//
//  EmployeesViewModel.swift
//  EmployeeDirectory
//
//  Created by Matt Bruce on 1/20/25.
//

import Foundation
import Combine

/// ViewModel that will be bound to an Employees model and used
/// specifically with the EmployeesViewController.
@MainActor
public class EmployeesViewModel: ObservableObject {
    private var employeeService: EmployeeServiceProtocol = EmployeeService()

    private var allEmployees: [Employee] = [] // Holds unfiltered employees
    @Published public private(set) var employees: [Employee] = []
    @Published public private(set) var errorMessage: String? = nil
    @Published public private(set) var isLoading: Bool = false
    @Published public var searchText: String = "" // User input from search bar
    private var cancellables = Set<AnyCancellable>()
    public init() {
        setupSearch()
    }
    
    /// Sets up Combine to filter employees as the search text changes
    private func setupSearch() {
        $searchText
            .debounce(for: .milliseconds(300), scheduler: DispatchQueue.main) // Add delay to avoid frequent filtering
            .removeDuplicates()
            .sink { [weak self] query in
                self?.filterEmployees(by: query)
            }
            .store(in: &cancellables)
    }
    
    public func fetchEmployees() {
        // resetting values out the values before fetching new data
        errorMessage = nil
        isLoading = true

        Task {
            do {
                // Fetch employees using the async method
                let wrapper = try await employeeService.getEmployees()
                
                // Update published properties
                allEmployees = wrapper.employees
                filterEmployees(by: searchText)
                isLoading = false

            } catch {
                // Handle errors
                employees = []
                isLoading = false
                errorMessage = "An unexpected error occurred, please try to refresh"
            }
        }

    }
    
    public func changeService(to employeeService: EmployeeServiceProtocol) {
        self.employeeService = employeeService
        fetchEmployees()
    }
    
    /// Filters employees based on search query
    private func filterEmployees(by query: String) {
        if query.isEmpty {
            employees = allEmployees // Reset to all employees if no search text
        } else {
            employees = allEmployees.filter { employee in
                employee.fullName.lowercased().contains(query.lowercased()) ||
                employee.team.lowercased().contains(query.lowercased()) ||
                employee.emailAddress.lowercased().contains(query.lowercased())
            }
        }
    }

}