import { randomBytes } from "node:crypto";

const DEFAULT_SESSION_TTL_MS = 12 * 60 * 60 * 1000;
const DEFAULT_VALIDATION_TTL_MS = 20_000;
const DEFAULT_VALIDATION_GRACE_MS = 30_000;

export function createDeviceManagerAuth({
  env = process.env,
  fetchImpl = fetch,
  now = Date.now,
} = {}) {
  const authRequired = booleanValue(
    env.NODEDC_DEVICE_MANAGER_AUTH_REQUIRED,
    env.NODE_ENV === "production",
  );
  const serviceSlug = textValue(env.NODEDC_DEVICE_MANAGER_SERVICE_SLUG, "device-core");
  const launcherBaseUrl = baseUrl(env.NODEDC_LAUNCHER_BASE_URL, "http://127.0.0.1:5173");
  const launcherInternalUrl = baseUrl(env.NODEDC_LAUNCHER_INTERNAL_URL, launcherBaseUrl);
  const internalToken = textValue(
    env.NODEDC_INTERNAL_ACCESS_TOKEN || env.NODEDC_PLATFORM_SERVICE_TOKEN,
    "",
  );
  const sessionCookie = textValue(
    env.NODEDC_DEVICE_MANAGER_SESSION_COOKIE,
    "nodedc_device_manager_session",
  );
  const sessionTtlMs = boundedInteger(
    env.NODEDC_DEVICE_MANAGER_SESSION_TTL_MS,
    DEFAULT_SESSION_TTL_MS,
    60_000,
    24 * 60 * 60 * 1000,
  );
  const validationTtlMs = boundedInteger(
    env.NODEDC_DEVICE_MANAGER_SESSION_VALIDATION_TTL_MS,
    DEFAULT_VALIDATION_TTL_MS,
    15_000,
    30_000,
  );
  const validationGraceMs = boundedInteger(
    env.NODEDC_DEVICE_MANAGER_SESSION_VALIDATION_GRACE_MS,
    DEFAULT_VALIDATION_GRACE_MS,
    0,
    60_000,
  );
  const secureCookie = booleanValue(
    env.NODEDC_DEVICE_MANAGER_COOKIE_SECURE,
    authRequired,
  );
  const sessions = new Map();

  function buildCookie(value, maxAgeSeconds) {
    return [
      `${sessionCookie}=${encodeURIComponent(value)}`,
      "Path=/",
      "HttpOnly",
      "SameSite=Lax",
      `Max-Age=${Math.max(0, Math.floor(maxAgeSeconds))}`,
      ...(secureCookie ? ["Secure"] : []),
    ].join("; ");
  }

  function createSession(response, handoff) {
    pruneSessions();
    const id = randomBytes(32).toString("base64url");
    const createdAt = now();
    sessions.set(id, {
      id,
      user: handoff.user,
      launcherSessionId: handoff.launcherSessionId,
      expiresAt: createdAt + sessionTtlMs,
      validatedAt: createdAt,
      validationInFlight: null,
    });
    appendCookie(response, buildCookie(id, sessionTtlMs / 1000));
  }

  function currentSession(request) {
    const id = parseCookies(request.headers.cookie)[sessionCookie];
    const session = id ? sessions.get(id) : null;
    if (!session || session.expiresAt <= now()) {
      if (id) sessions.delete(id);
      return null;
    }
    return session;
  }

  async function launcherRequest(pathname, payload) {
    if (!internalToken) throw serviceError("device_manager_auth_not_configured", 503);
    const response = await fetchImpl(new URL(pathname, launcherInternalUrl), {
      method: "POST",
      headers: {
        Authorization: `Bearer ${internalToken}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify(payload),
      signal: AbortSignal.timeout(8_000),
    });
    const body = await response.json().catch(() => null);
    return { response, body };
  }

  async function handleHandoff(request, response, url) {
    const nextPath = safeReturnTo(
      url.searchParams.get("next_path") || url.searchParams.get("returnTo"),
    );
    if (!authRequired) return redirect(response, nextPath);
    const token = String(url.searchParams.get("token") || "");
    if (!token) return sendText(response, 400, "Missing Launcher handoff token.");
    try {
      const result = await launcherRequest("/api/internal/handoff/consume", {
        token,
        serviceSlug,
      });
      if (!result.response.ok || result.body?.ok !== true || !result.body?.user) {
        return sendText(response, 401, "Launcher handoff rejected.");
      }
      createSession(response, {
        user: result.body.user,
        launcherSessionId: result.body.launcherSessionId ?? null,
      });
      return redirect(response, nextPath);
    } catch {
      return sendText(response, 401, "Launcher handoff failed.");
    }
  }

  async function validatedSession(request, response) {
    if (!authRequired) {
      return attachSession(request, {
        user: {
          id: "local-device-admin",
          email: "local-device-admin@nodedc.local",
          name: "Local Device Admin",
          avatarUrl: null,
          groups: ["nodedc:superadmin"],
        },
      });
    }
    const session = currentSession(request);
    if (!session) {
      clearCookie(response);
      return null;
    }
    if (now() - session.validatedAt <= validationTtlMs) {
      return attachSession(request, session);
    }
    if (!session.validationInFlight) {
      session.validationInFlight = launcherRequest("/api/internal/session/validate", {
        serviceSlug,
        launcherSessionId: session.launcherSessionId,
      }).finally(() => {
        session.validationInFlight = null;
      });
    }
    try {
      const { response: upstream, body } = await session.validationInFlight;
      if (upstream.ok && body?.ok === true && body.active === true) {
        session.user = body.user || session.user;
        session.validatedAt = now();
        return attachSession(request, session);
      }
      if (upstream.ok && body?.ok === true && body.active === false) {
        sessions.delete(session.id);
        clearCookie(response);
        return null;
      }
    } catch {
      // Read-only grace is resolved below; mutations always fail closed.
    }
    const readOnly = request.method === "GET" || request.method === "HEAD";
    if (readOnly && now() - session.validatedAt <= validationTtlMs + validationGraceMs) {
      return attachSession(request, session);
    }
    request.nodedcDeviceManagerAuthUnavailable = true;
    return null;
  }

  async function authorize(request, response, url) {
    if (
      url.pathname === "/healthz"
      || url.pathname === "/auth/nodedc/handoff"
      || url.pathname === "/auth/logout"
    ) return false;
    const session = await validatedSession(request, response);
    if (!session) {
      if (request.nodedcDeviceManagerAuthUnavailable) {
        sendJson(response, 503, { ok: false, error: "device_manager_auth_unavailable" });
        return true;
      }
      const loginUrl = new URL("/auth/login", launcherBaseUrl);
      const launch = new URL(`/api/services/${encodeURIComponent(serviceSlug)}/launch`, launcherBaseUrl);
      launch.searchParams.set("returnTo", safeReturnTo(`${url.pathname}${url.search}`));
      loginUrl.searchParams.set("returnTo", `${launch.pathname}${launch.search}`);
      if (isHtmlRequest(request, url)) return redirect(response, loginUrl.toString());
      sendJson(response, 401, {
        ok: false,
        error: "device_manager_auth_required",
        loginUrl: loginUrl.toString(),
      });
      return true;
    }
    const access = resolveAccess(session.user);
    if (!access.allowed) {
      sendJson(response, 403, {
        ok: false,
        error: access.blocked
          ? "device_manager_access_blocked"
          : "device_manager_access_denied",
      });
      return true;
    }
    request.nodedcDeviceManagerAccess = access;
    return false;
  }

  function handleLogout(request, response) {
    const id = parseCookies(request.headers.cookie)[sessionCookie];
    if (id) sessions.delete(id);
    clearCookie(response);
    redirect(response, "/");
  }

  function currentContext(request) {
    const user = request.nodedcDeviceManagerSession?.user;
    const access = request.nodedcDeviceManagerAccess ?? resolveAccess(user);
    if (!user || !access.allowed) return null;
    const id = cleanOpaque(user.id || user.subject || user.sub);
    if (!id) return null;
    const email = String(user.email || "").trim().slice(0, 240);
    const displayName = String(user.name || user.displayName || email || "NODE.DC")
      .trim()
      .slice(0, 240);
    const avatar = String(user.avatarUrl || user.avatar_url || user.picture || "").trim();
    const userRef = `user:${id}`;
    const ownerScopes = ["admin", "owner"].includes(access.hubRole)
      ? [{ scopeKind: "personal", ownerRef: userRef, displayName }]
      : [];
    return {
      user: {
        id,
        email,
        displayName,
        avatarUrl: /^https:\/\//i.test(avatar) || avatar.startsWith("/") ? avatar : null,
        initials: initials(displayName),
      },
      actor: {
        userRef,
        hubRole: access.hubRole,
        groupRefs: access.groups.map((group) => `group:${group}`),
        ownerScopes,
      },
      profileUrl: new URL("/profile", launcherBaseUrl).toString(),
    };
  }

  function clearCookie(response) {
    appendCookie(response, buildCookie("", 0));
  }

  function pruneSessions() {
    const current = now();
    for (const [id, session] of sessions) {
      if (session.expiresAt <= current) sessions.delete(id);
    }
  }

  return {
    authRequired,
    serviceSlug,
    authorize,
    currentContext,
    handleHandoff,
    handleLogout,
  };
}

function resolveAccess(user) {
  if (!user || typeof user !== "object") {
    return { allowed: false, blocked: false, hubRole: "viewer", groups: [] };
  }
  const groups = normalizedGroups(user);
  if (groups.includes("nodedc:device-core:blocked")) {
    return { allowed: false, blocked: true, hubRole: "viewer", groups };
  }
  const id = cleanOpaque(user.id || user.subject || user.sub);
  if (!id) return { allowed: false, blocked: false, hubRole: "viewer", groups };
  const hubRole = id === "user_root" || groups.includes("nodedc:superadmin")
    ? "owner"
    : groups.includes("nodedc:device-core:admin") || groups.includes("nodedc:launcher:admin")
      ? "admin"
      : groups.includes("nodedc:device-core:viewer")
        ? "viewer"
        : "member";
  return { allowed: true, blocked: false, hubRole, groups };
}

function normalizedGroups(user) {
  const values = [user.groups, user.roles, user.roleKeys, user.permissions];
  const groups = [];
  for (const value of values) {
    const items = Array.isArray(value) ? value : typeof value === "string" ? value.split(",") : [];
    for (const item of items) {
      const raw = typeof item === "string" ? item : item?.name || item?.key || item?.slug;
      const normalized = String(raw || "").trim().toLowerCase();
      if (/^[a-z0-9][a-z0-9._:-]{1,127}$/.test(normalized)) groups.push(normalized);
    }
  }
  return [...new Set(groups)].sort();
}

function attachSession(request, session) {
  request.nodedcDeviceManagerSession = session;
  return session;
}

function cleanOpaque(value) {
  const normalized = String(value || "").trim();
  return /^[A-Za-z0-9][A-Za-z0-9._:-]{2,255}$/.test(normalized)
    ? normalized
    : null;
}

function parseCookies(header = "") {
  const values = {};
  for (const part of String(header).split(";")) {
    const index = part.indexOf("=");
    if (index < 1) continue;
    const key = part.slice(0, index).trim();
    try {
      values[key] = decodeURIComponent(part.slice(index + 1).trim());
    } catch {
      values[key] = part.slice(index + 1).trim();
    }
  }
  return values;
}

function appendCookie(response, value) {
  const current = response.getHeader("Set-Cookie");
  response.setHeader("Set-Cookie", current ? [current, value].flat() : value);
}

function safeReturnTo(value) {
  return typeof value === "string" && value.startsWith("/") && !value.startsWith("//")
    ? value
    : "/";
}

function isHtmlRequest(request, url) {
  return request.method === "GET"
    && !url.pathname.startsWith("/api/")
    && (url.pathname === "/" || String(request.headers.accept || "").includes("text/html"));
}

function redirect(response, location) {
  response.statusCode = 302;
  response.setHeader("Location", location);
  response.setHeader("Cache-Control", "no-store");
  response.end();
}

function sendJson(response, status, body) {
  response.statusCode = status;
  response.setHeader("Content-Type", "application/json; charset=utf-8");
  response.setHeader("Cache-Control", "no-store");
  response.end(JSON.stringify(body));
}

function sendText(response, status, body) {
  response.statusCode = status;
  response.setHeader("Content-Type", "text/plain; charset=utf-8");
  response.setHeader("Cache-Control", "no-store");
  response.end(body);
}

function initials(value) {
  return value.split(/\s+/).filter(Boolean).slice(0, 2)
    .map((part) => part[0]).join("").toUpperCase() || "DC";
}

function booleanValue(value, fallback) {
  if (value == null || value === "") return fallback;
  return ["1", "true", "yes", "on"].includes(String(value).toLowerCase());
}

function boundedInteger(value, fallback, min, max) {
  const parsed = Number.parseInt(String(value ?? ""), 10);
  return Number.isFinite(parsed) ? Math.min(max, Math.max(min, parsed)) : fallback;
}

function textValue(value, fallback) {
  return String(value || fallback).trim();
}

function baseUrl(value, fallback) {
  return textValue(value, fallback).replace(/\/$/, "");
}

function serviceError(code, statusCode) {
  const error = new Error(code);
  error.statusCode = statusCode;
  return error;
}