/**
 * Helpers for creating the stable MCP launcher and MCP client configuration.
 *
 * The launcher lives outside the VS Code extension install directory (under
 * ~/.ra3modxml) so AI client configs do not break when the extension is
 * updated to a new version. The extension refreshes the launcher on every
 * activation/update.
 *
 * Pure TypeScript: no VS Code dependency.
 */

import { chmod, mkdir, readFile, writeFile } from "node:fs/promises";
import { homedir } from "node:os";
import { dirname, join } from "node:path";
import { defaultAgentHome } from "./snapshot";

export interface McpConfigTarget {
  id: string;
  label: string;
  path: string;
}

/** File name of the stable launcher on the current platform. */
export function launcherFileName(): string {
  return process.platform === "win32" ? "ra3-mod-xml-mcp.cmd" : "ra3-mod-xml-mcp";
}

/** Absolute path to the stable launcher under the agent home. */
export function launcherPath(agentHome = defaultAgentHome()): string {
  return join(agentHome, launcherFileName());
}

/**
 * Path to the bundled MCP server inside an extension install/dev directory.
 * The packaged extension ships this file under dist/agent/mcpServer.js.
 */
export function bundledMcpServerPath(extensionRoot: string): string {
  return join(extensionRoot, "dist", "agent", "mcpServer.js");
}

/**
 * Creates the stable launcher script. It points to the current extension's
 * bundled MCP server and passes the project directory.
 */
export async function writeLauncher(
  extensionRoot: string,
  projectDir: string,
  agentHome = defaultAgentHome(),
): Promise<string> {
  const server = bundledMcpServerPath(extensionRoot);
  const launcher = launcherPath(agentHome);
  await mkdir(dirname(launcher), { recursive: true });
  if (process.platform === "win32") {
    const content = [
      "@echo off",
      `node "${server}" --project "${projectDir}"`,
      "",
    ].join("\r\n");
    await writeFile(launcher, content, "utf8");
  } else {
    const content = [
      "#!/usr/bin/env sh",
      `exec node "${server}" --project "${projectDir}"`,
      "",
    ].join("\n");
    await writeFile(launcher, content, "utf8");
    await chmod(launcher, 0o755);
  }
  return launcher;
}

/** MCP client config entry for one project. */
export function mcpServerConfig(
  launcher: string,
  projectDir: string,
): Record<string, unknown> {
  return {
    mcpServers: {
      "ra3-mod-xml": {
        command: launcher,
        args: ["--project", projectDir],
      },
    },
  };
}

/** Human-readable JSON config block users can paste into AI clients. */
export function mcpConfigJson(
  launcher: string,
  projectDir: string,
): string {
  return JSON.stringify(mcpServerConfig(launcher, projectDir), null, 2);
}

/** Claude Desktop config path (Windows/macOS/Linux common locations). */
export function claudeDesktopConfigPath(): string {
  if (process.env.APPDATA) return join(process.env.APPDATA, "Claude", "claude_desktop_config.json");
  return join(homedir(), ".config", "Claude", "claude_desktop_config.json");
}

/** Cursor's global MCP config path. */
export function cursorGlobalConfigPath(): string {
  return join(homedir(), ".cursor", "mcp.json");
}

/** Cursor's project-scoped MCP config path. */
export function cursorProjectConfigPath(projectDir: string): string {
  return join(projectDir, ".cursor", "mcp.json");
}

/** Common local MCP config files this extension can offer to update. */
export function commonMcpConfigTargets(projectDir: string): McpConfigTarget[] {
  return [
    {
      id: "claude-desktop",
      label: "Claude Desktop",
      path: claudeDesktopConfigPath(),
    },
    {
      id: "cursor-global",
      label: "Cursor (global)",
      path: cursorGlobalConfigPath(),
    },
    {
      id: "cursor-project",
      label: "Cursor (current project)",
      path: cursorProjectConfigPath(projectDir),
    },
  ];
}

/**
 * Adds the RA3 Mod XML MCP server entry to a JSON config file, preserving any
 * existing keys and mcpServers. Creates the file when it does not exist.
 */
export async function addMcpServerToConfigFile(
  filePath: string,
  launcher: string,
  projectDir: string,
): Promise<void> {
  let config: Record<string, unknown> = {};
  try {
    config = JSON.parse(await readFile(filePath, "utf8")) as Record<string, unknown>;
  } catch {
    // File absent or malformed: start fresh.
  }
  const servers = (config.mcpServers as Record<string, unknown> | undefined) ?? {};
  servers["ra3-mod-xml"] = {
    command: launcher,
    args: ["--project", projectDir],
  };
  config.mcpServers = servers;
  await mkdir(dirname(filePath), { recursive: true });
  await writeFile(filePath, `${JSON.stringify(config, null, 2)}\n`, "utf8");
}

/** Default path used for the agent home. */
export function defaultAgentHomeForSetup(): string {
  return join(homedir(), ".ra3modxml");
}