import SwiftUI

@MainActor
class BooruManager: ObservableObject {
    @Published var posts: [BooruPost] = []
    @Published var allTags: [BooruTag] = []
    @Published var isLoading: Bool = false
    @Published var currentPage: Int = 1
    @Published var searchText = ""
    @Published var endOfData: Bool = false
    #if os(macOS)
        @Published var selectedPost: BooruPost?
    #endif
    private var currentTask: Task<Void, Never>?
    let provider: BooruProvider?
    var tags: [String] {
        if searchText.isEmpty {
            return []
        }

        return searchText
            .split(separator: " ")
            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
            .filter { !$0.isEmpty }
    }

    init(_ provider: BooruProvider? = nil) {
        self.provider = provider

        fetchAllTags()
    }

    func fetchPosts(page: Int = 1, limit: Int = 100, tags: [String] = [], replace: Bool = false) async {
        guard !isLoading else { return }
        guard provider != nil else { return }

        currentTask?.cancel()

        currentTask = Task {
            isLoading = true

            defer { isLoading = false }

            if replace {
                self.posts = []
                self.currentPage = 1
            }

            guard let url = urlForPosts(page: self.provider == .safebooru ? page - 1 : page, limit: limit, tags: tags) else {
                return
            }

            do {
                let (data, _) = try await URLSession.shared.data(from: url)

                if Task.isCancelled { return }

                DispatchQueue.main.async {
                    let newPosts = Array(Set(BooruPostXMLParser(data: data).parse())).sorted { $0.id > $1.id }

                    if newPosts.isEmpty {
                        self.endOfData = true
                    } else {
                        self.posts += Array(Set(newPosts))
                    }
                }
            } catch {
                if (error as? URLError)?.code != .cancelled {
                    #if DEBUG
                        print("fetchPosts: \(error)")
                    #endif
                }
            }
        }
    }

    func performSearch() {
        currentTask?.cancel()

        currentTask = Task {
            await fetchPosts(page: 1, tags: tags, replace: true)
        }
    }

    func loadNextPage() {
        guard !isLoading else { return }

        Task {
            await fetchPosts(page: currentPage + 1, tags: tags)

            DispatchQueue.main.async {
                self.currentPage += 1
            }
        }
    }

    func fetchAllTags(limit: Int = 100_000) {
        guard provider != nil else { return }

        Task {
            guard let url = urlForTags(limit: limit) else { return }

            do {
                let (data, _) = try await URLSession.shared.data(from: url)

                if Task.isCancelled { return }

                DispatchQueue.main.async {
                    self.allTags = BooruTagXMLParser(data: data).parse().sorted { $0.count > $1.count }
                }
            } catch {
                if (error as? URLError)?.code != .cancelled {
                    #if DEBUG
                        print("fetchAllTags: \(error)")
                    #endif
                }
            }
        }
    }

    private func urlForPosts(page: Int, limit: Int, tags: [String]) -> URL? {
        let tagString = tags.joined(separator: "+")

        switch provider {
        case .yandere:
            return URL(string: "https://yande.re/post.xml?page=\(page)&limit=\(limit)&tags=\(tagString)")
        case .safebooru:
            return URL(string: "https://safebooru.org/index.php?page=dapi&s=post&q=index&pid=\(page)&limit=\(limit)&tags=\(tagString)")
        default:
            return nil
        }
    }

    private func urlForTags(limit: Int) -> URL? {
        switch provider {
        case .yandere:
            return URL(string: "https://yande.re/tag.xml?limit=\(limit)")
        case .safebooru:
            return URL(string: "https://safebooru.org/index.php?page=dapi&s=tag&q=index&limit=\(limit)")
        default:
            return nil
        }
    }
}