Add JSBSim service backend

service/src/backends/jsbsimBackend.js

@@ -0,0 +1,171 @@
+import { spawnSync } from "node:child_process";
+import { fileURLToPath } from "node:url";
+import { dirname, resolve } from "node:path";
+
+const serviceRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..", "..");
+const DEFAULT_RUNNER = resolve(serviceRoot, "scripts", "jsbsim_runner.py");
+const runnerPath = process.env.JSBSIM_RUNNER ?? DEFAULT_RUNNER;
+const pythonCommand = process.env.JSBSIM_PYTHON ?? "python";
+
+export const backendInfo = {
+  id: "jsbsim",
+  name: "JSBSim",
+  ready: true,
+  runner: runnerPath,
+};
+
+export const AIRCRAFT = [
+  {
+    id: "f22cobra-jsbsim",
+    name: "F-22 Cobra Research JSBSim",
+    source: "JSBSim",
+    capabilities: {
+      basic6dof: true,
+      highAlpha: true,
+      postStall: "experimental",
+      thrustVectoring: true,
+      requiresNoTrimForManeuverResearch: true,
+    },
+  },
+  {
+    id: "f22-jsbsim",
+    name: "F-22 JSBSim",
+    source: "JSBSim",
+    capabilities: {
+      basic6dof: true,
+      highAlpha: true,
+      postStall: "experimental",
+      thrustVectoring: true,
+      requiresNoTrimForManeuverResearch: true,
+    },
+  },
+  {
+    id: "f16-jsbsim",
+    name: "F-16 JSBSim",
+    source: "JSBSim",
+    capabilities: {
+      basic6dof: true,
+      highAlpha: "limited",
+      postStall: false,
+      thrustVectoring: false,
+    },
+  },
+  {
+    id: "c172p-jsbsim",
+    name: "Cessna 172P JSBSim",
+    source: "JSBSim",
+    capabilities: {
+      basic6dof: true,
+      highAlpha: false,
+      postStall: false,
+      thrustVectoring: false,
+    },
+  },
+];
+
+export function trimInitialState(request) {
+  validateTrimRequest(request);
+
+  return runJsbsimRunner({
+    operation: "trim",
+    aircraftId: request.aircraftId,
+    sampleRateHz: 30,
+    integrationRateHz: numberOrDefault(request.integrationRateHz, 120),
+    trim: request,
+  });
+}
+
+export function simulateManeuver(request) {
+  validateSimulateRequest(request);
+
+  return runJsbsimRunner({
+    operation: "simulate",
+    aircraftId: request.aircraftId.replace("-jsbsim", ""),
+    sampleRateHz: numberOrDefault(request.sampleRateHz, 30),
+    integrationRateHz: numberOrDefault(request.integrationRateHz, 120),
+    durationSec: numberOrDefault(request.durationSec, 10),
+    trim: request.trim,
+    initialState: request.initialState,
+    maneuver: request.maneuver,
+  });
+}
+
+function runJsbsimRunner(payload) {
+  const result = spawnSync(pythonCommand, [runnerPath], {
+    input: JSON.stringify(payload),
+    encoding: "utf8",
+    maxBuffer: 20 * 1024 * 1024,
+  });
+
+  if (result.error) {
+    throw new Error(
+      `Unable to run JSBSim runner with "${pythonCommand}". Install Python and jsbsim, or set JSBSIM_PYTHON/JSBSIM_RUNNER. ${result.error.message}`
+    );
+  }
+
+  if (result.status !== 0) {
+    if (result.status === 9009) {
+      throw new Error(
+        `Unable to run JSBSim runner with "${pythonCommand}". Python is not available on PATH; install Python and jsbsim, or set JSBSIM_PYTHON to a Python executable.`
+      );
+    }
+
+    throw new Error(
+      `JSBSim runner failed with exit code ${result.status}: ${result.stderr.trim()}`
+    );
+  }
+
+  try {
+    const response = JSON.parse(extractJson(result.stdout));
+    return {
+      ...response,
+      backend: backendInfo.id,
+    };
+  } catch {
+    throw new Error(`JSBSim runner did not return valid JSON: ${result.stdout}`);
+  }
+}
+
+function extractJson(stdout) {
+  const firstObject = stdout.indexOf("{");
+  if (firstObject < 0) {
+    throw new Error("No JSON payload found.");
+  }
+  return stdout.slice(firstObject).trim();
+}
+
+function validateTrimRequest(request) {
+  if (!request || typeof request !== "object") {
+    throw new Error("Request body must be a JSON object.");
+  }
+
+  if (!AIRCRAFT.some((aircraft) => aircraft.id === request.aircraftId)) {
+    throw new Error(`Unknown aircraftId: ${request.aircraftId}`);
+  }
+}
+
+function validateSimulateRequest(request) {
+  if (!request || typeof request !== "object") {
+    throw new Error("Request body must be a JSON object.");
+  }
+
+  if (!AIRCRAFT.some((aircraft) => aircraft.id === request.aircraftId)) {
+    throw new Error(`Unknown aircraftId: ${request.aircraftId}`);
+  }
+
+  if (!request.initialState || typeof request.initialState !== "object") {
+    throw new Error("initialState is required.");
+  }
+
+  const maneuverType = request.maneuver?.type;
+  const supported = new Set(["straight", "climb", "descent", "control-script", "cobra"]);
+  if (!supported.has(maneuverType)) {
+    throw new Error(
+      `JSBSim minimal backend supports straight/climb/descent/control-script/cobra only. Unsupported maneuver.type: ${maneuverType}`
+    );
+  }
+}
+
+function numberOrDefault(value, fallback) {
+  return Number.isFinite(value) ? value : fallback;
+}