add support for encrypted schemas

Author: baileympearson

.eslintrc.js

@@ -14,7 +14,9 @@ module.exports = {
     '**/docs/js/native.js',
     '!.*',
     'node_modules',
-    '.git'
+    '.git',
+    'data',
+    '.config'
   ],
   overrides: [
     {

docs/field-level-encryption.md

@@ -112,3 +112,41 @@ With the above connection, if you create a model named 'Test' that uses the 'tes
 const Model = mongoose.model('Test', mongoose.Schema({ name: String }));
 await Model.create({ name: 'super secret' });
 ```
+
+## Automatic FLE in Mongoose
+
+Mongoose supports the declaration of encrypted schemas - schemas that, when connected to a model, utilize MongoDB's Client Side
+Field Level Encryption or Queryable Encryption under the hood.  Mongoose automatically generates either an `encryptedFieldsMap` or a
+`schemaMap` when instantiating a MongoClient and encrypts fields on write and decrypts fields on reads.
+
+### Encryption types
+
+MongoDB has to different automatic encryption implementations: client side field level encryption (CSFLE) and queryable encryption (QE).  
+See [choosing an in-use encryption approach](https://www.mongodb.com/docs/v7.3/core/queryable-encryption/about-qe-csfle/#choosing-an-in-use-encryption-approach).
+
+###  Declaring Encrypted Schemas
+
+The following schema declares two properties, `name` and `ssn`.  `ssn` is encrypted using queryable encryption, and
+is configured for equality queries:
+
+```javascript
+const encryptedUserSchema = new Schema({ 
+  name: String,
+  ssn: { 
+    type: String, 
+    // 1
+    encrypt: { 
+      keyId: '<uuid string of key id>',
+      queries: 'equality'
+    }
+  }
+  // 2
+}, { encryptionType: 'queryable encryption' });
+```
+
+To declare a field as encrypted, you must:
+
+1. Annotate the field with encryption metadata in the schema definition
+2. Choose an encryption type for the schema and configure the schema for the encryption type
+
+Not all schematypes are supported for CSFLE and QE.  For an overview of valid schema types, refer to MongoDB's documentation.

lib/encryption_utils.js

@@ -0,0 +1,72 @@
+'use strict';
+
+const { Array } = require('./schema/index.js');
+const SchemaBigInt = require('./schema/bigint');
+const SchemaBoolean = require('./schema/boolean');
+const SchemaBuffer = require('./schema/buffer');
+const SchemaDate = require('./schema/date');
+const SchemaDecimal128 = require('./schema/decimal128');
+const SchemaDouble = require('./schema/double');
+const SchemaInt32 = require('./schema/int32');
+const SchemaObjectId = require('./schema/objectId');
+const SchemaString = require('./schema/string');
+
+/**
+ * Given a schema and a path to a field in the schema, this returns the
+ * BSON type of the field, if it can be determined.  This method specifically
+ * **only** handles BSON types that are used for CSFLE and QE - any other
+ * BSON types will return `null`. (example: MinKey and MaxKey).
+ *
+ * @param {import('.').Schema} schema
+ * @param {string} path
+ * @returns
+ */
+function inferBSONType(schema, path) {
+  const type = schema.path(path);
+
+  if (type instanceof SchemaString) {
+    return 'string';
+  }
+
+  if (type instanceof SchemaInt32) {
+    return 'int';
+  }
+
+  if (type instanceof SchemaBigInt) {
+    return 'long';
+  }
+
+  if (type instanceof SchemaBoolean) {
+    return 'bool';
+  }
+
+  if (type instanceof SchemaDate) {
+    return 'date';
+  }
+
+  if (type instanceof SchemaBuffer) {
+    return 'binData';
+  }
+
+  if (type instanceof SchemaObjectId) {
+    return 'objectId';
+  }
+
+  if (type instanceof SchemaDecimal128) {
+    return 'decimal';
+  }
+
+  if (type instanceof SchemaDouble) {
+    return 'double';
+  }
+
+  if (type instanceof Array) {
+    return 'array';
+  }
+
+  return null;
+}
+
+module.exports = {
+  inferBSONType
+};