//
//  ProjectClock
//
//  Created by Hykilpikonna on 1/8/21.
//

import Foundation

/// Base URL of the HTTP server
let baseUrl = "http://localhost:8080/api" // TODO: Production settings

/// Json class
class JSON
{
    static let decoder = JSONDecoder()
    static let encoder = JSONEncoder()
    
    static func stringify<T: Encodable>(_ o: T) -> String?
    {
        guard let jsonData = try? encoder.encode(o) else { return nil }
        return String(data: jsonData, encoding: String.Encoding.utf8)
    }
    
    static func parse<T: Decodable>(_ type: T.Type, _ j: String) -> T?
    {
        return try? decoder.decode(type, from: j.data(using: .utf8)!)
    }
}

/// Local storage
let localStorage = UserDefaults(suiteName: "group.org.hydev.alarm.clock")!

/// Get alarms from local storage
func getLocalAlarms() -> [Alarm] { return JSON.parse([Alarm].self, localStorage.string(forKey: "alarms")!)! }

/// API class
struct API<T>
{
    let loc: String
}

/// Class to store static API endpoints
class APIs
{
    /**
     Register the user in the database.
     
     ## Parameters
     - name: The user's name (this is not username because it doesn't have to be unique)
     - email: The user's email (this does have to be unique)
     - pass: Password (initial hash)
     
     ## Returns
     Success or error
     */
    static let register = API<String>(loc: "/user/register")
    
    /**
     Delete a user from the database.
     
     ## Parameters
     - email: The user's email
     - pass: Password (initial hash)
     
     ## Returns
     Success or error
     */
    static let delete = API<String>(loc: "/user/delete")
    
    /**
     Upload curent config to the cloud.
     
     ## Parameters
     - config: The config json
     
     ## Returns
     Success or error
     */
    static let uploadConfig = API<String>(loc: "/backup/upload")
    
    /**
     Download the config from the cloud.
     
     ## Parameters
     None
     
     ## Returns
     Config Json
     */
    static let downloadConfig = API<String>(loc: "/backup/download")
    
    /**
     Create a family
     
     ## Parameters
     - fname: Family name
     - pin: Admin pin
     
     ## Returns
     Family object
     */
    static let familyCreate = API<Family>(loc: "/family/create")
    
    /**
     Delete a family
     
     ## Parameters
     - fid: Family ID
     - pin: Admin pin
     
     ## Returns
     Success or not
     */
    static let familyDelete = API<String>(loc: "/family/delete")
    
    /**
     Change a family's admin pin
     
     ## Parameters
     - fid: Family ID
     - orig_pin: Original admin pin
     - new_pin: New admin pin
     
     ## Returns
     Success or not
     */
    static let familyChangePin = API<String>(loc: "/family/update_pin")
    
    /**
     Join family
     
     ## Parameters
     - fid: Family ID
     - pin: Admin pin
     
     ## Returns
     Family object
     */
    static let familyJoin = API<Family>(loc: "/family/join")
    
    /**
     Leave family
     
     ## Parameters
     - fid: Family ID
     - pin: Admin pin
     
     ## Returns
     Success or not
     */
    static let familyLeave = API<String>(loc: "/family/leave")
    
    private init() {}
}

/**
 Build a URL with the node path and params
 
 - Parameter api: API Node (Eg. APIs.register)
 - Parameter params: Parameters to send to the server (Check the documentation of the API node to see which parameters you need)
 - Returns: URL
 */
func createUrl(_ node: String, _ params: [String: String]? = [:]) -> URL
{
    var url = URLComponents(string: baseUrl + node)
    if let params = params
    {
        url?.queryItems = params.map { URLQueryItem(name: $0, value: $1) }
    }
    return url!.url!
}

/**
 Send a HTTP request. Email and authentication token (the initial hash of a password) is automatically added if they exist in localStorage.
 
 - Parameter api: API Node (Eg. APIs.register)
 - Parameter params: Parameters to send to the server (Check the documentation of the API node to see which parameters you need)
 - Parameter success: Callback of what to do when the request successfully returned
 - Parameter err: Callback of what to do when an error happens
 */
func send<T: Decodable>(_ api: API<T>, _ params: [String: String]? = [:], _ success: @escaping (T) -> Void, err: @escaping (String) -> Void = {it in})
{
    // Add default params
    var params = params
    if params != nil
    {
        if params!["email"] == nil { params!["email"] = localStorage.string(forKey: "email") }
        if params!["pass"] == nil { params!["pass"] = localStorage.string(forKey: "pass") }
    }
    
    let url = createUrl(api.loc, params)
    
    // Create task
    let task = URLSession.shared.dataTask(with: url) { (raw, response, error) in
        
        // Check if raw data exists
        guard let response = response as? HTTPURLResponse, let raw = raw else { err("Data doesn't exist"); return }
        
        // If success
        if (200...299).contains(response.statusCode)
        {
            // Parse JSON
            guard let obj = try? JSON.decoder.decode(T.self, from: raw) else { err("JSON cannot be parsed"); return }
            
            // Call callback
            success(obj)
        }
        
        // Failed
        else
        {
            let data = String(data: raw, encoding: .utf8) ?? "Error"
            err("\(response.statusCode) - \(data)")
        }
    }

    // Execute task
    task.resume()
}