import fs from "fs";
import path from "path";

const BIN_NAME = "studioE5-agent";

// Build the public base URL from an incoming request, respecting common
// reverse-proxy headers (X-Forwarded-Proto / X-Forwarded-Host).
export function getBaseUrlFromRequest(req: Request): string {
  const headers = req.headers;
  const forwardedProto = headers.get("x-forwarded-proto");
  const forwardedHost = headers.get("x-forwarded-host");

  if (forwardedProto && forwardedHost) {
    return `${forwardedProto}://${forwardedHost}`;
  }

  const url = new URL(req.url);
  return `${url.protocol}//${url.host}`;
}

function findVersionFile(): string | null {
  // Try a few common paths relative to the server workspace and Next.js build output.
  const candidates = [
    path.join(process.cwd(), "..", "agent", "VERSION"),
    path.join(process.cwd(), "..", "..", "agent", "VERSION"),
    path.join(process.cwd(), "agent", "VERSION"),
    path.join(__dirname, "..", "..", "..", "agent", "VERSION"),
    path.join(__dirname, "..", "..", "agent", "VERSION"),
    "/app/agent-version",
  ];
  for (const candidate of candidates) {
    if (fs.existsSync(candidate)) {
      return candidate;
    }
  }
  return null;
}

export function getAgentVersion(): string {
  const versionFile = findVersionFile();
  if (versionFile) {
    return fs.readFileSync(versionFile, "utf-8").trim();
  }
  // Fallback used when the agent workspace is not mounted (should not happen).
  return "0.3.9";
}

export interface AgentDownloadUrls {
  windows: string;
  windowsZip: string;
  linux: string;
  mac: string;
}

export function getAgentDownloadUrls(
  version: string,
  baseUrl?: string
): AgentDownloadUrls {
  const prefix = baseUrl ? baseUrl.replace(/\/$/, "") : "";
  return {
    windows: `${prefix}/${BIN_NAME}-v${version}.exe`,
    windowsZip: `${prefix}/${BIN_NAME}-v${version}-windows.zip`,
    linux: `${prefix}/${BIN_NAME}-v${version}`,
    mac: `${prefix}/${BIN_NAME}-v${version}-mac`,
  };
}

export function getAgentVersionInfo(baseUrl?: string) {
  const version = getAgentVersion();
  return {
    version,
    downloadUrls: getAgentDownloadUrls(version, baseUrl),
  };
}