fix: adds "normalizeHeaders"

lib/api/test/unit/units/normalize/normalizeHeaders.test.js

@@ -0,0 +1,43 @@
+const { assert } = require('chai');
+const normalizeHeaders = require('../../../../units/normalize/normalizeHeaders');
+
+describe('normalizeHeaders', () => {
+  describe('when given nothing', () => {
+    const headers = normalizeHeaders(undefined);
+
+    it('coerces to empty object', () => {
+      assert.deepEqual(headers, {});
+    });
+  });
+
+  describe('when given headers object', () => {
+    const headers = {
+      'Accept-Language': 'en-US, en',
+      'Content-Type': 'application/json',
+      'Content-Length': 128
+    };
+    const normalizedHeaders = normalizeHeaders(headers);
+
+    it('lowercases the keys', () => {
+      const expectedKeys = Object.keys(headers).map((key) => key.toLowerCase());
+      assert.hasAllKeys(normalizedHeaders, expectedKeys);
+    });
+
+    it('lowercases the values', () => {
+      const expectedValues = Object.values(headers).map((value) =>
+        typeof value === 'string' ? value.toLowerCase() : value
+      );
+      assert.deepEqual(Object.values(normalizedHeaders), expectedValues);
+    });
+  });
+
+  describe('when given non-object headers', () => {
+    const unsupportedTypes = [['string', 'foo'], ['number', 2]];
+
+    unsupportedTypes.forEach(([typeName, dataType]) => {
+      it(`when given ${typeName}`, () => {
+        assert.throw(() => normalizeHeaders(dataType));
+      });
+    });
+  });
+});

lib/api/units/normalize/index.js

@@ -0,0 +1,8 @@
+const evolve = require('../../utils/evolve');
+const normalizeHeaders = require('./normalizeHeaders');
+
+const normalize = evolve({
+  headers: normalizeHeaders
+});
+
+module.exports = normalize;

lib/api/units/normalize/normalizeHeaders.js

@@ -0,0 +1,35 @@
+const normalizeStringValue = (value) => {
+  return value.toLowerCase().trim();
+};
+
+/**
+ * Normalizes the given headers.
+ * @param {Object} headers
+ * @returns {Object}
+ */
+const normalizeHeaders = (headers) => {
+  if (!headers) {
+    return {};
+  }
+
+  const headersType = typeof headers;
+
+  if (headersType === null || headersType !== 'object') {
+    throw new Error(
+      `Can't validate: expected "headers" to be an Object, but got: ${headersType}.`
+    );
+  }
+
+  return Object.keys(headers).reduce(
+    (acc, name) => ({
+      ...acc,
+      [name.toLowerCase()]:
+        typeof headers[name] === 'string'
+          ? normalizeStringValue(headers[name])
+          : headers[name]
+    }),
+    {}
+  );
+};
+
+module.exports = normalizeHeaders;