From 2cc2d9062184f69c012cab086f76a608a2eb2f1e Mon Sep 17 00:00:00 2001
From: JonasKruckenberg <iterpre@protonmail.com>
Date: Mon, 15 Mar 2021 15:14:44 +0100
Subject: [PATCH] feat: add caching utils

---
 packages/core/src/__tests__/cache.spec.ts | 114 ++++++++++++++++++++++
 packages/core/src/cache.ts                |  48 +++++++++
 2 files changed, 162 insertions(+)
 create mode 100644 packages/core/src/__tests__/cache.spec.ts
 create mode 100644 packages/core/src/cache.ts

diff --git a/packages/core/src/__tests__/cache.spec.ts b/packages/core/src/__tests__/cache.spec.ts
new file mode 100644
index 00000000..155a6425
--- /dev/null
+++ b/packages/core/src/__tests__/cache.spec.ts
@@ -0,0 +1,114 @@
+import { has, get, info, remove, generateKey } from '../cache'
+import mock from 'mock-fs'
+
+describe('cache', () => {
+    afterAll(() => {
+        mock.restore()
+    })
+
+    describe('has', () => {
+        it('returns true if file is present', async () => {
+            mock({
+                '/cache': {
+                    'test.png': 'foobar'
+                }
+            })
+
+            expect(await has('/cache', 'test.png')).toBeTruthy()
+        })
+
+        it('returns false if the file is missing', async () => {
+            mock({})
+
+            expect(await has('/cache', 'test.png')).toBeFalsy()
+        })
+    })
+
+    describe('get', () => {
+        it('returns the data', async () => {
+            mock({
+                '/cache': {
+                    'test.png': Buffer.from('foobar')
+                }
+            })
+
+            const res = await get('/cache', 'test.png')
+            expect(res).toHaveProperty('data', Buffer.from('foobar'))
+        })
+
+        it('returns the metadata if metadata file is present', async () => {
+            mock({
+                '/cache': {
+                    'test.png': Buffer.from('foobar'),
+                    'test.png.json': JSON.stringify({ foo: 'bar' })
+                }
+            })
+
+            const res = await get('/cache', 'test.png')
+
+            expect(res).toHaveProperty('data', Buffer.from('foobar'))
+            expect(res).toHaveProperty('metadata', { foo: 'bar' })
+        })
+
+        it('returns an empty object if metadata file is missing', async () => {
+            mock({
+                '/cache': {
+                    'test.png': Buffer.from('foobar')
+                }
+            })
+
+            const res = await get('/cache', 'test.png')
+
+            expect(res).toHaveProperty('data', Buffer.from('foobar'))
+            expect(res).toHaveProperty('metadata', {})
+        })
+
+        it('throws if no image is found', async (done) => {
+            mock({})
+
+            try {
+                await get('/cache', 'test.png')
+                fail()
+            } catch {
+                done()
+            }
+        })
+    })
+
+    describe('info', () => {
+        it('returns an object if metadata file is present', async () => {
+            mock({
+                '/cache': {
+                    'test.png.json': JSON.stringify({ foo: 'bar' })
+                }
+            })
+
+            const res = await info('/cache', 'test.png')
+
+            expect(res).toHaveProperty('foo', 'bar')
+        })
+
+        it('throws if not metadata file is found', async (done) => {
+            mock({})
+
+            try {
+                await info('/cache', 'test.png')
+                fail()
+            } catch {
+                done()
+            }
+        })
+    })
+
+    describe('remove', () => {
+        it('removes the image file', () => { })
+        it('removes the metadata file if present', () => { })
+        it('throws if no image is found', () => { })
+    })
+
+    describe('generateKey', () => {
+        it('returns a string', () => { })
+        test('returned string has file ending', () => { })
+        test('returned file ending matches config', () => { })
+    })
+})
\ No newline at end of file
diff --git a/packages/core/src/cache.ts b/packages/core/src/cache.ts
new file mode 100644
index 00000000..70efb928
--- /dev/null
+++ b/packages/core/src/cache.ts
@@ -0,0 +1,48 @@
+import { mkdir, readFile, writeFile, stat, unlink } from 'fs/promises'
+import { join, extname } from 'path'
+
+export async function has(cachePath: string, key: string): Promise<boolean> {
+    try {
+        const file = await stat(join(cachePath, key))
+        return file.isFile()
+    } catch {
+        return false
+    }
+}
+
+export async function get(cachePath: string, key: string): Promise<{ data: Uint8Array, metadata: Record<string, any> }> {
+    const [data, metadata] = await Promise.all([
+        readFile(join(cachePath, key)),
+        has(cachePath, key + '.json').then(has => has ? info(cachePath, key) : {})
+    ])
+
+    return { data, metadata }
+}
+
+export async function info(cachePath: string, key: string): Promise<Record<string, any>> {
+    const rawMeta = await readFile(join(cachePath, key + '.json'), 'utf-8')
+    return JSON.parse(rawMeta)
+}
+
+export async function put(cachePath: string, key: string, data: Uint8Array, metadata?: Record<string, any>): Promise<void> {
+    await mkdir(cachePath, { recursive: true })
+
+    await Promise.all([
+        writeFile(join(cachePath, key), data),
+        metadata ? writeFile(join(cachePath, key + '.json'), JSON.stringify(metadata)) : undefined
+    ])
+}
+
+export async function remove(cachePath: string, key: string): Promise<void> {
+    await Promise.all([
+        unlink(join(cachePath, key)),
+        has(cachePath, key + '.json').then(has => has ? unlink(join(cachePath, key + '.json')) : undefined)
+    ])
+}
+
+export function generateKey(url: URL, config: Record<string, any>) {
+    const name = Buffer.from(JSON.stringify(config)).toString('base64')
+    const ext = config.format ? `.${config.format}` : extname(url.pathname)
+
+    return name + ext
+}
\ No newline at end of file