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(ns cheshire.generate
"Namespace used to generate JSON from Clojure data structures."
(:import (com.fasterxml.jackson.core JsonGenerator JsonGenerationException)
(java.util Date Map List Set SimpleTimeZone UUID)
(java.sql Timestamp)
(java.text SimpleDateFormat)
(java.math BigInteger)
(clojure.lang IPersistentCollection Keyword Ratio Symbol)))
;; date format rebound for custom encoding
(def ^{:dynamic true :private true} *date-format*)
(defmacro tag
([obj]
`(vary-meta ~obj assoc :tag `JsonGenerator)))
(defprotocol JSONable
(to-json [t jg]))
(definline write-string [^JsonGenerator jg ^String str]
`(.writeString ~(tag jg) ~str))
(defmacro fail [obj jg ^Exception e]
`(try
(to-json ~obj ~jg)
(catch IllegalArgumentException _#
(throw (or ~e (JsonGenerationException.
(str "Cannot JSON encode object of class: "
(class ~obj) ": " ~obj)))))))
(defmacro number-dispatch [jg obj e]
(let [g (tag (gensym 'jg))
o (gensym 'obj)
common-clauses `[Integer (.writeNumber ~g (int ~o))
Long (.writeNumber ~g (long ~o))
Double (.writeNumber ~g (double ~o))
Float (.writeNumber ~g (float ~o))
BigInteger (.writeNumber
~g ~(with-meta o {:tag `BigInteger}))
BigDecimal (.writeNumber
~g ~(with-meta o {:tag `BigDecimal}))
Ratio (.writeNumber ~g (double ~o))
Short (.writeNumber ~g (int ~o))
Byte (.writeNumber ~g (int ~o))]]
`(let [~g ~jg
~o ~obj]
(condp instance? ~o
~@(if (< 2 (:minor *clojure-version*))
`[~@common-clauses
clojure.lang.BigInt (.writeNumber
~g (.toBigInteger
~(vary-meta obj assoc :tag
`clojure.lang.BigInt)))]
common-clauses)
(fail ~o ~g ~e)))))
(declare generate)
(definline generate-basic-map
[^JsonGenerator jg obj ^String date-format ^Exception e]
(let [jg (tag jg)]
`(do
(.writeStartObject ~jg)
(doseq [m# ~obj]
(let [k# (key m#)
v# (val m#)]
(.writeFieldName ~jg (if (keyword? k#)
(.substring (str k#) 1)
(str k#)))
(generate ~jg v# ~date-format ~e nil)))
(.writeEndObject ~jg))))
(definline generate-key-fn-map
[^JsonGenerator jg obj ^String date-format ^Exception e key-fn]
(let [k (gensym 'k)
name (gensym 'name)
jg (tag jg)]
`(do
(.writeStartObject ~jg)
(doseq [m# ~obj]
(let [~k (key m#)
v# (val m#)
^String name# (if (keyword? ~k)
(~key-fn ~k)
(str ~k))]
(.writeFieldName ~jg name#)
(generate ~jg v# ~date-format ~e ~key-fn)))
(.writeEndObject ~jg))))
(definline generate-map
[^JsonGenerator jg obj ^String date-format ^Exception e key-fn]
`(if (nil? ~key-fn)
(generate-basic-map ~jg ~obj ~date-format ~e)
(generate-key-fn-map ~jg ~obj ~date-format ~e ~key-fn)))
(definline generate-array [^JsonGenerator jg obj ^String date-format
^Exception e key-fn]
(let [jg (tag jg)]
`(do
(.writeStartArray ~jg)
(doseq [item# ~obj]
(generate ~jg item# ~date-format ~e ~key-fn))
(.writeEndArray ~jg))))
(defmacro i?
"Just to shorten 'instance?' and for debugging."
[k obj]
;;(println :inst? k obj)
`(instance? ~k ~obj))
(defn byte-array? [o]
(let [c (class o)]
(and (.isArray c)
(identical? (.getComponentType c) Byte/TYPE))))
(defn generate [^JsonGenerator jg obj ^String date-format ^Exception ex key-fn]
(cond
(nil? obj) (.writeNull ^JsonGenerator jg)
(get (:impls JSONable) (class obj)) (#'to-json obj jg)
(i? clojure.lang.IPersistentMap obj)
(generate-map jg obj date-format ex key-fn)
(i? clojure.lang.IPersistentVector obj)
(generate-array jg obj date-format ex key-fn)
(i? clojure.lang.IPersistentSet obj)
(generate-array jg obj date-format ex key-fn)
(i? clojure.lang.IPersistentList obj)
(generate-array jg obj date-format ex key-fn)
(i? clojure.lang.ISeq obj)
(generate-array jg obj date-format ex key-fn)
(i? clojure.lang.Associative obj)
(generate-map jg obj date-format ex key-fn)
(i? Number obj) (number-dispatch ^JsonGenerator jg obj ex)
(i? Boolean obj) (.writeBoolean ^JsonGenerator jg ^Boolean obj)
(i? String obj) (write-string ^JsonGenerator jg ^String obj)
(i? Character obj) (write-string ^JsonGenerator jg ^String (str obj))
(i? Keyword obj) (write-string ^JsonGenerator jg (.substring (str obj) 1))
(i? Map obj) (generate-map jg obj date-format ex key-fn)
(i? List obj) (generate-array jg obj date-format ex key-fn)
(i? Set obj) (generate-array jg obj date-format ex key-fn)
(byte-array? obj) (.writeBinary ^JsonGenerator jg ^bytes obj)
(i? UUID obj) (write-string ^JsonGenerator jg (.toString ^UUID obj))
(i? Symbol obj) (write-string ^JsonGenerator jg (.toString ^Symbol obj))
(i? Date obj) (let [sdf (doto (SimpleDateFormat. date-format)
(.setTimeZone (SimpleTimeZone. 0 "UTC")))]
(write-string ^JsonGenerator jg (.format sdf obj)))
(i? Timestamp obj) (let [date (Date. (.getTime ^Timestamp obj))
sdf (doto (SimpleDateFormat. date-format)
(.setTimeZone (SimpleTimeZone. 0 "UTC")))]
(write-string ^JsonGenerator jg (.format sdf obj)))
:else (fail obj jg ex)))
;; Generic encoders, these can be used by someone writing a custom
;; encoder if so desired, after transforming an arbitrary data
;; structure into a clojure one, these can just be called.
(defn encode-nil
"Encode null to the json generator."
[_ ^JsonGenerator jg]
(.writeNull jg))
(defn encode-str
"Encode a string to the json generator."
[^String s ^JsonGenerator jg]
(.writeString jg (str s)))
(defn encode-number
"Encode anything implementing java.lang.Number to the json generator."
[^java.lang.Number n ^JsonGenerator jg]
(number-dispatch jg n nil))
(defn encode-long
"Encode anything implementing java.lang.Number to the json generator."
[^Long n ^JsonGenerator jg]
(.writeNumber jg (long n)))
(defn encode-int
"Encode anything implementing java.lang.Number to the json generator."
[n ^JsonGenerator jg]
(.writeNumber jg (long n)))
(defn encode-ratio
"Encode a clojure.lang.Ratio to the json generator."
[^clojure.lang.Ratio n ^JsonGenerator jg]
(.writeNumber jg (double n)))
(defn encode-seq
"Encode a seq to the json generator."
[s ^JsonGenerator jg]
(.writeStartArray jg)
(doseq [i s]
(generate jg i *date-format* nil nil))
(.writeEndArray jg))
(defn encode-date
"Encode a date object to the json generator."
[^Date d ^JsonGenerator jg]
(let [sdf (SimpleDateFormat. *date-format*)]
(.setTimeZone sdf (SimpleTimeZone. 0 "UTC"))
(.writeString jg (.format sdf d))))
(defn encode-bool
"Encode a Boolean object to the json generator."
[^Boolean b ^JsonGenerator jg]
(.writeBoolean jg b))
(defn encode-named
"Encode a keyword to the json generator."
[^clojure.lang.Keyword k ^JsonGenerator jg]
(.writeString jg (if-let [ns (namespace k)]
(str ns "/" (name k))
(name k))))
(defn encode-map
"Encode a clojure map to the json generator."
[^clojure.lang.IPersistentMap m ^JsonGenerator jg]
(.writeStartObject jg)
(doseq [[k v] m]
(.writeFieldName jg (if (instance? clojure.lang.Keyword k)
(if-let [ns (namespace k)]
(str ns "/" (name k))
(name k))
(str k)))
(generate jg v *date-format* nil nil))
(.writeEndObject jg))
(defn encode-symbol
"Encode a clojure symbol to the json generator."
[^clojure.lang.Symbol s ^JsonGenerator jg]
(.writeString jg (str s)))
;; Utility methods to add and remove encoders
(defn add-encoder
"Provide an encoder for a type not handled by Cheshire.
ex. (add-encoder java.net.URL encode-string)
See encode-str, encode-map, etc, in the cheshire.custom
namespace for encoder examples."
[cls encoder]
(extend cls
JSONable
{:to-json encoder}))
(defn remove-encoder
"Remove encoder for a given type.
ex. (remove-encoder java.net.URL)"
[cls]
(alter-var-root #'JSONable #(assoc % :impls (dissoc (:impls %) cls)))
(clojure.core/-reset-methods JSONable))
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