import SwiftUI

/// The library presentation of `viewModel.bookmarks`: color cards on paper,
/// over a browser-tab strip of tag filters. Drops into BookmarksView's content
/// area in place of the List, and carries the same actions — tap to open, long
/// press for the full menu.
struct LibraryGridView: View {
    @Bindable var viewModel: BookmarksViewModel
    @Binding var filters: [LibraryFilter]
    @Binding var selection: LibraryFilter.ID?
    let onOpen: (Bookmark) -> Void
    let onEdit: (Bookmark) -> Void

    @Environment(\.openURL) private var openURL
    @State private var showFullPlayer = false
    @State private var episodePicker: Bookmark?

    private var items: [LibraryItem] {
        viewModel.bookmarks.map(LibraryItem.init(bookmark:))
    }

    /// Tags of everything currently loaded, heaviest first, minus what's
    /// already pinned as a tab.
    private var availableTags: [String] {
        let taken = Set(filters.compactMap(\.tag))
        var counts: [String: Int] = [:]
        for b in viewModel.bookmarks where !b.tagNames.isEmpty {
            for tag in b.tagNames where !taken.contains(tag) { counts[tag, default: 0] += 1 }
        }
        return counts.sorted { ($0.value, $1.key) > ($1.value, $0.key) }.map(\.key)
    }

    var body: some View {
        VStack(spacing: 0) {
            LibraryTagStrip(
                filters: $filters,
                selection: $selection,
                available: availableTags,
                onChange: applyFilter
            )

            ScrollView {
                LazyVGrid(
                    columns: Array(repeating: GridItem(.flexible(), spacing: 8), count: 3),
                    spacing: 8
                ) {
                    ForEach(items) { item in
                        card(item)
                    }
                }
                .padding(.horizontal, 18)
                .padding(.top, 16)
                .padding(.bottom, 40)

                if viewModel.isLoadingMore {
                    ProgressView().padding(.bottom, 28)
                }
            }
            .scrollBounceBehavior(.basedOnSize)
        }
        .background(Paper.sheet)
        .podcastSheets(
            viewModel: viewModel,
            showFullPlayer: $showFullPlayer,
            episodePicker: $episodePicker
        )
    }

    @ViewBuilder
    private func card(_ item: LibraryItem) -> some View {
        // The grid renders LibraryItems, but every action needs the Bookmark it
        // came from. Ids are linkding's, so this is a direct lookup.
        if let bookmark = viewModel.bookmarks.first(where: { $0.id == item.id }) {
            LibraryCard(item: item)
                .contentShape(.rect)
                .onTapGesture { onOpen(bookmark) }
                .contextMenu {
                    bookmarkMenuItems(
                        bookmark: bookmark,
                        viewModel: viewModel,
                        openURL: openURL,
                        onOpen: { onOpen(bookmark) },
                        onEdit: { onEdit(bookmark) },
                        onPodcast: {
                            launchPodcast(
                                for: bookmark,
                                viewModel: viewModel,
                                showFullPlayer: $showFullPlayer,
                                episodePicker: $episodePicker
                            )
                        }
                    )
                }
                .onAppear { maybeLoadMore(bookmark) }
        }
    }

    /// Tag tabs filter server-side through linkding's `#tag` search syntax —
    /// filtering the loaded page client-side would only ever search the most
    /// recent 50 of 600+ bookmarks and quietly look empty.
    private func applyFilter() {
        let tag = filters.first { $0.id == selection }?.tag
        viewModel.searchQuery = tag.map { "#\($0)" } ?? ""
        Task { await viewModel.search() }
    }

    private func maybeLoadMore(_ bookmark: Bookmark) {
        guard let last = viewModel.bookmarks.last, last.id == bookmark.id,
              viewModel.nextPageUrl != nil, !viewModel.isLoadingMore else { return }
        Task { await viewModel.loadMore() }
    }
}