/**
 * Platform detection for GitHub vs Forgejo environments.
 *
 * Detection priority:
 * 1. PLATFORM env var (set by action.yml detect step or explicit input)
 * 2. FORGEJO env var (set by Forgejo runner v7.0+)
 * 3. GITHUB_SERVER_URL heuristic (non-github.com = Forgejo)
 * 4. Default to GitHub
 *
 * The result is memoized after first detection — platform doesn't change
 * at runtime and this avoids redundant env reads across 12+ call sites.
 */

export type Platform = "github" | "forgejo";

let _cachedPlatform: Platform | undefined;

export function detectPlatform(): Platform {
  if (_cachedPlatform !== undefined) return _cachedPlatform;

  let result: Platform = "github";

  // 1. Explicit platform from action.yml detect step or user input
  const platformEnv = process.env.PLATFORM;
  if (platformEnv === "forgejo") {
    result = "forgejo";
  } else if (platformEnv === "github") {
    result = "github";
  }
  // 2. FORGEJO env var (set by Forgejo runner v7.0+)
  else if (process.env.FORGEJO === "true") {
    result = "forgejo";
  }
  // 3. GITHUB_SERVER_URL heuristic — if not github.com, likely Forgejo/Gitea
  else {
    const serverUrl = process.env.GITHUB_SERVER_URL || "";
    if (serverUrl && !serverUrl.includes("github.com")) {
      result = "forgejo";
    }
  }

  _cachedPlatform = result;
  return result;
}

/**
 * Reset the memoized platform detection result.
 * Only needed in tests that change platform-related env vars between cases.
 */
export function _resetPlatformCache(): void {
  _cachedPlatform = undefined;
}