Add `writeAttachmentData` module

app/types/attachment/write_attachment_data.js

@@ -0,0 +1,45 @@
+const crypto = require('crypto');
+const FSE = require('fs-extra');
+const isArrayBuffer = require('lodash/isArrayBuffer');
+const isBuffer = require('lodash/isBuffer');
+const isString = require('lodash/isString');
+const Path = require('path');
+
+
+exports.writeAttachmentData = (root) => {
+  if (!isString(root)) {
+    throw new TypeError('`root` must be a path');
+  }
+
+  return async (arrayBuffer) => {
+    if (!isArrayBuffer(arrayBuffer)) {
+      throw new TypeError('`arrayBuffer` must be an array buffer');
+    }
+
+    const buffer = new Buffer(arrayBuffer);
+    const path = Path.join(root, exports._getAttachmentPath(buffer));
+    await FSE.ensureFile(path);
+    await FSE.writeFile(path, buffer);
+    return path;
+  };
+};
+
+exports._getAttachmentName = (buffer) => {
+  if (!isBuffer(buffer)) {
+    throw new TypeError('`buffer` must be a buffer');
+  }
+
+  const hash = crypto.createHash('sha256');
+  hash.update(buffer);
+  return hash.digest('hex');
+};
+
+exports._getAttachmentPath = (buffer) => {
+  if (!isBuffer(buffer)) {
+    throw new TypeError('`buffer` must be a buffer');
+  }
+
+  const name = exports._getAttachmentName(buffer);
+  const prefix = name.slice(0, 3);
+  return Path.join(prefix, name);
+};

test/app/types/attachment/write_attachment_data_test.js

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+const FSE = require('fs-extra');
+const isEqual = require('lodash/isEqual');
+const Path = require('path');
+const stringToArrayBuffer = require('string-to-arraybuffer');
+const tempy = require('tempy');
+const { assert } = require('chai');
+
+const {
+  writeAttachmentData,
+  _getAttachmentName,
+  _getAttachmentPath,
+} = require('../../../../app/types/attachment/write_attachment_data');
+
+
+describe('writeAttachmentData', () => {
+  let TEMPORARY_DIRECTORY = null;
+  before(() => {
+    // Sync!
+    TEMPORARY_DIRECTORY = tempy.directory();
+  });
+
+  after(async () => {
+    await FSE.remove(TEMPORARY_DIRECTORY);
+  });
+
+  it('should write file to disk and return path', async () => {
+    const input = stringToArrayBuffer('test string');
+    const tempDirectory = Path.join(TEMPORARY_DIRECTORY, 'writeAttachmentData');
+    const expectedPath = Path.join(
+      tempDirectory,
+      'd55/d5579c46dfcc7f18207013e65b44e4cb4e2c2298f4ac457ba8f82743f31e930b'
+    );
+
+    const outputPath = await writeAttachmentData(tempDirectory)(input);
+    const output = await FSE.readFile(outputPath);
+
+    assert.strictEqual(outputPath, expectedPath);
+
+    const inputBuffer = Buffer.from(input);
+    assert.isTrue(isEqual(inputBuffer, output));
+  });
+
+  describe('_getAttachmentName', () => {
+    it('should return correct name', () => {
+      const input = Buffer.from('test string', 'utf8');
+      const expected = 'd5579c46dfcc7f18207013e65b44e4cb4e2c2298f4ac457ba8f82743f31e930b';
+      assert.strictEqual(_getAttachmentName(input), expected);
+    });
+  });
+
+  describe('_getAttachmentPath', () => {
+    it('should return correct path', () => {
+      const input = Buffer.from('test string', 'utf8');
+      const expected = 'd55/d5579c46dfcc7f18207013e65b44e4cb4e2c2298f4ac457ba8f82743f31e930b';
+      assert.strictEqual(_getAttachmentPath(input), expected);
+    });
+  });
+});