import fs from "node:fs";
import path from "node:path";
export interface VariantToolFlags {
abapLint: boolean;
abapFeatureMatrix: boolean;
}
export interface VariantServerIdentity {
stdioName: string;
stdioDescription: string;
streamableName: string;
streamableDescription: string;
httpStatusPort: number;
streamablePort: number;
pm2HttpName: string;
pm2StreamableName: string;
deployPath: string;
}
export interface VariantConfig {
metadataPath?: string;
id: string;
description: string;
sourceAllowlist: string[];
submodulePaths: string[];
tools: VariantToolFlags;
server: VariantServerIdentity;
}
const DEFAULT_VARIANT = "sap-docs";
const VARIANT_SELECTOR_FILE = ".mcp-variant";
const VARIANT_DIR = path.resolve(process.cwd(), "config", "variants");
let cachedVariantName: string | null = null;
let cachedVariantConfig: VariantConfig | null = null;
function resolveVariantName(): string {
const envVariant = process.env.MCP_VARIANT?.trim();
if (envVariant) {
return envVariant;
}
try {
const selectorPath = path.resolve(process.cwd(), VARIANT_SELECTOR_FILE);
if (fs.existsSync(selectorPath)) {
const fileVariant = fs.readFileSync(selectorPath, "utf8").trim();
if (fileVariant) {
return fileVariant;
}
}
} catch {
// Ignore read errors and use fallback.
}
return DEFAULT_VARIANT;
}
function readVariantConfig(variantName: string): VariantConfig {
const variantPath = path.resolve(VARIANT_DIR, `${variantName}.json`);
if (!fs.existsSync(variantPath)) {
const supported = fs
.readdirSync(VARIANT_DIR)
.filter((entry) => entry.endsWith(".json"))
.map((entry) => entry.replace(/\.json$/, ""));
throw new Error(
`Unknown MCP variant \"${variantName}\". Supported variants: ${supported.join(", ")}`
);
}
const parsed = JSON.parse(fs.readFileSync(variantPath, "utf8")) as VariantConfig;
return parsed;
}
export function getVariantName(): string {
if (!cachedVariantName) {
cachedVariantName = resolveVariantName();
}
return cachedVariantName;
}
export function getVariantConfig(): VariantConfig {
if (!cachedVariantConfig) {
cachedVariantConfig = readVariantConfig(getVariantName());
}
return cachedVariantConfig;
}
export function isSourceAllowed(sourceId: string): boolean {
const { sourceAllowlist } = getVariantConfig();
return sourceAllowlist.includes(sourceId);
}
export function getAllowedSources(): string[] {
return [...getVariantConfig().sourceAllowlist];
}
export function getAllowedSubmodulePaths(): string[] {
return [...getVariantConfig().submodulePaths];
}
export function isToolEnabled(tool: keyof VariantToolFlags): boolean {
return Boolean(getVariantConfig().tools[tool]);
}
export function clearVariantCache(): void {
cachedVariantName = null;
cachedVariantConfig = null;
}
