import { homedir, platform } from 'node:os';
import { join } from 'node:path';

/**
 * Get the module storage path based on environment and platform
 *
 * @returns Absolute path to module storage directory
 */
export function getModuleStoragePath(): string {
  return join(getDataDir(), 'modules');
}

/**
 * Get the base data directory for Celilo
 *
 * Priority:
 * 1. CELILO_DATA_DIR environment variable (explicit override)
 * 2. ENVIRONMENT=dev uses ./celilo-data/ (for testing)
 * 3. Platform defaults — always user-scoped so the CLI works without root:
 *    - macOS: ~/Library/Application Support/celilo/
 *    - Linux: $XDG_DATA_HOME/celilo/ (defaults to ~/.local/share/celilo/)
 *
 * @returns Absolute path to base data directory
 */
export function getDataDir(): string {
  // Explicit override
  if (process.env.CELILO_DATA_DIR) {
    return process.env.CELILO_DATA_DIR;
  }

  // Development mode
  if (process.env.ENVIRONMENT === 'dev') {
    return join(process.cwd(), 'celilo-data');
  }

  // macOS
  if (platform() === 'darwin') {
    return join(homedir(), 'Library', 'Application Support', 'celilo');
  }

  // Linux/other — XDG Base Directory spec, user-scoped (no sudo needed).
  // System-wide installs can opt in via CELILO_DATA_DIR=/var/lib/celilo.
  const xdgDataHome = process.env.XDG_DATA_HOME || join(homedir(), '.local', 'share');
  return join(xdgDataHome, 'celilo');
}

/**
 * Get the master key file path
 *
 * @returns Absolute path to master key file
 */
export function getMasterKeyPath(): string {
  // Explicit override
  if (process.env.CELILO_MASTER_KEY_PATH) {
    return process.env.CELILO_MASTER_KEY_PATH;
  }

  // Use base data directory + master.key
  return join(getDataDir(), 'master.key');
}

/**
 * Get database file path
 *
 * Priority:
 * 1. CELILO_DB_PATH environment variable (explicit override)
 * 2. <data-dir>/celilo.db (platform-specific)
 *
 * @returns Absolute path to database file
 */
export function getDbPath(): string {
  // Explicit override
  if (process.env.CELILO_DB_PATH) {
    return process.env.CELILO_DB_PATH;
  }

  // Use data directory + celilo.db
  return join(getDataDir(), 'celilo.db');
}

/**
 * Get the SQLite event-bus database file path.
 *
 * Priority:
 * 1. EVENT_BUS_DB environment variable (the bus library's native name —
 *    used by the event-bus CLI, defineHandler, and any standalone tool)
 * 2. <data-dir>/events.db (platform-specific)
 *
 * Kept separate from the main celilo.db so the bus library remains
 * standalone — the bus owns its own schema and migrations.
 *
 * @returns Absolute path to event-bus database
 */
export function getEventBusPath(): string {
  if (process.env.EVENT_BUS_DB) {
    return process.env.EVENT_BUS_DB;
  }
  return join(getDataDir(), 'events.db');
}

/**
 * Shorten a path by replacing the celilo data directory with $CELILO_DATA
 * For display purposes in CLI output.
 *
 * @param absolutePath - Absolute path to shorten
 * @returns Shortened path with $CELILO_DATA prefix
 */
export function shortenPath(absolutePath: string): string {
  const dataDir = getDataDir();
  if (absolutePath.startsWith(dataDir)) {
    return absolutePath.replace(dataDir, '$CELILO_DATA');
  }
  return absolutePath;
}