fix: infer database type from DSN protocol in API sources endpoint (#133)

When using DSN-based configuration in TOML files without explicit
'type' fields, the /api/sources endpoint was failing with "missing
required type field" errors. This fix allows the endpoint to work
correctly with DSN-only configurations by extracting the database
type from the protocol portion of the DSN string.

Changes:
- Add getDatabaseTypeFromDSN() utility function to dsn-obfuscate.ts
- Use centralized type inference in transformSourceConfig()
- Handle both 'postgres' and 'postgresql' protocols as PostgreSQL
- Maintain backward compatibility with explicit type configurations

Fixes API endpoint failure for DSN-only TOML configurations.

Author: petergithub

src/api/sources.ts

@@ -1,5 +1,6 @@
 import { Request, Response } from "express";
 import { ConnectorManager } from "../connectors/manager.js";
+import { getDatabaseTypeFromDSN } from "../utils/dsn-obfuscate.js";
 import type { SourceConfig } from "../types/config.js";
 import type { components } from "./openapi.js";
 
@@ -15,8 +16,14 @@ function transformSourceConfig(
   source: SourceConfig,
   isDefault: boolean
 ): DataSource {
-  // Type is guaranteed to be present for connected sources
-  // It's set during connection either from DSN parsing or explicit config
+  // Determine type from explicit config or infer from DSN
+  if (!source.type && source.dsn) {
+    const inferredType = getDatabaseTypeFromDSN(source.dsn);
+    if (inferredType) {
+      source.type = inferredType;
+    }
+  }
+
   if (!source.type) {
     throw new Error(`Source ${source.id} is missing required type field`);
   }

src/utils/dsn-obfuscate.ts

@@ -1,4 +1,5 @@
 import type { SSHTunnelConfig } from '../types/ssh.js';
+import type { ConnectorType } from '../connectors/interface.js';
 
 /**
  * Obfuscates the password in a DSN string for logging purposes
@@ -83,4 +84,27 @@ export function obfuscateSSHConfig(config: SSHTunnelConfig): Partial<SSHTunnelCo
   }
 
   return obfuscated;
+}
+
+/**
+ * Extracts the database type from a DSN string
+ * @param dsn The DSN string to analyze
+ * @returns The database type or undefined if cannot be determined
+ */
+export function getDatabaseTypeFromDSN(dsn: string): ConnectorType | undefined {
+  if (!dsn) {
+    return undefined;
+  }
+
+  const protocol = dsn.split(':')[0];
+  const protocolToType: Record<string, ConnectorType> = {
+    'postgres': 'postgres',
+    'postgresql': 'postgres',
+    'mysql': 'mysql',
+    'mariadb': 'mariadb',
+    'sqlserver': 'sqlserver',
+    'sqlite': 'sqlite'
+  };
+
+  return protocolToType[protocol];
 }