//
//  ArtistsView.swift
//  Mobile Music Assistant
//
//  Created by Sven Hanold on 26.03.26.
//

import SwiftUI

struct ArtistsView: View {
    @Environment(MAService.self) private var service
    @State private var errorMessage: String?
    @State private var showError = false
    
    private var artists: [MAArtist] {
        service.libraryManager.artists
    }
    
    private var isLoading: Bool {
        service.libraryManager.isLoadingArtists
    }
    
    private let columns = [
        GridItem(.adaptive(minimum: 160), spacing: 16)
    ]
    
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns, spacing: 16) {
                ForEach(artists) { artist in
                    NavigationLink(value: artist) {
                        ArtistGridItem(artist: artist)
                    }
                    .buttonStyle(.plain)
                    .task {
                        await loadMoreIfNeeded(currentItem: artist)
                    }
                }
                
                if isLoading {
                    ProgressView()
                        .gridCellColumns(columns.count)
                        .padding()
                }
            }
            .padding()
        }
        .navigationDestination(for: MAArtist.self) { artist in
            ArtistDetailView(artist: artist)
        }
        .refreshable {
            await loadArtists(refresh: true)
        }
        .task {
            if artists.isEmpty {
                await loadArtists(refresh: false)
            }
        }
        .alert("Error", isPresented: $showError) {
            Button("OK", role: .cancel) { }
        } message: {
            if let errorMessage {
                Text(errorMessage)
            }
        }
        .overlay {
            if artists.isEmpty && !isLoading {
                ContentUnavailableView(
                    "No Artists",
                    systemImage: "music.mic",
                    description: Text("Your library doesn't contain any artists yet")
                )
            }
        }
    }
    
    private func loadArtists(refresh: Bool) async {
        do {
            try await service.libraryManager.loadArtists(refresh: refresh)
        } catch {
            errorMessage = error.localizedDescription
            showError = true
        }
    }
    
    private func loadMoreIfNeeded(currentItem: MAArtist) async {
        do {
            try await service.libraryManager.loadMoreArtistsIfNeeded(currentItem: currentItem)
        } catch {
            errorMessage = error.localizedDescription
            showError = true
        }
    }
}

// MARK: - Artist Grid Item

struct ArtistGridItem: View {
    @Environment(MAService.self) private var service
    let artist: MAArtist
    
    var body: some View {
        VStack(spacing: 8) {
            // Artist Image
            if let imageUrl = artist.imageUrl {
                let coverURL = service.imageProxyURL(path: imageUrl, size: 256)
                
                CachedAsyncImage(url: coverURL) { image in
                    image
                        .resizable()
                        .aspectRatio(contentMode: .fill)
                } placeholder: {
                    Circle()
                        .fill(Color.gray.opacity(0.2))
                }
                .frame(width: 160, height: 160)
                .clipShape(Circle())
            } else {
                Circle()
                    .fill(Color.gray.opacity(0.2))
                    .frame(width: 160, height: 160)
                    .overlay {
                        Image(systemName: "music.mic")
                            .font(.system(size: 40))
                            .foregroundStyle(.secondary)
                    }
            }
            
            // Artist Name
            Text(artist.name)
                .font(.subheadline)
                .fontWeight(.medium)
                .lineLimit(2)
                .multilineTextAlignment(.center)
                .foregroundStyle(.primary)
        }
    }
}

#Preview {
    NavigationStack {
        ArtistsView()
            .environment(MAService())
    }
}