//
//  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

protocol HTTPRequestPath {

    /// The base URL for requests to this path.
    static var serverHostURL: URL { get }

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

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

    /// Whether requests to this path can be cached using `ETagManager`.
    var shouldSendEtag: Bool { get }

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

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

    /// The name of the endpoint.
    var name: String { get }

    /// The full relative path for this endpoint.
    var relativePath: String { get }

    /// The full relative path for this endpoint when using IAM tokens.
    var relativeIAMPath: String { get }

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

    /// 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 { get }

    /// 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 { get }

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

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

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

/// 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 HTTPRequestPath {

    var fallbackUrls: [URL] {
        return []
    }

    var supportsFallbackURLs: Bool {
        !fallbackUrls.isEmpty
    }

    var fallbackRelativePath: String? {
        return nil
    }

    var relativeIAMPath: String {
        return self.relativePath
    }

    var usesAPISources: Bool {
        return false
    }

    var isFallbackHostPath: Bool {
        return false
    }

    var additionalHeaders: HTTPRequest.Headers {
        return [:]
    }

    var responseSignatureContextProvider: ResponseSignatureContextProvider {
        return DefaultResponseSignatureContextProvider()
    }

    var isIAMPath: Bool {
        return false
    }

    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)
    }
}

// MARK: - Main paths

extension HTTPRequest {

    enum Path: Hashable {

        case getCustomerInfo(appUserID: String)
        case getOfferings(appUserID: String)
        case getIntroEligibility(appUserID: String)
        case logIn
        case postAttributionData(appUserID: String)
        case postOfferForSigning
        case postReceiptData
        case postSubscriberAttributes(appUserID: String)
        case postAdServicesToken(appUserID: String)
        case health
        case appHealthReport(appUserID: String)
        case appHealthReportAvailability(appUserID: String)
        case getProductEntitlementMapping
        case getCustomerCenterConfig(appUserID: String)
        case getVirtualCurrencies(appUserID: String)
        case spendVirtualCurrencies
        case postRedeemWebPurchase
        case postExternalPurchaseToken
        case postCreateTicket
        case isPurchaseAllowedByRestoreBehavior(appUserID: String)
        case rewardVerificationStatus(appUserID: String, clientTransactionID: String, adUnitID: String?)
        case remoteConfig(domain: String)

        case tokenLogin
        case tokenRefresh
        case tokenLogOut
    }

    enum FallbackPath: Hashable {

        case remoteConfig(domain: String)

    }

    enum FeatureEventsPath: Hashable {

        case postEvents

    }

    enum DiagnosticsPath: Hashable {

        case postDiagnostics

    }

    enum WebBillingPath: Hashable {

        case getWebOfferingProducts(appUserID: String)
        case getWebBillingProducts(userId: String, productIds: Set<String>)
        case postHostedCheckout

    }

    enum AdPath: Hashable {

        case postEvents

    }

}

extension HTTPRequest.Path: HTTPRequestPath {

    static var serverHostURL: URL {
        SystemInfo.apiBaseURL
    }

    var usesAPISources: Bool {
        return true
    }

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

    var fallbackRelativePath: String? {
        switch self {
        case .getOfferings:
            return "/v1/offerings"
        case .getProductEntitlementMapping:
            return "/v1/product_entitlement_mapping"
        default:
            return nil
        }
    }

    var fallbackUrls: [URL] {
        guard let fallbackRelativePath = self.fallbackRelativePath else {
            return []
        }

        return 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: \(self.name)"
                assertionFailure(errorMessage)
                Logger.error(errorMessage)
                return nil
            }
            return fallbackUrl
        }
    }

    var authenticated: Bool {
        switch self {
        case .getCustomerInfo,
                .getOfferings,
                .getIntroEligibility,
                .logIn,
                .postAttributionData,
                .postOfferForSigning,
                .postReceiptData,
                .postSubscriberAttributes,
                .postAdServicesToken,
                .postRedeemWebPurchase,
                .postExternalPurchaseToken,
                .getProductEntitlementMapping,
                .getCustomerCenterConfig,
                .getVirtualCurrencies,
                .spendVirtualCurrencies,
                .appHealthReport,
                .postCreateTicket,
                .isPurchaseAllowedByRestoreBehavior,
                .rewardVerificationStatus,
                .remoteConfig,
                .tokenLogin,
                .tokenRefresh,
                .tokenLogOut:
            return true

        case .health,
             .appHealthReportAvailability:
            return false
        }
    }

    var shouldSendEtag: Bool {
        switch self {
        case .getCustomerInfo,
                .getOfferings,
                .getIntroEligibility,
                .logIn,
                .postAttributionData,
                .postOfferForSigning,
                .postReceiptData,
                .postSubscriberAttributes,
                .postAdServicesToken,
                .postRedeemWebPurchase,
                .getProductEntitlementMapping,
                .getCustomerCenterConfig,
                .getVirtualCurrencies,
                .spendVirtualCurrencies,
                .appHealthReport,
                .postCreateTicket,
                .isPurchaseAllowedByRestoreBehavior,
                .rewardVerificationStatus,
                .tokenLogin,
                .tokenRefresh,
                .tokenLogOut:
            return true
        case .remoteConfig,
             .health,
             .appHealthReportAvailability,
             .postExternalPurchaseToken:
            return false
        }
    }

    var supportsSignatureVerification: Bool {
        switch self {
        case .getCustomerInfo,
                .logIn,
                .postReceiptData,
                .postRedeemWebPurchase,
                .health,
                .getOfferings,
                .getProductEntitlementMapping,
                .getVirtualCurrencies,
                .spendVirtualCurrencies,
                .appHealthReport,
                .appHealthReportAvailability,
                .isPurchaseAllowedByRestoreBehavior,
                .remoteConfig,
                .rewardVerificationStatus:
            return true
        case .getIntroEligibility,
                .postSubscriberAttributes,
                .postAttributionData,
                .postAdServicesToken,
                .postOfferForSigning,
                .postExternalPurchaseToken,
                .getCustomerCenterConfig,
                .postCreateTicket,
                .tokenLogin,
                .tokenRefresh,
                .tokenLogOut:
            return false
        }
    }

    var needsNonceForSigning: Bool {
        switch self {
        case .getCustomerInfo,
                .logIn,
                .postReceiptData,
                .postRedeemWebPurchase,
                .getVirtualCurrencies,
                .spendVirtualCurrencies,
                .health,
                .appHealthReportAvailability,
                .isPurchaseAllowedByRestoreBehavior,
                .remoteConfig,
                .rewardVerificationStatus,
                .tokenLogin,
                .tokenRefresh,
                .tokenLogOut:
            return true
        case .getOfferings,
                .getIntroEligibility,
                .postSubscriberAttributes,
                .postAttributionData,
                .postAdServicesToken,
                .postOfferForSigning,
                .postExternalPurchaseToken,
                .getProductEntitlementMapping,
                .getCustomerCenterConfig,
                .appHealthReport,
                .postCreateTicket:
            return false
        }
    }

    var responseSignatureContextProvider: ResponseSignatureContextProvider {
        switch self {
        case .remoteConfig:
            return RemoteConfigSignatureContextProvider()
        default:
            return DefaultResponseSignatureContextProvider()
        }
    }

    var relativePath: String {
        let component = self.pathComponent
        if component.hasPrefix("/") { return component }
        return "/v1/\(component)"
    }

    var relativeIAMPath: String {
        let component = self.iamPathComponent
        if component.hasPrefix("/") { return component }
        return "/v1/\(component)"
    }

    var pathComponent: String {
        switch self {
        case let .getCustomerInfo(appUserID):
            return "subscribers/\(Self.escape(appUserID))"

        case let .getOfferings(appUserID):
            return "subscribers/\(Self.escape(appUserID))/offerings"

        case let .getIntroEligibility(appUserID):
            return "subscribers/\(Self.escape(appUserID))/intro_eligibility"

        case let .appHealthReport(appUserID):
            return "subscribers/\(Self.escape(appUserID))/health_report"

        case let .appHealthReportAvailability(appUserID):
            return "subscribers/\(Self.escape(appUserID))/health_report_availability"

        case .logIn:
            return "subscribers/identify"

        case let .postAttributionData(appUserID):
            return "subscribers/\(Self.escape(appUserID))/attribution"

        case let .postAdServicesToken(appUserID):
            return "subscribers/\(Self.escape(appUserID))/adservices_attribution"

        case .postOfferForSigning:
            return "offers"

        case .postReceiptData:
            return "receipts"

        case let .postSubscriberAttributes(appUserID):
            return "subscribers/\(Self.escape(appUserID))/attributes"

        case .health:
            return "health"

        case .getProductEntitlementMapping:
            return "product_entitlement_mapping"

        case let .getCustomerCenterConfig(appUserID):
            return "customercenter/\(Self.escape(appUserID))"

        case .postRedeemWebPurchase:
            return "subscribers/redeem_purchase"

        case .postExternalPurchaseToken:
            return "external_purchase_tokens"

        case let .getVirtualCurrencies(appUserID):
            return "subscribers/\(Self.escape(appUserID))/virtual_currencies"

        case .spendVirtualCurrencies:
            return "customer/virtual_currencies/spend"

        case .postCreateTicket:
            return "customercenter/support/create-ticket"
        case let .isPurchaseAllowedByRestoreBehavior(appUserID):
            return "subscribers/\(Self.escape(appUserID))/restore/eligibility"

        case let .rewardVerificationStatus(appUserID, clientTransactionID, adUnitID):
            let path = "subscribers/\(Self.escape(appUserID))/ads/reward_verifications/"
                + Self.escape(clientTransactionID)
            guard let adUnitID = adUnitID?.notEmptyOrWhitespaces,
                  let encodedAdUnitID = adUnitID.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)
            else {
                return path
            }
            return "\(path)?ad_unit_id=\(encodedAdUnitID)"

        case let .remoteConfig(domain):
            return "config/\(Self.escape(domain))"

        case .tokenLogin:
            return "/auth/login"

        case .tokenRefresh:
            return "/auth/token"

        case .tokenLogOut:
            return "/auth/revoke"
        }
    }

    var iamPathComponent: String {
        // NOTE: cases below that "return self.pathComponent" are indicating
        // that the corresponding server paths have not yet been migrated to
        // support access token authorization
        switch self {
        case .getCustomerInfo:
            return "customer"
        case .getOfferings:
            return "customer/offerings"
        case .getIntroEligibility:
            return "customer/intro_eligibility"
        case .logIn:
            assertionFailure("The .login endpoint is not allowed when IAM is enabled")
            Logger.error("The .login endpoint is not allowed when IAM is enabled")
            return self.pathComponent
        case .postAttributionData:
            return "customer/attribution"
        case .postOfferForSigning:
            return "offers"
        case .postReceiptData:
            return "receipts"
        case .postSubscriberAttributes:
            return "customer/attributes"
        case .postAdServicesToken:
            return "customer/adservices_attribution"
        case .health:
            return self.pathComponent
        case .appHealthReport:
            return "customer/health_report"
        case .appHealthReportAvailability:
            return self.pathComponent
        case .getProductEntitlementMapping:
            return "product_entitlement_mapping"
        case .getCustomerCenterConfig:
            return "customer/customercenter"
        case .getVirtualCurrencies:
            return "customer/virtual_currencies"
        case .spendVirtualCurrencies:
            return "customer/virtual_currencies/spend"
        case .postRedeemWebPurchase:
            return self.pathComponent
        case .postExternalPurchaseToken:
            return self.pathComponent
        case .postCreateTicket:
            return self.pathComponent
        case .isPurchaseAllowedByRestoreBehavior:
            return "customer/restore/eligibility"
        case .rewardVerificationStatus:
            return self.pathComponent
        case .remoteConfig:
            return self.pathComponent
        case .tokenLogin:
            return "/auth/login"
        case .tokenRefresh:
            return "/auth/token"
        case .tokenLogOut:
            return "/auth/revoke"
        }
    }

    var name: String {
        switch self {
        case .getCustomerInfo:
            return "get_customer"

        case .getOfferings:
            return "get_offerings"

        case .getIntroEligibility:
            return "get_intro_eligibility"

        case .logIn:
            return "log_in"

        case .postAttributionData:
            return "post_attribution"

        case .postAdServicesToken:
            return "post_adservices_token"

        case .postOfferForSigning:
            return "post_offer_for_signing"

        case .postReceiptData:
            return "post_receipt"

        case .postSubscriberAttributes:
            return "post_attributes"

        case .health:
            return "post_health"

        case .getProductEntitlementMapping:
            return "get_product_entitlement_mapping"

        case .getCustomerCenterConfig:
            return "customer_center"

        case .postRedeemWebPurchase:
            return "post_redeem_web_purchase"

        case .postExternalPurchaseToken:
            return "post_external_purchase_token"

        case .appHealthReport:
            return "get_app_health_report"

        case .getVirtualCurrencies:
            return "get_virtual_currencies"

        case .spendVirtualCurrencies:
            return "spend_virtual_currencies"

        case .appHealthReportAvailability:
            return "get_app_health_report_availability"

        case .postCreateTicket:
            return "post_create_ticket"
        case .isPurchaseAllowedByRestoreBehavior:
            return "post_restore_eligibility"

        case .rewardVerificationStatus:
            return "get_reward_verification_status"

        case .remoteConfig:
            return "remote_config"

        case .tokenLogin:
            return "token_login"

        case .tokenRefresh:
            return "token_refresh"

        case .tokenLogOut:
            return "token_logout"
        }
    }

    var additionalHeaders: HTTPRequest.Headers {
        switch self {
        case .remoteConfig:
            return [
                HTTPClient.RequestHeader.accept.rawValue: HTTPClient.rcContainerFormatAcceptHeaderValue,
                HTTPClient.RequestHeader.acceptRCElementEncoding.rawValue:
                    HTTPClient.rcContainerFormatElementEncodingHeaderValue
            ]
        default:
            return [:]
        }
    }

    var isIAMPath: Bool {
        switch self {
        case .tokenLogin, .tokenRefresh, .tokenLogOut:
            return true
        default: return false
        }
    }

    private static func escape(_ appUserID: String) -> String {
        return appUserID.trimmedAndEscaped
    }
}

extension HTTPRequest.FallbackPath: HTTPRequestPath {

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

    var isFallbackHostPath: Bool {
        switch self {
        case .remoteConfig:
            return true
        }
    }

    var authenticated: Bool {
        switch self {
        case .remoteConfig:
            return true
        }
    }

    var shouldSendEtag: Bool {
        switch self {
        case .remoteConfig:
            return true
        }
    }

    var supportsSignatureVerification: Bool {
        switch self {
        case .remoteConfig:
            return true
        }
    }

    var needsNonceForSigning: Bool {
        switch self {
        case .remoteConfig:
            return false
        }
    }

    var responseSignatureContextProvider: ResponseSignatureContextProvider {
        switch self {
        case .remoteConfig:
            return FallbackSignatureContextProvider()
        }
    }

    var relativePath: String {
        switch self {
        case let .remoteConfig(domain):
            return "/v1/config/\(domain.trimmedAndEscaped)"
        }
    }

    var name: String {
        switch self {
        case .remoteConfig:
            return "remote_config_fallback"
        }
    }

    var additionalHeaders: HTTPRequest.Headers {
        switch self {
        case .remoteConfig:
            return [:]
        }
    }

}