const http = require("node:http");
const os = require("node:os");
const {
  readFileSync,
  readdirSync,
  existsSync,
  mkdirSync,
  writeFileSync,
  renameSync,
  unlinkSync,
} = require("node:fs");
const path = require("node:path");
const { createHash, timingSafeEqual } = require("node:crypto");
const { collectMetrics } = require("./metrics.js");

const PORT = parseInt(process.env.PORT || "3001", 10);
const TOKEN = process.env.HEALTH_TOKEN;
const REPORTS_DIR = process.env.REPORTS_DIR || "/data/defenseurs/reports";
const AGENTS_MAP_PATH =
  process.env.DEFENSEURS_AGENTS_MAP_PATH || "/data/defenseurs/agents-map.json";
const LOGTO_HEALTH_URL =
  process.env.LOGTO_HEALTH_URL ||
  "https://auth.lacompagniemaximus.com/oidc/.well-known/openid-configuration";
const LOGTO_TIMEOUT_MS = 3000;
const SCAN_DATE_RE = /^\d{4}-\d{2}-\d{2}$/;

const SEVERITY_RANK = { CRITICAL: 4, HIGH: 3, MEDIUM: 2, LOW: 1, INFO: 0 };
const VALID_SEVERITIES = Object.keys(SEVERITY_RANK);
const VALID_CATEGORIES = ["deps", "secrets", "code", "acces", "infra"];

// --- Workstation snapshots (POST /hosts/<id>, GET /hosts) -------------------

const HOSTS_DIR = process.env.HOSTS_DIR || "/data/hosts";
const HOSTS_INGEST_TOKEN = process.env.HOSTS_INGEST_TOKEN;
const MAX_BODY_BYTES = 4096;
const MAX_STRING_LENGTH = 128;

// Single source of truth for what a host id may look like. The allowlist check
// and the route matcher are both built from it, so they can never drift apart.
//
// This narrow pattern IS the path-traversal control. Verified in Node: URL()
// normalises `/hosts/../../etc/passwd` to `/etc/passwd`, while `..%2f..%2f` and
// `THINKPAD` simply fail the match — every hostile id therefore lands on 404,
// before any handler runs. 403 is reserved for well-formed ids that are not in
// the allowlist. Never widen this to `^/hosts/(.+)$` to make a test pass.
const HOST_ID_PATTERN = "[a-z0-9][a-z0-9-]{0,31}";
const HOST_ID_RE = new RegExp(`^${HOST_ID_PATTERN}$`);
const HOST_ROUTE_RE = new RegExp(`^/hosts/(${HOST_ID_PATTERN})$`);

const staleSecondsRaw = parseInt(process.env.HOSTS_STALE_SECONDS || "", 10);
const HOSTS_STALE_SECONDS =
  Number.isFinite(staleSecondsRaw) && staleSecondsRaw > 0 ? staleSecondsRaw : 900;

// Parse HOSTS_ALLOWED_IDS once at startup and drop anything that is not a valid
// host id. Entries feed path.join(HOSTS_DIR, `${id}.json`), so a stray space or
// an entry like `../defenseurs/status` must never survive into a file path.
// Rejections are logged rather than silently swallowed: a typo in the env var
// would otherwise look exactly like a workstation that never checked in.
function parseAllowedIds(raw) {
  const allowed = new Set();
  for (const entry of String(raw).split(",")) {
    const id = entry.trim();
    if (!id) continue;
    if (!HOST_ID_RE.test(id)) {
      console.warn(
        `WARNING: HOSTS_ALLOWED_IDS entry rejected (not a valid host id): ${safeLogValue(id)}`,
      );
      continue;
    }
    allowed.add(id);
  }
  return allowed;
}

const HOSTS_ALLOWED_IDS = parseAllowedIds(process.env.HOSTS_ALLOWED_IDS || "thinkpad");

// Severity filter. Asymmetric rule (issue #3):
//   - no threshold       -> MEDIUM+HIGH+CRITICAL (default hides noise LOW+INFO)
//   - threshold "INFO"   -> INFO only (explicit opt-in)
//   - any other          -> everything at or above threshold, EXCEPT INFO
// INFO is therefore reachable only via explicit ?severity=INFO.
function allowedSeverities(threshold) {
  if (!threshold) return ["CRITICAL", "HIGH", "MEDIUM"];
  if (threshold === "INFO") return ["INFO"];
  const min = SEVERITY_RANK[threshold];
  return VALID_SEVERITIES.filter(
    (s) => s !== "INFO" && SEVERITY_RANK[s] >= min,
  );
}

if (!TOKEN) {
  console.warn("WARNING: HEALTH_TOKEN is not set. All requests will be rejected (fail-closed).");
}

// No startup warning for a missing HOSTS_INGEST_TOKEN: the ingestion path
// fail-closes to 503 and logs the reason on the request that hits it, which is
// the moment an operator actually needs to see it.

async function getLogtoHealth() {
  const ac = new AbortController();
  const timer = setTimeout(() => ac.abort(), LOGTO_TIMEOUT_MS);
  const start = performance.now();
  try {
    const res = await fetch(LOGTO_HEALTH_URL, { signal: ac.signal });
    const responseTimeMs = Math.round(performance.now() - start);
    if (res.ok) return { status: "up", responseTimeMs };
    return { status: "down", responseTimeMs, error: `HTTP ${res.status}` };
  } catch (err) {
    const responseTimeMs = Math.round(performance.now() - start);
    const error = err.name === "AbortError" ? "timeout" : err.message || "network error";
    return { status: "down", responseTimeMs, error };
  } finally {
    clearTimeout(timer);
  }
}

// Reproduce the isScanReport guard from defenseurs/src/report.ts. The
// defenseur-auto run report has shape { actions[], skipped[] } with no
// findings[] — it must be filtered out so it never reaches the auto pipeline
// (which expects scan-shaped reports only).
function isScanReport(value) {
  return (
    typeof value === "object" &&
    value !== null &&
    Array.isArray(value.findings) &&
    typeof value.agent === "string" &&
    typeof value.timestamp === "string"
  );
}

// Read all `defenseur-<agent>_<date>*.json` files under `dir` matching the
// given UTC date. Returns parsed scan reports keyed by filename so the caller
// can dedupe across REPORTS_DIR + REPORTS_DIR/archive.
function collectScanReportsFromDir(dir, date) {
  const collected = new Map();
  if (!existsSync(dir)) return collected;

  const files = readdirSync(dir).filter(
    (f) => f.startsWith("defenseur-") && f.includes(`_${date}`) && f.endsWith(".json"),
  );

  for (const file of files) {
    try {
      const raw = readFileSync(path.join(dir, file), "utf-8");
      const parsed = JSON.parse(raw);
      if (!isScanReport(parsed)) continue;
      if (!parsed.timestamp.startsWith(date)) continue;
      collected.set(file, parsed);
    } catch (err) {
      console.error(`[reports/scans] failed to parse ${file}:`, err.message);
    }
  }

  return collected;
}

// Read all `defenseur-<agent>_<date>*.json` files under REPORTS_DIR for the
// given UTC date. The scan reports use an ISO timestamp with `:` and `.`
// rewritten as `-` in the filename (e.g. defenseur-booking_2026-05-06T05-30-11-249Z.json).
// We match `_<date>` then re-confirm via parsed.timestamp.startsWith(date).
//
// The Sergent rotates fresh reports out of REPORTS_DIR into REPORTS_DIR/archive
// at 07:30 UTC daily (cf. defenseurs/src/sergent.ts renameSync). For ~22h/day
// the only copy lives in archive/ — so we scan both and concatenate. Top-level
// files take precedence on filename collision (more recent by definition).
function readScanReportsForDate(date) {
  const topLevel = collectScanReportsFromDir(REPORTS_DIR, date);
  const archive = collectScanReportsFromDir(path.join(REPORTS_DIR, "archive"), date);

  // Merge with top-level priority — only insert archive entries whose filename
  // is not already present at the top level.
  for (const [file, report] of archive) {
    if (!topLevel.has(file)) topLevel.set(file, report);
  }

  // Stable sort by timestamp asc — same convention as readReports() in
  // defenseurs/src/report.ts.
  return [...topLevel.values()].sort(
    (a, b) => new Date(a.timestamp).getTime() - new Date(b.timestamp).getTime(),
  );
}

// Find the latest scan report for a given agent across REPORTS_DIR and
// REPORTS_DIR/archive. Files are named `defenseur-<agent>_<iso>.json`.
// The trailing underscore in the prefix prevents collisions on agent names
// that share a prefix (e.g. "booking" vs "booking-staging").
function findLatestReportForAgent(agent) {
  // `agent` is the full identifier as written by the Sergent into
  // agents-map.json (e.g. "defenseur-booking") — matches both the JSON
  // `agent` field and the filename prefix `<agent>_<iso>.json`.
  const prefix = `${agent}_`;
  const dirs = [REPORTS_DIR, path.join(REPORTS_DIR, "archive")];
  let latest = null;

  for (const dir of dirs) {
    if (!existsSync(dir)) continue;
    const files = readdirSync(dir).filter(
      (f) => f.startsWith(prefix) && f.endsWith(".json"),
    );
    for (const file of files) {
      try {
        const raw = readFileSync(path.join(dir, file), "utf-8");
        const parsed = JSON.parse(raw);
        if (!isScanReport(parsed)) continue;
        if (parsed.agent !== agent) continue;
        const ts = new Date(parsed.timestamp).getTime();
        if (Number.isNaN(ts)) continue;
        if (!latest || ts > latest._ts) {
          latest = parsed;
          latest._ts = ts;
        }
      } catch (err) {
        console.error(`[defenseurs/findings] failed to parse ${file}:`, err.message);
      }
    }
  }

  if (latest) delete latest._ts;
  return latest;
}

async function getHealth() {
  // Keep the Promise.all: the 500ms CPU sample inside collectMetrics() and the
  // up-to-3s Logto check must stay concurrent. Awaiting them one after the
  // other would push the p99 of /health to ~3.5s.
  const [metrics, logto] = await Promise.all([
    collectMetrics(),
    getLogtoHealth(),
  ]);

  return {
    timestamp: new Date().toISOString(),
    hostname: os.hostname(),
    uptime: Math.floor(os.uptime()),
    ...metrics,
    logto,
  };
}

// --- Hosts helpers ----------------------------------------------------------

// Printable-ASCII-only, length-capped rendering for anything attacker-supplied
// that reaches a log line (X-Real-IP, host id, env entries). Keeps a crafted
// value from forging extra log records.
function safeLogValue(value, max = 64) {
  return String(value).replace(/[^\x20-\x7e]/g, "?").slice(0, max);
}

// Log every 401/403. This is the first publicly writable surface on the API:
// without a trace, a token-guessing campaign would leave nothing behind.
function logRejection(req, status, reason, id) {
  const ip = safeLogValue(req.headers["x-real-ip"] || req.socket?.remoteAddress || "unknown");
  const method = safeLogValue(req.method, 8);
  const url = safeLogValue(req.url, 120);
  console.warn(
    `[auth] ${status} ${method} ${url} ip=${ip} id=${id ? safeLogValue(id, 32) : "-"} reason=${reason}`,
  );
}

// Constant-time bearer comparison for the ingestion path. Both sides are hashed
// first, so the buffers are always 32 bytes: timingSafeEqual never throws on
// mismatched lengths, and the length of the real token cannot leak.
//
// Deliberately scoped to the new write path. Realigning the existing
// HEALTH_TOKEN comparison touches every read route in production and is tracked
// separately (issue #17).
function tokenMatches(provided, expected) {
  if (typeof provided !== "string" || typeof expected !== "string") return false;
  const a = createHash("sha256").update(provided).digest();
  const b = createHash("sha256").update(expected).digest();
  return timingSafeEqual(a, b);
}

// Read the request body with a hard 4 KiB ceiling. The counter runs on the
// bytes actually received, never on Content-Length: a client can lie in the
// header, and chunked transfer-encoding omits it altogether.
//
// Resolves to the raw string, or to null when the response has already been
// written (413) or the socket died — in which case the caller must not answer.
function readBody(req, res) {
  return new Promise((resolve) => {
    const chunks = [];
    let size = 0;
    let settled = false;

    req.on("data", (chunk) => {
      if (settled) return;
      size += chunk.length;
      if (size > MAX_BODY_BYTES) {
        settled = true;
        req.pause();
        res.writeHead(413);
        // Destroy only once the 413 has been flushed: req.destroy() tears down
        // the socket, so cutting first would leave the client with a network
        // error instead of a status code.
        res.end(JSON.stringify({ error: "Payload too large" }), () => req.destroy());
        resolve(null);
        return;
      }
      chunks.push(chunk);
    });

    req.on("end", () => {
      if (settled) return;
      settled = true;
      resolve(Buffer.concat(chunks).toString("utf-8"));
    });

    req.on("error", () => {
      if (settled) return;
      settled = true;
      resolve(null);
    });
  });
}

function cleanString(value) {
  if (typeof value !== "string") return null;
  return value.slice(0, MAX_STRING_LENGTH);
}

function cleanNumber(value) {
  return Number.isFinite(value) ? value : null;
}

// { totalGB, usedGB, freeGB, usagePercent } — the shape shared by memory and disk.
function sanitizeUsage(value, label) {
  if (typeof value !== "object" || value === null || Array.isArray(value)) {
    return { error: `${label} must be an object` };
  }
  const out = {};
  for (const key of ["totalGB", "usedGB", "freeGB", "usagePercent"]) {
    const num = cleanNumber(value[key]);
    if (num === null) return { error: `${label}.${key} must be a finite number` };
    out[key] = num;
  }
  return { value: out };
}

function sanitizeCpu(value) {
  if (typeof value !== "object" || value === null || Array.isArray(value)) {
    return { error: "cpu must be an object" };
  }
  const model = cleanString(value.model);
  if (model === null) return { error: "cpu.model must be a string" };
  const cores = cleanNumber(value.cores);
  if (cores === null) return { error: "cpu.cores must be a finite number" };
  const usagePercent = cleanNumber(value.usagePercent);
  if (usagePercent === null) return { error: "cpu.usagePercent must be a finite number" };
  if (!Array.isArray(value.loadAvg)) return { error: "cpu.loadAvg must be an array" };
  const loadAvg = [];
  for (const entry of value.loadAvg.slice(0, 3)) {
    const num = cleanNumber(entry);
    if (num === null) return { error: "cpu.loadAvg must contain finite numbers" };
    loadAvg.push(num);
  }
  return { value: { model, cores, loadAvg, usagePercent } };
}

// Rebuild the persisted object field by field from a whitelist — never store
// the payload verbatim. The file is read back by GET /hosts and ends up in the
// admin dashboard's React tree, so an unknown key (`__proto__` among them) or a
// 4 KiB hostname must never make it that far.
function sanitizeSnapshot(payload) {
  if (typeof payload !== "object" || payload === null || Array.isArray(payload)) {
    return { error: "body must be a JSON object" };
  }

  const hostname = cleanString(payload.hostname);
  if (hostname === null) return { error: "hostname must be a string" };

  const uptime = cleanNumber(payload.uptime);
  if (uptime === null) return { error: "uptime must be a finite number" };

  const cpu = sanitizeCpu(payload.cpu);
  if (cpu.error) return cpu;
  const memory = sanitizeUsage(payload.memory, "memory");
  if (memory.error) return memory;
  const disk = sanitizeUsage(payload.disk, "disk");
  if (disk.error) return disk;

  return {
    snapshot: {
      hostname,
      uptime,
      cpu: cpu.value,
      memory: memory.value,
      disk: disk.value,
    },
  };
}

// Atomic write: temp file in the SAME directory, then renameSync. rename is
// atomic within a filesystem, so a concurrent GET /hosts either sees the old
// snapshot or the new one — never a half-written JSON.
function writeHostSnapshot(id, record) {
  mkdirSync(HOSTS_DIR, { recursive: true });
  const finalPath = path.join(HOSTS_DIR, `${id}.json`);
  const tmpPath = path.join(HOSTS_DIR, `.${id}.${process.pid}.${Date.now()}.tmp`);
  try {
    writeFileSync(tmpPath, JSON.stringify(record), { mode: 0o600 });
    renameSync(tmpPath, finalPath);
  } catch (err) {
    try {
      unlinkSync(tmpPath);
    } catch {
      // Best effort — the temp file may never have been created.
    }
    throw err;
  }
}

// Read one persisted snapshot. Anything missing, unparsable, off-shape or
// without a usable server timestamp degrades to null: GET /hosts then reports
// that entry as neverSeen instead of failing the whole response.
//
// The file was written by this service, but it lives on a writable bind-mount:
// it is re-run through the same whitelist on the way out rather than trusted.
function readHostSnapshot(id) {
  const file = path.join(HOSTS_DIR, `${id}.json`);
  let parsed;
  try {
    parsed = JSON.parse(readFileSync(file, "utf-8"));
  } catch (err) {
    if (err.code !== "ENOENT") {
      console.error(`[hosts] failed to read snapshot for ${id}:`, err.message);
    }
    return null;
  }

  const result = sanitizeSnapshot(parsed);
  if (result.error) {
    console.error(`[hosts] snapshot for ${id} rejected on read: ${result.error}`);
    return null;
  }

  const receivedAt = typeof parsed.receivedAt === "string" ? parsed.receivedAt : null;
  if (!receivedAt || Number.isNaN(new Date(receivedAt).getTime())) {
    console.error(`[hosts] snapshot for ${id} has no usable receivedAt`);
    return null;
  }

  return { ...result.snapshot, receivedAt };
}

// --- Route handlers ---------------------------------------------------------

async function handleHealth(req, res) {
  try {
    const data = await getHealth();
    res.writeHead(200);
    res.end(JSON.stringify(data));
  } catch (err) {
    res.writeHead(500);
    res.end(JSON.stringify({ error: "Internal error", message: err.message }));
  }
}

function handleDefenseurs(req, res) {
  const statusPath = process.env.DEFENSEURS_STATUS_PATH || "/data/defenseurs/status.json";
  try {
    const status = readFileSync(statusPath, "utf-8");
    res.writeHead(200);
    res.end(status);
  } catch {
    res.writeHead(200);
    res.end(JSON.stringify({ status: "no_data" }));
  }
}

function handleFindings(req, res, ctx) {
  const project = ctx.parsedUrl.searchParams.get("project");
  const category = ctx.parsedUrl.searchParams.get("category");
  const severity = ctx.parsedUrl.searchParams.get("severity");

  if (!project) {
    res.writeHead(400);
    res.end(JSON.stringify({ error: "Bad request: project=<name> required" }));
    return;
  }
  if (category && !VALID_CATEGORIES.includes(category)) {
    res.writeHead(400);
    res.end(JSON.stringify({ error: `Bad request: category must be one of ${VALID_CATEGORIES.join(",")}` }));
    return;
  }
  if (severity && !VALID_SEVERITIES.includes(severity)) {
    res.writeHead(400);
    res.end(JSON.stringify({ error: `Bad request: severity must be one of ${VALID_SEVERITIES.join(",")}` }));
    return;
  }

  let agentsMap;
  try {
    agentsMap = JSON.parse(readFileSync(AGENTS_MAP_PATH, "utf-8"));
  } catch (err) {
    res.writeHead(500);
    res.end(JSON.stringify({ error: "Internal error", message: err.message }));
    return;
  }

  const agent = agentsMap[project];
  if (!agent) {
    res.writeHead(404);
    res.end(JSON.stringify({ error: `Unknown project: ${project}` }));
    return;
  }

  try {
    const report = findLatestReportForAgent(agent);
    if (!report) {
      res.writeHead(200);
      res.end(JSON.stringify({ findings: [], status: "no_data" }));
      return;
    }
    const allowed = new Set(allowedSeverities(severity));
    const findings = report.findings.filter(
      (f) => allowed.has(f.severity) && (!category || f.category === category),
    );
    res.writeHead(200);
    res.end(JSON.stringify({
      agent,
      project,
      timestamp: report.timestamp,
      findings,
    }));
  } catch (err) {
    res.writeHead(500);
    res.end(JSON.stringify({ error: "Internal error", message: err.message }));
  }
}

function handleReportsScans(req, res, ctx) {
  const date = ctx.parsedUrl.searchParams.get("date");
  // Regex short-circuit before any filesystem access — blocks path
  // traversal (`../../etc/passwd` -> 400) and bogus inputs.
  if (!date || !SCAN_DATE_RE.test(date)) {
    res.writeHead(400);
    res.end(JSON.stringify({ error: "Bad request: date=YYYY-MM-DD required" }));
    return;
  }

  try {
    const reports = readScanReportsForDate(date);
    res.writeHead(200);
    res.end(JSON.stringify({ date, count: reports.length, reports }));
  } catch (err) {
    res.writeHead(500);
    res.end(JSON.stringify({ error: "Internal error", message: err.message }));
  }
}

// Serve one entry per allowlisted workstation, whether or not it ever reported.
// Keeping the neverSeen entries visible is what turns the commissioning window
// (deployed, no heartbeat yet) into "agent not installed" on the dashboard
// instead of a silently missing card.
function handleHostsList(req, res) {
  const now = Date.now();
  const hosts = [];

  for (const id of [...HOSTS_ALLOWED_IDS].sort()) {
    const record = readHostSnapshot(id);
    if (!record) {
      hosts.push({ id, receivedAt: null, ageSeconds: null, online: false, neverSeen: true });
      continue;
    }
    // Freshness is computed server-side from the server-stamped receivedAt —
    // the client never gets a say in whether it looks online.
    const ageSeconds = Math.max(
      0,
      Math.floor((now - new Date(record.receivedAt).getTime()) / 1000),
    );
    hosts.push({
      id,
      hostname: record.hostname,
      uptime: record.uptime,
      cpu: record.cpu,
      memory: record.memory,
      disk: record.disk,
      receivedAt: record.receivedAt,
      ageSeconds,
      online: ageSeconds <= HOSTS_STALE_SECONDS,
    });
  }

  res.writeHead(200);
  res.end(JSON.stringify({ staleAfterSeconds: HOSTS_STALE_SECONDS, hosts }));
}

async function handleHostIngest(req, res, ctx) {
  const id = ctx.hostId;

  // The id already matched HOST_ROUTE_RE, so 403 here means "well-formed but
  // not one of ours" — the only case that reaches this branch.
  if (!HOSTS_ALLOWED_IDS.has(id)) {
    logRejection(req, 403, "host id not in HOSTS_ALLOWED_IDS", id);
    res.writeHead(403);
    res.end(JSON.stringify({ error: "Forbidden" }));
    return;
  }

  const raw = await readBody(req, res);
  if (raw === null) return; // 413 already answered, or the socket is gone.

  let payload;
  try {
    payload = JSON.parse(raw);
  } catch {
    res.writeHead(400);
    res.end(JSON.stringify({ error: "Bad request: body must be valid JSON" }));
    return;
  }

  const result = sanitizeSnapshot(payload);
  if (result.error) {
    res.writeHead(400);
    res.end(JSON.stringify({ error: `Bad request: ${result.error}` }));
    return;
  }

  // receivedAt is stamped by the SERVER on arrival. A client-supplied timestamp
  // would let a stale (or hostile) agent claim to be fresher than it is.
  const record = { id, ...result.snapshot, receivedAt: new Date().toISOString() };

  try {
    writeHostSnapshot(id, record);
    res.removeHeader("Content-Type");
    res.writeHead(204);
    res.end();
  } catch (err) {
    console.error(`[hosts] failed to persist snapshot for ${id}:`, err.message);
    res.writeHead(500);
    res.end(JSON.stringify({ error: "Internal error" }));
  }
}

// --- Routing ----------------------------------------------------------------

// Route descriptors. `tokenKind` is the ONLY thing that varies between the read
// routes and the ingestion route: authentication itself happens once, in the
// single gate below. Adding a route here therefore cannot accidentally ship
// unauthenticated — which is exactly what a per-branch check invites.
const ROUTES = [
  { method: "GET", path: "/health", tokenKind: "read", handle: handleHealth },
  { method: "GET", path: "/defenseurs", tokenKind: "read", handle: handleDefenseurs },
  { method: "GET", path: "/defenseurs/findings", tokenKind: "read", handle: handleFindings },
  { method: "GET", path: "/reports/scans", tokenKind: "read", handle: handleReportsScans },
  { method: "GET", path: "/hosts", tokenKind: "read", handle: handleHostsList },
  { method: "POST", pattern: HOST_ROUTE_RE, tokenKind: "ingest", handle: handleHostIngest },
];

// Deny by default: no descriptor match -> null -> 404.
function resolveRoute(method, pathname) {
  for (const route of ROUTES) {
    if (route.method !== method) continue;
    if (route.path !== undefined) {
      if (route.path === pathname) return { route, hostId: null };
      continue;
    }
    const match = route.pattern.exec(pathname);
    if (match) return { route, hostId: match[1] };
  }
  return null;
}

// THE single authentication checkpoint. Returns null when the caller may
// proceed, otherwise the rejection to write. Only the expected token varies
// per descriptor.
function checkAuth(req, route) {
  const isIngest = route.tokenKind === "ingest";
  const expected = isIngest ? HOSTS_INGEST_TOKEN : TOKEN;

  if (!expected) {
    return isIngest
      ? { status: 503, body: { error: "HOSTS_INGEST_TOKEN not configured" }, reason: "ingest token not configured" }
      : { status: 401, body: { error: "HEALTH_TOKEN not configured" }, reason: "health token not configured" };
  }

  const header = req.headers["authorization"];
  const ok = isIngest
    ? typeof header === "string" &&
      header.startsWith("Bearer ") &&
      tokenMatches(header.slice("Bearer ".length), expected)
    : header === `Bearer ${expected}`;

  if (!ok) {
    return { status: 401, body: { error: "Unauthorized" }, reason: "missing or invalid bearer token" };
  }
  return null;
}

async function handler(req, res) {
  res.setHeader("Content-Type", "application/json");

  // Parse the URL so /reports/scans can carry a `?date=` query string. The
  // placeholder host is required because URL() needs an absolute URL.
  const parsedUrl = new URL(req.url, "http://localhost");
  const pathname = parsedUrl.pathname;

  // ORDER IS PART OF THE CONTRACT: routing resolves FIRST, so an unknown path
  // or a wrong method answers 404 — not 401 — exactly as before this route
  // table existed. Two tests in __tests__/auth.test.js pin that ordering.
  const resolved = resolveRoute(req.method, pathname);
  if (!resolved) {
    res.writeHead(404);
    res.end(JSON.stringify({ error: "Not found" }));
    return;
  }

  const rejection = checkAuth(req, resolved.route);
  if (rejection) {
    logRejection(req, rejection.status, rejection.reason, resolved.hostId);
    res.writeHead(rejection.status);
    res.end(JSON.stringify(rejection.body));
    return;
  }

  try {
    await resolved.route.handle(req, res, { parsedUrl, hostId: resolved.hostId });
  } catch (err) {
    // Safety net: every handler already owns its error paths, this only catches
    // what none of them anticipated.
    console.error(`[handler] unhandled error on ${safeLogValue(pathname, 120)}:`, err.message);
    if (!res.headersSent) {
      res.writeHead(500);
      res.end(JSON.stringify({ error: "Internal error" }));
    }
  }
}

if (require.main === module) {
  const server = http.createServer(handler);
  server.listen(PORT, () => {
    console.log(`vps-health-api listening on :${PORT}`);
  });
}

module.exports = {
  handler,
  allowedSeverities,
  findLatestReportForAgent,
  tokenMatches,
  sanitizeSnapshot,
  HOST_ID_RE,
  HOST_ROUTE_RE,
};