdUnitID = adUnitID.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
            path += "?ad_unit_id=\(encodedAdUnitID)"
        }

        return HTTPRequest.Path(name: "get_reward_verification_status",
                                etagBehavior: .send,
                                supportsSignatureVerification: true,
                                needsNonceForSigning: true,
                                pathComponent: path)
    }

    static func remoteConfig(domain: String) -> Self {
        HTTPRequest.Path(name: "remote_config",
                         etagBehavior: .ignore,
                         supportsSignatureVerification: true,
                         needsNonceForSigning: true,
                         pathComponent: "config/\(domain.trimmedAndEscaped)",
                         additionalHeaders: [
                            HTTPClient.RequestHeader.accept.rawValue: HTTPClient.rcContainerFormatAcceptHeaderValue,
                            HTTPClient.RequestHeader.acceptRCElementEncoding.rawValue:
                                HTTPClient.rcContainerFormatElementEncodingHeaderValue
                         ],
                         responseSignatureContextProvider: RemoteConfigSignatureContextProvider())
    }

    // MARK: - Web Billing Paths

    static func getWebOfferingProducts(appUserID: String) -> Self {
        HTTPRequest.Path(name: "get_web_offering_products",
                         etagBehavior: .send,
                         supportsSignatureVerification: false,
                         needsNonceForSigning: false,
                         pathComponent: "/rcbilling/v1/subscribers/\(appUserID.trimmedAndEscaped)/offering_products",
                         iamPathComponent: "/rcbilling/v1/customer/offering_products")
    }

    static func getWebBillingProducts(userId: String, productIds: Set<String>) -> Self {
        let encodedUserId = userId.trimmedAndEscaped
        let encodedProductIds = productIds.map { productId in
            "id=\(productId.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? productId)"
        }.joined(separator: "&")

        let path = "/rcbilling/v1/subscribers/\(encodedUserId)/products?\(encodedProductIds)"
        let iamPath = "/rcbilling/v1/customer/products?\(encodedProductIds)"

        return HTTPRequest.Path(name: "get_web_products",
                                etagBehavior: .send,
                                supportsSignatureVerification: false,
                                needsNonceForSigning: false,
                                pathComponent: path,
                                iamPathComponent: iamPath)
    }

    static let postHostedCheckout = HTTPRequest.Path(name: "post_hosted_checkout",
                                                     etagBehavior: .ignore,
                                                     supportsSignatureVerification: false,
                                                     needsNonceForSigning: false,
                                                     pathComponent: "/rcbilling/v1/hosted-checkout")

    static func getHostedCheckoutStatus(operationSessionID: String, appUserID: String) -> Self {
        let path = "/rcbilling/v1/hosted-checkout/\(operationSessionID.trimmedAndEscaped)" +
        "?app_user_id=\(appUserID.trimmedAndEscapedForQuery)"

        return HTTPRequest.Path(name: "get_hosted_checkout_status",
                                etagBehavior: .ignore,
                                supportsSignatureVerification: false,
                                needsNonceForSigning: false,
                                pathComponent: path)
    }

    // MARK: - IAM Token Paths

    static let tokenLogin = HTTPRequest.Path(name: "token_login",
                                             etagBehavior: .send,
                                             supportsSignatureVerification: false,
                                             needsNonceForSigning: true,
                                             pathComponent: "/auth/login",
                                             isIAMPath: true)

    static let tokenRefresh = HTTPRequest.Path(name: "token_refresh",
                                               etagBehavior: .send,
                                               supportsSignatureVerification: false,
                                               needsNonceForSigning: true,
                                               pathComponent: "/auth/token",
                                               isIAMPath: true)

    static let tokenLogOut = HTTPRequest.Path(name: "token_logout",
                                              etagBehavior: .send,
                                              supportsSignatureVerification: false,
                                              needsNonceForSigning: true,
                                              pathComponent: "/auth/revoke",
                                              isIAMPath: true)
}