// SPDX-License-Identifier: MIT

import { readFile } from "node:fs/promises";
import os from "node:os";
import path from "node:path";

type Config = {
  tenantId?: string;
  clientId?: string;
};

type ConfigCandidate = {
  tenantId?: unknown;
  clientId?: unknown;
};

export function getUserConfigDir(): string {
  if (process.platform === "win32") {
    return process.env.LOCALAPPDATA ?? path.join(os.homedir(), "AppData", "Local");
  }

  return process.env.XDG_CONFIG_HOME ?? path.join(os.homedir(), ".config");
}

async function loadConfig(configFileName: string): Promise<Config> {
  if (typeof configFileName !== "string" || configFileName.trim() === "") {
    throw new Error(
      'Invalid config file name. Expected a non-empty string like "public-config.json" or "confidential-config.json".',
    );
  }

  const envConfig: Config = {
    tenantId: process.env.AZURE_TENANT_ID,
    clientId: process.env.AZURE_CLIENT_ID,
  };

  const configPath = path.join(getUserConfigDir(), "sk-az-tools", configFileName);
  return readFile(configPath, "utf8")
    .then((configJson) => JSON.parse(configJson) as ConfigCandidate)
    .catch((err: unknown) => {
      if ((err as { code?: string } | null)?.code === "ENOENT") {
        return {} as ConfigCandidate;
      }
      throw err;
    })
    .then((json) => ({
      tenantId: typeof json.tenantId === "string" && json.tenantId ? json.tenantId : envConfig.tenantId,
      clientId: typeof json.clientId === "string" && json.clientId ? json.clientId : envConfig.clientId,
    }));
}

export function loadPublicConfig(): Promise<Config> {
  return loadConfig("public-config.json");
}

export function loadConfidentialConfig(): Promise<Config> {
  return loadConfig("confidential-config.json");
}