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;;; graphql.el --- GraphQL utilities -*- lexical-binding: t; -*-
;; Copyright (C) 2017 Sean Allred
;; Author: Sean Allred <code@seanallred.com>
;; Keywords: hypermedia, tools, lisp
;; Homepage: https://github.com/vermiculus/graphql.el
;; Package-Version: 0.1.1
;; Package-Requires: ((emacs "25"))
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; GraphQL.el provides a generally-applicable domain-specific language
;; for creating and executing GraphQL queries against your favorite
;; web services.
;;; Code:
(require 'pcase)
(defun graphql--encode-object (obj)
"Encode OBJ as a GraphQL string."
(cond
((stringp obj)
obj)
((symbolp obj)
(symbol-name obj))
((numberp obj)
(number-to-string obj))
((and (consp obj)
(not (consp (cdr obj))))
(symbol-name (car obj)))))
(defun graphql--encode-argument-spec (spec)
"Encode an argument spec SPEC.
SPEC is of the form..."
(graphql--encode-argument (car spec) (cdr spec)))
(defun graphql--encode-argument (key value)
"Encode an argument KEY with value VALUE."
(format "%s:%s" key (graphql--encode-argument-value value)))
(defun graphql--encode-argument-value (value)
"Encode an argument value VALUE.
VALUE is expected to be one of the following:
* a symbol
* a 'variable', i.e. \\='($ variableName)
* an object (as a list)
* a string
* a vector of values (e.g., symbols)
* a number
* something encode-able by `graphql-encode'."
(cond
((symbolp value)
(symbol-name value))
((eq '$ (car-safe value))
(format "$%s" (cadr value)))
((listp value)
(format "{%s}" (mapconcat #'graphql--encode-argument-spec value ",")))
((stringp value)
(format "\"%s\"" value))
((vectorp value)
(format "[%s]" (mapconcat #'graphql-encode value ",")))
((numberp value)
(number-to-string value))
(t
(graphql-encode value))))
(defun graphql--encode-parameter-spec (spec)
"Encode a parameter SPEC.
SPEC is expected to be of the following form:
(NAME TYPE [REQUIRED] . [DEFAULT])
NAME is the name of the parameter.
TYPE is the parameter's type.
A non-nil value for REQUIRED will indicate the parameter is
required. A value of `!' is recommended.
A non-nil value for DEFAULT will provide a default value for the
parameter."
;; Unfortunately can't use `pcase' here because the first DEFAULT
;; value (in the case of a complex value) might be misunderstood as
;; the value for REQUIRED. We need to know if the third cons is the
;; very last one; not just that the list has at least three
;; elements.
(if (eq (last spec) (nthcdr 2 spec))
(graphql--encode-parameter (nth 0 spec)
(nth 1 spec)
(car (last spec))
(cdr (last spec)))
(graphql--encode-parameter (nth 0 spec)
(nth 1 spec)
nil
(nthcdr 2 spec))))
(defun graphql--encode-parameter (name type &optional required default)
"Encode a GraphQL parameter with a NAME and TYPE.
If REQUIRED is non-nil, mark the parameter as required.
If DEFAULT is non-nil, is the default value of the parameter."
(format "$%s:%s%s%s"
(symbol-name name)
(symbol-name type)
(if required "!" "")
(if default
(concat "=" (graphql--encode-argument-value default))
"")))
(defun graphql--get-keys (g)
"Get the keyword arguments from a graph G.
Returns a list where the first element is a plist of arguments
and the second is a 'clean' copy of G."
(or (and (not (consp g))
(list nil g))
(let (graph keys)
(while g
(if (keywordp (car g))
(let* ((param (pop g))
(value (pop g)))
(push (cons param value) keys))
(push (pop g) graph)))
(list keys (nreverse graph)))))
(defun graphql-encode (g)
"Encode graph G as a GraphQL string."
(pcase (graphql--get-keys g)
(`(,keys ,graph)
(let ((object (or (car-safe graph) graph))
(name (alist-get :op-name keys))
(params (alist-get :op-params keys))
(arguments (alist-get :arguments keys))
(fields (cdr-safe graph)))
(concat
(graphql--encode-object object)
(when name
(format " %S" name))
(when arguments
;; Format arguments "key:value,key:value,..."
(format "(%s)"
(mapconcat #'graphql--encode-argument-spec arguments ",")))
(when params
(format "(%s)"
(mapconcat #'graphql--encode-parameter-spec params ",")))
(when fields
(format "{%s}"
(mapconcat #'graphql-encode fields " "))))))))
(defun graphql-simplify-response-edges (data)
"Simplify DATA to collapse edges into their nodes."
(pcase data
;; When we encounter a collection of edges, simplify those edges
;; into their nodes
(`(,object (edges . ,edges))
(cons object (mapcar #'graphql-simplify-response-edges
(mapcar (lambda (edge) (alist-get 'node edge))
edges))))
;; When we encounter a plain cons cell (not a list), let it pass
(`(,(and key (guard (not (consp key)))) . ,(and value (guard (not (consp value)))))
(cons key value))
;; symbols should pass unaltered
(`,(and symbol (guard (symbolp symbol)))
symbol)
;; everything else should be mapped
(_ (mapcar #'graphql-simplify-response-edges data))))
(defun graphql--genform-operation (args kind)
"Generate the Lisp form for an operation.
ARGS is is a list ([NAME [PARAMETERS]] GRAPH) where NAME is the
name of the operation, PARAMETERS are its parameters, and GRAPH
is the form of the actual operation.
KIND can be `query' or `mutation'."
(pcase args
(`(,name ,parameters ,graph)
`(graphql-encode '(,kind :op-name ,name
:op-params ,parameters
,@graph)))
(`(,name ,graph)
`(graphql-encode '(,kind :op-name ,name
,@graph)))
(`(,graph)
`(graphql-encode '(,kind ,@graph)))
(_ (error "Bad form"))))
(defmacro graphql-query (&rest args)
"Construct a Query object.
ARGS is a listof the form described by `graphql--genform-operation'.
\(fn [NAME] [(PARAMETER-SPEC...)] GRAPH)"
(graphql--genform-operation args 'query))
(defmacro graphql-mutation (&rest args)
"Construct a Mutation object.
ARGS is a listof the form described by `graphql--genform-operation'.
\(fn [NAME] [(PARAMETER-SPEC...)] GRAPH)"
(graphql--genform-operation args 'mutation))
(provide 'graphql)
;;; graphql.el ends here
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