From 6a282f712b2e7adb4699a0a8ead2e1a5122a995e Mon Sep 17 00:00:00 2001
From: simon3000 <simon30002021@icloud.com>
Date: Tue, 31 Mar 2020 13:01:55 +0200
Subject: [PATCH] local cache

---
 api/latest.js  | 72 +++++++++++++++++++++++++++++++++++++++++++++++---
 cache/.gitkeep |  0
 2 files changed, 68 insertions(+), 4 deletions(-)
 create mode 100644 cache/.gitkeep

diff --git a/api/latest.js b/api/latest.js
index 240a81b..4a29a7b 100644
--- a/api/latest.js
+++ b/api/latest.js
@@ -1,6 +1,9 @@
 const Router = require('koa-router')
 const got = require('got')
 const yaml = require('js-yaml')
+const { promises: { stat, writeFile, unlink }, createReadStream, createWriteStream } = require('fs')
+const { join } = require('path')
+const { createHash } = require('crypto')
 
 const { getLatestURL, relays } = require('./shared')
 
@@ -14,6 +17,66 @@ const fileMap = {
   windows: 'latest.yml'
 }
 
+const cachingMap = new Map()
+
+const calculateHash = path => new Promise(resolve => {
+  const hash = createHash('sha512')
+  const stream = createReadStream(path)
+  stream.on('readable', () => {
+    const data = stream.read()
+    if (data) {
+      hash.update(data)
+    } else {
+      resolve(hash.digest())
+    }
+  })
+})
+
+const checkCache = async (url, sha512) => {
+  console.log('check cache', url)
+  const fileName = url.split('/').reverse()[0]
+  const cachePath = join('./cache', fileName)
+  const hash = Buffer.from(sha512, 'base64')
+  const cacheHash = await calculateHash(cachePath)
+  if (!hash.equals(cacheHash)) {
+    console.log('remake cache', url)
+    await unlink(cachePath)
+    return makeCache(url, sha512)
+  }
+}
+
+const makeCache = async (url, sha512) => {
+  console.log('make cache', url)
+  const fileName = url.split('/').reverse()[0]
+  const cachePath = join('./cache', fileName)
+  await writeFile(cachePath, '')
+  cachingMap.set(url, new Promise(resolve => {
+    const writeStream = createWriteStream(cachePath, { emitClose: true })
+    got.stream(url).pipe(writeStream)
+    writeStream.on('close', async () => {
+      await checkCache(url, sha512)
+      resolve()
+    })
+  }))
+  return cachingMap.get(url)
+}
+
+const getCache = async (url, sha512) => {
+  const fileName = url.split('/').reverse()[0]
+  const cachePath = join('./cache', fileName)
+  const cacheExist = await stat(cachePath).catch(() => false)
+  if (!cacheExist) {
+    await makeCache(url, sha512)
+  }
+  if (cachingMap.has(url)) {
+    await cachingMap.get(url)
+  } else {
+    cachingMap.set(url, checkCache(url, sha512))
+    await cachingMap.get(url)
+  }
+  return createReadStream(cachePath)
+}
+
 latest.get('/:name/:platform', async ctx => {
   const { name, platform } = ctx.params
   const match = relays[name]
@@ -22,12 +85,13 @@ latest.get('/:name/:platform', async ctx => {
     const ymlUrl = await getLatestURL({ file: ymlFile, ...match })
     const yml = await got(ymlUrl).text()
     const { files } = yaml.safeLoad(yml)
-    const file = files
-      .map(({ url }) => url)
-      .find(url => ['exe', 'dmg', 'AppImage'].find(ext => url.endsWith(ext)))
+    const { url: file, sha512 } = files
+      .find(({ url }) => ['exe', 'dmg', 'AppImage'].find(ext => url.endsWith(ext))) || {}
     if (file) {
       const url = await getLatestURL({ file, ...match })
-      ctx.body = got.stream(url)
+      const fileName = url.split('/').reverse()[0]
+      ctx.response.attachment(fileName)
+      ctx.body = await getCache(url, sha512)
     }
   }
 })
diff --git a/cache/.gitkeep b/cache/.gitkeep
new file mode 100644
index 0000000..e69de29