deltachat-ios/DcShare/ViewModel/ChatListViewModel.swift

import UIKit
import DcCore


// MARK: - ChatListViewModel
class ChatListViewModel: NSObject {

    var onChatListUpdate: VoidFunction?

    enum ChatListSectionType {
        case chats
        case contacts
    }

    private let dcContext: DcContext

    var searchActive: Bool = false

    // if searchfield is empty we show default chat list
    private var showSearchResults: Bool {
        return searchActive && searchText.containsCharacters()
    }

    private var chatList: DcChatlist!

    // for search filtering
    private var searchText: String = ""
    private var searchResultChatList: DcChatlist?
    private var searchResultContactIds: [Int] = []

    // to manage sections dynamically
    private var searchResultsChatsSection: ChatListSectionType = .chats
    private var searchResultsContactsSection: ChatListSectionType = .contacts
    private var searchResultSections: [ChatListSectionType] = []

    init(dcContext: DcContext) {
        self.dcContext = dcContext
        super.init()
        updateChatList(notifyListener: true)
    }

    private func updateChatList(notifyListener: Bool) {
        self.chatList = dcContext.getChatlist(flags: DC_GCL_ADD_ALLDONE_HINT | DC_GCL_FOR_FORWARDING | DC_GCL_NO_SPECIALS, queryString: nil, queryId: 0)
        if notifyListener {
            onChatListUpdate?()
        }
    }

    func getChatId(section: Int, row: Int) -> Int? {
        if showSearchResults {
            switch searchResultSections[section] {
            case .chats:
                let list: DcChatlist? = searchResultChatList
                return list?.getChatId(index: row)
            case .contacts:
                return searchResultContactIds[row]
            }
        }
        return chatList.getChatId(index: row)
    }

    var numberOfSections: Int {
        if showSearchResults {
            return searchResultSections.count
        }
        return 1
    }

    func numberOfRowsIn(section: Int) -> Int {
        if showSearchResults {
            switch searchResultSections[section] {
            case .chats:
                return searchResultChatList?.length ?? 0
            case .contacts:
                return searchResultContactIds.count
            }
        }
        return chatList.length
    }

    func titleForHeaderIn(section: Int) -> String? {
        if showSearchResults {
            let title: String
            switch searchResultSections[section] {
            case .chats:
                title = "n_chats"
            case .contacts:
                title = "n_contacts"
            }
            return String.localized(stringID: title, count: numberOfRowsIn(section: section))
        }
        return nil
    }

    func refreshData() {
        updateChatList(notifyListener: true)
    }

    func beginSearch() {
        searchActive = true
    }

    func endSearch() {
        searchActive = false
        searchText = ""
        resetSearch()
    }

    var emptySearchText: String? {
        if searchActive && numberOfSections == 0 {
            return searchText
        }
        return nil
    }

    // MARK: - search
    func updateSearchResultSections() {
        var sections: [ChatListSectionType] = []
        if let chatList = searchResultChatList, chatList.length > 0 {
            sections.append(searchResultsChatsSection)
        }
        if !searchResultContactIds.isEmpty {
            sections.append(searchResultsContactsSection)
        }
        searchResultSections = sections
    }

    func resetSearch() {
        searchResultChatList = nil
        searchResultContactIds = []
        updateSearchResultSections()
    }

    func filterContentForSearchText(_ searchText: String) {
           if !searchText.isEmpty {
               filterAndUpdateList(searchText: searchText)
           } else {
               // when search input field empty we show default chatList
               resetSearch()
           }
           onChatListUpdate?()
       }

    func filterAndUpdateList(searchText: String) {

           // #1 chats with searchPattern in title bar
           var flags: Int32 = 0
           flags |= DC_GCL_NO_SPECIALS
           searchResultChatList = dcContext.getChatlist(flags: flags, queryString: searchText, queryId: 0)

           // #2 contacts with searchPattern in name or in email
           searchResultContactIds = dcContext.getContacts(flags: DC_GCL_ADD_SELF, queryString: searchText)

           updateSearchResultSections()
       }
}

// MARK: UISearchResultUpdating
extension ChatListViewModel: UISearchResultsUpdating {
    func updateSearchResults(for searchController: UISearchController) {
        self.searchText = searchController.searchBar.text ?? ""
        if let searchText = searchController.searchBar.text {
            filterContentForSearchText(searchText)
            return
        }
    }
}