import { isIP } from "node:net";
import { resolveFeatureFlag } from "@/shared/utils/featureFlags";

const TRUE_ENV_VALUES = new Set(["1", "true", "yes", "on"]);

export const PROVIDER_URL_BLOCKED_MESSAGE = "Blocked private or local provider URL";
export const CLOUD_METADATA_BLOCKED_MESSAGE = "Blocked cloud-metadata endpoint";
export const PRIVATE_PROVIDER_URLS_ENV = "OMNIROUTE_ALLOW_PRIVATE_PROVIDER_URLS";
// #5066: scoped to provider validation/use. Allows local/private provider endpoints
// (127.0.0.1, localhost, LAN) so local-first OpenAI-compatible providers validate, while
// cloud-metadata endpoints stay blocked. Defaults ON (OmniRoute is local-first); operators
// who only use public providers can disable it to restore strict SSRF blocking.
export const LOCAL_PROVIDER_URLS_ENV = "OMNIROUTE_ALLOW_LOCAL_PROVIDER_URLS";

// "block-metadata": allow private/LAN hosts but still reject cloud-metadata / link-local
// endpoints (the SSRF→IAM-credential pivot). Used by the provider-validation path under the
// local-first default; never relaxes the metadata block.
export type OutboundUrlGuardMode = "none" | "public-only" | "block-metadata";
export type OutboundUrlGuardErrorCode = "OUTBOUND_URL_GUARD_BLOCKED" | "OUTBOUND_URL_INVALID";

type OutboundUrlGuardErrorInit = {
  code: OutboundUrlGuardErrorCode;
  url: string;
  hostname?: string | null;
};

export class OutboundUrlGuardError extends Error {
  code: OutboundUrlGuardErrorCode;
  url: string;
  hostname?: string | null;

  constructor(message: string, init: OutboundUrlGuardErrorInit) {
    super(message);
    this.name = "OutboundUrlGuardError";
    this.code = init.code;
    this.url = init.url;
    this.hostname = init.hostname ?? null;
  }
}

function normalizeHost(hostname: string) {
  const normalized = hostname.trim().toLowerCase();
  if (normalized.startsWith("[") && normalized.endsWith("]")) {
    return normalized.slice(1, -1);
  }
  return normalized;
}

export function isPrivateHost(hostname: string) {
  const normalized = normalizeHost(hostname);
  if (!normalized) return true;

  if (
    normalized === "localhost" ||
    normalized === "0.0.0.0" ||
    normalized === "127.0.0.1" ||
    normalized === "::1" ||
    normalized.endsWith(".localhost") ||
    normalized.endsWith(".local") ||
    // `.internal` is reserved for private use (ICANN-style) and is the
    // hostname suffix used by GCP/Azure metadata probes
    // (e.g. `metadata.google.internal`).
    normalized.endsWith(".internal") ||
    normalized.startsWith("::ffff:")
  ) {
    return true;
  }

  if (isIP(normalized) === 4) {
    const octets = normalized.split(".").map((segment) => parseInt(segment, 10));
    const [a, b] = octets;

    if (a === 0 || a === 10 || a === 127) return true;
    if (a === 169 && b === 254) return true;
    if (a === 192 && b === 168) return true;
    if (a === 172 && b >= 16 && b <= 31) return true;
    if (a === 100 && b >= 64 && b <= 127) return true;
    return false;
  }

  if (isIP(normalized) === 6) {
    return (
      normalized === "::1" ||
      normalized.startsWith("fc") ||
      normalized.startsWith("fd") ||
      normalized.startsWith("fe80:")
    );
  }

  return false;
}

const CLOUD_METADATA_HOSTNAMES = new Set([
  "169.254.169.254", // AWS / GCP / Azure / Oracle IMDS
  "metadata.google.internal", // GCP
  "metadata.goog", // GCP
  "100.100.100.200", // Alibaba Cloud
  "fd00:ec2::254", // AWS IPv6 IMDS
]);

/**
 * Cloud-metadata and IPv4 link-local (169.254.0.0/16) endpoints are the classic
 * SSRF→IAM-credential pivot and have no legitimate webhook/automation use case. They are
 * blocked UNCONDITIONALLY — even when private targets are explicitly opted in. (#3269)
 */
export function isCloudMetadataHost(hostname: string): boolean {
  const host = normalizeHost(hostname);
  if (!host) return false;
  if (CLOUD_METADATA_HOSTNAMES.has(host)) return true;
  if (host.startsWith("169.254.")) return true; // IPv4 link-local /16
  return false;
}

export function parseOutboundUrl(input: string | URL) {
  let url: URL;
  try {
    url = input instanceof URL ? input : new URL(String(input));
  } catch {
    throw new OutboundUrlGuardError(`Invalid outbound URL: ${String(input)}`, {
      code: "OUTBOUND_URL_INVALID",
      url: String(input),
    });
  }

  if (url.protocol !== "http:" && url.protocol !== "https:") {
    throw new OutboundUrlGuardError(`Invalid outbound URL protocol for ${url.toString()}`, {
      code: "OUTBOUND_URL_INVALID",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  if (url.username || url.password) {
    throw new OutboundUrlGuardError("Blocked outbound URL with embedded credentials", {
      code: "OUTBOUND_URL_GUARD_BLOCKED",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  return url;
}

export function parseAndValidatePublicUrl(input: string | URL) {
  const url = parseOutboundUrl(input);

  if (isPrivateHost(url.hostname)) {
    throw new OutboundUrlGuardError(PROVIDER_URL_BLOCKED_MESSAGE, {
      code: "OUTBOUND_URL_GUARD_BLOCKED",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  return url;
}

/**
 * #5066: provider-validation variant. Allows private/LAN hosts (so a local OpenAI-compatible
 * provider at 127.0.0.1 validates) but ALWAYS rejects cloud-metadata / link-local endpoints —
 * the classic SSRF→IAM-credential pivot, which is never a legitimate provider endpoint.
 * Protocol and embedded-credential checks from {@link parseOutboundUrl} still apply.
 */
export function parseAndValidateNonMetadataUrl(input: string | URL) {
  const url = parseOutboundUrl(input);

  if (isCloudMetadataHost(url.hostname)) {
    throw new OutboundUrlGuardError(CLOUD_METADATA_BLOCKED_MESSAGE, {
      code: "OUTBOUND_URL_GUARD_BLOCKED",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  return url;
}

/**
 * Webhook variant of {@link parseAndValidatePublicUrl}. Webhooks legitimately point at
 * internal services (n8n, Home Assistant, a LAN box) in Docker/self-hosted deployments,
 * so the private-host block is gated behind the same explicit opt-in used for private
 * provider URLs (`OMNIROUTE_ALLOW_PRIVATE_PROVIDER_URLS`, default OFF). Protocol and
 * embedded-credential checks in {@link parseOutboundUrl} remain unconditional. (#3269)
 */
export function parseAndValidateWebhookUrl(input: string | URL) {
  const url = parseOutboundUrl(input);

  // Cloud-metadata / link-local endpoints are NEVER a valid webhook target — block them
  // even when the private opt-in is enabled (SSRF→IAM-credential pivot). (#3269)
  if (isCloudMetadataHost(url.hostname)) {
    throw new OutboundUrlGuardError(PROVIDER_URL_BLOCKED_MESSAGE, {
      code: "OUTBOUND_URL_GUARD_BLOCKED",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  if (!arePrivateProviderUrlsAllowed() && isPrivateHost(url.hostname)) {
    throw new OutboundUrlGuardError(PROVIDER_URL_BLOCKED_MESSAGE, {
      code: "OUTBOUND_URL_GUARD_BLOCKED",
      url: url.toString(),
      hostname: url.hostname || null,
    });
  }

  return url;
}

function isTrueValue(raw: unknown): boolean {
  if (typeof raw !== "string") return false;
  return TRUE_ENV_VALUES.has(raw.trim().toLowerCase());
}

export function arePrivateProviderUrlsAllowed() {
  // 1) DB override takes precedence — it represents an explicit user toggle in
  //    the dashboard ("Allow Private Provider URLs"). This is critical for the
  //    Electron build (#2575) where the server is spawned with the env value
  //    captured at boot, so subsequent UI toggles only land in the DB and the
  //    env-first ordering would otherwise mask them.
  try {
    const dbValue = resolveFeatureFlag(PRIVATE_PROVIDER_URLS_ENV);
    if (isTrueValue(dbValue)) return true;
  } catch {
    // DB not initialized yet — fall through to env-only check.
  }

  // 2) Explicit env opt-in (for headless/Docker users who set it before boot).
  if (isTrueValue(process.env[PRIVATE_PROVIDER_URLS_ENV])) return true;

  // 3) Legacy escape hatch — disabling the outbound guard implies allowing
  //    private URLs.
  const legacyValue = process.env["OUTBOUND_SSRF_GUARD_ENABLED"];
  if (
    typeof legacyValue === "string" &&
    ["false", "0", "no", "off"].includes(legacyValue.trim().toLowerCase())
  ) {
    return true;
  }

  return false;
}

export function getProviderOutboundGuard(): OutboundUrlGuardMode {
  return arePrivateProviderUrlsAllowed() ? "none" : "public-only";
}

/**
 * #5066: whether provider endpoints on local/private addresses are permitted. Defaults ON
 * (OmniRoute is local-first — local OpenAI-compatible providers should validate out of the
 * box). Disable via the `OMNIROUTE_ALLOW_LOCAL_PROVIDER_URLS` flag (DB toggle or env) to
 * restore strict public-only SSRF blocking. Cloud-metadata stays blocked regardless.
 */
export function areLocalProviderUrlsAllowed(): boolean {
  try {
    const dbValue = resolveFeatureFlag(LOCAL_PROVIDER_URLS_ENV);
    if (dbValue !== undefined && dbValue !== "") return isTrueValue(dbValue);
  } catch {
    // DB not initialized yet — fall through to env / default.
  }
  const envValue = process.env[LOCAL_PROVIDER_URLS_ENV];
  if (typeof envValue === "string" && envValue !== "") return isTrueValue(envValue);
  // Default ON.
  return true;
}

/**
 * Guard mode for the provider VALIDATION/use path (not webhooks or remote images). Precedence:
 *  1. explicit full opt-in (`arePrivateProviderUrlsAllowed`) → "none" (no checks; power users).
 *  2. local-first default (`areLocalProviderUrlsAllowed`) → "block-metadata" (allow LAN, block IMDS).
 *  3. otherwise → "public-only" (strict).
 */
export function getProviderValidationGuard(): OutboundUrlGuardMode {
  if (arePrivateProviderUrlsAllowed()) return "none";
  if (areLocalProviderUrlsAllowed()) return "block-metadata";
  return "public-only";
}