Difference between revisions of "W3911 Sudoku Server"

Latest revision as of 08:59, 11 February 2023

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

Getting Started[edit]

Background[edit]

A Sudoku board is made up of nine boxes. The boxes (containers for nine cells) are listed from top to bottom, left to right, and indexed from zero. Cells are listed from top to bottom, left to right, and indexed from zero. All valid payloads and responses must use well-formed JSON. The value of “cells” is returned as follows: “cells”: [[<nine values from top-left>], [<nine values from top-middle>], …]

End Points[edit]

POST /games?difficulty=<difficulty>
Creates a new game and associated board

   Parameters: 
   difficulty: easy | medium | hard | hell

   Body: none

   Status code: 201 Created

   Response: ID (integer) of newly created game
   {"id":<id>}
   
   {"id": 728134}

   Errors:
   
   400 Bad Request (difficulty specified doesn't match requirements)

GET /games/<id>/cells?filter=<filter>
Returns the current cells for the specified game

   Parameters: 
   filter: all | repeated | incorrect


   Body: none


   Status code: 200 OK


   Response: {"board":
   [{"cells":[{"position":{"boxIndex":<boxIndex>,"cellIndex":<cellIndex>},"value":<value>}...
   

   {"board":
   [{"cells":[{"position":{"boxIndex":0,"cellIndex":0},"value":0},{"position":{"boxIndex":0,"cellIndex":1},"value":1},
              {"position":{"boxIndex":0,"cellIndex":2},"value":2},{"position":{"boxIndex":0,"cellIndex":3},"value":3},
              {"position":{"boxIndex":0,"cellIndex":4},"value":4},{"position":{"boxIndex":0,"cellIndex":5},"value":5},
              {"position":{"boxIndex":0,"cellIndex":6},"value":6},{"position":{"boxIndex":0,"cellIndex":7},"value":7},
              {"position":{"boxIndex":0,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
    {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
              {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
              {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
              {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
              {"position":{"boxIndex":1,"cellIndex":8},"value":8}]}
 ]}


   Errors:
   

   400 Bad Request (filter specified doesn't match requirements)

PUT /games/<id>/cells/<boxIndex>/<cellIndex>
Place specified value at in game at boxIndex, cellIndex

   Parameters: 
   none

   Body: {"value":<value>}

   Status code: 200 OK

   Response: none
   
   none

   Errors:
   
   400 Bad Request (boxIndex is out of range 0 ... 8)
 400 Bad Request (cellIndex is out of range 0 ... 8)
 400 Bad Request (value is out of range 1 ... 9 or null)

JSON Encoding[edit]

JSON Decoding[edit]

import Foundation

let json = 
#"""
{"board":
    [{"cells":[{"position":{"boxIndex":0,"cellIndex":0},"value":0},{"position":{"boxIndex":0,"cellIndex":1},"value":1},
               {"position":{"boxIndex":0,"cellIndex":2},"value":2},{"position":{"boxIndex":0,"cellIndex":3},"value":3},
               {"position":{"boxIndex":0,"cellIndex":4},"value":4},{"position":{"boxIndex":0,"cellIndex":5},"value":5},
               {"position":{"boxIndex":0,"cellIndex":6},"value":6},{"position":{"boxIndex":0,"cellIndex":7},"value":7},
               {"position":{"boxIndex":0,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]}
]}
"""#
let decoder = JSONDecoder()

guard let data = json.data(using: .utf8), 
      let board: Board = try? decoder.decode(Board.self, from: data) else {
    fatalError("Failed to decode json into board.")
}
dump(board)

// Structure definitions
struct Position: Codable {
    let boxIndex: Int
    let cellIndex: Int
}

struct Cell: Codable {
    let position: Position
    let value: Int?
}

struct Box: Codable {
     let cells: [Cell]
  }

struct Board: Codable {
     let board: [Box]
}

Issue Request from Client to Server[edit]

import Foundation                                                                                                                                                                                                                           
import FoundationNetworking                                                                                                                                                                                                                 
 
// Form the request                                                                                                                                                                                                                                           
var request = URLRequest(url: URL(string: "https://language-server.codermerlin.com/now")!)                                                                                                                                                  
request.httpMethod = "GET"

// Execute synchronously (uses extension in code below)                                                                                                                                                                                                                 
let (data, response, error) = URLSession.shared.syncRequest(with: request)
if let data = data,                                                                                                                                                                          
   let string = String(data: data, encoding: .utf8) {                                                                                                                                     
   print(string)                                                                                                                                                                            
} else if let error = error {
    print("Error: \(error)")
} else {
    print("An unexpected error occurred.")
}

// Reference: https://stackoverflow.com/questions/26784315/can-i-somehow-do-a-synchronous-http-request-via-nsurlsession-in-swift
extension URLSession {
   func syncRequest(with request: URLRequest) -> (Data?, URLResponse?, Error?) {
      var data: Data?
      var response: URLResponse?
      var error: Error?
      
      let dispatchGroup = DispatchGroup()
      let task = dataTask(with: request) {
         data = $0
         response = $1
         error = $2
         dispatchGroup.leave()
      }
      dispatchGroup.enter()
      task.resume()
      dispatchGroup.wait()
      
      return (data, response, error)
   }  
}

Server-side Query String Access[edit]

  let difficulty: String? = request.query["difficulty"]

Server-side Content Access for JSON[edit]

  app.put("value") { req -> String in
      struct CellValue: Decodable {
          let value: Int?
      }
      let cellValue = try req.content.decode(CellValue.self)
      return "Done"
  }

Server-side Parameter Access and Error Handling[edit]

    guard let boxIndex = req.parameters.get("boxIndex", as: Int.self),
        let cellIndex = req.parameters.get("cellIndex", as: Int.self) else {
        throw Abort(.badRequest, reason: "boxIndex and cellIndex MUST be integers")
    }

Server-side Returning "No Content"[edit]

  return Response(status: .noContent)

@@ Line 1: / Line 1: @@
-Background
+== Getting Started ==
+See [[Vapor]]
+== Background ==
 A Sudoku board is made up of nine boxes.
-Boxes (container for nine cells) are listed from top-to-bottom, left-to-right indexed from zero.
+The boxes (containers for nine cells) are listed from top to bottom, left to right, and indexed from zero.
-Cells are listed from top-to-bottom, left-to-right, indexed from zero.
+Cells are listed from top to bottom, left to right, and indexed from zero.
 All valid payloads and responses must use well-formed JSON.
-“cells” is returned as follows:
+The value of “cells” is returned as follows:
 “cells”: [[<nine values from top-left>], [<nine values from top-middle>], …]
-End Points
+== End Points ==
 {{RestAPI
 |endpoint=POST /games?difficulty=<difficulty>
@@ Line 18: / Line 21: @@
      {"id":<id>}
 |responseExample={"id": 728134}
+|errors=400 Bad Request (difficulty specified doesn't match requirements)
 }}
 {{RestAPI
-|endpoint=GET /games/<id>/cells
+|endpoint=GET /games/<id>/cells?filter=<filter>
 |action=Returns the current cells for the specified game
+|parameters=filter: all {{Bar}} repeated {{Bar}} incorrect
+|body=<span style="font-style: italic;">none</span>
+|statusCode=200 OK
+|response=
+  {"board":
+    [{"cells":[{"position":{"boxIndex":<boxIndex>,"cellIndex":<cellIndex>},"value":<value>}...
+|responseExample=
+  {"board":
+    [{"cells":[{"position":{"boxIndex":0,"cellIndex":0},"value":0},{"position":{"boxIndex":0,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":0,"cellIndex":2},"value":2},{"position":{"boxIndex":0,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":0,"cellIndex":4},"value":4},{"position":{"boxIndex":0,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":0,"cellIndex":6},"value":6},{"position":{"boxIndex":0,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":0,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]}
+  ]}
+|errors=400 Bad Request (filter specified doesn't match requirements)
+}}
+{{RestAPI
+|endpoint=PUT /games/<id>/cells/<boxIndex>/<cellIndex>
+|action=Place specified value at in game at boxIndex, cellIndex
 |parameters=<span style="font-style: italic;">none</span>
-|body=<span style="font-style: italic;">none</span>
+|body=
+  {"value":<value>}
 |statusCode=200 OK
-|response=Cells
+|response=<span style="font-style: italic;">none</span>
-    {"id":<id>}
+|responseExample=<span style="font-style: italic;">none</span>
-|responseExample={"id": 728134}
+|errors=
+Bad Request (boxIndex is out of range 0 ... 8)
+Bad Request (cellIndex is out of range 0 ... 8)
+Bad Request (value is out of range 1 ... 9 or null)
 }}
-* PUT /games/<id>/cells/<boxIndex>/<cellIndex>
+== JSON Encoding ==
-    * Action: Place specified value at in game at boxIndex, cellIndex
-    * Payload: value (null for removing value)
-    * Response: Nothing
-    * Status: 204 No Content
-=== JSON Encoding ===
 {{CodeExplorer
 |exerciseID=1
-|mode=swift
+|language=swift
 |height=400
 |initialCode=import Foundation
-struct Cell: Codable {
+let board = Board()
-    let value: Int?
-}
-let cell = Cell(value: 17)
 let encoder = JSONEncoder()
-guard let data = try? encoder.encode(cell),
+guard let data = try? encoder.encode(board),
        let json = String(data: data, encoding: .utf8) else {
      fatalError("Failed to encode data into json.")
 }
 print(json)
+// Structure definitions
+struct Position: Codable {
+    let boxIndex: Int
+    let cellIndex: Int
+}
+struct Cell: Codable {
+    let position: Position
+    let value: Int?
+}
+struct Box: Codable {
+     let cells: [Cell]
+     init(boxIndex: Int) {
+         var cells = [Cell]()
+         for cellIndex in 0 ..< 9 {
+             cells.append(Cell(position: Position(boxIndex: boxIndex, cellIndex: cellIndex), value: cellIndex))
+         }
+         self.cells = cells
+     }
+}
+struct Board: Codable {
+     let board: [Box]
+     init() {
+         var board = [Box]()
+         for boxIndex in 0 ..< 9 {
+             board.append(Box(boxIndex: boxIndex))
+         }
+         self.board = board
+     }
+}
 }}
-=== JSON Decoding ===
+== JSON Decoding ==
 {{CodeExplorer
 |exerciseID=2
-|mode=swift
+|language=swift
 |height=400
 |initialCode=import Foundation
+let json =
+#"""
+{"board":
+    [{"cells":[{"position":{"boxIndex":0,"cellIndex":0},"value":0},{"position":{"boxIndex":0,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":0,"cellIndex":2},"value":2},{"position":{"boxIndex":0,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":0,"cellIndex":4},"value":4},{"position":{"boxIndex":0,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":0,"cellIndex":6},"value":6},{"position":{"boxIndex":0,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":0,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]},
+     {"cells":[{"position":{"boxIndex":1,"cellIndex":0},"value":0},{"position":{"boxIndex":1,"cellIndex":1},"value":1},
+               {"position":{"boxIndex":1,"cellIndex":2},"value":2},{"position":{"boxIndex":1,"cellIndex":3},"value":3},
+               {"position":{"boxIndex":1,"cellIndex":4},"value":4},{"position":{"boxIndex":1,"cellIndex":5},"value":5},
+               {"position":{"boxIndex":1,"cellIndex":6},"value":6},{"position":{"boxIndex":1,"cellIndex":7},"value":7},
+               {"position":{"boxIndex":1,"cellIndex":8},"value":8}]}
+]}
+"""#
+let decoder = JSONDecoder()
+guard let data = json.data(using: .utf8),
+      let board: Board = try? decoder.decode(Board.self, from: data) else {
+    fatalError("Failed to decode json into board.")
+}
+dump(board)
+// Structure definitions
+struct Position: Codable {
+    let boxIndex: Int
+    let cellIndex: Int
+}
 struct Cell: Codable {
+    let position: Position
      let value: Int?
 }
-let json = #"{"value":17}"#
+struct Box: Codable {
-let decoder = JSONDecoder()
+     let cells: [Cell]
+  }
-guard let data = json.data(using: .utf8),
+struct Board: Codable {
-      let cell: Cell = try? decoder.decode(Cell.self, from: data) else {
+     let board: [Box]
-    fatalError("Failed to decode json into cell.")
 }
-dump(cell)
 }}
-=== Issue Request from Client to Server ===
+== Issue Request from Client to Server ==
 {{CodeExplorer
 |exerciseID=3
-|mode=swift
+|language=swift
 |height=400
 |initialCode=import Foundation
@@ Line 124: / Line 282: @@
 }
 }}
+== Server-side Query String Access ==
+<syntaxhighlight lang="swift">
+  let difficulty: String? = request.query["difficulty"]
+</syntaxhighlight>
+== Server-side Content Access for JSON ==
+<syntaxhighlight lang="swift">
+  app.put("value") { req -> String in
+      struct CellValue: Decodable {
+          let value: Int?
+      }
+      let cellValue = try req.content.decode(CellValue.self)
+      return "Done"
+  }
+</syntaxhighlight>
+== Server-side Parameter Access and Error Handling ==
+<syntaxhighlight lang="swift">
+    guard let boxIndex = req.parameters.get("boxIndex", as: Int.self),
+        let cellIndex = req.parameters.get("cellIndex", as: Int.self) else {
+        throw Abort(.badRequest, reason: "boxIndex and cellIndex MUST be integers")
+    }
+</syntaxhighlight>
+== Server-side Returning "No Content" ==
+<syntaxhighlight lang="swift">
+  return Response(status: .noContent)
+</syntaxhighlight>