damus

Zap.swift (14823B)

---

 //
 //  Zap.swift
 //  damus
 //
 //  Created by William Casarin on 2023-01-15.
 //
 
 import Foundation
 
 struct NoteZapTarget: Equatable, Hashable {
     public let note_id: NoteId
     public let author: Pubkey
 }
 
 enum ZapTarget: Equatable, Hashable {
     case profile(Pubkey)
     case note(NoteZapTarget)
     
     static func note(id: NoteId, author: Pubkey) -> ZapTarget {
         return .note(NoteZapTarget(note_id: id, author: author))
     }
 
     var pubkey: Pubkey {
         switch self {
         case .profile(let pk):
             return pk
         case .note(let note_target):
             return note_target.author
         }
     }
 
     var note_id: NoteId? {
         switch self {
         case .profile:
             return nil
         case .note(let noteZapTarget):
             return noteZapTarget.note_id
         }
     }
 
     var id: Data {
         switch self {
         case .profile(let pubkey):
             return pubkey.id
         case .note(let noteZapTarget):
             return noteZapTarget.note_id.id
         }
     }
 }
 
 struct ZapRequest {
     let ev: NostrEvent
     let marked_hidden: Bool
 
     var id: ZapRequestId {
         ZapRequestId(from_zap_request: self)
     }
 
     var is_in_thread: Bool {
         return !self.ev.content.isEmpty && !marked_hidden
     }
     
     init(ev: NostrEvent) {
         self.ev = ev
         self.marked_hidden = ev.tags.first(where: { t in t.count > 0 && t[0].matches_str("hidden") }) != nil
     }
 }
 
 enum ExtPendingZapStateType {
     case fetching_invoice
     case done
 }
 
 class ExtPendingZapState: Equatable {
     static func == (lhs: ExtPendingZapState, rhs: ExtPendingZapState) -> Bool {
         return lhs.state == rhs.state
     }
     
     var state: ExtPendingZapStateType
     
     init(state: ExtPendingZapStateType) {
         self.state = state
     }
 }
 
 enum PendingZapState: Equatable {
     case nwc(NWCPendingZapState)
     case external(ExtPendingZapState)
 }
 
 
 enum NWCStateType: Equatable {
     case fetching_invoice
     case cancel_fetching_invoice
     case postbox_pending(NostrEvent)
     case confirmed
     case failed
 }
 
 class NWCPendingZapState: Equatable {
     private(set) var state: NWCStateType
     let url: WalletConnectURL
     
     init(state: NWCStateType, url: WalletConnectURL) {
         self.state = state
         self.url = url
     }
     
     //@discardableResult  -- not discardable, the ZapsDataModel may need to send objectWillChange but we don't force it
     func update_state(state: NWCStateType) -> Bool {
         guard state != self.state else {
             return false
         }
         self.state = state
         return true
     }
     
     static func == (lhs: NWCPendingZapState, rhs: NWCPendingZapState) -> Bool {
         return lhs.state == rhs.state && lhs.url == rhs.url
     }
 }
 
 class PendingZap {
     let amount_msat: Int64
     let target: ZapTarget
     let request: ZapRequest
     let type: ZapType
     private(set) var state: PendingZapState
     
     init(amount_msat: Int64, target: ZapTarget, request: MakeZapRequest, type: ZapType, state: PendingZapState) {
         self.amount_msat = amount_msat
         self.target = target
         self.request = request.private_inner_request
         self.type = type
         self.state = state
     }
     
     @discardableResult
     func update_state(model: ZapsDataModel, state: PendingZapState) -> Bool {
         guard self.state != state else {
             return false
         }
         
         self.state = state
         model.objectWillChange.send()
         return true
     }
 }
 
 struct ZapRequestId: Equatable, Hashable {
     let reqid: NoteId
 
     init(from_zap_request: ZapRequest) {
         self.reqid = from_zap_request.ev.id
     }
 
     init(from_zap: Zapping) {
         self.reqid = from_zap.request.ev.id
     }
     
     init(from_makezap: MakeZapRequest) {
         self.reqid = from_makezap.private_inner_request.ev.id
     }
     
     init(from_pending: PendingZap) {
         self.reqid = from_pending.request.ev.id
     }
 }
 
 enum Zapping {
     case zap(Zap)
     case pending(PendingZap)
     
     var is_pending: Bool {
         switch self {
         case .zap:
             return false
         case .pending:
             return true
         }
     }
     
     var is_paid: Bool {
         switch self {
         case .zap:
             // we have a zap so this is proof of payment
             return true
         case .pending(let pzap):
             switch pzap.state {
             case .external:
                 // It could be but we don't know. We have to wait for a zap to know.
                 return false
             case .nwc(let nwc_state):
                 // nwc confirmed that we have a payment, but we might not have zap yet
                 return nwc_state.state == .confirmed
             }
         }
     }
     
     var is_private: Bool {
         switch self {
         case .zap(let zap):
             return zap.private_request != nil
         case .pending(let pzap):
             return pzap.type == .priv
         }
     }
     
     var amount: Int64 {
         switch self {
         case .zap(let zap):
             return zap.invoice.amount
         case .pending(let pzap):
             return pzap.amount_msat
         }
     }
     
     var target: ZapTarget {
         switch self {
         case .zap(let zap):
             return zap.target
         case .pending(let pzap):
             return pzap.target
         }
     }
     
     var request: ZapRequest {
         switch self {
         case .zap(let zap):
             return zap.request
         case .pending(let pzap):
             return pzap.request
         }
     }
     
     var created_at: UInt32 {
         switch self {
         case .zap(let zap):
             return zap.event.created_at
         case .pending(let pzap):
             // pending zaps are created right away
             return pzap.request.ev.created_at
         }
     }
     
     var event: NostrEvent? {
         switch self {
         case .zap(let zap):
             return zap.event
         case .pending:
             // pending zaps don't have a zap event
             return nil
         }
     }
     
     var is_in_thread: Bool {
         switch self {
         case .zap(let zap):
             return zap.request.is_in_thread
         case .pending(let pzap):
             return pzap.request.is_in_thread
         }
     }
     
     var is_anon: Bool {
         switch self {
         case .zap(let zap):
             return zap.is_anon
         case .pending(let pzap):
             return pzap.type == .anon
         }
     }
 }
 
 struct Zap {
     public let event: NostrEvent
     public let invoice: ZapInvoice
     public let zapper: Pubkey /// zap authorizer
     public let target: ZapTarget
     public let raw_request: ZapRequest
     public let is_anon: Bool
     public let private_request: ZapRequest?
     
     var request: ZapRequest {
         return private_request ?? self.raw_request
     }
     
     public static func from_zap_event(zap_ev: NostrEvent, zapper: Pubkey, our_privkey: Privkey?) -> Zap? {
         /// Make sure that we only create a zap event if it is authorized by the profile or event
         guard zapper == zap_ev.pubkey else {
             return nil
         }
         guard let bolt11_str = event_tag(zap_ev, name: "bolt11") else {
             return nil
         }
         guard let bolt11 = decode_bolt11(bolt11_str) else {
             return nil
         }
         /// Any amount invoices are not allowed
         guard let zap_invoice = invoice_to_zap_invoice(bolt11) else {
             return nil
         }
         // Some endpoints don't have this, let's skip the check for now. We're mostly trusting the zapper anyways
         /*
         guard let preimage = event_tag(zap_ev, name: "preimage") else {
             return nil
         }
         guard preimage_matches_invoice(preimage, inv: zap_invoice) else {
             return nil
         }
          */
         guard let desc = get_zap_description(zap_ev, inv_desc: zap_invoice.description) else {
             return nil
         }
 
         guard let zap_req = decode_nostr_event_json(desc) else {
             return nil
         }
         
         guard validate_event(ev: zap_req) == .ok else {
             return nil
         }
         
         guard let target = determine_zap_target(zap_req) else {
             return nil
         }
         
         let private_request = our_privkey.flatMap {
             decrypt_private_zap(our_privkey: $0, zapreq: zap_req, target: target)
         }
         
         let is_anon = private_request == nil && event_is_anonymous(ev: zap_req)
         let preq = private_request.map { pr in ZapRequest(ev: pr) }
         
         return Zap(event: zap_ev, invoice: zap_invoice, zapper: zapper, target: target, raw_request: ZapRequest(ev: zap_req), is_anon: is_anon, private_request: preq)
     }
 }
 
 func decrypt_private_zap(our_privkey: Privkey, zapreq: NostrEvent, target: ZapTarget) -> NostrEvent? {
     guard let anon_tag = zapreq.tags.first(where: { t in
         t.count >= 2 && t[0].matches_str("anon")
     }) else {
         return nil
     }
     
     let enc_note = anon_tag[1].string()
 
     var note = decrypt_note(our_privkey: our_privkey, their_pubkey: zapreq.pubkey, enc_note: enc_note, encoding: .bech32)
     
     // check to see if the private note was from us
     if note == nil {
         guard let our_private_keypair = generate_private_keypair(our_privkey: our_privkey, id: NoteId(target.id), created_at: zapreq.created_at) else {
             return nil
         }
         // use our private keypair and their pubkey to get the shared secret
         note = decrypt_note(our_privkey: our_private_keypair.privkey, their_pubkey: target.pubkey, enc_note: enc_note, encoding: .bech32)
     }
     
     guard let note else {
         return nil
     }
         
     guard note.kind == 9733 else {
         return nil
     }
     
     let zr_etag = zapreq.referenced_ids.first
     let note_etag = note.referenced_ids.first
     
     guard zr_etag == note_etag else {
         return nil
     }
     
     let zr_ptag = zapreq.referenced_pubkeys.first
     let note_ptag = note.referenced_pubkeys.first
     
     guard let zr_ptag, let note_ptag, zr_ptag == note_ptag else {
         return nil
     }
     
     guard validate_event(ev: note) == .ok else {
         return nil
     }
     
     return note
 }
 
 func event_is_anonymous(ev: NostrEvent) -> Bool {
     return ev.known_kind == .zap_request && event_has_tag(ev: ev, tag: "anon")
 }
 
 func event_has_tag(ev: NostrEvent, tag: String) -> Bool {
     for t in ev.tags {
         if t.count >= 1 && t[0].matches_str(tag) {
             return true
         }
     }
     
     return false
 }
 
 /// Fetches the description from either the invoice, or tags, depending on the type of invoice
 func get_zap_description(_ ev: NostrEvent, inv_desc: InvoiceDescription) -> String? {
     switch inv_desc {
     case .description(let string):
         return string
     case .description_hash(let deschash):
         guard let desc = event_tag(ev, name: "description") else {
             return nil
         }
         guard let data = desc.data(using: .utf8) else {
             return nil
         }
         guard sha256(data) == deschash else {
             return nil
         }
         
         return desc
     }
 }
 
 func invoice_to_zap_invoice(_ invoice: Invoice) -> ZapInvoice? {
     guard case .specific(let amt) = invoice.amount else {
         return nil
     }
     
     return ZapInvoice(description: invoice.description, amount: amt, string: invoice.string, expiry: invoice.expiry, payment_hash: invoice.payment_hash, created_at: invoice.created_at)
 }
 
 func determine_zap_target(_ ev: NostrEvent) -> ZapTarget? {
     guard let ptag = ev.referenced_pubkeys.first else {
         return nil
     }
     
     if let etag = ev.referenced_ids.first {
         return ZapTarget.note(id: etag, author: ptag)
     }
     
     return .profile(ptag)
 }
                    
 func decode_bolt11(_ s: String) -> Invoice? {
     var bs = note_blocks()
     bs.num_blocks = 0
     blocks_init(&bs)
     
     let bytes = s.utf8CString
     let _ = bytes.withUnsafeBufferPointer { p in
         damus_parse_content(&bs, p.baseAddress)
     }
     
     guard bs.num_blocks == 1 else {
         blocks_free(&bs)
         return nil
     }
     
     let block = bs.blocks[0]
     
     guard let converted = Block(block) else {
         blocks_free(&bs)
         return nil
     }
     
     guard case .invoice(let invoice) = converted else {
         blocks_free(&bs)
         return nil
     }
     
     blocks_free(&bs)
     return invoice
 }
 
 func event_tag(_ ev: NostrEvent, name: String) -> String? {
     for tag in ev.tags {
         if tag.count >= 2 && tag[0].matches_str(name) {
             return tag[1].string()
         }
     }
     
     return nil
 }
 
 func decode_nostr_event_json(_ desc: String) -> NostrEvent? {
     return NostrEvent.owned_from_json(json: desc)
 }
 
 
 func fetch_zapper_from_lnurl(lnurls: LNUrls, pubkey: Pubkey, lnurl: String) async -> Pubkey? {
     guard let endpoint = await lnurls.lookup_or_fetch(pubkey: pubkey, lnurl: lnurl),
           let allows = endpoint.allowsNostr, allows,
           let key = endpoint.nostrPubkey,
           let pk = hex_decode_pubkey(key)
     else {
         return nil
     }
     
     return pk
 }
 
 func fetch_zap_invoice(_ payreq: LNUrlPayRequest, zapreq: NostrEvent?, msats: Int64, zap_type: ZapType, comment: String?) async -> String? {
     guard var base_url = payreq.callback.flatMap({ URLComponents(string: $0) }) else {
         return nil
     }
     
     let zappable = payreq.allowsNostr ?? false
     
     var query = [URLQueryItem(name: "amount", value: "\(msats)")]
     
     if zappable && zap_type != .non_zap, let json = encode_json(zapreq) {
         print("zapreq json: \(json)")
         query.append(URLQueryItem(name: "nostr", value: json))
     }
    
     // add a lud12 comment as well if we have it
     if zap_type != .priv, let comment, let limit = payreq.commentAllowed, limit != 0 {
         let limited_comment = String(comment.prefix(limit))
         query.append(URLQueryItem(name: "comment", value: limited_comment))
     }
     
     base_url.queryItems = query
     
     guard let url = base_url.url else {
         return nil
     }
     
     print("url \(url)")
     
     var ret: (Data, URLResponse)? = nil
     do {
         ret = try await URLSession.shared.data(from: url)
     } catch {
         print(error.localizedDescription)
         return nil
     }
     
     guard let ret else {
         return nil
     }
     
     let json_str = String(decoding: ret.0, as: UTF8.self)
     guard let result: LNUrlPayResponse = decode_json(json_str) else {
         print("fetch_zap_invoice error: \(json_str)")
         return nil
     }
     
     // make sure it's the correct amount
     guard let bolt11 = decode_bolt11(result.pr),
           .specific(msats) == bolt11.amount
     else {
         return nil
     }
     
     return result.pr
 }