damus/damus/Core/Nostr/Relay.swift

//
//  Relay.swift
//  damus
//
//  Created by William Casarin on 2022-04-11.
//

import Foundation

public struct LegacyKind3RelayRWConfiguration: Codable, Sendable {
    public let read: Bool?
    public let write: Bool?
    
    init(read: Bool, write: Bool) {
        self.read = read
        self.write = write
    }

    static let rw = LegacyKind3RelayRWConfiguration(read: true, write: true)
    
    func toNIP65RWConfiguration() -> NIP65.RelayList.RelayItem.RWConfiguration? {
        switch (self.read, self.write) {
        case (false, true): return .write
        case (true, false): return .read
        case (true, true): return .readWrite
        default: return nil
        }
    }
}

enum RelayVariant {
    case regular
    case ephemeral
    case nwc
}

extension RelayPool {
    /// Describes a relay for use in `RelayPool`
    public struct RelayDescriptor {
        let url: RelayURL
        var info: NIP65.RelayList.RelayItem.RWConfiguration
        let variant: RelayVariant
        
        init(url: RelayURL, info: NIP65.RelayList.RelayItem.RWConfiguration, variant: RelayVariant = .regular) {
            self.url = url
            self.info = info
            self.variant = variant
        }
        
        var ephemeral: Bool {
            switch variant {
            case .regular:
                return false
            case .ephemeral:
                return true
            case .nwc:
                return true
            }
        }
        
        static func nwc(url: RelayURL) -> RelayDescriptor {
            return RelayDescriptor(url: url, info: .readWrite, variant: .nwc)
        }
    }
}

enum RelayFlags: Int {
    case none = 0
    case broken = 1
}

enum RelayAuthenticationError {
    /// Only a public key was provided in keypair to sign challenge.
    ///
    /// A private key is required to sign `auth` challenge.
    case no_private_key
    /// No keypair was provided to sign challenge.
    case no_key
}
enum RelayAuthenticationState: Equatable {
    /// No `auth` request has been made from this relay
    case none
    /// We have received an `auth` challenge, but have not yet replied to the challenge
    case pending
    /// We have received an `auth` challenge and replied with an `auth` event
    case verified
    /// We received an `auth` challenge but failed to reply to the challenge
    case error(RelayAuthenticationError)
}

struct Limitations: Codable {
    let payment_required: Bool?
    
    static var empty: Limitations {
        Limitations(payment_required: nil)
    }
}

struct Admission: Codable {
    let amount: Int64
    let unit: String
}

struct Subscription: Codable {
    let amount: Int64
    let unit: String
    let period: Int
}

struct Publication: Codable {
    let kinds: [Int]
    let amount: Int64
    let unit: String
}

struct Fees: Codable {
    let admission: [Admission]?
    let subscription: [Subscription]?
    let publication: [Publication]?
    
    static var empty: Fees {
        Fees(admission: nil, subscription: nil, publication: nil)
    }
}

struct RelayMetadata: Codable {
    let name: String?
    let description: String?
    let pubkey: Pubkey?
    let contact: String?
    let supported_nips: [Int]?
    let software: String?
    let version: String?
    let limitation: Limitations?
    let payments_url: String?
    let icon: String?
    let fees: Fees?
    
    var is_paid: Bool {
        return limitation?.payment_required ?? false
    }
}

extension RelayPool {
    class Relay: Identifiable {
        var descriptor: RelayDescriptor
        let connection: RelayConnection
        var authentication_state: RelayAuthenticationState
        
        var flags: Int
        
        init(descriptor: RelayDescriptor, connection: RelayConnection) {
            self.flags = 0
            self.descriptor = descriptor
            self.connection = connection
            self.authentication_state = RelayAuthenticationState.none
        }
        
        var is_broken: Bool {
            return (flags & RelayFlags.broken.rawValue) == RelayFlags.broken.rawValue
        }
        
        var id: RelayURL {
            return descriptor.url
        }
    }
}

extension RelayPool {
    enum RelayError: Error {
        case RelayAlreadyExists
    }
}


// MARK: - Extension to bridge NIP-65 relay list structs with app-native objects

extension NIP65.RelayList {
    static func fromLegacyContactList(_ contactList: NdbNote) throws(BridgeError) -> Self {
        guard let relayListInfo = decode_json_relays(contactList.content) else { throw .couldNotDecodeRelayListInfo }
        let relayItems = relayListInfo.map({ url, rwConfiguration in
            return RelayItem(url: url, rwConfiguration: rwConfiguration.toNIP65RWConfiguration() ?? .readWrite)
        })
        return NIP65.RelayList(relays: relayItems)
    }
    
    static func fromLegacyContactList(_ contactList: NdbNote?) throws(BridgeError) -> Self? {
        guard let contactList = contactList else { return nil }
        return try fromLegacyContactList(contactList)
    }
    
    enum BridgeError: Error {
        case couldNotDecodeRelayListInfo
    }
}