---

src/utils/validateLogin.ts

@@ -0,0 +1,59 @@
+import { isValidEmail } from '.'
+import { FieldError } from '../graphql-types'
+
+interface LoginValidation {
+  input: 'Email' | 'Username'
+  errors: FieldError[] | null
+}
+
+export const validateLogin = (emailOrUsername: string, password: string): LoginValidation => {
+  const result: LoginValidation = {
+    input: 'Email',
+    errors: []
+  }
+  if (emailOrUsername.includes('@')) { // email provided 
+    if (!isValidEmail(emailOrUsername)) {
+      result.errors!.push({
+        field: 'emailOrUsername',
+        message: 'Invalid email.'
+      })
+    }
+  }
+  else {                               // username provided
+    result.input = 'Username'
+    if (emailOrUsername.length <= 2) {
+      result.errors!.push({
+        field: 'emailOrUsername',
+        message: 'Username must be longer than 2 characters.'
+      })
+    }
+    if (emailOrUsername.length > 32) {
+      result.errors!.push({
+        field: 'emailOrUsername',
+        message: 'Username must not be longer than 32 characters.'
+      })
+    }
+    if (!/^[A-Za-z0-9_-]*$/.test(emailOrUsername)) {
+      result.errors!.push({
+        field: 'emailOrUsername',
+        message: 'Username must contain only letters, numbers, underscores and dashes.'
+      })
+    }
+  }
+  if (password.length < 8) {
+    result.errors!.push({
+      field: 'password',
+      message: 'Password must be at least 8 characters.'
+    })
+  }
+  if (password.length > 128) {
+    result.errors!.push({
+      field: 'password',
+      message: 'Password must not be longer than 128 characters.'
+    })
+  }
+  return {
+    input: result.input,
+    errors: result.errors!.length > 0 ? result.errors : null
+  }
+}