//
//  InstancesDataManager.swift
//  elpha-ios
//
//  Created by Dwayne Harris on 9/18/18.
//  Copyright © 2018 Elpha. All rights reserved.
//

import Alamofire
import CoreData
import UIKit

class InstancesDataManager {
    static let shared = InstancesDataManager()
    
    let fetchLimit = 20
    var instances: [ISInstanceMO] = []
    var nextID: String?
    var finished = false
    
    func upsertLanguage(string: String) -> ISLanguageMO? {
        let context = CoreDataManager.shared.context
        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        
        let request = NSFetchRequest<ISLanguageMO>(entityName: "ISLanguage")
        request.predicate = NSPredicate(format: "id == %@", string)
        
        do {
            let results = try context.fetch(request)
            if let language = results.first {
                return language
            } else {
                let language = ISLanguageMO(context: context)
                language.id = string
                
                return language
            }
        } catch {
            print("\(error)")
            return nil
        }
    }
    
    func upsertCategory(string: String) -> ISCategoryMO? {
        let context = CoreDataManager.shared.context
        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        
        let request = NSFetchRequest<ISCategoryMO>(entityName: "ISCategory")
        request.predicate = NSPredicate(format: "id == %@", string)
        
        do {
            let results = try context.fetch(request)
            if let category = results.first {
                return category
            } else {
                let category = ISCategoryMO(context: context)
                category.id = string
                
                return category
            }
        } catch {
            print("\(error)")
            return nil
        }
    }
    
    func setAttributes(on instance: ISInstanceMO, with attributes: [String: Any]) {
        guard let id = attributes["id"] as? String, let name = attributes["name"] as? String else {
            return
        }
        
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
        
        instance.id = id
        instance.name = name
        instance.url = URL(string: "https://\(name)")!
        instance.uptime = attributes["uptime"] as! Int32
        instance.up = attributes["up"] as! Bool
        instance.dead = attributes["dead"] as! Bool
        instance.version = attributes["version"] as? String
        instance.ipv6 = attributes["ipv6"] as! Bool
        instance.users = Int64(attributes["users"] as! String)!
        instance.statuses = Int64(attributes["statuses"] as! String)!
        instance.connections = Int64(attributes["connections"] as! String)!
        instance.openRegistrations = attributes["open_registrations"] as! Bool
        instance.fetchedAt = Date()
        
        if let activeUsers = attributes["active_users"] as? Int64 {
            instance.activeUsers = activeUsers
        }
        
        if let updatedAt = attributes["updated_at"] as? String {
            instance.updatedAt = dateFormatter.date(from: updatedAt)
        }
        
        if let checkedAt = attributes["checked_at"] as? String {
            instance.checkedAt = dateFormatter.date(from: checkedAt)
        }
        
        if let thumbnail = attributes["thumbnail"] as? String {
            instance.thumbnail = URL(string: thumbnail)!
        }
        
        if let info = attributes["info"] as? [String: Any] {
            instance.shortDesc = info["short_description"] as? String
            instance.fullDescription = info["full_description"] as? String
            instance.topic = info["topic"] as? String
            
            for language in info["languages"] as! [String] {
                if let l = upsertLanguage(string: language) {
                    instance.mutableSetValue(forKey: "languages").add(l)
                }
            }
            
            for category in info["categories"] as! [String] {
                if let c = upsertCategory(string: category) {
                    instance.mutableSetValue(forKey: "categories").add(c)
                }
            }
        }
    }
    
    func clearInstances() {
        let request = NSFetchRequest<ISInstanceMO>(entityName: "ISInstance")
        
        do {
            let instances = try CoreDataManager.shared.context.fetch(request)
            instances.forEach { instance in
                CoreDataManager.shared.context.delete(instance)
            }
        } catch {
            print("\(error)")
        }
    }
    
    func reloadInstances(completion: @escaping (Error?) -> Void) {
        nextID = nil
        finished = false
        
        loadInstances(completion: completion)
    }
    
    func loadInstances(completion: @escaping (Error?) -> Void) {
        var params = [
            "count=\(fetchLimit)",
            "sort_by=users",
            "sort_order=desc",
            "include_closed=true",
            "include_down=false",
        ]
        
        if let nextID = nextID {
            params.append("min_id=\(nextID)")
        }
        
        let requestURL = "\(Config.instancesServiceURL)\(Config.instancesServiceListEndpoint)?\(params.joined(separator: "&"))"
        let headers: HTTPHeaders = ["Authorization": "Bearer \(Config.instancesServiceSecret)"]
        
        Alamofire.request(requestURL, headers: headers).validate().responseJSON { response in
            switch response.result {
            case .success(let value):
                guard let result = value as? [String: Any],
                    let pagination = result["pagination"] as? [String: Any],
                    let instances = result["instances"] as? [Any] else {
                        completion(NSError())
                        return
                }
                
                if let nextID = pagination["next_id"] as? String {
                    self.nextID = nextID
                } else {
                    self.nextID = nil
                    self.finished = true
                }
                
                do {
                    for case let instance as [String: Any] in instances {
                        if let id = instance["id"] as? String {
                            let request = NSFetchRequest<ISInstanceMO>(entityName: "ISInstance")
                            request.predicate = NSPredicate(format: "id == %@", id)
                            
                            let results: [ISInstanceMO] = try CoreDataManager.shared.context.fetch(request)
                            if let i = results.first {
                                self.setAttributes(on: i, with: instance)
                            } else {
                                let i = ISInstanceMO(context: CoreDataManager.shared.context)
                                self.setAttributes(on: i, with: instance)
                            }
                        }
                    }
                    
                    CoreDataManager.shared.saveContext()
                    completion(nil)
                } catch {
                    completion(error)
                    return
                }
            case .failure(let error):
                completion(error)
            }
        }
    }
}