import QuickLook
import SwiftUI

@MainActor
public class QuickLook: ObservableObject {
  @Published public var url: URL?
  @Published public private(set) var urls: [URL] = []
  @Published public private(set) var isPreparing: Bool = false
  @Published public private(set) var latestError: Error?

  public init() {}

  public func prepareFor(urls: [URL], selectedURL: URL) async {
    withAnimation {
      isPreparing = true
    }
    do {
      let paths: [URL] = try await withThrowingTaskGroup(of: URL.self, body: { group in
        var paths: [URL] = []
        for url in urls {
          group.addTask {
            try await self.localPathFor(url: url)
          }
        }
        for try await path in group {
          paths.append(path)
        }
        return paths
      })
      self.urls = paths
      url = paths.first(where: { $0.lastPathComponent == selectedURL.lastPathComponent })
      withAnimation {
        isPreparing = false
      }
    } catch {
      withAnimation {
        isPreparing = false
      }
      self.urls = []
      url = nil
      latestError = error
    }
  }

  private func localPathFor(url: URL) async throws -> URL {
    let tempDir = URL(fileURLWithPath: NSTemporaryDirectory())
    let path = tempDir.appendingPathComponent(url.lastPathComponent)
    let data = try await URLSession.shared.data(from: url).0
    try data.write(to: path)
    return path
  }
}