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lens.clj
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lens.clj
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(ns pronto.lens
(:require [pronto.utils :as u])
(:import [pronto ProtoMap TransientProtoMap]))
(defn clear-field [^ProtoMap m k]
(if (.isMutable m)
(throw (IllegalAccessError. "cannot clear-field on a transient"))
(.clearField m k)))
(defn clear-field! [^ProtoMap m k]
(if-not (.isMutable m)
(throw (IllegalAccessError. "cannot clear-field! on a non-transient"))
(.clearField m k)))
(defn assoc-or-else [m k v f]
(if (some? v)
(assoc m k v)
(f m k v)))
(defn assoc-if [m k v]
(assoc-or-else m k v (fn [m _k _v] m)))
(defmacro transform-in [m kvs]
(let [m (u/with-type-hint m ProtoMap)
m2 (u/with-type-hint (gensym 'm2) TransientProtoMap)
new-submap (gensym 'newsubmap)
submap (gensym 'submap)
pmap? (gensym 'pmap?)
kv-forest (u/kv-forest kvs)]
`(let [~pmap? (u/proto-map? ~m)
~m2 (if (and ~pmap? (.isMutable ~m)) ~m (transient ~m))
was-in-transaction?# (and ~pmap? (.isInTransaction ~m2))]
(when ~pmap?
(.setInTransaction ~m2 true))
~@(doall
(for [[k vs] kv-forest
v (partition-by u/leaf? vs)]
(if (u/leaf? (first v))
`(do
~@(doall
(for [leaf v]
(let [val-fn (eval (u/leaf-val leaf))]
(val-fn m2 k)))))
`(let [~submap (or (get ~m2 ~k nil)
(when ~pmap?
(.empty ~m2 ~k)))
~new-submap (pronto.lens/transform-in ~submap ~(u/flatten-forest v))]
(assoc! ~m2 ~k ~new-submap)))))
(if was-in-transaction?#
~m2
(persistent! ~m2)))))
(defn- assoc-transform-kvs [rewrite-fn kvs]
(->> kvs
(partition 2)
(map
(fn [[ks v]]
[ks
(fn [msym k]
(rewrite-fn
`(assoc! ~msym ~k ~v)))]))))
(defn- update-transform-kv [rewrite-fn ks f args]
[[ks
(fn [msym k]
(rewrite-fn
`(let [x# (get ~msym ~k nil)
x# (~f x# ~@args)]
(assoc! ~msym ~k x#))))]])
(defn- clear-field-transform-kv [rewrite-fn k]
[[[k]
(fn [msym k]
(rewrite-fn
`(clear-field! ~msym ~k)))]])
(defn- assoc-if-transform-kvs [rewrite-fn k v]
[[[k]
(fn [msym k]
(let [v2 (gensym 'v)]
(rewrite-fn
`(let [~v2 ~v]
(if (some? ~v2)
(assoc! ~msym ~k ~v2)
~msym)))))]])
(defn- assoc-args->assoc-in-args [k v kvs]
(->> kvs
(cons v)
(cons k)
(partition 2)
(mapcat
(fn [[k v]]
[[k] v]))))
(defn- fn-name [form]
(when (coll? form)
(when-let [fst (first form)]
(when (symbol? fst)
(symbol (name fst))))))
(def ^:private update?
(comp #{'update 'update-in} fn-name))
(def ^:private assoc?
(comp #{'assoc 'assoc-in 'assoc-if 'assoc-or-else} fn-name))
(def ^:private clear?
(comp #{'clear-field} fn-name))
(defn- transient-proto-fn? [form]
(let [fn-name (fn-name form)
v (u/safe-resolve fn-name)
m (meta v)]
(->> m
:arglists
(some #(when (= (count form) (count %)) %))
first
meta
:transient-proto
boolean)))
(defn- transformation? [form]
(or
(assoc? form)
(update? form)
(transient-proto-fn? form)
(clear? form)))
(defn- rewrite-transformation [g transforms]
`(transform-in
~g
~(mapcat
(fn [form]
(let [rewrite-fn (let [pred (-> form meta :predicate)]
(if (some? pred)
(fn [form]
`(when ~pred
~form))
identity))]
(case (name (fn-name form))
"assoc"
(let [[_ k v & kvs] form]
(assoc-transform-kvs
rewrite-fn
(assoc-args->assoc-in-args k v kvs)))
"assoc-in"
(let [[_ [k & ks] v] form]
(assoc-transform-kvs
rewrite-fn
[(into [k] ks) v]))
"assoc-if"
(let [[_ k v] form]
(assoc-if-transform-kvs
rewrite-fn
k v))
"update"
(let [[_ k f & args] form]
(update-transform-kv rewrite-fn [k] f args))
"update-in"
(let [[_ ks f & args] form]
(update-transform-kv rewrite-fn ks f args))
"clear-field"
(let [[_ k] form]
(clear-field-transform-kv rewrite-fn k))
(let [[f & args] form]
[[[(keyword (gensym))]
(fn [msym _]
(rewrite-fn
(if args
`(~f ~msym ~@args)
`(~f ~msym))))]]))))
transforms)))
(defn- rewrite-forms [g forms]
(->> forms
(partition-by
(fn [form]
(if (transformation? form)
::transformation
form)))
(map
(fn [subform]
(let [x (first subform)
predicate (-> x meta :predicate)
wrap-pred (fn [form]
(if (nil? predicate)
form
`(if ~predicate
~form
~g)))]
(if (and (coll? subform)
(transformation? x))
(rewrite-transformation g subform)
(wrap-pred
(cond
(keyword? x) `(get ~g ~x ~(second subform))
(= 'get (fn-name x)) `(p-> ~g ~(second x))
(= 'get-in (fn-name x)) `(p-> ~g ~@(second x))
:else `(-> ~g ~x)))))))))
(defmacro p->
"Like `->` but meant to be used where the initial expression evaluates to a proto-map. Under the hood, `p->` will operate on a transient version of the proto-map and `persistent!` it back when done. Expressions will be pipelined as much as possible (but never reordered) such that `(p-> person-proto (assoc-in [:pet :name] \"patch\") (assoc-in [:pet :kind] :cat))` will only generate a single instance of a pet transient map to which both operations will be applied in succession."
[x & forms]
(let [g (gensym)]
`(clojure.core/as-> ~x ~g
~@(rewrite-forms g forms))))
(defmacro pcond->
"Equivalent to cond->. See `p->`"
[expr & clauses]
(assert (even? (count clauses)))
(let [clauses' (->> clauses
(partition 2)
(map
(fn [[test form]]
(let [form (if (keyword? form)
`(get ~form nil)
form)]
(vary-meta
form
assoc
:predicate
test)
))))]
`(p->
~expr
~@clauses')))