//
//  Resource.swift
//  Pods
//
//  Created by Mauro Bender on 13/8/16.
//
//

import Alamofire

public protocol JSONSerializable {
	init( fromJSON json: [ String: AnyObject ] )
	func toJSON() -> [ String: AnyObject ]
}

public enum ApiError: ErrorType {
	case Network( error: NSError, response: NSURLResponse )
	case JSONSerialization(error: NSError)
	case Unknown( error: NSError )
}

public class Resource {
	public let api: Api
	public let path: String
	
	init( api: Api, path: String ) {
		self.api  = api
		self.path = path
	}
}

// MARK: REQUESTS
extension Resource {
	public func request( method: ApiMethod, path: String? = nil,
	                     parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL,
	                     headers: [String: String]? = nil, completion: Response<AnyObject, NSError> -> Void )
	{
		let requestPath = path != nil ? "\(self.path)/\(path!)" : self.path
		api.request( method, path: requestPath, parameters: parameters, encoding: encoding,
		             headers: headers, completion: completion )
	}
	
	public func get( path: String? = nil, parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL,
	                 headers: [String: String]? = nil, completion: Response<AnyObject, NSError> -> Void )
	{
		return request( .GET, path: path, parameters: parameters, encoding: encoding,
		                headers: headers, completion: completion)
	}
	
	public func post( path: String? = nil, parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL,
	                  headers: [String: String]? = nil, completion: Response<AnyObject, NSError> -> Void )
	{
		return request( .POST, path: path, parameters: parameters, encoding: encoding,
		                headers: headers, completion: completion)
	}
	
	public func put( path: String? = nil, parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL,
	                 headers: [String: String]? = nil, completion: Response<AnyObject, NSError> -> Void )
	{
		return request( .PUT, path: path, parameters: parameters, encoding: encoding,
		                headers: headers, completion: completion)
	}
	
	public func delete( path: String? = nil, parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL,
	                    headers: [String: String]? = nil, completion: Response<AnyObject, NSError> -> Void )
	{
		return request( .DELETE, path: path, parameters: parameters, encoding: encoding,
		                headers: headers, completion: completion)
	}
}

// MARK: CRUD
extension Resource {
	public func item<T: JSONSerializable>( id: AnyObject, parameters: [ String: String ]? = nil,
	                 headers: [ String: String]? = nil, completion: ( ( T?, error: ApiError? ) -> Void ) )
	{
		get( "\(id)", parameters: parameters, headers: headers ) { response in
			self.handleItemResult( response, handler: completion )
		}
	}
	
	public func list<T: JSONSerializable>( parameters: [ String: String ]? = nil,
	                 headers: [ String: String]? = nil, completion: ( ( [ T ]?, error: ApiError? ) -> Void ) )
	{
		get( parameters: parameters, headers: headers ) { response in
			self.handleListResult( response, handler: completion )
		}
	}
	
	public func create<T: JSONSerializable>( item: T, parameters: [ String: String ]? = nil,
	                   headers: [ String: String]? = nil, encoding: ParameterEncoding = .JSON,
	                   completion: ( ( T?, error: ApiError? ) -> Void ) )
	{
		var requestParameters = item.toJSON()
		if parameters != nil { requestParameters += parameters! }
		
		post( parameters: requestParameters, encoding: encoding, headers: headers ) { response in
			self.handleItemResult( response, handler: completion )
		}
	}
	
	public func destroy( id: AnyObject, parameters: [ String: String ]? = nil,
	                     headers: [ String: String]? = nil, completion: ( ( error: ApiError? ) -> Void ) )
	{
		delete( "\(id)", parameters: parameters, headers: headers ) { response in
			self.handleEmptyResult( response, handler: completion )
		}
	}
	
	
	// MARK: UTILS
	private func handleItemResult<T: JSONSerializable>( response: Response<AnyObject, NSError>,
	                              handler: ( T?, error: ApiError? ) -> Void )
	{
		switch(response.result) {
		case .Success(let JSON):
			handler( T( fromJSON: JSON as! [String : AnyObject] ), error: nil )
		case .Failure(let error):
			handler( nil, error: handleError( response ) )
		}
	}
	
	private func handleListResult<T: JSONSerializable>( response: Response<AnyObject, NSError>,
	                              handler: ( [ T ]?, error: ApiError? ) -> Void )
	{
		switch(response.result) {
		case .Success(let JSON):
			if let JSONList = JSON as? [ [String: AnyObject] ] {
				let list = JSONList.map { T( fromJSON: $0 ) }
				handler( list, error: nil )
			}
		case .Failure(let error):
			handler( nil, error: handleError( response ) )
		}
	}
	
	private func handleEmptyResult( response: Response<AnyObject, NSError>, handler: ( error: ApiError? ) -> Void )
	{
		switch(response.result) {
		case .Success(let JSON):
			handler( error: nil )
		case .Failure(let error):
			handler( error: handleError( response ) )
		}
	}
	
	private func handleError( response: Response<AnyObject, NSError> ) -> ApiError {
		let error = response.result.error!
		
		if let statusCode = response.response?.statusCode where !(200...299).contains( statusCode ) {
			return .Network( error: error, response: response.response! )
		} else if error.code == -6006 {
			return .JSONSerialization( error: error )
		}
		
		return .Unknown( error: error )
	}
}

// MARK: NESTED RESOURCES
extension Resource {
	public func member( memberID: AnyObject ) -> Resource {
		let memberPath = resourceMemberPath( memberID )
		return Resource( api: api, path: memberPath )
	}
	
	public func resource( resourcePath: String ) -> Resource {
		let nestedPath = nestedResourcePath( resourcePath )
		return Resource( api: api, path: nestedPath )
	}
	
	func resourceMemberPath( memberId: AnyObject ) -> String {
		return "\(path)/\(memberId)"
	}
	
	func nestedResourcePath( nestedResourcePath: String ) -> String {
		return "\(path)/\(nestedResourcePath)"
	}
}