/**
 * MCP Bridge Extension
 *
 * WHAT: Pi has no built-in MCP. This bridge reads config/mcp.json, and for each
 *       ENABLED server launches it (stdio) via the MCP SDK and registers its
 *       tools into pi. URLs come from config/company.json ({config:KEY}), tokens
 *       from the environment ({env:VAR}) — nothing hardcoded. All servers are
 *       disabled by default; `/mcp-status` shows their state.
 *
 * ENABLE: set a server's "enabled": true in config/mcp.json, provide its token
 *       env var, install the MCP SDK once (`npm i @modelcontextprotocol/sdk` in
 *       the package, or globally) and the launcher (uvx/npx), then restart pi.
 *       Requires network access to the corporate services (VPN).
 *
 * DISABLE: keep servers disabled, or remove/rename this file.
 */

import * as fs from "node:fs";
import * as path from "node:path";
import { fileURLToPath } from "node:url";
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

const HERE = path.dirname(fileURLToPath(import.meta.url));
const MCP_CONFIG = path.join(HERE, "..", "config", "mcp.json");
const COMPANY_CONFIG = path.join(HERE, "..", "config", "company.json");
const CONNECT_TIMEOUT_MS = 8000;

interface ServerSpec {
	enabled?: boolean;
	description?: string;
	command: string;
	args?: string[];
	env?: Record<string, string>;
}

type Status = "disabled" | "connected" | "error" | "no-sdk" | "missing-env";
interface ServerState {
	description: string;
	status: Status;
	tools: string[];
	detail?: string;
}

function readJson(file: string): Record<string, unknown> {
	try {
		return JSON.parse(fs.readFileSync(file, "utf8"));
	} catch {
		return {};
	}
}

/** Replace {config:KEY} and {env:VAR} tokens; returns null if any resolve empty. */
function resolveEnv(
	env: Record<string, string>,
	company: Record<string, unknown>,
): Record<string, string> | null {
	const out: Record<string, string> = {};
	for (const [key, template] of Object.entries(env)) {
		let missing = false;
		const value = template.replace(/\{(config|env):([^}]+)\}/g, (_m, kind, name) => {
			const v = kind === "config" ? company[name] : process.env[name];
			if (typeof v !== "string" || v === "" || v === "TODO") missing = true;
			return typeof v === "string" ? v : "";
		});
		if (missing) return null;
		out[key] = value;
	}
	return out;
}

export default async function mcpBridgeExtension(pi: ExtensionAPI) {
	const mcpCfg = readJson(MCP_CONFIG);
	const company = readJson(COMPANY_CONFIG);
	const servers = (mcpCfg.servers ?? {}) as Record<string, ServerSpec>;
	const state = new Map<string, ServerState>();
	const closers: Array<() => Promise<void> | void> = [];

	// Seed status for every configured server.
	for (const [key, spec] of Object.entries(servers)) {
		state.set(key, { description: spec.description ?? key, status: spec.enabled ? "error" : "disabled", tools: [] });
	}

	pi.registerCommand("mcp-status", {
		description: "Показать сконфигурированные MCP-серверы (Jira/Confluence/GitLab) и их статус",
		handler: async (_args, ctx) => {
			const lines: string[] = [];
			for (const [key, s] of state) {
				const t = s.tools.length ? ` — ${s.tools.length} tools` : "";
				lines.push(`${key}: ${s.status}${t}${s.detail ? ` (${s.detail})` : ""}`);
				lines.push(`   ${s.description}`);
			}
			if (lines.length === 0) lines.push("MCP-серверы не сконфигурированы (config/mcp.json).");
			lines.push("", "Включить: enabled:true в config/mcp.json + токен в env + перезапуск pi.");
			if (ctx.hasUI) await ctx.ui.select("MCP-серверы", lines);
			else ctx.ui.notify(lines.join("\n"), "info");
		},
	});

	// Connect enabled servers. Nothing runs here when all are disabled (default).
	for (const [key, spec] of Object.entries(servers)) {
		if (!spec.enabled) continue;
		const st = state.get(key)!;

		const env = resolveEnv(spec.env ?? {}, company);
		if (env === null) {
			st.status = "missing-env";
			st.detail = "нет URL/токена (config/env)";
			continue;
		}

		try {
			// Dynamically import so a missing SDK never breaks loading for others.
			const { Client } = await import("@modelcontextprotocol/sdk/client/index.js");
			const { StdioClientTransport } = await import("@modelcontextprotocol/sdk/client/stdio.js");

			const transport = new StdioClientTransport({
				command: spec.command,
				args: spec.args ?? [],
				env: { ...process.env, ...env } as Record<string, string>,
			});
			const client = new Client({ name: `pi-kit-${key}`, version: "0.1.0" }, { capabilities: {} });
			await Promise.race([
				client.connect(transport),
				new Promise((_r, reject) => setTimeout(() => reject(new Error("timeout")), CONNECT_TIMEOUT_MS)),
			]);
			closers.push(() => client.close().catch(() => {}));

			const { tools } = await client.listTools();
			for (const tool of tools ?? []) {
				const toolName = `${key}_${tool.name}`;
				pi.registerTool({
					name: toolName,
					label: toolName,
					description: tool.description ?? `${key} MCP tool ${tool.name}`,
					// MCP inputSchema is JSON Schema; pi accepts a JSON-Schema-shaped object.
					parameters: (tool.inputSchema as unknown) ?? { type: "object", properties: {} },
					async execute(_id: string, params: unknown) {
						const res: any = await client.callTool({ name: tool.name, arguments: (params ?? {}) as Record<string, unknown> });
						return { content: res.content ?? [{ type: "text", text: JSON.stringify(res) }], details: {} };
					},
				});
				st.tools.push(toolName);
			}
			st.status = "connected";
			// Connection status is visible via /mcp-status (no ctx in the factory).
		} catch (err) {
			const msg = err instanceof Error ? err.message : String(err);
			st.status = /Cannot find( package)?|ERR_MODULE_NOT_FOUND|@modelcontextprotocol/.test(msg) ? "no-sdk" : "error";
			st.detail = st.status === "no-sdk" ? "установи @modelcontextprotocol/sdk" : msg.slice(0, 80);
		}
	}

	pi.on("session_shutdown", async () => {
		for (const close of closers) await close();
	});
}