import path from "node:path";

// Cross-platform detection. android-arm64 (Termux) is a supported target:
// modern Termux Node builds report process.platform === "android"; older
// builds report "linux" with $PREFIX and $ANDROID_ROOT set — detect both.
// 64-bit only: supported architectures are arm64 and x64.

export type PiPlatform = "android" | "linux" | "darwin" | "win32";

export interface PlatformInfo {
  platform: PiPlatform;
  arch: string;
  isTermux: boolean;
  isWindows: boolean;
  /** true only for 64-bit architectures (arm64/x64). */
  supported: boolean;
  /** GitHub-release asset naming; undefined on unsupported architectures. */
  assetPlatform: "linux" | "darwin" | "windows" | undefined;
  assetArch: string | undefined;
}

export function detectPlatform(
  env: NodeJS.ProcessEnv = process.env,
  platform: NodeJS.Platform = process.platform,
  arch: string = process.arch,
): PlatformInfo {
  const isTermux =
    platform === "android" ||
    (platform === "linux" && Boolean(env.PREFIX) && Boolean(env.ANDROID_ROOT));
  const effective: PiPlatform = isTermux ? "android" : (platform as PiPlatform);
  const supported = arch === "arm64" || arch === "x64";
  const assetPlatform: PlatformInfo["assetPlatform"] = supported
    ? effective === "darwin"
      ? "darwin"
      : effective === "win32"
        ? "windows"
        : "linux"
    : undefined;
  const assetArch: PlatformInfo["assetArch"] = supported
    ? arch === "arm64"
      ? "aarch64"
      : "x86_64"
    : undefined;
  return {
    platform: effective,
    arch,
    isTermux,
    isWindows: effective === "win32",
    supported,
    assetPlatform,
    assetArch,
  };
}

/** Managed-install directory for LSP server binaries. */
export function managedBinDir(env: NodeJS.ProcessEnv = process.env): string {
  const base = env.XDG_CACHE_HOME || path.join(env.HOME ?? env.PREFIX ?? ".", ".cache");
  return path.join(base, "pi-lsp", "bin");
}