damus/damus/Views/PostView.swift

//
//  Post.swift
//  damus
//
//  Created by William Casarin on 2022-04-03.
//

import SwiftUI

enum NostrPostResult {
    case post(NostrPost)
    case cancel
}

let POST_PLACEHOLDER = NSLocalizedString("Type your post here...", comment: "Text box prompt to ask user to type their post.")

struct PostView: View {
    @State var post: String = ""
    @FocusState var focus: Bool
    
    let replying_to: NostrEvent?
    let references: [ReferencedId]
    let damus_state: DamusState

    @Environment(\.presentationMode) var presentationMode

    enum FocusField: Hashable {
      case post
    }

    func cancel() {
        NotificationCenter.default.post(name: .post, object: NostrPostResult.cancel)
        dismiss()
    }

    func dismiss() {
        self.presentationMode.wrappedValue.dismiss()
    }

    func send_post() {
        var kind: NostrKind = .text
        if replying_to?.known_kind == .chat {
            kind = .chat
        }
        let content = self.post.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
        let new_post = NostrPost(content: content, references: references, kind: kind)

        NotificationCenter.default.post(name: .post, object: NostrPostResult.post(new_post))
        dismiss()
    }

    var is_post_empty: Bool {
        return post.allSatisfy { $0.isWhitespace }
    }

    var body: some View {
        VStack {
            HStack {
                Button(NSLocalizedString("Cancel", comment: "Button to cancel out of posting a note.")) {
                    self.cancel()
                }
                .foregroundColor(.primary)

                Spacer()

                if !is_post_empty {
                    Button(NSLocalizedString("Post", comment: "Button to post a note.")) {
                        self.send_post()
                    }
                }
            }
            .padding([.top, .bottom], 4)

            ZStack(alignment: .topLeading) {
                TextEditor(text: $post)
                    .focused($focus)
                    .textInputAutocapitalization(.sentences)

                if post.isEmpty {
                    Text(POST_PLACEHOLDER)
                        .padding(.top, 8)
                        .padding(.leading, 4)
                        .foregroundColor(Color(uiColor: .placeholderText))
                        .allowsHitTesting(false)
                }
            }

            // This if-block observes @ for tagging
            if let searching = get_searching_string(post) {
                VStack {
                    Spacer()
                    UserSearch(damus_state: damus_state, search: searching, post: $post)
                }.zIndex(1)
            }
        }
        .onAppear() {
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                self.focus = true
            }
        }
        .padding()
    }
}

func get_searching_string(_ post: String) -> String? {
    guard let last_word = post.components(separatedBy: .whitespacesAndNewlines).last else {
        return nil
    }
    
    guard last_word.count >= 2 else {
        return nil
    }
    
    guard last_word.first! == "@" else {
        return nil
    }
    
    // don't include @npub... strings
    guard last_word.count != 64 else {
        return nil
    }
    
    return String(last_word.dropFirst())
}