From c77d794a124dda98a1ebdcba44febaf5f8806da5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kat=20March=C3=A1n?= <kzm@sykosomatic.org>
Date: Wed, 1 Mar 2017 18:48:22 -0800
Subject: [PATCH] feat(get): added memoization support for get

---
 get.js | 136 +++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 118 insertions(+), 18 deletions(-)

diff --git a/get.js b/get.js
index 13f0576..2e6b03b 100644
--- a/get.js
+++ b/get.js
@@ -4,7 +4,9 @@ const Promise = require('bluebird')
 
 const index = require('./lib/entry-index')
 const finished = Promise.promisify(require('mississippi').finished)
+const memo = require('./lib/memoization')
 const pipe = require('mississippi').pipe
+const pipeline = require('mississippi').pipeline
 const read = require('./lib/content/read')
 const through = require('mississippi').through
 
@@ -16,39 +18,137 @@ module.exports.byDigest = function getByDigest (cache, digest, opts) {
 }
 function getData (byDigest, cache, key, opts) {
   opts = opts || {}
-  const src = (byDigest ? getStream.byDigest : getStream)(cache, key, opts)
-  let data = ''
-  let meta
-  src.on('data', function (d) { data += d })
-  src.on('metadata', function (m) { meta = m })
-  return finished(src).then(() => ({ data, meta }))
+  opts.hashAlgorithm = opts.hashAlgorithm || 'sha1'
+  const memoized = (
+    byDigest
+    ? memo.get.byDigest(cache, key, opts.hashAlgorithm)
+    : memo.get(cache, key)
+  )
+  if (memoized && opts.memoize !== false) {
+    return Promise.resolve({
+      metadata: memoized.entry.metadata,
+      data: memoized.data,
+      digest: memoized.entry.digest,
+      hashAlgorithm: memoized.entry.hashAlgorithm
+    })
+  }
+  const src = (byDigest ? getStreamDigest : getStream)(cache, key, opts)
+  let acc = []
+  let dataTotal = 0
+  let metadata
+  let digest
+  let hashAlgorithm
+  if (!byDigest) {
+    src.on('digest', d => {
+      digest = d
+    })
+    src.on('hashAlgorithm', d => { hashAlgorithm = d })
+    src.on('metadata', d => { metadata = d })
+  }
+  src.on('data', d => {
+    acc.push(d)
+    dataTotal += d.length
+  })
+  return finished(src).then(() => {
+    const data = Buffer.concat(acc, dataTotal)
+    return byDigest ? data : { metadata, data, digest, hashAlgorithm }
+  })
 }
 
 module.exports.stream = getStream
-module.exports.stream.byDigest = read.readStream
 function getStream (cache, key, opts) {
-  const stream = through()
-  index.find(cache, key).catch(err => {
-    stream.emit('error', err)
-  }).then(data => {
-    if (!data) {
+  opts = opts || {}
+  let stream = through()
+  const memoized = memo.get(cache, key)
+  if (memoized && opts.memoize !== false) {
+    stream.on('newListener', function (ev, cb) {
+      ev === 'metadata' && cb(memoized.entry.metadata)
+      ev === 'digest' && cb(memoized.entry.digest)
+      ev === 'hashAlgorithm' && cb(memoized.entry.hashAlgorithm)
+    })
+    stream.write(memoized.data, () => stream.end())
+    return stream
+  }
+  index.find(cache, key).then(entry => {
+    if (!entry) {
       return stream.emit(
         'error', index.notFoundError(cache, key)
       )
     }
-    stream.emit('metadata', data)
+    let memoStream
+    if (opts.memoize) {
+      let memoData = []
+      let memoLength = 0
+      memoStream = through((c, en, cb) => {
+        memoData && memoData.push(c)
+        memoLength += c.length
+        cb(null, c, en)
+      }, cb => {
+        memoData && memo.put(cache, entry, Buffer.concat(memoData, memoLength))
+        cb()
+      })
+    } else {
+      memoStream = through()
+    }
+    // TODO - don't overwrite someone else's `opts`.
+    opts.hashAlgorithm = entry.hashAlgorithm
+    stream.emit('metadata', entry.metadata)
+    stream.emit('hashAlgorithm', entry.hashAlgorithm)
+    stream.emit('digest', entry.digest)
     stream.on('newListener', function (ev, cb) {
-      ev === 'metadata' && cb(data)
+      ev === 'metadata' && cb(entry.metadata)
+      ev === 'digest' && cb(entry.digest)
+      ev === 'hashAlgorithm' && cb(entry.hashAlgorithm)
     })
     pipe(
-      read.readStream(cache, data.digest, opts),
+      read.readStream(cache, entry.digest, opts),
+      memoStream,
       stream
     )
-  })
+  }, err => stream.emit('error', err))
   return stream
 }
 
+module.exports.stream.byDigest = getStreamDigest
+function getStreamDigest (cache, digest, opts) {
+  opts = opts || {}
+  opts.hashAlgorithm = opts.hashAlgorithm || 'sha1'
+  const memoized = memo.get.byDigest(cache, digest, opts.hashAlgorithm)
+  if (memoized && opts.memoize !== false) {
+    const stream = through()
+    stream.write(memoized, () => stream.end())
+    return stream
+  } else {
+    let stream = read.readStream(cache, digest, opts)
+    if (opts.memoize) {
+      let memoData = []
+      let memoLength = 0
+      const memoStream = through((c, en, cb) => {
+        memoData && memoData.push(c)
+        memoLength += c.length
+        cb(null, c, en)
+      }, cb => {
+        memoData && memo.put.byDigest(
+          cache,
+          digest,
+          opts.hashAlgorithm,
+          Buffer.concat(memoData, memoLength)
+        )
+        cb()
+      })
+      stream = pipeline(stream, memoStream)
+    }
+    return stream
+  }
+}
+
 module.exports.info = info
-function info (cache, key) {
-  return index.find(cache, key)
+function info (cache, key, opts) {
+  opts = opts || {}
+  const memoized = memo.get(cache, key)
+  if (memoized && opts.memoize !== false) {
+    return Promise.resolve(memoized.entry)
+  } else {
+    return index.find(cache, key)
+  }
 }