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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-filters*))
(in-package #:json-template)
(defvar *template-filters*
`(;;("html" . filter-html)
;;("html-attr-value" . filter-html-attr-value)
("raw" . identity)))
(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
(char= (char string position) #\.)))
until (null terminator)))
(defun parse-template-string (stream)
(parse-raw-tokens (tokenize-template-string stream)))
(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
(if (char= (char data 0) #\.)
(list* :directive (parse-directive data))
(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))))
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)))
(setq tokens (rest rest-tokens))
(let ((alternative
(and (equal sub-end-tag '(:directive :or nil nil))
(multiple-value-bind (altresult rest-tokens2)
(parse-tokens tokens)
(setq tokens (rest rest-tokens2))
altresult))))
(ecase (first token-data)
(:section
(list :section
(second token-data)
subresult
alternative))
(:repeated
(list :repeated-section
(third token-data)
subresult
alternative))))))
else if (member token-kind '(:variable :text))
collect token
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 context out)))
(defun expand-template-to-stream (template context stream)
(dolist (thing template)
(ecase (first thing)
(:text
(write-string (second thing) stream))
(:variable
(destructuring-bind (variable filter) (cdr thing)
(let ((value (getf context
(intern (string-upcase variable)
'#:keyword)
nil)))
(format stream "~A"
(if filter
(funcall (cdr (assoc filter *template-filters*))
value)
value)))))
(:section
(destructuring-bind (section branch alternative) (cdr thing)
(let ((value (getf context (intern (string-upcase section) '#:keyword) nil)))
(expand-template-to-stream (if value branch alternative)
value
stream))))
(:repeated-section
(destructuring-bind (section branch alternative) (cdr thing)
(let ((value (if (string= section "@")
context
(getf context (intern (string-upcase section) '#:keyword)
nil))))
(if value
(mapc (lambda (ctx)
(expand-template-to-stream branch ctx stream))
value)
(expand-template-to-stream alternative value stream))))))))
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