import express from "express";
import { randomUUID, timingSafeEqual } from "node:crypto";
import { createServer } from "node:http";
import { Pool } from "pg";
import { GELIOS_CAPABILITIES } from "./capabilities.mjs";
import { readConfig, unitIsInScope } from "./config.mjs";
import { FLEET_POSITIONS_CURRENT, toFleetPositionPatch, toFleetPositionsSnapshot } from "./data-products.mjs";
import { extractUnitItems, hash, normalizeUnit } from "./normalize.mjs";
import { migrate } from "./schema.mjs";

const config = readConfig();
const pool = new Pool({ connectionString: config.databaseUrl, max: config.databasePoolSize });
const app = express();
const httpServer = createServer(app);
const streamClients = new Set();
let intakeInFlight = null;

app.disable("x-powered-by");
app.use(express.json({ limit: "1mb" }));

app.get("/healthz", asyncRoute(async (_req, res) => {
  await pool.query("select 1");
  res.json({
    ok: true,
    service: "nodedc-gelios-gateway",
    database: "ready",
    internalApiConfigured: Boolean(config.internalAccessToken),
    intakeEnabled: config.intakeEnabled,
    unitScope: config.unitScope,
    credentialOwner: "engine",
    providerTransport: "absent",
    commandTransport: "absent",
  });
}));

app.get("/internal/gelios/v1/status", requireInternalApi, asyncRoute(async (req, res) => {
  const scope = requireConnectionScope(req);
  const latestRun = await pool.query(
    `select id, capability_id, status, unit_count, inserted_snapshots, error_code, started_at, completed_at
     from gelios_collection_runs
     where tenant_id = $1 and connection_id = $2
     order by started_at desc
     limit 1`,
    [scope.tenantId, scope.connectionId],
  );
  res.json({
    ok: true,
    provider: "gelios",
    tenantId: scope.tenantId,
    connectionId: scope.connectionId,
    unitScope: config.unitScope,
    approvedUnitCount: config.unitScope === "all" ? null : config.allowedUnitIds.length,
    intakeEnabled: config.intakeEnabled,
    credentialOwner: "engine",
    providerTransport: "absent",
    commandTransport: "absent",
    lastRun: latestRun.rows[0] || null,
  });
}));

app.get("/internal/gelios/v1/capabilities", requireInternalApi, (_req, res) => {
  res.json({ ok: true, provider: "gelios", capabilities: GELIOS_CAPABILITIES, commandTransport: "absent" });
});

app.post("/internal/gelios/v1/intake/units", requireInternalApi, asyncRoute(async (req, res) => {
  const scope = requireConnectionScope(req);
  const result = await runIntake({
    scope,
    payload: req.body,
    receivedAt: parseReceivedAt(req.body?.receivedAt),
  });
  res.status(result.status === "completed" ? 200 : 409).json(result);
}));

app.get("/internal/gelios/v1/units/current", requireInternalApi, asyncRoute(async (req, res) => {
  const scope = requireConnectionScope(req);
  const limit = boundedLimit(req.query.limit, 200, 1, 1000);
  const rows = await listCurrentRows(scope, limit);
  res.json({
    ok: true,
    contract: "gelios.current-position.v1",
    tenantId: scope.tenantId,
    connectionId: scope.connectionId,
    units: rows,
  });
}));

app.get("/internal/gelios/v1/data-products/fleet.positions.current.v1/snapshot", requireInternalApi, asyncRoute(async (req, res) => {
  const scope = requireConnectionScope(req);
  const limit = boundedLimit(req.query.limit, 200, 1, 1000);
  const rows = await listCurrentRows(scope, limit);
  res.json({
    ok: true,
    ...toFleetPositionsSnapshot(rows, { ...scope, staleAfterMs: config.positionStaleAfterMs }),
  });
}));

app.get("/internal/gelios/v1/data-products/fleet.positions.current.v1/stream", requireInternalApi, (req, res) => {
  let scope;
  try {
    scope = requireConnectionScope(req);
  } catch (error) {
    res.status(Number(error.status || 400)).json({ ok: false, error: error.message });
    return;
  }
  const client = openSseClient(req, res, scope, "data-product");
  writeSse(res, "nodedc.data-product.ready.v1", {
    dataProduct: FLEET_POSITIONS_CURRENT,
    scope,
    bootstrap: "fetch-snapshot",
  });
  return client;
});

app.get("/internal/gelios/v1/stream", requireInternalApi, (req, res) => {
  let scope;
  try {
    scope = requireConnectionScope(req);
  } catch (error) {
    res.status(Number(error.status || 400)).json({ ok: false, error: error.message });
    return;
  }
  const client = openSseClient(req, res, scope, "legacy");
  writeSse(res, "gelios.ready", {
    ok: true,
    contract: "gelios.current-position.v1",
    tenantId: scope.tenantId,
    connectionId: scope.connectionId,
    commandTransport: "absent",
  });
  return client;
});

async function listCurrentRows(scope, limit) {
  const rows = await pool.query(
    `select
       stable_subject_id as "subjectId", source_unit_id as "sourceUnitId", name,
       observed_at as "observedAt", received_at as "receivedAt", latitude, longitude,
       speed, course, gps_valid as "gpsValid", satellites, hdop,
       accuracy_m as "accuracyM", telemetry
     from gelios_unit_current
     where tenant_id = $1 and connection_id = $2
     order by observed_at desc, source_unit_id asc
     limit $3`,
    [scope.tenantId, scope.connectionId, limit],
  );
  return rows.rows;
}

app.use((error, _req, res, _next) => {
  const status = Number(error?.status || 500);
  const publicStatus = status >= 400 && status < 600 ? status : 500;
  console.error(JSON.stringify({ event: "gelios_gateway_error", error: safeErrorCode(error), status: publicStatus }));
  res.status(publicStatus).json({ ok: false, error: publicStatus >= 500 ? "internal_error" : safeErrorCode(error) });
});

await migrate(pool);
await upsertConnection();

httpServer.listen(config.port, "0.0.0.0", () => {
  console.log(`NODE.DC Gelios Gateway listening on http://0.0.0.0:${config.port}`);
});

process.on("SIGTERM", shutdown);
process.on("SIGINT", shutdown);

async function upsertConnection() {
  await pool.query(
    `insert into gelios_connections (
      tenant_id, connection_id, unit_scope, allowed_unit_ids, collection_enabled, updated_at
    ) values ($1, $2, $3, $4::jsonb, $5, now())
    on conflict (tenant_id, connection_id) do update
    set unit_scope = excluded.unit_scope,
        allowed_unit_ids = excluded.allowed_unit_ids,
        collection_enabled = excluded.collection_enabled,
        updated_at = now()`,
    [config.tenantId, config.connectionId, config.unitScope, JSON.stringify(config.allowedUnitIds), config.intakeEnabled],
  );
}

async function runIntake({ scope, payload, receivedAt }) {
  if (!config.intakeEnabled) return { ok: false, status: "disabled" };
  if (config.unitScope === "allowlist" && !config.allowedUnitIds.length) {
    return { ok: false, status: "scope_missing" };
  }
  if (intakeInFlight) return { ok: false, status: "busy" };
  intakeInFlight = ingestCurrentUnits({ scope, payload, receivedAt }).finally(() => {
    intakeInFlight = null;
  });
  return intakeInFlight;
}

async function ingestCurrentUnits({ scope, payload, receivedAt }) {
  const runId = randomUUID();
  await pool.query(
    `insert into gelios_collection_runs (id, tenant_id, connection_id, capability_id, status)
     values ($1, $2, $3, 'gelios.units.current_intake', 'running')`,
    [runId, scope.tenantId, scope.connectionId],
  );

  try {
    const sourcePayload = payload?.units ? { units: payload.units } : payload;
    const items = extractUnitItems(sourcePayload);
    if (!items.length) throw Object.assign(new Error("intake_units_required"), { status: 422 });
    await storeRawEnvelope({ runId, scope, payload: sourcePayload, receivedAt });
    const normalized = items
      .map((item) => normalizeUnit(item, { ...scope, receivedAt }))
      .filter(Boolean)
      .filter((item) => unitIsInScope(config, item.sourceUnitId));

    let insertedSnapshots = 0;
    for (const unit of normalized) {
      const result = await persistCurrentUnit(unit);
      insertedSnapshots += result.insertedSnapshot ? 1 : 0;
      if (result.current) broadcastCurrentUnit(result.current, scope.tenantId, scope.connectionId);
    }
    await pruneExpiredRawEnvelopes();
    await pool.query(
      `update gelios_collection_runs
       set status = 'completed', unit_count = $2, inserted_snapshots = $3, completed_at = now()
       where id = $1`,
      [runId, normalized.length, insertedSnapshots],
    );
    return { ok: true, status: "completed", runId, unitCount: normalized.length, insertedSnapshots };
  } catch (error) {
    await pool.query(
      `update gelios_collection_runs
       set status = 'failed', error_code = $2, completed_at = now()
       where id = $1`,
      [runId, safeErrorCode(error)],
    );
    throw error;
  }
}

async function storeRawEnvelope({ runId, scope, payload, receivedAt }) {
  const serialized = JSON.stringify(payload);
  await pool.query(
    `insert into gelios_raw_envelopes (
       id, tenant_id, connection_id, collection_run_id, capability_id,
       payload_hash, payload, payload_bytes, received_at, expires_at
     ) values ($1, $2, $3, $4, 'gelios.units.current_intake', $5, $6::jsonb, $7, $8, $9)
     on conflict (tenant_id, connection_id, capability_id, payload_hash) do nothing`,
    [
      randomUUID(), scope.tenantId, scope.connectionId, runId, hash(payload), serialized,
      Buffer.byteLength(serialized), receivedAt,
      new Date(receivedAt.getTime() + config.rawRetentionDays * 24 * 60 * 60 * 1000),
    ],
  );
}

async function persistCurrentUnit(unit) {
  const client = await pool.connect();
  try {
    await client.query("begin");
    await client.query(
      `insert into gelios_units (
         tenant_id, connection_id, source_unit_id, stable_subject_id, name, last_seen_at
       ) values ($1, $2, $3, $4, $5, $6)
       on conflict (tenant_id, connection_id, source_unit_id) do update
       set stable_subject_id = excluded.stable_subject_id,
           name = excluded.name,
           last_seen_at = excluded.last_seen_at`,
      [unit.tenantId, unit.connectionId, unit.sourceUnitId, unit.stableSubjectId, unit.name, unit.receivedAt],
    );
    const current = await client.query(
      `insert into gelios_unit_current (
         tenant_id, connection_id, source_unit_id, stable_subject_id, name,
         observed_at, received_at, latitude, longitude, position, speed, course,
         gps_valid, satellites, hdop, accuracy_m, telemetry, fingerprint
       ) values (
         $1, $2, $3, $4, $5, $6, $7, $8, $9,
         case when $8::double precision is not null and $9::double precision is not null
           then ST_SetSRID(ST_MakePoint($9, $8), 4326)::geography else null end,
         $10, $11, $12, $13, $14, $15, $16::jsonb, $17
       )
       on conflict (tenant_id, connection_id, source_unit_id) do update
       set stable_subject_id = excluded.stable_subject_id,
           name = excluded.name,
           observed_at = excluded.observed_at,
           received_at = excluded.received_at,
           latitude = excluded.latitude,
           longitude = excluded.longitude,
           position = excluded.position,
           speed = excluded.speed,
           course = excluded.course,
           gps_valid = excluded.gps_valid,
           satellites = excluded.satellites,
           hdop = excluded.hdop,
           accuracy_m = excluded.accuracy_m,
           telemetry = excluded.telemetry,
           fingerprint = excluded.fingerprint,
           updated_at = now()
       where excluded.observed_at >= gelios_unit_current.observed_at
       returning stable_subject_id as "subjectId", source_unit_id as "sourceUnitId", name,
         observed_at as "observedAt", received_at as "receivedAt", latitude, longitude,
         speed, course, gps_valid as "gpsValid", satellites, hdop, accuracy_m as "accuracyM", telemetry`,
      [
        unit.tenantId, unit.connectionId, unit.sourceUnitId, unit.stableSubjectId, unit.name,
        unit.observedAt, unit.receivedAt, unit.latitude, unit.longitude, unit.speed, unit.course,
        unit.gpsValid, unit.satellites, unit.hdop, unit.accuracyM, JSON.stringify(unit.telemetry), unit.fingerprint,
      ],
    );
    const snapshot = await client.query(
      `insert into gelios_telemetry_snapshots (
         tenant_id, connection_id, source_unit_id, observed_at, received_at, fingerprint, telemetry
       ) values ($1, $2, $3, $4, $5, $6, $7::jsonb)
       on conflict do nothing`,
      [unit.tenantId, unit.connectionId, unit.sourceUnitId, unit.observedAt, unit.receivedAt, unit.fingerprint, JSON.stringify(unit.telemetry)],
    );
    await client.query("commit");
    return { current: current.rows[0] || null, insertedSnapshot: snapshot.rowCount > 0 };
  } catch (error) {
    await client.query("rollback");
    throw error;
  } finally {
    client.release();
  }
}

async function pruneExpiredRawEnvelopes() {
  await pool.query("delete from gelios_raw_envelopes where expires_at < now()");
}

function requireInternalApi(req, res, next) {
  const expected = Buffer.from(config.internalAccessToken || "");
  const received = Buffer.from(String(req.get("authorization") || "").replace(/^Bearer\s+/i, "").trim());
  if (!expected.length) {
    res.status(503).json({ ok: false, error: "internal_api_not_configured" });
    return;
  }
  if (expected.length !== received.length || !timingSafeEqual(expected, received)) {
    res.status(401).json({ ok: false, error: "internal_authorization_required" });
    return;
  }
  next();
}

function requireConnectionScope(req) {
  const tenantId = String(req.get("x-nodedc-tenant-id") || "").trim();
  const connectionId = String(req.query.connectionId || req.get("x-nodedc-connection-id") || config.connectionId).trim();
  if (tenantId !== config.tenantId) throw Object.assign(new Error("tenant_scope_required"), { status: 403 });
  if (connectionId !== config.connectionId) throw Object.assign(new Error("connection_scope_denied"), { status: 403 });
  return { tenantId, connectionId };
}

function broadcastCurrentUnit(unit, tenantId, connectionId) {
  for (const client of streamClients) {
    if (client.tenantId === tenantId && client.connectionId === connectionId) {
      if (client.kind === "data-product") {
        writeSse(client.res, "nodedc.data-product.patch.v1", toFleetPositionPatch(unit, {
          staleAfterMs: config.positionStaleAfterMs,
        }));
      } else {
        writeSse(client.res, "gelios.current.updated", unit);
      }
    }
  }
}

function openSseClient(req, res, scope, kind) {
  const client = { id: randomUUID(), res, kind, ...scope };
  res.setHeader("Content-Type", "text/event-stream");
  res.setHeader("Cache-Control", "no-cache, no-transform");
  res.setHeader("Connection", "keep-alive");
  res.setHeader("X-Accel-Buffering", "no");
  res.flushHeaders?.();
  const keepAlive = setInterval(() => res.write(": keep-alive\n\n"), 30000);
  streamClients.add(client);
  req.on("close", () => {
    clearInterval(keepAlive);
    streamClients.delete(client);
  });
  return client;
}

function writeSse(res, event, payload) {
  res.write(`event: ${event}\ndata: ${JSON.stringify(payload)}\n\n`);
}

function parseReceivedAt(value) {
  if (value === undefined || value === null || value === "") return new Date();
  const parsed = new Date(value);
  if (Number.isNaN(parsed.getTime())) throw Object.assign(new Error("intake_received_at_invalid"), { status: 422 });
  return parsed;
}

function boundedLimit(value, fallback, min, max) {
  const parsed = Number.parseInt(String(value || ""), 10);
  if (!Number.isInteger(parsed)) return fallback;
  return Math.max(min, Math.min(max, parsed));
}

function safeErrorCode(error) {
  return String(error?.message || "internal_error").replace(/[^a-zA-Z0-9_:.-]+/g, "_").slice(0, 160);
}

function asyncRoute(handler) {
  return (req, res, next) => Promise.resolve(handler(req, res, next)).catch(next);
}

async function shutdown() {
  await new Promise((resolve) => httpServer.close(resolve));
  await pool.end();
  process.exit(0);
}