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;; -*- mode: lisp; coding: utf-8 -*-
;;
;; Copyright 2011, Matthias Andreas Benkard.
;;
;; Licensed under the Apache License, Version 2.0 (the "License");
;; you may not use this file except in compliance with the License.
;; You may obtain a copy of the License at
;;
;; http://www.apache.org/licenses/LICENSE-2.0
;;
;; Unless required by applicable law or agreed to in writing, software
;; distributed under the License is distributed on an "AS IS" BASIS,
;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;; See the License for the specific language governing permissions and
;; limitations under the License.
(defpackage #:json-template
(:use #:common-lisp)
(:export #:parse-template-string
#:expand-template
#:*template-formatters*))
(in-package #:json-template)
(defconstant +not-found+
(if (boundp '+not-found+)
(symbol-value '+not-found+)
'#:not-found))
(defclass template ()
((things :initarg :things :accessor template-things)))
(defun tokenize-template-string (string)
(loop with in-command-p = nil
with skip-newline-p = nil
with position = 0
for terminator = (position (if in-command-p #\} #\{) string
:start position)
collect (cons in-command-p
(subseq string
position
(or terminator (length string))))
do (setq position (and terminator (1+ terminator)))
when (and skip-newline-p
position
(< position (length string))
(char= (char string position) #\Newline))
do (incf position)
do (setq in-command-p (not in-command-p)
skip-newline-p (and in-command-p
position
(member (char string position)
(list #\. #\#))))
until (null terminator)))
(defun parse-template-string (string)
(make-instance 'template
:things (parse-raw-tokens (tokenize-template-string string))))
(defun parse-directive (string)
(let* ((space1 (position #\Space string))
(space2 (and space1 (position #\Space string :start (1+ space1)))))
(list (intern (string-upcase (subseq string 1 (or space1 (length string))))
'#:keyword)
(if space1
(subseq string (1+ space1) (or space2 (length string)))
nil)
(if space2
(subseq string (1+ space2))
nil))))
(defun parse-variable (string)
(let ((pipe (position #\| string)))
(if pipe
(list (subseq string 0 pipe)
(subseq string (1+ pipe)))
(list string nil))))
(defun parse-token (token)
(destructuring-bind (command-p . data)
token
(if command-p
(case (char data 0)
((#\.)
(list* :directive (parse-directive data)))
((#\#)
(list* :comment data))
(otherwise
(list* :variable (parse-variable data))))
(list :text data))))
(defun parse-raw-tokens (tokens)
(parse-tokens (mapcar #'parse-token tokens)))
(defun parse-tokens (tokens)
(let ((result (loop for token = (and tokens (car tokens))
for token-kind = (first token)
for token-data = (rest token)
until (or (null tokens)
(and (eq token-kind :directive)
(member (second token) '(:or :end :alternates))))
do (setq tokens (cdr tokens))
if (eq token-kind :directive)
collect (multiple-value-bind (subresult rest-tokens)
(parse-tokens tokens)
(let ((sub-end-tag (first rest-tokens))
(separator nil)
(alternative nil))
(setq tokens (rest rest-tokens))
(when (equal sub-end-tag '(:directive :alternates "with" nil))
(multiple-value-bind (altresult rest-tokens2)
(parse-tokens tokens)
(setq tokens (rest rest-tokens2)
sub-end-tag (first rest-tokens2)
separator altresult)))
(when (equal sub-end-tag '(:directive :or nil nil))
(multiple-value-bind (altresult rest-tokens2)
(parse-tokens tokens)
(setq tokens (rest rest-tokens2)
sub-end-tag (first rest-tokens2)
alternative altresult)))
(ecase (first token-data)
(:section
(list :section
(second token-data)
subresult
alternative))
(:repeated
(list :repeated-section
(third token-data)
subresult
alternative
separator)))))
else if (member token-kind '(:variable :text))
collect token
else if (eq token-kind :comment)
do (progn)
else do (error "Encountered invalid token: ~S" token))))
(values result tokens)))
(defun expand-template (template context)
(with-output-to-string (out)
(expand-template-to-stream template (list context) out)))
(defun getcontext (context key &aux (result context))
(dolist (key-component key result)
(handler-case
(setq result
(getf result
key-component
+not-found+))
(error (condition)
(declare (ignore condition))
(return-from getcontext +not-found+)))))
(defun listify-key (key &optional (start 0))
(let ((dot (position #\. key :start start)))
(if dot
(cons (intern (string-upcase (subseq key start dot))
'#:keyword)
(listify-key key (1+ dot)))
(list (intern (string-upcase (subseq key start))
'#:keyword)))))
(defun lookup-context (contexts key)
(when (string= key "@")
(return-from lookup-context (first contexts)))
(unless (listp key)
(setq key (listify-key key)))
(labels ((lookup-in-stack (context-stack)
(if (endp context-stack)
nil
(let ((thing (getcontext (first context-stack) key)))
(if (eql thing +not-found+)
(lookup-in-stack (rest context-stack))
thing)))))
(lookup-in-stack contexts)))
(defun expand-things-to-stream (template contexts stream)
(dolist (thing template)
(ecase (first thing)
(:text
(write-string (second thing) stream))
(:variable
(destructuring-bind (variable formatter) (cdr thing)
(let* ((value (lookup-context contexts variable))
(formatted-value (if formatter
(funcall (cdr (assoc formatter *template-formatters*
:test #'equal))
value)
value)))
(typecase formatted-value
(null (values))
(t (format stream "~A" formatted-value))))))
(:section
(destructuring-bind (section branch alternative) (cdr thing)
(let ((value (lookup-context contexts section)))
(expand-things-to-stream (if value branch alternative)
(cons value contexts)
stream))))
(:repeated-section
(destructuring-bind (section branch alternative separator) (cdr thing)
(let ((value (lookup-context contexts section)))
(if value
(let ((first-loop t))
(map nil
(lambda (ctx)
(unless first-loop
(expand-things-to-stream separator contexts stream))
(expand-things-to-stream branch (cons ctx contexts) stream)
(setq first-loop nil))
value))
(expand-things-to-stream alternative contexts stream))))))))
(defun expand-template-to-stream (template contexts stream)
(expand-things-to-stream (template-things template) contexts stream))
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