Paginate requests based on Fluent model queries in Vapor

QueryPaginator.swift

import Foundation
import Vapor
import FluentProvider

struct Paginator<T: Model> where T: JSONRepresentable {
    let query: Query<T>
    let request: Request
    let perPage: Int
    
    init(query: Query<T>, request: Request, perPage: Int = 25) {
        self.query = query
        self.request = request
        self.perPage = perPage
    }
}

extension Paginator: JSONRepresentable {
    func makeJSON() throws -> JSON {
        let requestedPage = request.query?["page"]?.int ?? 0
        let requestedOffset = perPage * requestedPage
        let totalCount = try query.count()
        
        let page = requestedOffset <= totalCount ? requestedPage : 0
        let offset = perPage * page
        
        var nextPage: String? = nil
        var previousPage: String? = nil
        if offset + perPage <= totalCount {
            nextPage = "\(request.uri.path)?page=\(page + 1)"
        }
        
        if page > 0 {
            previousPage = "\(request.uri.path)?page=\(page - 1)"
        }
        
        let entities = try query.limit(perPage, offset: offset).all()
        
        var response = Node.object([:])
        var paginator = Node.object([:])
        
        try paginator.set("total", totalCount)
        try paginator.set("page", page)
        try paginator.set("count", entities.count)
        try paginator.set("per_page", perPage)
        
        try paginator.set("next_page", nextPage)
        try paginator.set("prev_page", previousPage)
        
        try response.set(T.entity, try entities.makeJSON())
        try response.set("paginator", paginator)
        
        return JSON(response)
    }
}