Tusker/Tusker/Screens/Lists/EditListSearchFollowingViewController.swift

//
//  EditListSearchFollowingViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 11/11/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class EditListSearchFollowingViewController: EnhancedTableViewController {
    
    private let mastodonController: MastodonController
    private let didSelectAccount: (String) -> Void
    
    private var dataSource: UITableViewDiffableDataSource<Section, String>!
    
    private var query: String?
    private var accountIDs: [String] = []
    private var nextRange: RequestRange?
    
    init(mastodonController: MastodonController, didSelectAccount: @escaping (String) -> Void) {
        self.mastodonController = mastodonController
        self.didSelectAccount = didSelectAccount
        
        super.init(style: .grouped)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.register(UINib(nibName: "AccountTableViewCell", bundle: .main), forCellReuseIdentifier: "accountCell")
        dataSource = UITableViewDiffableDataSource(tableView: tableView) { tableView, indexPath, itemIdentifier in
            let cell = tableView.dequeueReusableCell(withIdentifier: "accountCell", for: indexPath) as! AccountTableViewCell
            cell.delegate = self
            cell.updateUI(accountID: itemIdentifier)
            return cell
        }
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        if dataSource.snapshot().numberOfItems == 0 {
            Task {
                await load()
            }
        }
    }
    
    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        print("will display: \(indexPath)")
        if indexPath.row == tableView.numberOfRows(inSection: indexPath.section) - 1 {
            Task {
                await load()
            }
        }
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        guard let id = dataSource.itemIdentifier(for: indexPath) else {
            return
        }
        didSelectAccount(id)
    }
    
    private func load() async {
        do {
            let ownAccount = try await mastodonController.getOwnAccount()
            let req = Account.getFollowing(ownAccount.id, range: nextRange ?? .default)
            let (following, pagination) = try await mastodonController.run(req)
            await withCheckedContinuation { continuation in
                mastodonController.persistentContainer.addAll(accounts: following) {
                    continuation.resume()
                }
            }
            accountIDs.append(contentsOf: following.lazy.map(\.id))
            nextRange = pagination?.older
            updateDataSource(appending: following.map(\.id))
        } catch {
            let config = ToastConfiguration(from: error, with: "Error Loading Following", in: self) { toast in
                toast.dismissToast(animated: true)
                await self.load()
            }
            self.showToast(configuration: config, animated: true)
        }
    }
    
    private func updateDataSourceForQueryChanged() {
        guard let query, !query.isEmpty else {
            let snapshot = NSDiffableDataSourceSnapshot<Section, String>()
            dataSource.apply(snapshot, animatingDifferences: true)
            return
        }
        
        let ids = filterAccounts(ids: accountIDs, with: query)
        
        var snapshot = dataSource.snapshot()
        if snapshot.indexOfSection(.accounts) == nil {
            snapshot.appendSections([.accounts])
        } else {
            snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .accounts))
        }
        snapshot.appendItems(ids)
        dataSource.apply(snapshot, animatingDifferences: true)
        
        // if there aren't any results for the current query, try to load more
        if ids.isEmpty {
            Task {
                await load()
            }
        }
    }
    
    private func updateDataSource(appending ids: [String]) {
        guard let query, !query.isEmpty else {
            let snapshot = NSDiffableDataSourceSnapshot<Section, String>()
            dataSource.apply(snapshot, animatingDifferences: true)
            return
        }
        
        let ids = filterAccounts(ids: ids, with: query)
        
        var snapshot = dataSource.snapshot()
        if snapshot.indexOfSection(.accounts) == nil {
            snapshot.appendSections([.accounts])
        }
        let existing = snapshot.itemIdentifiers(inSection: .accounts)
        snapshot.appendItems(ids.filter { !existing.contains($0) })
        dataSource.apply(snapshot, animatingDifferences: true)
        
        // if there aren't any results for the current query, try to load more
        if ids.isEmpty {
            Task {
                await load()
            }
        }
    }
    
    private func filterAccounts(ids: [String], with query: String) -> [String] {
        let req = AccountMO.fetchRequest()
        req.predicate = NSPredicate(format: "id in %@", ids)
        let accounts = try! mastodonController.persistentContainer.viewContext.fetch(req)
        
        return accounts
            .map { (account) -> (AccountMO, Bool) in
                let displayNameMatch = FuzzyMatcher.match(pattern: query, str: account.displayNameWithoutCustomEmoji)
                let usernameMatch = FuzzyMatcher.match(pattern: query, str: account.acct)
                return (account, displayNameMatch.matched || usernameMatch.matched)
            }
            .filter(\.1)
            .map(\.0.id)
    }
    
    func updateQuery(_ query: String) {
        self.query = query
        updateDataSourceForQueryChanged()
    }
    
}

extension EditListSearchFollowingViewController {
    enum Section {
        case accounts
    }
}

extension EditListSearchFollowingViewController: TuskerNavigationDelegate {
    var apiController: MastodonController! { mastodonController }
}

extension EditListSearchFollowingViewController: MenuActionProvider {
}