feat: add connection config

Author: nirinchev

src/config.ts

@@ -4,21 +4,34 @@ import argv from "yargs-parser";
 
 import packageJson from "../package.json" with { type: "json" };
 import fs from "fs";
+import { ReadConcernLevel, ReadPreferenceMode, W } from "mongodb";
 const { localDataPath, configPath } = getLocalDataPath();
 
 // If we decide to support non-string config options, we'll need to extend the mechanism for parsing
 // env variables.
-interface UserConfig extends Record<string, string | undefined> {
+interface UserConfig extends Record<string, unknown> {
     apiBaseUrl: string;
     clientId: string;
     stateFile: string;
     connectionString?: string;
+    connectOptions: {
+        readConcern: ReadConcernLevel;
+        readPreference: ReadPreferenceMode;
+        writeConcern: W;
+        timeoutMS: number;
+    };
 }
 
 const defaults: UserConfig = {
     apiBaseUrl: "https://cloud.mongodb.com/",
     clientId: "0oabtxactgS3gHIR0297",
     stateFile: path.join(localDataPath, "state.json"),
+    connectOptions: {
+        readConcern: "local",
+        readPreference: "secondaryPreferred",
+        writeConcern: "majority",
+        timeoutMS: 30_000,
+    },
 };
 
 const mergedUserConfig = {
@@ -66,21 +79,51 @@ function getLocalDataPath(): { localDataPath: string; configPath: string } {
 // are prefixed with `MDB_MCP_` and the keys match the UserConfig keys, but are converted
 // to SNAKE_UPPER_CASE.
 function getEnvConfig(): Partial<UserConfig> {
-    const camelCaseToSNAKE_UPPER_CASE = (str: string): string => {
-        return str.replace(/([a-z])([A-Z])/g, "$1_$2").toUpperCase();
-    };
+    function setValue(obj: Record<string, unknown>, path: string[], value: string): void {
+        const currentField = path.shift()!;
+        if (path.length === 0) {
+            const numberValue = Number(value);
+            if (!isNaN(numberValue)) {
+                obj[currentField] = numberValue;
+                return;
+            }
+
+            const booleanValue = value.toLocaleLowerCase();
+            if (booleanValue === "true" || booleanValue === "false") {
+                obj[currentField] = booleanValue === "true";
+                return;
+            }
+
+            obj[currentField] = value;
+            return;
+        }
 
-    const result: Partial<UserConfig> = {};
-    for (const key of Object.keys(defaults)) {
-        const envVarName = `MDB_MCP_${camelCaseToSNAKE_UPPER_CASE(key)}`;
-        if (process.env[envVarName]) {
-            result[key] = process.env[envVarName];
+        if (!obj[currentField]) {
+            obj[currentField] = {};
         }
+
+        setValue(obj[currentField] as Record<string, unknown>, path, value);
+    }
+
+    const result: Record<string, unknown> = {};
+    for (const [key, value] of Object.entries(process.env).filter(
+        ([key, value]) => value !== undefined && key.startsWith("MDB_MCP_")
+    )) {
+        const fieldPath = key
+            .replace("MDB_MCP_", "")
+            .split(".")
+            .map((part) => SNAKE_CASE_toCamelCase(part));
+
+        setValue(result, fieldPath, value!);
     }
 
     return result;
 }
 
+function SNAKE_CASE_toCamelCase(str: string): string {
+    return str.toLowerCase().replace(/([-_][a-z])/g, (group) => group.toUpperCase().replace("_", ""));
+}
+
 // Gets the config supplied by the user as a JSON file. The file is expected to be located in the local data path
 // and named `config.json`.
 function getFileConfig(): Partial<UserConfig> {

src/tools/mongodb/connect.ts

@@ -69,6 +69,12 @@ export class ConnectTool extends MongoDBToolBase {
         const provider = await NodeDriverServiceProvider.connect(connectionString, {
             productDocsLink: "https://docs.mongodb.com/todo-mcp",
             productName: "MongoDB MCP",
+            readConcern: config.connectOptions.readConcern,
+            readPreference: config.connectOptions.readPreference,
+            writeConcern: {
+                w: config.connectOptions.writeConcern,
+            },
+            timeoutMS: config.connectOptions.timeoutMS,
         });
 
         this.state.serviceProvider = provider;