// swiftlint:disable file_length

import SwiftUI
import WaterfallGrid

struct PostGridView: View {  // swiftlint:disable:this type_body_length
  @EnvironmentObject var settings: SettingsManager
  @EnvironmentObject var manager: BooruManager
  @State private var isSearchHistoryPresented = false
  @Binding var selectedTab: Int
  @State private var isSearchablePresented = false
  @State private var cachedSuggestions: [Either<BooruTag, BooruSearchQuery>] = []
  @State private var suppressNextSearchSubmit = false
  @State private var searchTask: Task<Void, Never>?
  @State private var suggestions: [BooruTag] = []
  @State private var cachedColumnsData: ColumnsDataCache?
  let initialTag: String?
  @Binding var navigationPath: NavigationPath
  @State private var localPosts: [BooruPost] = []
  @State private var localIsLoading = false
  @State private var localCurrentPage = 1
  @State private var localSearchText = ""
  @State private var localEndOfData = false
  @State private var localError: Error?

  init(
    selectedTab: Binding<Int>, navigationPath: Binding<NavigationPath>, initialTag: String? = nil
  ) {
    self._selectedTab = selectedTab
    self.initialTag = initialTag
    self._navigationPath = navigationPath
  }

  @Environment(\.isSearching)
  private var isSearching

  private var activePosts: [BooruPost] {
    let posts = initialTag != nil ? localPosts : manager.posts

    return posts.filter { settings.displayRatings.contains($0.rating) }
  }

  private var isLoading: Bool {
    initialTag != nil ? localIsLoading : manager.isLoading
  }

  private var searchText: Binding<String> {
    if initialTag != nil {
      return Binding(
        get: { localSearchText },
        set: { localSearchText = $0 }
      )
    }

    return Binding(
      get: { manager.searchText },
      set: { manager.searchText = $0 }
    )
  }

  @ViewBuilder private var gridContent: some View {
    if let error = (initialTag != nil ? localError : manager.error) {
      ContentUnavailableView(
        "Provider Error",
        systemImage: "exclamationmark.triangle.fill",
        description: Text(error.localizedDescription)
      )
    }

    if activePosts.isEmpty, isLoading {
      placeholderGrid
    } else {
      gridView(columnCount: settings.thumbnailGridColumns)
    }
  }

  @ViewBuilder private var placeholderGrid: some View {
    let gridItems = Array(
      repeating: GridItem(.flexible()),
      count: settings.thumbnailGridColumns
    )

    LazyVGrid(columns: gridItems) {
      ForEach(0..<(50 / settings.thumbnailGridColumns), id: \.self) { _ in
        PostGridThumbnailPlaceholderView()
      }
    }
    #if os(macOS)
      .padding(8)
    #else
      .padding(.horizontal)
    #endif
    .transition(.opacity)
  }

  @ViewBuilder
  private func gridView(columnCount: Int) -> some View {
    if settings.alternativeThumbnailGrid {
      let columnsData = getColumnsData(columnCount: columnCount)

      HStack(alignment: .top) {
        ForEach(0..<columnCount, id: \.self) { columnIndex in
          LazyVStack {
            ForEach(columnsData[columnIndex], id: \.id) { post in
              waterfallGridContent(post: post)
                .id(post.id)
            }
          }
          .transaction { $0.animation = nil }
        }
      }
      #if os(macOS)
        .padding(8)
      #else
        .padding(.horizontal)
      #endif
      .transition(.opacity)
    } else {
      WaterfallGrid(activePosts, id: \.id) { post in
        waterfallGridContent(post: post)
          .id(post.id)
      }
      .gridStyle(columns: columnCount)
      .transaction { $0.animation = nil }
      #if os(macOS)
        .padding(8)
      #else
        .padding(.horizontal)
      #endif
      .transition(.opacity)
    }
  }

  private func getColumnsData(columnCount: Int) -> [[BooruPost]] {
    if let cached = cachedColumnsData,
      cached
        == ColumnsDataCache(
          data: cached.data,
          columnCount: columnCount,
          posts: activePosts
        )
    {
      return cached.data
    }

    let computedData = (0..<columnCount).map { columnIndex in
      activePosts.enumerated().compactMap { index, post in
        index % columnCount == columnIndex ? post : nil
      }
    }

    cachedColumnsData = ColumnsDataCache(
      data: computedData,
      columnCount: columnCount,
      posts: activePosts
    )

    return computedData
  }

  var body: some View {
    ScrollView {
      gridContent
        .transition(.opacity)
    }
    #if os(iOS)
      .searchable(
        text: searchText,
        isPresented: $isSearchablePresented,
        placement: .navigationBarDrawer(displayMode: .automatic),
        prompt: "Tags"
      )
    #else
      .searchable(
        text: searchText,
        isPresented: $isSearchablePresented,
        prompt: "Tags"
      )
    #endif
    .searchSuggestions {
      if settings.searchSuggestionsMode != .disabled && isSearchablePresented {
        SearchSuggestionsView(
          items: searchSuggestionsItems(),
          searchText: searchText,
          suppressNextSearchSubmit: $suppressNextSearchSubmit
        )
      }
    }
    .onChange(of: searchText.wrappedValue) { _, newValue in
      if settings.searchSuggestionsMode == .tags {
        searchTask?.cancel()

        searchTask = Task {
          try? await Task.sleep(nanoseconds: 300_000_000)

          guard !Task.isCancelled else { return }

          let searchTag = newValue.split(separator: " ").last.map(String.init) ?? ""

          if !searchTag.isEmpty {
            suggestions = await manager.searchTags(name: searchTag)
          } else {
            suggestions = []
          }
        }
      }
    }
    .onSubmit(of: .search) {
      if suppressNextSearchSubmit {
        suppressNextSearchSubmit = false
        return
      }

      Task(priority: .userInitiated) {
        if initialTag != nil {
          await performLocalSearch()
        } else {
          await manager.performSearch(settings: settings)
        }
      }
    }
    .navigationDestination(for: PostWithContext.self) { context in
      PostDetailsView(post: context.post, navigationPath: $navigationPath, posts: context.posts)
    }
    .onChange(of: isSearchablePresented) { _, isPresented in
      if !isPresented, searchText.wrappedValue.isEmpty, !manager.isNavigatingHistory {
        Task(priority: .userInitiated) {
          if initialTag != nil {
            await performLocalSearch()
          } else {
            await manager.performSearch()
          }
        }
      }
    }
    .onAppear {
      if let initialTag {
        localSearchText = initialTag

        Task(priority: .userInitiated) {
          await performLocalSearch()
        }
      }
    }
    .toolbar {
      #if os(macOS)
        ToolbarItem {
          Button(action: {
            Task {
              if initialTag != nil {
                await fetchLocalPosts(
                  page: 1,
                  tags: localSearchText.components(separatedBy: .whitespaces).filter { component in
                    !component.isEmpty
                  },
                  replace: true
                )
              } else {
                await manager.fetchPosts(page: 1, tags: manager.tags, replace: true)
              }
            }
          }) {
            Label("Refresh", systemImage: "arrow.clockwise")
          }
          .disabled(isLoading)
        }
      #endif

      #if !os(macOS)
        PlatformSpecificToolbarItem {
          Button(action: { Task { isSearchHistoryPresented.toggle() } }) {
            Label("Search History", systemImage: "clock.arrow.circlepath")
          }
        }

        if #available(iOS 26, *), isLoading || manager.isNavigatingHistory {
          ToolbarItem(placement: .status) { ProgressView() }
        }
      #endif

      PlatformSpecificToolbarItem {
        PostGridBookmarkButtonView(
          tags: initialTag != nil
            ? localSearchText.components(separatedBy: .whitespaces).filter { component in
              !component.isEmpty
            }
            : manager.tags,
          provider: manager.provider
        )
        .disabled(searchText.wrappedValue.isEmpty)
      }

      PlatformSpecificToolbarItem {
        Button(
          action: {
            Task(priority: .userInitiated) {
              if initialTag != nil {
                await loadLocalNextPage()
              } else {
                await manager.loadNextPage()
              }
            }
          }
        ) {
          Label(
            "Manually Load Next Page",
            systemImage: "arrow.down.to.line"
          )
        }
        .disabled(isLoading)
      }

      #if !os(macOS)
        if #unavailable(iOS 26), isLoading || manager.isNavigatingHistory {
          ToolbarItem(placement: .topBarTrailing) { ProgressView() }
        }
      #endif

      if initialTag == nil {
        PlatformSpecificToolbarItem(placement: .navigation) {
          Menu {
            ForEach(
              Array(manager.searchHistory.enumerated().filter { $0.offset < manager.historyIndex }),
              id: \.offset
            ) { offset, query in
              Button(action: {
                manager.historyIndex = offset
              }) {
                Text(query.tags.isEmpty ? "No Tags" : query.tags.joined(separator: " "))
              }
            }
          } label: {
            Label("Previous Search", systemImage: "chevron.left")
          } primaryAction: {
            withAnimation {
              manager.goBackInHistory()
            }
          }
          .disabled(!manager.canGoBackInHistory)
          .id("previousSearchMenu")
        }

        PlatformSpecificToolbarItem(placement: .navigation) {
          Menu {
            ForEach(
              Array(manager.searchHistory.enumerated().filter { $0.offset > manager.historyIndex }),
              id: \.offset
            ) { offset, query in
              Button(action: {
                manager.historyIndex = offset
              }) {
                Text(query.tags.isEmpty ? "No Tags" : query.tags.joined(separator: " "))
              }
            }
          } label: {
            Label("Next Search", systemImage: "chevron.right")
          } primaryAction: {
            withAnimation {
              manager.goForwardInHistory()
            }
          }
          .disabled(!manager.canGoForwardInHistory)
          .id("nextSearchMenu")
        }
      }
    }
    .navigationTitle(initialTag != nil ? initialTag! : "Posts")
    .refreshable {
      if initialTag != nil {
        await fetchLocalPosts(
          page: 1,
          tags: localSearchText.components(separatedBy: .whitespaces).filter { component in
            !component.isEmpty
          },
          replace: true
        )
      } else {
        manager.clearCachedPages()
        Task(priority: .userInitiated) {
          await manager.fetchPosts(page: 1, tags: manager.tags, replace: true)
        }
      }
    }
    .sheet(isPresented: $isSearchHistoryPresented) {
      PostGridSearchHistoryView(
        selectedTab: $selectedTab,
        isPresented: $isSearchHistoryPresented
      )
    }
    #if os(iOS)
      .gesture(
        DragGesture()
          .onEnded { value in
            if initialTag == nil {
              if value.startLocation.x < 50 && value.translation.width > 100 {
                withAnimation {
                  manager.goBackInHistory()
                }

                debugPrint("ContentView: Swipe left, \(manager.searchHistory)")
              }

              if value.startLocation.x > (UIScreen.main.bounds.width - 50)
                && value.translation.width < -100
              {
                withAnimation {
                  manager.goForwardInHistory()
                }

                debugPrint("ContentView: Swipe right, \(manager.searchHistory)")
              }
            }
          }
      )
    #endif
  }

  private func waterfallGridContent(post: BooruPost) -> some View {
    NavigationLink(
      value: PostWithContext(post: post, posts: initialTag != nil ? localPosts : nil)
    ) {
      PostGridThumbnailView(
        post: post,
        posts: activePosts,
        isNestedView: initialTag != nil,
        endOfData: initialTag != nil ? localEndOfData : manager.endOfData,
        onLoadNextPage: {
          if initialTag != nil {
            await loadLocalNextPage()
          } else {
            await manager.loadNextPage()
          }
        },
        selectedPost: initialTag != nil ? nil : manager.selectedPost
      )
    }
    .buttonStyle(PlainButtonStyle())
  }

  private func searchSuggestionsItems() -> [Either<BooruTag, BooruSearchQuery>] {
    switch settings.searchSuggestionsMode {
    case .tags:
      return suggestions.map { .left($0) }

    case .history:
      return settings.searchHistory.map { .right($0) }

    case .disabled:
      return []
    }
  }

  // MARK: - Local Search Methods
  private func performLocalSearch() async {
    let inputTags = localSearchText.components(separatedBy: .whitespaces).filter { component in
      !component.isEmpty
    }

    await fetchLocalPosts(page: 1, tags: inputTags, replace: true)
  }

  private func loadLocalNextPage() async {
    guard !localIsLoading else { return }

    localCurrentPage += 1

    let inputTags = localSearchText.components(separatedBy: .whitespaces).filter { component in
      !component.isEmpty
    }

    await fetchLocalPosts(page: localCurrentPage, tags: inputTags, replace: false)
  }

  private func fetchLocalPosts(
    page: Int = 1, limit: Int = 100, tags: [String] = [], replace: Bool = false
  ) async {
    guard !localIsLoading else { return }

    localIsLoading = true

    defer { localIsLoading = false }

    let flavor = manager.flavor
    let provider = manager.provider
    let pageValue = flavor == .gelbooru ? page - 1 : page

    guard let url = manager.urlForPosts(page: pageValue, limit: limit, tags: tags) else { return }

    do {
      let data = try await manager.requestURL(url)
      let newPosts = await withCheckedContinuation { continuation in
        DispatchQueue.global(qos: .userInitiated).async {
          let parsedPosts = BooruManager.parsePosts(
            from: data,
            flavor: flavor,
            provider: provider
          )
          .sorted { $0.createdAt > $1.createdAt }

          continuation.resume(returning: parsedPosts)
        }
      }

      withAnimation(nil) {
        if replace {
          localPosts = newPosts
          localCurrentPage = 1
        } else {
          localPosts.append(contentsOf: newPosts)
        }

        localEndOfData = newPosts.isEmpty
      }
    } catch {
      localError = error

      debugPrint("PostGridView.fetchLocalPosts: \(error)")
    }
  }
}