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

import Foundation

/// ViewModel that will be bound to an Employees model and used
/// specifically with the EmployeesViewController.
@MainActor
public class EmployeesViewModel: ObservableObject {
    private var serviceMode: EmployeeServiceMode = .production

    @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 private(set) var hasMorePages: Bool = true

    private var currentPage = 1
    private let perPage = 10
    private var totalEmployees = 0

    public init() {}

    /// Fetch employees for the given page
    public func fetchEmployees(page: Int = 1) {
        // Prevent duplicate calls
        guard !isLoading else { return }
        isLoading = true

        Task {
            do {
                // Fetch employees using the paginated API
                let wrapper = try await MockEmployeeService.shared.getEmployees(.empty ,page: page, perPage: perPage)
                
                // Update published properties
                if page == 1 {
                    employees = wrapper.employees // Replace list for the first page
                } else {
                    employees.append(contentsOf: wrapper.employees) // Append for subsequent pages
                }
                
                totalEmployees = wrapper.total
                currentPage = page
                hasMorePages = employees.count < totalEmployees
                isLoading = false

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

    /// Load the next page of employees
    public func loadNextPage() {
        guard hasMorePages else { return }
        fetchEmployees(page: currentPage + 1)
    }

    /// Change the service mode (e.g., production, malformed, empty)
    public func changeMode(to mode: EmployeeServiceMode) {
        serviceMode = mode
        currentPage = 1
        employees = []
        hasMorePages = true
        fetchEmployees(page: 1)
    }
}