// Linearized mode frequencies of the simulated sheet (with its initial bow), for
// comparing the model's partials with a recording without running the simulator.
//
// Usage: node modes.ts OUT.bin [key=value ...]
// Writes the mass-symmetrized stiffness of all three displacement fields over the
// nodes of the sheet as float64, and prints JSON with the degrees of freedom and the
// grid; eigenvalues are then omega^2 (see modes.py).
import { writeFileSync } from "node:fs";
import { accelerations, type Fields } from "../src/sim/cpuRef.ts";
import { defaultParams, initialShape, makeGrid, makeMaterial, nodeWeight, type PhysParams } from "../src/params.ts";

const out = process.argv[2];
const p: PhysParams = { ...defaultParams };
for (const a of process.argv.slice(3)) {
  const [k, v] = a.split("=");
  const d = (p as unknown as Record<string, unknown>)[k];
  (p as unknown as Record<string, unknown>)[k] = typeof d === "number" ? parseFloat(v) : v;
}
const g = makeGrid(p);
const m = makeMaterial(p);
const w0 = Float64Array.from(initialShape(p, g));
const nodes: number[] = [];
for (let k = 0; k < g.n; k++) if (nodeWeight(g, k % g.nx, Math.floor(k / g.nx)) > 0) nodes.push(k);
const N = nodes.length;
const n = 3 * N;
const mass = (d: number) => m.rhoh * g.hx * g.hy * nodeWeight(g, nodes[d % N] % g.nx, Math.floor(nodes[d % N] / g.nx));
const x: Fields = { u: new Float64Array(g.n), v: new Float64Array(g.n), w: new Float64Array(g.n) };
const y: Fields = { u: new Float64Array(g.n), v: new Float64Array(g.n), w: new Float64Array(g.n) };
const y0: Fields = { u: new Float64Array(g.n), v: new Float64Array(g.n), w: new Float64Array(g.n) };
accelerations(g, m, x, y0, w0); // rest state (zero for a stress-free bow)
const eps = 1e-9;
const K = new Float64Array(n * n);
const arr = (f: Fields, c: number) => (c === 0 ? f.u : c === 1 ? f.v : f.w);
for (let col = 0; col < n; col++) {
  const c = Math.floor(col / N), k = nodes[col % N];
  arr(x, c)[k] = eps;
  accelerations(g, m, x, y, w0);
  arr(x, c)[k] = 0;
  const sc = Math.sqrt(1 / mass(col)) / eps;
  for (let row = 0; row < n; row++) {
    const rc = Math.floor(row / N), rk = nodes[row % N];
    const acc = arr(y, rc)[rk] - arr(y0, rc)[rk];
    K[row * n + col] = -acc * Math.sqrt(mass(row)) * sc;
  }
}
writeFileSync(out, Buffer.from(K.buffer));
console.log(JSON.stringify({ n, N, nx: g.nx, ny: g.ny, params: { E: p.E, nu: p.nu, rho: p.rho, h: p.h, bowShape: p.bowShape, bowAmplitude: p.bowAmplitude, spacing: p.spacing } }));