import Models
import Network
import SwiftUI

public enum AccountsListMode {
  case following(accountId: String), followers(accountId: String)
  case favouritedBy(statusId: String), rebloggedBy(statusId: String)

  var title: String {
    switch self {
    case .following:
      return "Following"
    case .followers:
      return "Followers"
    case .favouritedBy:
      return "Favourited by"
    case .rebloggedBy:
      return "Boosted by"
    }
  }
}

@MainActor
class AccountsListViewModel: ObservableObject {
  var client: Client?

  let mode: AccountsListMode

  public enum State {
    public enum PagingState {
      case hasNextPage, loadingNextPage, none
    }

    case loading
    case display(accounts: [Account],
                 relationships: [Relationshionship],
                 nextPageState: PagingState)
    case error(error: Error)
  }

  private var accounts: [Account] = []
  private var relationships: [Relationshionship] = []

  @Published var state = State.loading

  private var nextPageId: String?

  init(mode: AccountsListMode) {
    self.mode = mode
  }

  func fetch() async {
    guard let client else { return }
    do {
      state = .loading
      let link: LinkHandler?
      switch mode {
      case let .followers(accountId):
        (accounts, link) = try await client.getWithLink(endpoint: Accounts.followers(id: accountId,
                                                                                     maxId: nil))
      case let .following(accountId):
        (accounts, link) = try await client.getWithLink(endpoint: Accounts.following(id: accountId,
                                                                                     maxId: nil))
      case let .rebloggedBy(statusId):
        (accounts, link) = try await client.getWithLink(endpoint: Statuses.rebloggedBy(id: statusId,
                                                                                       maxId: nil))
      case let .favouritedBy(statusId):
        (accounts, link) = try await client.getWithLink(endpoint: Statuses.favouritedBy(id: statusId,
                                                                                        maxId: nil))
      }
      nextPageId = link?.maxId
      relationships = try await client.get(endpoint:
        Accounts.relationships(ids: accounts.map { $0.id }))
      state = .display(accounts: accounts,
                       relationships: relationships,
                       nextPageState: link?.maxId != nil ? .hasNextPage : .none)
    } catch {}
  }

  func fetchNextPage() async {
    guard let client, let nextPageId else { return }
    do {
      state = .display(accounts: accounts, relationships: relationships, nextPageState: .loadingNextPage)
      let newAccounts: [Account]
      let link: LinkHandler?
      switch mode {
      case let .followers(accountId):
        (newAccounts, link) = try await client.getWithLink(endpoint: Accounts.followers(id: accountId,
                                                                                        maxId: nextPageId))
      case let .following(accountId):
        (newAccounts, link) = try await client.getWithLink(endpoint: Accounts.following(id: accountId,
                                                                                        maxId: nextPageId))
      case let .rebloggedBy(statusId):
        (newAccounts, link) = try await client.getWithLink(endpoint: Statuses.rebloggedBy(id: statusId,
                                                                                          maxId: nextPageId))
      case let .favouritedBy(statusId):
        (newAccounts, link) = try await client.getWithLink(endpoint: Statuses.favouritedBy(id: statusId,
                                                                                           maxId: nextPageId))
      }
      accounts.append(contentsOf: newAccounts)
      let newRelationships: [Relationshionship] =
        try await client.get(endpoint: Accounts.relationships(ids: newAccounts.map { $0.id }))

      relationships.append(contentsOf: newRelationships)
      self.nextPageId = link?.maxId
      state = .display(accounts: accounts,
                       relationships: relationships,
                       nextPageState: link?.maxId != nil ? .hasNextPage : .none)
    } catch {
      print(error)
    }
  }
}