Add TODOs
| author |
Steve Losh <steve@stevelosh.com> |
| date |
Tue, 28 Jul 2020 22:54:19 -0400 |
| parents |
3dbd9b45cf55 |
| children |
4c59ba2362d8 |
(in-package :jarl)
;;;; Input --------------------------------------------------------------------
(defstruct input
(stream nil :type stream)
(line 1 :type (and fixnum (integer 0)))
(column 0 :type (and fixnum (integer 0))))
(defun p (input &optional (eof :eof)) ; peek
(peek-char nil (input-stream input) nil eof))
(defun r (input) ; read
(let ((character (read-char (input-stream input) nil :eof)))
(case character
(#\newline (progn
(incf (input-line input))
(setf (input-column input) 0)))
(#\tab (incf (input-column input) 8))
(t (incf (input-column input))))
character))
;;;; Errors -------------------------------------------------------------------
(define-condition json-parsing-error (error)
((line :accessor line :initarg :line)
(class-designator :accessor class-designator :initarg :class-designator)
(column :accessor column :initarg :column)
(message :accessor message :initarg :message))
(:report (lambda (c stream)
(format stream "Error parsing JSON~@[ into ~S~] at line ~D column ~D: ~A"
(class-designator c)
(line c)
(column c)
(message c)))))
(defun e (class input format-string &rest args) ; error
(error 'json-parsing-error
:class-designator class
:line (input-line input)
:column (input-column input)
:message (apply #'format nil format-string args)))
;;;; Parsing Utilities --------------------------------------------------------
(defun skip-whitespace (input)
(loop :for ch = (p input)
:while (member ch '(#\space #\tab #\newline #\linefeed #\return))
:do (r input)))
(defun requires-escape-p (character)
(or (char= #\" character)
(char= #\\ character)
(<= (char-code character) #x1F)))
(defun parse-literal (input literal remaining-characters)
(loop :for next :across remaining-characters
:for char = (r input)
:unless (eql next char)
:do (e 'keyword input "expected ~S when parsing ~S but got ~S" next literal char))
literal)
(defun parse-hex-digit (input)
(let ((ch (r input)))
(if (eql :eof ch)
(e nil input "cannot parse \\u escape sequence, got ~S" :eof)
(or (digit-char-p ch 16)
(e nil input "cannot parse \\u escape sequence, ~S is not a hexadecimal digit" ch)))))
(defun parse-escaped-character (input)
(let ((ch (r input)))
(case ch
(#\" #\")
(#\\ #\\)
(#\/ #\/)
(#\b #\backspace)
(#\f (code-char #x0C))
(#\n #\linefeed)
(#\r #\return)
(#\t #\tab)
(#\u (let ((a (parse-hex-digit input)) ; todo handle surrogate pairs
(b (parse-hex-digit input))
(c (parse-hex-digit input))
(d (parse-hex-digit input)))
(code-char (+ (* a (expt 16 3)) ; todo maybe do this more portably
(* b (expt 16 2))
(* c (expt 16 1))
(* d (expt 16 0))))))
(t (e nil input "bad escape sequence ~S ~S" #\\ ch)))))
(defun parse-int (input &optional (allow-leading-zero t))
(loop :with i = 0
:with n = 0
:for ch = (p input #\e)
:for digit = (digit-char-p ch)
:while digit
:do (progn (r input)
(when (and (not allow-leading-zero)
(zerop n) ; leading
(zerop digit) ; zero
(digit-char-p (p input #\e))) ; but not a bare zero
(e nil input "bad leading zero"))
(incf n)
(setf i (+ (* 10 i) digit)))
:finally (if (zerop n)
(e nil input "expected an integer")
(return (values i n)))))
(defun parse-exponent (input)
(let* ((char (p input))
(sign (if (member char '(#\+ #\-))
(progn (r input)
(case char
(#\+ 1)
(#\- -1)))
1)))
(* sign (parse-int input))))
(defun parse-number (input)
(let ((sign 1) integer
(fractional 0) (fractional-length 0)
(exponent 0) has-exponent)
(when (eql #\- (p input))
(r input)
(setf sign -1))
(setf integer (parse-int input nil))
(when (eql #\. (p input))
(r input)
(setf (values fractional fractional-length) (parse-int input)))
(when (member (p input) '(#\e #\E))
(r input)
(setf exponent (parse-exponent input)
has-exponent t))
(if (and (zerop fractional-length) (not has-exponent))
(* sign integer)
(values
(coerce ;; todo make this less horrifying
(read-from-string (format nil "~A~D.~V,'0Dd~D"
(if (= -1 sign) #\- #\+)
integer
fractional-length
fractional
exponent))
'double-float)))))
(defun parse-kv-separator (class input)
(skip-whitespace input)
(let ((ch (r input)))
(unless (eql #\: ch)
(e class input "expected separator ~S but got ~S" #\: ch))
(skip-whitespace input)))
(defun json-type-of (object)
(typecase object
(integer 'integer)
(float 'float)
(t (type-of object))))
;;;; Primitive Readers --------------------------------------------------------
(defgeneric read% (class contained-class input))
(defmethod read% ((class (eql 'keyword)) contained-class input)
(let ((ch (r input)))
(case ch
(#\t (parse-literal input :true "rue"))
(#\f (parse-literal input :false "alse"))
(t (e 'keyword input "expected ~S or ~S but got ~S" #\t #\f ch)))))
(defmethod read% ((class (eql 'null)) contained-class input)
(let ((ch (r input)))
(if (eql ch #\n)
(parse-literal input nil "ull")
(e 'null input "expected ~S but got ~S" #\n ch))))
(defmethod read% ((class (eql 'vector)) contained-class input)
(let ((ch (r input)))
(unless (eql ch #\[)
(e 'vector input "expected ~S but got ~S" #\[ ch)))
(skip-whitespace input)
;; todo allow specialized vectors?
(if (eql (p input) #\])
(progn (r input) (vector))
(coerce
(loop
:with (c cc) = contained-class
:collect (read% c cc input)
:do (progn
(skip-whitespace input)
(let ((ch (r input)))
(case ch
(#\] (loop-finish))
(#\, (skip-whitespace input))
(t (e 'vector input "expected ~S or ~S but got ~S." #\] #\, ch))))))
'vector)))
(defmethod read% ((class (eql 'string)) contained-class input)
(let ((ch (r input)))
(unless (eql ch #\")
(e 'string input "expected opening ~S but got ~S" #\" ch)))
(with-output-to-string (s)
(loop :for ch = (r input)
:collect (cond
((eql ch :eof) (e 'string input "got ~S" :eof))
((eql ch #\\) (write-char (parse-escaped-character input) s))
((eql ch #\") (loop-finish))
((requires-escape-p ch) (e 'string input "bad unescaped character ~S" ch))
(t (write-char ch s))))))
(defmethod read% ((class (eql 'hash-table)) contained-class input)
(let ((ch (r input)))
(unless (eql ch #\{)
(e 'hash-table input "expected ~S but got ~S" #\{ ch)))
(skip-whitespace input)
(let ((result (make-hash-table :test #'equal)))
(if (eql (p input) #\})
(r input)
(loop
:with (c cc) = contained-class
:for name = (read% 'string nil input)
:for sep = (parse-kv-separator 'hash-table input)
:for value = (progn (skip-whitespace input)
(read% c cc input))
:do (progn
(setf (gethash name result) value)
(skip-whitespace input)
(let ((ch (r input)))
(case ch
(#\} (loop-finish))
(#\, (skip-whitespace input))
(t (e 'hash-table input "expected ~S or ~S but got ~S" #\} #\, ch)))))))
result))
(defmethod read% ((class (eql 'number)) contained-class input)
(let ((ch (p input)))
(unless (member ch '(#\- #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9))
(r input) ; chomp to ensure accurate column count
(e 'number input "expected digit or ~S but got ~S" #\- ch)))
(parse-number input))
(defmethod read% ((class (eql 'nullable)) contained-class input)
(case (p input)
(:eof (e `(or null ,input) input "got ~S" :eof))
(#\n (read% 'null nil input))
(t (read% (first contained-class) (second contained-class) input))))
(defmethod read% ((class (eql t)) contained-class input)
(skip-whitespace input)
(ecase (p input)
(:eof (r input) (e 't input "got ~S" :eof))
((#\t #\f) (read% 'keyword nil input))
(#\n (read% 'null nil input))
(#\" (read% 'string nil input))
(#\{ (read% 'hash-table '(t) input))
(#\[ (read% 'vector '(t) input))
((#\- #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9) (read% 'number nil input))))
;;;; Object Parsers -----------------------------------------------------------
(defun lisp-case-to-snake-case (string)
"Convert a Lisp-cased string designator `\"FOO-BAR\"` into snake cased `\"foo_bar\"`."
(substitute #\_ #\- (string-downcase string)))
(defclass json-class (standard-class)
((slot-name-to-json-name :accessor slot-name-to-json-name
:initarg :slot-name-to-json-name
:initform 'lisp-case-to-snake-case)
(unknown-slots :accessor unknown-slots
:initarg :unknown-slots
:initform :discard)
(name-initarg-map :accessor name-initarg-map)
(slot-name-alist :accessor slot-name-alist)))
(defmethod c2mop:validate-superclass ((class json-class) (superclass standard-class))
t)
(defclass json-direct-slot-definition (c2mop:standard-direct-slot-definition)
((json-class :initarg :json :accessor json-class)
(json-name :initarg :json/name :accessor json-name)))
(defclass json-effective-slot-definition (c2mop:standard-effective-slot-definition)
((json-class :initarg :json :accessor json-class)
(json-name :initarg :json/name :accessor json-name)
(json-initarg :accessor json-initarg)))
(defmethod c2mop:direct-slot-definition-class ((class json-class) &rest initargs)
(if (getf initargs :json)
(find-class 'json-direct-slot-definition)
(call-next-method)))
(defvar *effective-slot-definition-class* nil)
(defmethod c2mop:effective-slot-definition-class ((class json-class) &rest initargs)
(declare (ignore initargs))
;; I'm not sure why we need to use this hack here, but for some reason
;; initargs doesn't contain the slot options like :json and :json/name here
;; like it does in direct-slot-definition-class. So we need another way to
;; know which class to use here.
(or *effective-slot-definition-class* (call-next-method)))
(defmethod c2mop:compute-effective-slot-definition ((class json-class) name direct-slots)
(if (not (some (lambda (dslot)
(typep dslot 'json-direct-slot-definition))
direct-slots))
(call-next-method)
(let* ((*effective-slot-definition-class* (find-class 'json-effective-slot-definition))
(eslot (call-next-method))
(dslot (first direct-slots)) ; todo be smarter about coalescing these
(initarg (gensym (format nil "json-initarg-~A" name)))) ; todo nicer name
(setf (json-name eslot) (if (slot-boundp dslot 'json-name)
(json-name dslot)
(funcall (slot-name-to-json-name class) name)) ; todo make this less shitty
(json-class eslot) (if (slot-boundp dslot 'json-class)
(canonicalize-class-designator (json-class dslot))
'(t))
(json-initarg eslot) initarg) ; todo nicer name
(push initarg (c2mop:slot-definition-initargs eslot))
eslot)))
(defun json-slots (class)
(remove-if-not (lambda (slot) (typep slot 'json-effective-slot-definition))
(c2mop:class-slots class)))
(defun make-name-initarg-map (class)
"Return a name/initarg map for the JSON slots of `class`.
The result will be a hash table of `{name: (initarg class contained-class)}`.
"
(let* ((slots (json-slots class))
(result (make-hash-table :test #'equal :size (length slots))))
(dolist (slot slots)
(destructuring-bind (c &optional cc) (json-class slot)
(setf (gethash (json-name slot) result)
(list (json-initarg slot) c cc))))
result))
(defun make-slot-name-alist (class)
(mapcar (lambda (slot)
(cons (c2mop:slot-definition-name slot)
(json-name slot)))
(json-slots class)))
(defmethod shared-initialize ((class json-class) slot-names
&rest initargs
&key slot-name-to-json-name unknown-slots
&allow-other-keys)
(apply #'call-next-method class slot-names
(append
(when slot-name-to-json-name ; todo assert length = 1
(list :slot-name-to-json-name (first slot-name-to-json-name)))
(when unknown-slots ; todo assert length = 1
(list :unknown-slots (first unknown-slots)))
initargs)))
(defmethod c2mop:finalize-inheritance :after ((class json-class))
(setf (name-initarg-map class) (make-name-initarg-map class)
(slot-name-alist class) (make-slot-name-alist class)))
(defun parse-json-class (class-name class input)
(let ((ch (r input)))
(unless (eql ch #\{)
(e class-name input "expected ~S but got ~S" #\{ ch)))
(skip-whitespace input)
(if (eql (p input) #\})
(progn
(r input)
(make-instance class))
(loop
:with unknown = (unknown-slots class)
:with map = (name-initarg-map class)
:with init = (list)
:for name = (read% 'string nil input)
:for sep = (parse-kv-separator class-name input)
:for (initarg c cc) = (gethash name map)
:do (progn
(if (null initarg)
(ecase unknown
(:discard (read% t nil input))
(:error (e class-name input "got unknown object attribute ~S" name)))
(progn
(push (read% c cc input) init)
(push initarg init)))
(skip-whitespace input)
(let ((ch (r input)))
(case ch
(#\} (loop-finish))
(#\, (skip-whitespace input))
(t (e class-name input "expected ~S or ~S but got ~S." #\} #\, ch)))))
:finally (return (apply #'make-instance class init)))))
(defmethod read% ((class-name symbol) (contained-class null) (input input))
(let ((class (find-class class-name nil)))
(typecase class
(json-class
(c2mop:ensure-finalized class)
(parse-json-class class-name class input))
(null (error "Cannot find class ~S to parse JSON into." class-name))
(t (error "Cannot parse JSON into class ~S because that class is not a ~S"
class-name 'json-class)))))
;;;; Printing -----------------------------------------------------------------
(defun write-escaped-char (char stream)
(case char
((#\newline #\linefeed) (write-string "\\n" stream))
(#\return (write-string "\\r" stream))
(#\\ (write-string "\\\\" stream))
(t (format stream "\\u~4,'0X" (char-code char)))))
(defgeneric print% (thing stream))
(defmethod print% ((thing null) stream)
(write-string "null" stream))
(defmethod print% ((thing string) stream)
(write-char #\" stream)
(loop :for char :across thing
:do (if (requires-escape-p char)
(write-escaped-char char stream)
(write-char char stream)))
(write-char #\" stream))
(defmethod print% ((thing vector) stream)
(write-char #\[ stream)
(loop :with first = t
:for object :across thing
:do (progn (if first
(setf first nil)
(write-char #\, stream))
(print% object stream)))
(write-char #\] stream))
(defmethod print% ((thing hash-table) stream)
(write-char #\{ stream)
(loop :with first = t
:for name :being :the hash-keys :in thing :using (hash-value value)
:do (progn (if first
(setf first nil)
(write-char #\, stream))
(assert (stringp name))
(print% name stream)
(write-char #\: stream)
(print% value stream)))
(write-char #\} stream))
(defmethod print% ((thing single-float) stream)
(let ((*read-default-float-format* 'single-float))
(princ thing stream)))
(defmethod print% ((thing double-float) stream)
(let ((*read-default-float-format* 'double-float))
(princ thing stream)))
(defmethod print% ((thing integer) stream)
(format stream "~D" thing))
(defmethod print% ((thing (eql :false)) stream)
(write-string "false" stream))
(defmethod print% ((thing (eql :true)) stream)
(write-string "true" stream))
(defmethod print% (thing stream)
(let ((class (class-of thing)))
(if (typep class 'json-class)
(progn
(write-char #\{ stream)
(loop :with first = t
:for (slot . name) :in (slot-name-alist class)
:when (slot-boundp thing slot)
:do (progn (if first
(setf first nil)
(write-char #\, stream))
(print% name stream)
(write-char #\: stream)
(print% (slot-value thing slot) stream)))
(write-char #\} stream))
(error "Don't know how to print object ~S of class ~S as JSON." thing class))))
;;;; API ----------------------------------------------------------------------
(defun canonicalize-class-designator (class-designator)
(flet ((fail () (error "Malformed class designator ~S" class-designator)))
(etypecase class-designator
(cons (destructuring-bind (head a &optional (b nil b?)) class-designator
(ecase head
; (vector foo)
((hash-table vector)
(progn (when b? (fail))
(list head (canonicalize-class-designator a))))
; (or null foo)
(or (progn
(unless b? (fail)) ; must have a second option
(when (eql 'null b) (rotatef a b)) ; sort a/b
(unless (eql 'null a) (fail)) ; no arbitrary ors
(list 'nullable (canonicalize-class-designator b)))))))
(symbol (case class-designator
(vector '(vector (t)))
(hash-table '(hash-table (t)))
(t (list class-designator)))))))
(defun ensure-stream (stream-or-string)
(etypecase stream-or-string
(stream stream-or-string)
(string (make-string-input-stream stream-or-string))))
(defun read (class-designator stream-or-string &optional (eof-error-p t) eof)
(let ((input (make-input :stream (ensure-stream stream-or-string))))
(skip-whitespace input)
(if (eql :eof (p input))
(if eof-error-p
(error 'end-of-file)
eof)
(destructuring-bind (class &optional contained)
(canonicalize-class-designator class-designator)
(read% class contained input)))))
(defun print (object &optional (stream *standard-output*))
(let ((*read-default-float-format* 'double-float)
(*print-base* 10))
(etypecase stream
((or stream (eql t)) (progn (print% object stream)
(values)))
(null (with-output-to-string (s)
(print% object s))))))