import SwiftUI

struct PostList: View {

    @EnvironmentObject
    private var content: Content

    @Environment(\.language)
    private var language: ContentLanguage

    @State
    private var selected: Post? = nil

    @State
    private var showNewPostView = false

    @State
    private var newPostId = ""

    @State
    private var newPostIdIsValid = false

    private let allowedCharactersInPostId = CharacterSet.alphanumerics.union(CharacterSet(charactersIn: "-")).inverted

    private var cleanPostId: String {
        newPostId.trimmingCharacters(in: .whitespacesAndNewlines)
    }

    var body: some View {
        NavigationSplitView {
            List(content.posts, selection: $selected) { post in
                Text(post.localized(in: language).title)
                    .tag(post)
            }
            .toolbar {
                ToolbarItem(placement: .primaryAction) {
                    Button(action: { showNewPostView = true }) {
                        Label("New post", systemSymbol: .plus)
                    }
                }
            }
            .navigationSplitViewColumnWidth(min: 250, ideal: 250, max: 250)
        } content: {
            if let selected {
                PostContentView(post: selected)
                    .layoutPriority(1)
            } else {
                HStack {
                    Spacer()
                    Text("Select a post to show the content")
                        .font(.largeTitle)
                        .foregroundColor(.secondary)
                    Spacer()
                }.layoutPriority(1)
            }
        } detail: {
            if let selected {
                PostDetailView(post: selected)
                    .frame(minWidth: 280)
            } else {
                Text("No post selected")
                    .frame(minWidth: 280)
            }
        }
        .sheet(isPresented: $showNewPostView,
               onDismiss: addNewPost) {
            TextEntrySheet(
                title: "Enter the id for the new post",
                text: $newPostId,
                isValid: $newPostIdIsValid)
        }
        .onChange(of: newPostId) { _, newValue in
            newPostIdIsValid = isValid(id: newValue)
        }
        .onAppear {
            if selected == nil {
                selected = content.posts.first
            }
        }
    }

    private func isValid(id: String) -> Bool {
        let id = cleanPostId
        guard id != "" else {
            return false
        }

        guard !content.posts.contains(where: { $0.id == id }) else {
            return false
        }
        // Only allow alphanumeric characters and hyphens
        return id.rangeOfCharacter(from: allowedCharactersInPostId) == nil
    }

    private func addNewPost() {
        let id = cleanPostId
        guard isValid(id: id) else {
            return
        }

        let post = Post(
            id: id,
            isDraft: true,
            createdDate: .now,
            startDate: .now,
            endDate: nil,
            tags: [],
            german: .init(title: "Titel", content: "Text"),
            english: .init(title: "Title", content: "Text"))
        content.posts.insert(post, at: 0)
        selected = post
    }
}

#Preview {
    PostList()
        .environmentObject(Content())
}