Swift DynamicJSON

indirect enum JSON: Hashable, Codable, CustomStringConvertible, ... {
  case null
  case boolean(Bool)
  case integer(Int64)
  case float(Double)
  case string(String)
  case array([JSON])
  case object([String : JSON])
  ...
}

let json0: JSON = [
  "foo": true,
  "str": "one two",
  "object": [
    "value": nil,
    "arr": [1, 2, 3],
    "obj": [ "x" : 17.6 ]
  ]
]

let json1 = try JSON(string: """
  {
    "foo": true,
    "str": "one two",
    "object": {
      "value": null,
      "arr": [1, 2, 3],
      "obj": { "x" : 17.6 }
    }
  }
""")

struct Person: Codable {
  let name: String
  let age: Int
  let children: [Person]
}
let person = Person(name: "John", age: 34,
                    children: [ Person(name: "Sofia", age: 5, children: []) ])
let json2 = try JSON(encodable: person)
print(json2.description)

let json3: JSON = [
  "name": "Matthew",
  "age": 29,
  "children": []
]
let person2: Person = try json3.coerce()

protocol JSONReference: CustomStringConvertible {
  // Returns a new JSONReference with the given member selected.
  func select(member: String) -> Self
  // Returns a new JSONReference with the given index selected.
  func select(index: Int) -> Self
  // Retrieve value at which this reference is pointing from JSON document `value`.
  func get(from value: JSON) -> JSON?
  // Replace value at which this reference is pointing with `json` within `value`.
  func set(to json: JSON, in value: JSON) throws -> JSON
  // Mutate value at which this reference is pointing within JSON document `value`
  // with function `proc`.
  func mutate(_ json: inout JSON, with proc: (inout JSON) throws -> Void) throws
}

protocol SegmentableJSONReference: JSONReference {
  associatedtype Segment: JSONReferenceSegment
  // An array of segments representing the reference.
  var segments: [Segment] { get }
  // Creates a new `SegmentableJSONReference` on top of this reference.
  func select(segment: Segment) -> Self
  // Decomposes this reference into the top segment selector and its parent.
  var deselect: (Self, Segment)? { get }
}

indirect enum JSONLocation: SegmentableJSONReference, Codable, Hashable, CustomStringConvertible {
  case root
  case member(JSONLocation, String)
  case index(JSONLocation, Int)
  
  enum Segment: JSONReferenceSegment, Codable, Hashable, CustomStringConvertible {
    case member(String)
    case index(Int)
    ...
  }
  ...
}

let r1 = try JSONLocation("$['store']['book'][0]['title']")
let r2 = JSONLocation(segments: [.member("store"),
                                 .member("book"),
                                 .index(0),
                                 .member("title")])

indirect enum JSONLocation: SegmentableJSONReference, ... {
  // The segments defining this `JSONLocation`.
  var segments: [Segment]
  // Returns a new JSONLocation with the given member selected.
  func select(member: String) -> JSONLocation
  // Returns a new JSONLocation with the given index selected.
  func select(index: Int) -> JSONLocation
  // Returns a new JSONLocation by appending the given segment.
  func select(segment: Segment) -> JSONLocation
  // Returns a matching `JSONPointer` reference if possible.
  var pointer: JSONPointer?
  // Returns a matching `JSONPath` query.
  var path: JSONPath
  // Retrieve value at this location within `value`.
  func get(from value: JSON) -> JSON?
  // Replace value at this location within `in` with `value`.
  func set(to json: JSON, in value: JSON) throws -> JSON
  // Mutate value at this location within `value` with function `proc`.
  // `proc` is provided a reference, enabling efficient in-place mutations.
  func mutate(_ json: inout JSON, with proc: (inout JSON) throws -> Void) throws
}

struct JSONPointer: SegmentableJSONReference, Codable, Hashable, CustomStringConvertible {
  let segments: [ReferenceToken]
  
  enum ReferenceToken: JSONReferenceSegment, Hashable, CustomStringConvertible {
    case member(String)
    case index(String, Int?)
    ...
  }
  ...
}

let p1 = try JSONPointer("/store/book/0/title")
let p2 = JSONPointer(components: ["store", "book", "0", "title"])

struct JSONPointer: SegmentableJSONReference, ... {
  // Returns this JSONPointer as an array of reference tokens.
  var segments: [ReferenceToken]
  // Returns a new JSONPointer with the given member selected.
  func select(member: String) -> JSONPointer
  // Returns a new JSONPointer with the given index selected.
  func select(index: Int) -> JSONPointer
  // Constructs a new JSONPointer by appending the given segment to this pointer.
  func select(segment: ReferenceToken) -> JSONPointer
  // Decomposes this JSONPointer into a parent pointer and a selector reference token.
  var deselect: (JSONPointer, ReferenceToken)?
  // The reference tokens defining this `JSONPointer` value.
  var components: [String]
  // Returns all JSON locations corresponding to this `JSONPointer`.
  func locations() -> [JSONLocation]
  // Retrieve value at which this reference is pointing from JSON document `value`.
  func get(from value: JSON) -> JSON?
  // Replace value at which this reference is pointing with `json` within `value`.
  func set(to json: JSON, in value: JSON) throws -> JSON
  // Mutate value at this location within `value` with function `proc`. `proc`
  // is provided a reference, enabling efficient, in-place mutations.
  func mutate(_ json: inout JSON, with proc: (inout JSON) throws -> Void) throws
}

let jval = try JSON(string: """
  { "store": {
      "book": [
        { "category": "reference",
          "author": "Nigel Rees",
          "title": "Sayings of the Century",
          "price": 8.95 },
        { "category": "fiction",
          "author": "Evelyn Waugh",
          "title": "Sword of Honour",
          "price": 12.99 },
        { "category": "fiction",
          "author": "Herman Melville",
          "title": "Moby Dick",
          "isbn": "0-553-21311-3",
          "price": 8.99 },
        { "category": "fiction",
          "author": "J. R. R. Tolkien",
          "title": "The Lord of the Rings",
          "isbn": "0-395-19395-8",
          "price": 22.99 }
      ],
      "bicycle": {
        "color": "red",
        "price": 399
      }
    }
  }
  """)

let path = try JSONPath(query: "$.store.book[?@.price < 10].title")
var results = try value.query(path)
for result in results {
  print(result)
}

$['store']['book'][0]['title'] => "Sayings of the Century"
$['store']['book'][2]['title'] => "Moby Dick"

enum JSON: Hashable, ... {
  // Mutates this JSON value if it represents either an array or a string by
  // appending the given JSON value `json`. For arrays, `json` is appended as a
  // new element. For strings it is expected that `json` also refers to a string
  // and `json` gets appended as a string. For all other types of JSON values,
  // an error is thrown.
  mutating func append(_ json: JSON) throws
  
  // Mutates this JSON value if it represents either an array or a string by
  // inserting the given JSON value `json`. For arrays, `json` is inserted as a
  // new element at `index`. For strings it is expected that `json` also refers to
  // a string and `json` gets inserted into this string at position `index`. For
  // all other types of JSON values, an error is thrown.
  mutating func insert(_ json: JSON, at index: Int) throws
  
  // Adds a new key/value mapping or updates an existing key/value mapping in this
  // JSON object. If this JSON value is not an object, an error is thrown.
  mutating func assign(_ member: String, to json: JSON) throws
  
  // Replaces the value the location reference `ref` is referring to with `json`.
  // The replacement is done in place, i.e. it mutates this JSON value. `ref` can
  // be implemented by any abstraction implementing the `JSONReference` procotol.
  mutating func update(_ ref: JSONReference, with json: JSON) throws
  
  // Replaces the value the location reference string `ref` is referring to with
  // `json`. The replacement is done in place, i.e. it mutates this JSON value.
  // `ref` is a string representation of either `JSONLocation` or `JSONPointer`
  // references.
  mutating func update(_ ref: String, with json: JSON) throws
  
  // Mutates the JSON value the reference `ref` is referring to with function
  // `proc`. `proc` receives a reference to the JSON value, allowing efficient in
  // place mutations without automatically doing any copying. `ref` can be
  // implemented by any abstraction implementing the `JSONReference` procotol.
  mutating func mutate(_ ref: JSONReference,
                       with proc: (inout JSON) throws -> Void) throws
  
  // Mutates the JSON value the reference `ref` is referring to with function
  // `arrProc` if the value is an array or `objProc` if the value is an object. For
  // all other cases, an error is thrown. This method allows for efficient in place
  // mutations without automatically doing any copying. `ref` can be implemented by
  // any abstraction implementing the `JSONReference` procotol.
  mutating func mutate(_ ref: JSONReference,
                       array arrProc: ((inout [JSON]) throws -> Void)? = nil,
                       object objProc: ((inout [String : JSON]) throws -> Void)? = nil,
                       other proc: ((inout JSON) throws -> Void)? = nil) throws
  
  // Mutates the JSON value the reference string `ref` is referring to with function
  // `proc`. `proc` receives a reference to the JSON value, allowing efficient in
  // place mutations without automatically doing any copying. `ref` is a string
  // representation of either `JSONLocation` or `JSONPointer` references.
  mutating func mutate(_ ref: String, with proc: (inout JSON) throws -> Void) throws
  
  // Mutates the JSON array the reference string `ref` is referring to with function
  // `arrProc` if the value is an array or `objProc` if the value is an object. For
  // all other cases, an error is thrown. This method allows for efficient in place
  // mutations without automatically doing any copying. `ref` is a string
  // representation of either `JSONLocation` or `JSONPointer` references.
  mutating func mutate(_ ref: String,
                       array arrProc: ((inout [JSON]) throws -> Void)? = nil,
                       object objProc: ((inout [String : JSON]) throws -> Void)? = nil,
                       other proc: ((inout JSON) throws -> Void)? = nil) throws
  ...
}

mutating func mutate(_ ref: JSONReference,
                     with proc: (inout JSON) throws -> Void) throws
mutating func mutate(_ ref: JSONReference,
                     array arrProc: ((inout [JSON]) throws -> Void)? = nil,
                     object objProc: ((inout [String : JSON]) throws -> Void)? = nil,
                     other proc: ((inout JSON) throws -> Void)? = nil) throws

enum JSONPatchOperation: Codable, Hashable, CustomStringConvertible, CustomDebugStringConvertible {
  // add(path, value): Add `value` to the JSON value at `path`
  case add(JSONPointer, JSON)
  // remove(path): Remove the value at location `path` in a JSON value.
  case remove(JSONPointer)
  // replace(path, value): Replace the value at location `path` with `value`.
  case replace(JSONPointer, JSON)
  // move(path, from): Move the value at `from` to `path`. This is equivalent
  // to first removing the value at `from` and then adding it to `path`.
  case move(JSONPointer, JSONPointer)
  // copy(path, from): Copy the value at `from` to `path`. This is equivalent
  // to looking up the value at `from` and then adding it to `path`.
  case copy(JSONPointer, JSONPointer)
  // test(path, value): Compares value at `path` with `value` and fails if the
  // two are different.
  case test(JSONPointer, JSON)
  ...
}

struct JSONPatch: Codable, Hashable, CustomStringConvertible, CustomDebugStringConvertible {
  // Sequence of operations.
  let operations: [JSONPatchOperation]
  // Initializer based on a sequence of operations
  init(operations: [JSONPatchOperation]) { ... }
  // Decodes the provided data with the given decoding strategies.
  init(data: Data,
       dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .deferredToDate,
       floatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy = .throw,
       userInfo: [CodingUserInfoKey : Any]? = nil) throws { ... }
  // Decodes the provided string with the given decoding strategies.
  init(string: String,
       dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .deferredToDate,
       floatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy = .throw,
       userInfo: [CodingUserInfoKey : Any]? = nil) throws { ... }
  // Decodes the content at the provided URL with the given decoding strategies.
  init(url: URL,
       dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .deferredToDate,
       floatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy = .throw,
       userInfo: [CodingUserInfoKey : Any]? = nil) throws { ... }
  ...
  // Applies this patch object to `json` mutating `json` in place.
  func apply(to json: inout JSON) throws { ... }
  ...
}

let jsonstr = """
  [
    { "op": "test", "path": "/a/b/c", "value": "foo" },
    { "op": "remove", "path": "/a/b/c" },
    { "op": "add", "path": "/a/b/c", "value": [ "foo", "bar" ] },
    { "op": "replace", "path": "/a/b/c", "value": 42 },
    { "op": "move", "from": "/a/b/c", "path": "/a/b/d" },
    { "op": "copy", "from": "/a/b/d", "path": "/a/b/e" }
  ]
  """
let patch = try JSONPatch(string: jsonstr)
var json: JSON = ...
try json.apply(patch: patch)

let a = try JSON(string: #"""
  {
    "a": [1, { "b": 2 }],
    "c": { "d": [{}] }
  }
"""#)
let b = try JSON(string: #"""
  {
    "a": [1, { "b": 2, "e": 4 }],
    "c": { "d": [{"f": 5}] }
  }
"""#)
b.isRefinement(of: a) ⇒ true

let c = try JSON(string: #"""
  { "a": [1, {"e": 8}],
    "c": {"f": "hello"},
    "g": 9 }
"""#)
a.merging(value: c) 
⇒
{
  "a": [1, { "b": 2, "e": 8 }],
  "c": { "d": [{}], "f": "hello" },
  "g": 9
}

let d = try JSON(string: #"""
  {
    "a": [1, { "e": 2 }, 3],
    "c": { "d": "hello" },
    "f": 5
  }
"""#)
a.overriding(with: d)
⇒
{
  "a": [1, { "b": 2, "e": 2 }, 3],
  "c": { "d": "hello" },
  "f": 5
}

// Merges this JSON value with the given JSON value `patch` recursively. Objects are
// merged key by key with values from `patch` overriding values of the object represented
// by this JSON value. All other types of JSON values are not merged and `patch` overrides
// this JSON value.
func merging(patch: JSON) -> JSON { ... }

// Create a new schema registry
let registry = JSONSchemaRegistry()
// Register a schema resource from a string literal
try registry.register(resource: JSONSchemaResource(string: #"""
  {
    "$id": "https://example.com/schema/test",
    "$schema": "https://json-schema.fullstack.org.cn/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "prop1": {
        ...
      }
    }
  }
"""#))
...
// Load a schema resource from a file
try registry.loadSchema(from: URL(filePath: "/Users/objecthub/foo.json"))
...
// Make JSON schema stored in json files under the given directory discoverable
registry.register(provider:
  StaticJSONSchemaFileProvider(
    directory: URL(filePath: "/Users/objecthub/myschema"),
    base: JSONSchemaIdentifier(string: "http://example.com/schemas")!))
...
// Obtain a validator for a schema
guard let validator = try? registry.validator(for: "https://example.com/schema/test") else {
  // Throw error stating that the schema could not be found
}
// Validate a JSON instance `json`
let result = validator.validate(json)
print("valid = \(result.isValid)")

enum JSON: Hashable, ... {
  // Returns true if this JSON document is valid for the given JSON schema (using
  // `registry` for resolving references to schema referred to from `schema`).
  func valid(for schema: JSONSchema,
             dialect: JSONSchemaDialect? = nil,
             using registry: JSONSchemaRegistry? = nil) -> Bool
  
  // Returns a schema validation result for this JSON document validated against the
  // JSON schema `schema` (using`registry` for resolving references to schema
  // referred to from `schema`).
  func validate(with schema: JSONSchema,
                dialect: JSONSchemaDialect? = nil,
                using registry: JSONSchemaRegistry? = nil) throws -> JSONSchemaValidationResult
  
  // Returns true if this JSON document is valid for the given JSON schema (using
  // `registry` for resolving references to schema referred to from `schema`).
  func valid(for resource: JSONSchemaResource,
             dialect: JSONSchemaDialect? = nil,
             using registry: JSONSchemaRegistry? = nil) -> Bool
  
  // Returns a schema validation result for this JSON document validated against the
  // JSON schema `schema` (using`registry` for resolving references to schema
  // referred to from `schema`).
  func validate(with resource: JSONSchemaResource,
                dialect: JSONSchemaDialect? = nil,
                using registry: JSONSchemaRegistry? = nil) throws  -> JSONSchemaValidationResult
  ...
}

val res: JSONSchemaValidationResult = ...
for constraint in res.formatConstraints where constraint.message.valid == false {
  print("value \(constraint.value) does not match format '\(constraint.message.format)'")
}

let schema = try JSONSchema(string: #"""
  {
    "$id": "https://objecthub.com/example/person",
    "$schema": "https://json-schema.fullstack.org.cn/draft/2020-12/schema",
    "title": "person",
    "type": "object",
    "properties": {
      "name": {
        "type": "string",
        "minLength": 1
      },
      "birthday": {
        "type": "string",
        "format": "date"
      },
      "numChildren": {
        "type": "integer",
        "default": 0
      },
      "address": {
        "oneOf": [
          { "type": "string", "default": "12345 Mcity" },
          { "$ref": "#address",
            "default": { "city": "Mcity", "postalCode": "12345" } }
        ]
      },
      "email": {
        "type": "array",
        "maxItems": 3,
        "items": {
          "type": "string",
          "format": "email"
        }
      }
    },
    "required": ["name", "birthday"],
    "$defs": {
      "address": {
        "$anchor": "address",
        "type": "object",
        "properties": {
          "street": {
            "type": "string"
          },
          "city": {
            "type": "string"
          },
          "postalCode": {
            "type": "string",
            "pattern": "\\d{5}"
          }
        },
        "required": ["city", "postalCode"]
      }
    }
  }
"""#)
/// `instance0` is a valid instance of `schema`
let instance0: JSON = [
  "name": "John Doe",
  "birthday": "1983-03-19",
  "numChildren": 2,
  "email": ["john@doe.com", "john.doe@gmail.com"]
]
instance0.valid(for: schema) ⇒ true
/// `instance1` is not a valid instance of `schema`
let instance1: JSON = [
  "name": "John Doe",
  "email": ["john@doe.com", "john.doe@gmail.com"]
]
instance1.valid(for: schema) ⇒ false
/// `instance2` is a valid instance of `schema`
let instance2: JSON = [
  "name": "John Doe",
  "birthday": "1983-03-19",
  "address": "12 Main Street, 17445 Noname"
]
let res2 = try instance2.validate(with: schema)
res2.isValid ⇒ true
for (location, (exists, values)) in res2.defaults {
  if exists {
    print("\(location) exists; defaults: \(values)")
  } else {
    print("\(location) does not exist; defaults: \(values)")
  }
}