import Foundation

enum WallhavenError: Error {
  case invalidURL
  case networkError(Error)
  case decodingError(Error)
  case noData
  case apiError(String)
}

/// Sort order for Wallhaven search results. Maps to the `sorting` query
/// parameter on the public API. `random` returns a fresh batch per page.
enum WallhavenSorting: String {
  case dateAdded = "date_added"
  case toplist
  case random
}

@MainActor
protocol WallhavenSearching {
  func searchWallpapers(
    query: String, categories: String, purity: String, sorting: WallhavenSorting,
    resolutions: [String], ratios: [String], limit: Int, page: Int
  ) async throws -> ([Wallpaper], Meta?)
}

class WallhavenAPI: WallhavenSearching {
  private let session: URLSession

  init(session: URLSession = .shared) {
    self.session = session
  }

  func searchWallpapers(
    query: String,
    categories: String = "111",
    purity: String = "100",
    sorting: WallhavenSorting = .dateAdded,
    resolutions: [String] = [],
    ratios: [String] = [],
    limit: Int = 24,
    page: Int = 1
  ) async throws -> ([Wallpaper], Meta?) {
    var queryItems = [
      URLQueryItem(name: "q", value: query),
      URLQueryItem(name: "categories", value: categories),
      URLQueryItem(name: "purity", value: purity),
      URLQueryItem(name: "sorting", value: sorting.rawValue),
      URLQueryItem(name: "limit", value: String(limit)),
      URLQueryItem(name: "page", value: String(page)),
    ]

    if !resolutions.isEmpty {
      queryItems.append(
        URLQueryItem(name: "resolutions", value: resolutions.joined(separator: ",")))
    }

    if !ratios.isEmpty {
      queryItems.append(URLQueryItem(name: "ratios", value: ratios.joined(separator: ",")))
    }

    return try await performSearch(queryItems: queryItems)
  }

  private func performSearch(queryItems: [URLQueryItem]) async throws -> ([Wallpaper], Meta?) {
    var urlComponents = URLComponents(
      url: Configuration.baseURL.appendingPathComponent("search"), resolvingAgainstBaseURL: true)!
    urlComponents.queryItems = queryItems

    let url = urlComponents.url!

    let (data, response) = try await session.data(from: url)

    guard let httpResponse = response as? HTTPURLResponse,
      (200...299).contains(httpResponse.statusCode)
    else {
      throw WallhavenError.apiError("Server returned an error")
    }

    do {
      let decodedResponse = try JSONDecoder().decode(WallhavenResponse.self, from: data)
      return (decodedResponse.data, decodedResponse.meta)
    } catch {
      throw WallhavenError.decodingError(error)
    }
  }
}