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chunk.cljc
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chunk.cljc
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(ns promisespromises.stream.chunk
(:require
#?(:clj [clojure.core :refer [print-method]])
[promesa.core :as pr]
[promisespromises.error :as err]
[promisespromises.stream.protocols :as pt]
[promisespromises.stream.transport :as transport]
[promisespromises.stream.types :as types]))
(def default-chunk-size 1000)
(deftype StreamChunkBuilder [records-a]
pt/IStreamChunkBuilder
(-start-chunk [_]
(when (some? @records-a)
(throw (err/ex-info ::chunk-already-building {:records-a @records-a})))
(reset! records-a (transient [])))
(-start-chunk [_ val]
(when (some? @records-a)
(throw (err/ex-info ::chunk-already-building {:records-a @records-a})))
(reset! records-a (transient [val])))
(-add-to-chunk [_ val]
(when (nil? @records-a)
(throw (err/ex-info ::no-chunk-building {})))
(swap! records-a conj! val))
(-add-all-to-chunk [_ vals]
(when (nil? @records-a)
(throw (err/ex-info ::no-chunk-building {})))
(swap!
records-a
(fn [records]
(reduce
(fn [r v] (conj! r v))
records
vals))))
(-finish-chunk [_]
(when (nil? @records-a)
(throw (err/ex-info ::no-chunk-building {})))
(let [records (persistent! @records-a)]
(reset! records-a nil)
(types/stream-chunk records)))
(-finish-chunk [_ val]
(when (nil? @records-a)
(throw (err/ex-info ::no-chunk-building {})))
(swap! records-a conj! val)
(let [records (persistent! @records-a)]
(reset! records-a nil)
(types/stream-chunk records)))
(-discard-chunk [_]
(reset! records-a nil))
(-building-chunk? [_] (some? @records-a))
(-chunk-state [_] @records-a))
#?(:clj
(defmethod print-method StreamChunkBuilder [x writer]
(.write writer "#promisespromises.stream.ChunkBuilder<")
(print-method (pt/-chunk-state x) writer)
(.write writer ">")))
(defn stream-chunk-builder
[]
(->StreamChunkBuilder (atom nil)))
(defn should-finish-chunk?
"true if building a chunk and:
- (nil? partition-by) and (>= chunk-size target-chunk-size)
- (some? partition-by-fn)
and (>= chunk-size target-chunk-size)
and (not= (partition-by-fn (last chunk-state) (partition-by next-value)))"
[chunk-builder target-chunk-size partition-by-fn next-value]
(if (pt/-building-chunk? chunk-builder)
(or
(and (nil? partition-by-fn)
(>= (count (pt/-chunk-state chunk-builder))
target-chunk-size))
(let [ch-data(pt/-chunk-state chunk-builder)]
(and (some? partition-by-fn)
(>= (count ch-data)
target-chunk-size)
(not= (partition-by-fn (nth ch-data (-> ch-data count dec)))
(partition-by-fn next-value)))))
false))
(defn make-chunker-xform
"return a transducer which builds chunks from a stream, optionally
partition-by the stream ensuring that partitions never span
chunk boundaries
NOTE that no timeout is possible with a transducer
- target-chunk-size : will wrap a chunk when this size is exceeded,
or as soon as possible afterwards (if a chunk is received, or
partition-by is given)
- partition-by-fn : also partition-by the stream with this fn and
ensure partitions never cross chunk boundaries"
([target-chunk-size]
(make-chunker-xform target-chunk-size nil))
([target-chunk-size partition-by-fn]
(let [cb (stream-chunk-builder)]
(fn [rf]
(fn
([] (rf))
([result]
(when (pt/-building-chunk? cb)
(let [ch (pt/-finish-chunk cb)]
(rf result (if (some? partition-by-fn)
(types/stream-chunk
(partition-by
partition-by-fn
(pt/-chunk-values ch)))
ch))))
(rf result))
([result input]
(if (pt/-building-chunk? cb)
(if (should-finish-chunk? cb target-chunk-size partition-by-fn input)
(do
(let [ch (pt/-finish-chunk cb)]
(rf result (if (some? partition-by-fn)
(types/stream-chunk
(partition-by
partition-by-fn
(pt/-chunk-values ch)))
ch)))
(pt/-start-chunk cb input))
(pt/-add-to-chunk cb input))
(pt/-start-chunk cb input))
result))))))
(defn dechunk
"given a stream of mixed unchunked-values and chunks
return a stream of
[::unchunked|::chunk-start|::chunk|::chunk-end val]"
[s]
(let [s' (transport/stream)]
(transport/connect-via
s
(fn [v]
(cond
(types/stream-chunk? v)
(let [vals (pt/-chunk-values v)
n (count vals)]
(pr/chain
(transport/put! s' [::chunk-start (first vals)])
(fn [_]
(when (> n 2)
(transport/put-all!
s'
(-> vals
(subvec 1 (- n 2))
(as-> %
(map (fn [v]
[::chunk v])
%))))))
(fn [_]
(transport/put! s' [::chunk-end (last vals)]))))
:else
(transport/put! s' [::unchunked v])))
s')))
(defn rechunk
"given a stream of
[::unchunked|::chunk-start|::chunk|::chunk-end val]
return a stream of unchunked values and chunks"
[s]
(let [s' (transport/stream)
chunk-builder-a (atom (stream-chunk-builder))]
(transport/connect-via
s
(fn [[k v]]
(condp = k
::chunk-start
(do
(pt/-start-chunk @chunk-builder-a v)
true)
::chunk
(do
(pt/-add-to-chunk @chunk-builder-a v)
true)
::chunk-end
(let [chunk (pt/-finish-chunk @chunk-builder-a v)]
(transport/put! s' chunk))
::unchunked
(transport/put! s' v)))
s')))