// The design: a MATLAB-syntax script, run by numbl, that fills in a struct
// named `design` with the material, the bounding box, the outline, the
// thickness field, the stress-free profile, and the loss constants of the
// material (from which the decay is derived, loss.ts).
// The outline, the thickness, and the profile are function handles
// @(x, y, r, theta), vectorized over grid matrices (or plain numbers).
// compileDesign runs the script and checks the struct; evaluatePlate runs it
// again with a short trailer that samples the fields on meshgrid matrices of
// the requested spacing, inside numbl, and reads the matrices back.
//
// Lengths are meters throughout. A script is self-contained: nothing is in
// scope but numbl's own functions and whatever the script defines itself,
// including ordinary MATLAB functions written at its bottom (numbl hoists
// them, so the trailer may still follow them).

import { executeCode, type RuntimeValue, type RuntimeTensor, type RuntimeStruct } from "numbl";
import { RUNTIME_FILES } from "./mruntime.ts";
import {
  type Grid,
  type Material,
  type Plate,
  type Thermal,
  ROOM_TEMPERATURE,
  insideNode,
  makeGrid,
  nodeWeight,
  nodeX,
  nodeY,
  withCellMask,
} from "./params.ts";

/** A compiled design: the checked contents of the `design` struct, plus the script that produced it. */
export interface Design {
  name: string;
  material: Material;
  Lx: number;
  Ly: number;
  /** Whether the script gave an outline; without one the plate is the whole bounding box. */
  hasInside: boolean;
  /** The thickness when it is a plain number; null for a function. */
  thicknessConst: number | null;
  /** The profile when it is a plain number (or absent); null for a function. */
  profileConst: number | null;
  /** Temperature of the plate [K], for the thermoelastic damping. */
  temperature: number;
  source: string;
}

/** Message of an error thrown by the script or by the checks. */
export class DesignError extends Error {}

const FILE_NAME = "design.m";

/**
 * Runs a design script and returns its workspace variables. `userLines` is
 * the length of the part of the source the user wrote, so that an error in
 * the appended trailer is not reported at a line the user cannot see.
 */
export function runDesignScript(source: string, userLines = Infinity): Record<string, RuntimeValue> {
  try {
    return executeCode(source, { displayResults: false, onOutput: () => {} }, RUNTIME_FILES, FILE_NAME).variableValues;
  } catch (e) {
    throw new DesignError(describeError(e, Math.min(source.split("\n").length, userLines)));
  }
}

function describeError(e: unknown, userLines: number): string {
  if (!(e instanceof Error)) return String(e);
  const { line, file } = e as { line?: unknown; file?: unknown };
  const inScript = file === undefined || file === null || file === FILE_NAME;
  const where = inScript && typeof line === "number" && line >= 1 && line <= userLines ? `line ${line}: ` : "";
  return `${where}${e.message}`;
}

// ---------- Reading runtime values ----------

function isStruct(v: RuntimeValue | undefined): v is RuntimeStruct {
  return typeof v === "object" && v !== null && (v as { kind?: string }).kind === "struct";
}
function isTensor(v: RuntimeValue | undefined): v is RuntimeTensor {
  return typeof v === "object" && v !== null && (v as { kind?: string }).kind === "tensor";
}
function isFunction(v: RuntimeValue | undefined): boolean {
  return typeof v === "object" && v !== null && (v as { kind?: string }).kind === "function";
}
function isEmpty(v: RuntimeValue | undefined): boolean {
  return v === undefined || (isTensor(v) && v.data.length === 0);
}

/** A scalar number from a runtime value, or null when it is not one. */
function scalar(v: RuntimeValue | undefined): number | null {
  if (typeof v === "number") return v;
  if (typeof v === "boolean") return v ? 1 : 0;
  if (isTensor(v) && v.data.length === 1 && (!v.imag || v.imag[0] === 0)) return v.data[0];
  return null;
}

function num(v: RuntimeValue | undefined, what: string, min = -Infinity): number {
  const s = scalar(v);
  if (s === null || !isFinite(s)) throw new DesignError(`${what} must be a finite number`);
  if (s < min) throw new DesignError(`${what} must be at least ${min}`);
  return s;
}

function field(s: RuntimeStruct, name: string): RuntimeValue | undefined {
  return s.fields.get(name);
}

function text(v: RuntimeValue | undefined): string | null {
  if (typeof v === "string") return v;
  if (typeof v === "object" && v !== null && (v as { kind?: string }).kind === "char") return (v as { value: string }).value;
  return null;
}

// ---------- Compilation ----------

/**
 * Runs the script and checks the `design` struct it leaves in the
 * workspace. The field functions are not called here; evaluatePlate samples
 * them on the grid.
 */
export function compileDesign(source: string): Design {
  const vars = runDesignScript(source);
  const d = vars.design;
  if (d === undefined) throw new DesignError("the script must fill in a struct named design (design.material, design.bounds, design.thickness, ...)");
  if (!isStruct(d)) throw new DesignError("design must be a struct");

  const nameV = field(d, "name");
  const name = (nameV !== undefined ? text(nameV) : null)?.trim() || "Untitled design";

  const m = field(d, "material");
  if (!isStruct(m)) throw new DesignError("design.material must be a struct with fields E, nu, rho, lossFactor, and the thermal constants alpha, cp, k");
  const has = (s: RuntimeStruct, k: string) => field(s, k) !== undefined && !isEmpty(field(s, k));
  const thermalKeys = ["alpha", "cp", "k"];
  const given = thermalKeys.filter((k) => has(m, k));
  let thermal: Thermal | null = null;
  if (given.length === 3) {
    thermal = { alpha: num(field(m, "alpha"), "design.material.alpha (thermal expansion, 1/K)", 0), cp: num(field(m, "cp"), "design.material.cp (specific heat, J/(kg K))", 1), k: num(field(m, "k"), "design.material.k (thermal conductivity, W/(m K))", 1e-3) };
  } else if (given.length > 0) {
    throw new DesignError("design.material needs all three thermal constants for the thermoelastic damping, alpha (1/K), cp (J/(kg K)) and k (W/(m K)), or none of them");
  }
  const material: Material = {
    E: num(field(m, "E"), "design.material.E", 1e6),
    nu: num(field(m, "nu"), "design.material.nu", 0),
    rho: num(field(m, "rho"), "design.material.rho", 1),
    eta: has(m, "lossFactor") ? num(field(m, "lossFactor"), "design.material.lossFactor", 0) : 0,
    thermal,
  };
  if (material.nu >= 0.5) throw new DesignError("design.material.nu must be below 0.5");
  if (material.eta >= 0.1) throw new DesignError("design.material.lossFactor must be small (metals have loss factors of 1e-4 to 1e-3)");
  if (field(d, "loss") !== undefined) throw new DesignError("design.loss is no longer used: the decay of each mode follows from design.material.lossFactor, the thermal constants alpha, cp and k, and the radiation of the plate");
  const temperature = has(d, "temperature") ? num(field(d, "temperature"), "design.temperature (K)", 1) : ROOM_TEMPERATURE;

  const b = field(d, "bounds");
  if (!isStruct(b)) throw new DesignError("design.bounds must be a struct with fields width, height");
  const Lx = num(field(b, "width"), "design.bounds.width", 1e-3), Ly = num(field(b, "height"), "design.bounds.height", 1e-3);

  const inside = field(d, "inside");
  let hasInside = false;
  if (!isEmpty(inside)) {
    if (!isFunction(inside)) throw new DesignError("design.inside must be a function handle @(x, y, r, theta) returning true inside the plate, for example @(x, y, r, theta) r <= D/2");
    hasInside = true;
  }

  const th = field(d, "thickness");
  if (th === undefined) throw new DesignError("design.thickness is required (a number in meters, or a function handle @(x, y, r, theta))");
  let thicknessConst: number | null = null;
  if (!isFunction(th)) {
    thicknessConst = scalar(th);
    if (thicknessConst === null || !isFinite(thicknessConst)) throw new DesignError("design.thickness must be a number or a function handle @(x, y, r, theta)");
    if (thicknessConst <= 0) throw new DesignError("design.thickness must be positive");
  }

  const pr = field(d, "profile");
  let profileConst: number | null = 0;
  if (pr !== undefined && !isEmpty(pr)) {
    if (isFunction(pr)) profileConst = null;
    else {
      profileConst = scalar(pr);
      if (profileConst === null || !isFinite(profileConst)) throw new DesignError("design.profile must be a number or a function handle @(x, y, r, theta)");
    }
  }

  return { name, material, Lx, Ly, hasInside, thicknessConst, profileConst, temperature, source };
}

// ---------- Evaluation on a grid ----------

/** Subtracts the weighted least-squares plane a + b x + c y from f over the plate nodes. */
export function removePlane(f: Float64Array, g: Grid): void {
  let sw = 0, sx = 0, sy = 0, sxx = 0, sxy = 0, syy = 0, sf = 0, sxf = 0, syf = 0;
  for (let j = 0; j < g.ny; j++) {
    for (let i = 0; i < g.nx; i++) {
      const wgt = nodeWeight(g, i, j);
      if (wgt === 0) continue;
      const x = nodeX(g, i), y = nodeY(g, j), v = f[j * g.nx + i];
      sw += wgt; sx += wgt * x; sy += wgt * y;
      sxx += wgt * x * x; sxy += wgt * x * y; syy += wgt * y * y;
      sf += wgt * v; sxf += wgt * x * v; syf += wgt * y * v;
    }
  }
  if (sw === 0) return;
  const det = sw * (sxx * syy - sxy * sxy) - sx * (sx * syy - sxy * sy) + sy * (sx * sxy - sxx * sy);
  if (Math.abs(det) < 1e-300) return;
  const a = (sf * (sxx * syy - sxy * sxy) - sx * (sxf * syy - sxy * syf) + sy * (sxf * sxy - sxx * syf)) / det;
  const b = (sw * (sxf * syy - sxy * syf) - sf * (sx * syy - sxy * sy) + sy * (sx * syf - sxf * sy)) / det;
  const c = (sw * (sxx * syf - sxf * sxy) - sx * (sx * syf - sxf * sy) + sf * (sx * sxy - sxx * sy)) / det;
  for (let j = 0; j < g.ny; j++) for (let i = 0; i < g.nx; i++) f[j * g.nx + i] -= a + b * nodeX(g, i) + c * nodeY(g, j);
}

/** The trailer appended to the script to sample the fields on the grid (all names start with cymbalsim_). */
function trailer(d: Design, g: Grid): string {
  const fmt = (v: number) => v.toPrecision(17);
  return [
    "",
    "% ---- appended by the simulator: sample the fields on the grid ----",
    `cymbalsim_nx = ${g.nx}; cymbalsim_ny = ${g.ny};`,
    `cymbalsim_hx = ${fmt(g.hx)}; cymbalsim_hy = ${fmt(g.hy)};`,
    `[cymbalsim_X, cymbalsim_Y] = meshgrid(((0:cymbalsim_nx-1) - (cymbalsim_nx-1)/2) * cymbalsim_hx, ((0:cymbalsim_ny-1) - (cymbalsim_ny-1)/2) * cymbalsim_hy);`,
    "cymbalsim_R = hypot(cymbalsim_X, cymbalsim_Y); cymbalsim_T = atan2(cymbalsim_Y, cymbalsim_X);",
    "cymbalsim_H = cymbalsim_field(design.thickness, 'thickness', cymbalsim_X, cymbalsim_Y, cymbalsim_R, cymbalsim_T);",
    d.profileConst === null
      ? "cymbalsim_Z = cymbalsim_field(design.profile, 'profile', cymbalsim_X, cymbalsim_Y, cymbalsim_R, cymbalsim_T);"
      : `cymbalsim_Z = ${fmt(d.profileConst)} * ones(cymbalsim_ny, cymbalsim_nx);`,
    d.hasInside
      ? [
          `[cymbalsim_XC, cymbalsim_YC] = meshgrid(((0:cymbalsim_nx-2) - (cymbalsim_nx-2)/2) * cymbalsim_hx, ((0:cymbalsim_ny-2) - (cymbalsim_ny-2)/2) * cymbalsim_hy);`,
          "cymbalsim_IN = cymbalsim_field(design.inside, 'inside', cymbalsim_XC, cymbalsim_YC, hypot(cymbalsim_XC, cymbalsim_YC), atan2(cymbalsim_YC, cymbalsim_XC));",
        ].join("\n")
      : "",
    "",
  ].join("\n");
}

/** A real [rows, cols] matrix from the workspace as a Float64Array in column-major order. */
function matrix(vars: Record<string, RuntimeValue>, name: string, rows: number, cols: number, what: string): Float64Array {
  const v = vars[name];
  if (!isTensor(v) || v.shape.length !== 2 || v.shape[0] !== rows || v.shape[1] !== cols) throw new DesignError(`${what} did not produce a ${rows} x ${cols} matrix`);
  if (v.imag && v.imag.some((x) => x !== 0)) throw new DesignError(`${what} returned complex values`);
  return v.data;
}

/**
 * Samples the design on a grid of about the requested spacing: the mask from
 * the outline at the cell centers, the thickness at the nodes (which must be
 * positive on the plate), the profile at the nodes with its mean plane
 * removed. Only the slopes of
 * the profile enter the physics, so its mean is immaterial, but its tilt is
 * not: the von Karman strains are not invariant under rotation, and a tilted
 * stress-free shape would add a spurious membrane coupling.
 */
export function evaluatePlate(d: Design, spacing: number): Plate {
  const full = makeGrid(d.Lx, d.Ly, spacing);
  const { nx, ny } = full;
  const vars = runDesignScript(d.source + trailer(d, full), d.source.split("\n").length);
  // meshgrid matrices are [ny, nx] in column-major order: entry (i, j) sits at i * ny + j.
  const H = matrix(vars, "cymbalsim_H", ny, nx, "thickness");
  const Z = matrix(vars, "cymbalsim_Z", ny, nx, "profile");
  let g = full;
  if (d.hasInside) {
    const IN = matrix(vars, "cymbalsim_IN", ny - 1, nx - 1, "inside");
    g = withCellMask(full, (ci, cj) => IN[ci * (ny - 1) + cj] !== 0);
  }
  const h = new Float64Array(g.n), w0 = new Float64Array(g.n);
  let any = false;
  for (let j = 0; j < ny; j++) {
    for (let i = 0; i < nx; i++) {
      if (!insideNode(g, i, j)) continue;
      any = true;
      const k = j * nx + i, m = i * ny + j;
      const x = nodeX(g, i), y = nodeY(g, j);
      const at = `(${x.toFixed(4)}, ${y.toFixed(4)})`;
      if (!isFinite(H[m])) throw new DesignError(`thickness is ${H[m]} at ${at}`);
      if (H[m] <= 0) throw new DesignError(`thickness must be positive; it is ${H[m]} at ${at}`);
      if (!isFinite(Z[m])) throw new DesignError(`profile is ${Z[m]} at ${at}`);
      h[k] = H[m];
      w0[k] = Z[m];
    }
  }
  if (!any) throw new DesignError("the outline contains no grid cells; enlarge it or reduce the grid spacing");
  removePlane(w0, g);
  for (let j = 0; j < ny; j++) for (let i = 0; i < nx; i++) if (!insideNode(g, i, j)) w0[j * nx + i] = 0;
  return { name: d.name, Lx: d.Lx, Ly: d.Ly, grid: g, mat: d.material, h, w0, temperature: d.temperature };
}

/** Whether the plate is flat (no profile), in which case bending and in-plane motion decouple in the linear model. */
export function isFlat(pl: Plate): boolean {
  for (let k = 0; k < pl.w0.length; k++) if (pl.w0[k] !== 0) return false;
  return true;
}

/** Peak-to-peak height and the largest slope of the profile over the plate nodes. */
export function profileStats(pl: Plate): { peakToPeak: number; maxSlope: number } {
  const g = pl.grid, w0 = pl.w0;
  let lo = Infinity, hi = -Infinity, maxSlope = 0;
  const at = (i: number, j: number) => w0[j * g.nx + i];
  const slope = (i: number, j: number, di: number, dj: number, hg: number) => {
    const hasP = insideNode(g, i + di, j + dj), hasM = insideNode(g, i - di, j - dj);
    if (hasP && hasM) return (at(i + di, j + dj) - at(i - di, j - dj)) / (2 * hg);
    if (hasP) return (at(i + di, j + dj) - at(i, j)) / hg;
    if (hasM) return (at(i, j) - at(i - di, j - dj)) / hg;
    return 0;
  };
  for (let j = 0; j < g.ny; j++) {
    for (let i = 0; i < g.nx; i++) {
      if (!insideNode(g, i, j)) continue;
      const v = at(i, j);
      lo = Math.min(lo, v); hi = Math.max(hi, v);
      maxSlope = Math.max(maxSlope, Math.hypot(slope(i, j, 1, 0, g.hx), slope(i, j, 0, 1, g.hy)));
    }
  }
  return { peakToPeak: isFinite(hi - lo) ? hi - lo : 0, maxSlope };
}