org-social-ios/App/ViewModels/GroupsViewModel.swift

import Foundation
import Observation
import OrgSocialKit

@Observable @MainActor
final class GroupsViewModel {

    struct GroupItem: Identifiable, Hashable {
        let name: String
        let slug: String
        var id: String { slug }
    }

    var groups: [GroupItem] = []
    var selectedGroup: GroupItem?
    var posts: [OrgSocialPost] = []

    var isLoadingGroups = false
    var isLoadingPosts = false
    var groupsError: String?
    var postsError: String?

    private var relayURL: URL? {
        guard let raw = UserDefaults.standard.string(forKey: "relayURL"),
              let url = URL(string: raw) else { return nil }
        return url
    }

    var useRelay: Bool {
        UserDefaults.standard.object(forKey: "useRelay") as? Bool ?? true
    }

    func loadGroups() async {
        guard useRelay else {
            groupsError = "Groups require a relay. Enable Use Relay in Settings."
            groups = []
            return
        }
        guard let relay = relayURL else {
            groupsError = "No relay URL configured."
            return
        }
        isLoadingGroups = true
        groupsError = nil
        defer { isLoadingGroups = false }
        do {
            let raw = try await RelayClient().fetchGroupList(from: relay)
            groups = raw.map { GroupItem(name: $0.name, slug: $0.slug) }
        } catch {
            groupsError = error.localizedDescription
        }
    }

    func loadPosts(for group: GroupItem) async {
        guard let relay = relayURL else { return }
        selectedGroup = group
        isLoadingPosts = true
        postsError = nil
        posts = []
        defer { isLoadingPosts = false }
        do {
            let postURLs = try await RelayClient().fetchGroupPostURLs(slug: group.slug, from: relay)
            posts = try await resolvePosts(from: postURLs)
        } catch {
            postsError = error.localizedDescription
        }
    }

    private func resolvePosts(from postURLs: [String]) async throws -> [OrgSocialPost] {
        // Group post URLs by feed URL so we fetch each feed only once
        var byFeed: [String: [String]] = [:]
        for postURL in postURLs {
            guard let hashIdx = postURL.lastIndex(of: "#") else { continue }
            let feedStr = String(postURL[..<hashIdx])
            byFeed[feedStr, default: []].append(postURL)
        }

        var result: [OrgSocialPost] = []
        for (feedStr, urls) in byFeed {
            guard let feedURL = URL(string: feedStr),
                  let content = try? await FeedFetcher().fetch(from: feedURL) else { continue }
            var profile = OrgSocialParser().parse(content)
            profile.feedURL = feedURL
            let timestamps = Set(urls.compactMap { $0.components(separatedBy: "#").last })
            for post in profile.posts where timestamps.contains(post.timestamp) {
                var enriched = post
                enriched.authorNick = profile.nick
                enriched.authorURL = feedURL
                enriched.authorAvatar = profile.avatar
                enriched.feedURL = feedURL
                result.append(enriched)
            }
        }
        return result.sorted { $0.date > $1.date }
    }
}