project-math/src/components/workbench/modules/electronics/simulateElectronics.ts

import {
  ElectronicCircuitState,
  ElectronicComponent,
  SimulationResult,
} from '@/types/electronics';

/**
 * Simplified DC circuit simulator using node-voltage analysis.
 *
 * Supports: voltage sources, resistors, ground, switches, LEDs, NMOS/PMOS (ideal).
 * MOSFETs are modeled as ideal switches:
 *   NMOS: ON (low Rds) when Vgs > threshold (2V), OFF (high Rds) otherwise
 *   PMOS: ON when Vgs < -threshold (-2V), OFF otherwise
 *
 * Uses iterative approach for nonlinear elements (transistors):
 *   1. Assume all transistors OFF
 *   2. Solve linear circuit
 *   3. Check transistor states, update if changed
 *   4. Repeat until stable (max 10 iterations)
 */

const VTH = 2;              // MOSFET threshold voltage
const R_ON = 1;             // MOSFET ON resistance (Ω)
const R_OFF = 1e9;          // MOSFET OFF resistance (Ω)
const R_LED = 100;          // LED effective resistance when forward biased
const V_LED = 1.8;          // LED forward voltage drop

export function simulateElectronics(circuit: ElectronicCircuitState): SimulationResult {
  const { components, wires } = circuit;

  if (components.length === 0) {
    return { success: false, error: 'No hay componentes', nodeVoltages: new Map(), branchCurrents: new Map(), meterReadings: new Map() };
  }

  // Build net list: group connected terminals into nodes
  const terminalToNode = new Map<string, string>();
  let nodeCounter = 0;

  function getTerminalId(compId: string, terminal: string): string {
    return `${compId}:${terminal}`;
  }

  function findNode(termId: string): string {
    let node = terminalToNode.get(termId);
    if (!node) {
      node = `n${nodeCounter++}`;
      terminalToNode.set(termId, node);
    }
    return node;
  }

  function mergeNodes(a: string, b: string) {
    const nodeA = findNode(a);
    const nodeB = findNode(b);
    if (nodeA === nodeB) return;
    // Replace all nodeB references with nodeA
    for (const [key, val] of terminalToNode.entries()) {
      if (val === nodeB) terminalToNode.set(key, nodeA);
    }
  }

  // Initialize all component terminals
  for (const comp of components) {
    const terminals = getComponentTerminals(comp.type);
    for (const t of terminals) {
      findNode(getTerminalId(comp.id, t));
    }
  }

  // Process wires to merge nodes
  for (const wire of wires) {
    mergeNodes(wire.from, wire.to);
  }

  // Find ground node
  let groundNode: string | null = null;
  for (const comp of components) {
    if (comp.type === 'ground') {
      groundNode = findNode(getTerminalId(comp.id, 'gnd'));
      break;
    }
  }

  if (!groundNode) {
    return { success: false, error: 'Necesitas un nodo de tierra (GND)', nodeVoltages: new Map(), branchCurrents: new Map(), meterReadings: new Map() };
  }

  // Get unique node names (excluding ground)
  const allNodes = [...new Set(terminalToNode.values())];
  const nodeList = allNodes.filter((n) => n !== groundNode);
  const nodeIndex = new Map<string, number>();
  nodeList.forEach((n, i) => nodeIndex.set(n, i));

  const N = nodeList.length;
  if (N === 0) {
    return { success: true, nodeVoltages: new Map(), branchCurrents: new Map(), meterReadings: new Map() };
  }

  // Count voltage sources for MNA
  const voltageSources = components.filter((c) => c.type === 'voltage-source');
  const M = voltageSources.length;
  const size = N + M;

  // Transistor states (start all OFF)
  const mosfetState = new Map<string, boolean>();
  for (const comp of components) {
    if (comp.type === 'nmos' || comp.type === 'pmos') {
      mosfetState.set(comp.id, false);
    }
  }

  let voltages: Float64Array = new Float64Array(size);
  let converged = false;

  for (let iter = 0; iter < 10; iter++) {
    // Build MNA matrix: [G B; C D] * [v; i] = [I; E]
    const A = Array.from({ length: size }, () => new Float64Array(size));
    const b = new Float64Array(size);

    function nodeIdx(termId: string): number {
      const node = terminalToNode.get(termId);
      if (!node || node === groundNode) return -1;
      return nodeIndex.get(node) ?? -1;
    }

    // Stamp resistor: G(i,i) += 1/R, G(j,j) += 1/R, G(i,j) -= 1/R, G(j,i) -= 1/R
    function stampResistor(termA: string, termB: string, R: number) {
      const i = nodeIdx(termA);
      const j = nodeIdx(termB);
      const g = 1 / R;
      if (i >= 0) A[i][i] += g;
      if (j >= 0) A[j][j] += g;
      if (i >= 0 && j >= 0) { A[i][j] -= g; A[j][i] -= g; }
    }

    // Stamp voltage source
    function stampVoltageSource(posTerminal: string, negTerminal: string, voltage: number, vsIdx: number) {
      const i = nodeIdx(posTerminal);
      const j = nodeIdx(negTerminal);
      const k = N + vsIdx;
      if (i >= 0) { A[i][k] += 1; A[k][i] += 1; }
      if (j >= 0) { A[j][k] -= 1; A[k][j] -= 1; }
      b[k] = voltage;
    }

    // Process each component
    let vsCount = 0;
    for (const comp of components) {
      switch (comp.type) {
        case 'resistor': {
          const R = comp.value ?? 1000;
          stampResistor(getTerminalId(comp.id, 'a'), getTerminalId(comp.id, 'b'), R);
          break;
        }
        case 'voltage-source': {
          const V = comp.value ?? 5;
          stampVoltageSource(
            getTerminalId(comp.id, 'pos'),
            getTerminalId(comp.id, 'neg'),
            V, vsCount++
          );
          break;
        }
        case 'capacitor': {
          // In DC steady state, capacitor = open circuit (very high R)
          // But we model it so voltage across it can be measured
          stampResistor(getTerminalId(comp.id, 'a'), getTerminalId(comp.id, 'b'), R_OFF);
          break;
        }
        case 'led': {
          // Simplified: resistor + voltage drop (model as resistor for now)
          stampResistor(getTerminalId(comp.id, 'anode'), getTerminalId(comp.id, 'cathode'), R_LED);
          break;
        }
        case 'switch': {
          // Switches modeled as low resistance when "on" (value=1), high when "off" (value=0)
          const isOn = (comp.value ?? 0) > 0;
          stampResistor(getTerminalId(comp.id, 'a'), getTerminalId(comp.id, 'b'), isOn ? 0.01 : R_OFF);
          break;
        }
        case 'nmos': {
          const isOn = mosfetState.get(comp.id) ?? false;
          const R = isOn ? R_ON : R_OFF;
          stampResistor(getTerminalId(comp.id, 'drain'), getTerminalId(comp.id, 'source'), R);
          break;
        }
        case 'pmos': {
          const isOn = mosfetState.get(comp.id) ?? false;
          const R = isOn ? R_ON : R_OFF;
          stampResistor(getTerminalId(comp.id, 'drain'), getTerminalId(comp.id, 'source'), R);
          break;
        }
        case 'voltmeter': {
          // Voltmeter = very high resistance (doesn't affect circuit)
          stampResistor(getTerminalId(comp.id, 'pos'), getTerminalId(comp.id, 'neg'), 1e9);
          break;
        }
        case 'ammeter': {
          // Ammeter = very low resistance (passes all current)
          stampResistor(getTerminalId(comp.id, 'a'), getTerminalId(comp.id, 'b'), 0.001);
          break;
        }
        case 'ground':
          break;
      }
    }

    // Solve A * x = b using Gaussian elimination
    const solved = solveLinearSystem(A, b, size);
    if (!solved) {
      return { success: false, error: 'El circuito no tiene solución (¿cortocircuito?)', nodeVoltages: new Map(), branchCurrents: new Map(), meterReadings: new Map() };
    }
    voltages = solved;

    // Update MOSFET states based on solved voltages
    let changed = false;
    for (const comp of components) {
      if (comp.type !== 'nmos' && comp.type !== 'pmos') continue;

      const gateNode = terminalToNode.get(getTerminalId(comp.id, 'gate'));
      const sourceNode = terminalToNode.get(getTerminalId(comp.id, 'source'));

      const vGate = getNodeVoltage(gateNode, groundNode, nodeIndex, voltages);
      const vSource = getNodeVoltage(sourceNode, groundNode, nodeIndex, voltages);
      const vgs = vGate - vSource;

      let shouldBeOn = false;
      if (comp.type === 'nmos') shouldBeOn = vgs > VTH;
      if (comp.type === 'pmos') shouldBeOn = vgs < -VTH;

      const wasOn = mosfetState.get(comp.id) ?? false;
      if (shouldBeOn !== wasOn) {
        mosfetState.set(comp.id, shouldBeOn);
        changed = true;
      }
    }

    if (!changed) {
      converged = true;
      break;
    }
  }

  if (!converged && mosfetState.size > 0) {
    // Still usable, just warn
  }

  // Build result maps
  const nodeVoltages = new Map<string, number>();
  for (const [termId, node] of terminalToNode.entries()) {
    const v = getNodeVoltage(node, groundNode!, nodeIndex, voltages);
    nodeVoltages.set(termId, Math.round(v * 1000) / 1000);
  }

  const branchCurrents = new Map<string, number>();
  // Calculate currents through resistors
  for (const comp of components) {
    if (comp.type === 'resistor') {
      const va = nodeVoltages.get(getTerminalId(comp.id, 'a')) ?? 0;
      const vb = nodeVoltages.get(getTerminalId(comp.id, 'b')) ?? 0;
      const R = comp.value ?? 1000;
      branchCurrents.set(comp.id, Math.round(((va - vb) / R) * 10000) / 10000);
    }
  }

  // Compute meter readings
  const meterReadings = new Map<string, { value: number; unit: string }>();
  for (const comp of components) {
    if (comp.type === 'voltmeter') {
      const vPos = nodeVoltages.get(getTerminalId(comp.id, 'pos')) ?? 0;
      const vNeg = nodeVoltages.get(getTerminalId(comp.id, 'neg')) ?? 0;
      const diff = Math.round((vPos - vNeg) * 1000) / 1000;
      meterReadings.set(comp.id, { value: diff, unit: 'V' });
    }
    if (comp.type === 'ammeter') {
      const vA = nodeVoltages.get(getTerminalId(comp.id, 'a')) ?? 0;
      const vB = nodeVoltages.get(getTerminalId(comp.id, 'b')) ?? 0;
      const current = Math.round(((vA - vB) / 0.001) * 10000) / 10000;
      meterReadings.set(comp.id, { value: Math.abs(current) * 1000, unit: 'mA' });
    }
  }

  return { success: true, nodeVoltages, branchCurrents, meterReadings };
}

function getNodeVoltage(
  node: string | undefined,
  groundNode: string,
  nodeIndex: Map<string, number>,
  voltages: Float64Array
): number {
  if (!node || node === groundNode) return 0;
  const idx = nodeIndex.get(node);
  if (idx === undefined) return 0;
  return voltages[idx];
}

function getComponentTerminals(type: string): string[] {
  switch (type) {
    case 'voltage-source': return ['pos', 'neg'];
    case 'resistor': return ['a', 'b'];
    case 'capacitor': return ['a', 'b'];
    case 'led': return ['anode', 'cathode'];
    case 'switch': return ['a', 'b'];
    case 'ground': return ['gnd'];
    case 'nmos': return ['gate', 'drain', 'source'];
    case 'pmos': return ['gate', 'drain', 'source'];
    case 'voltmeter': return ['pos', 'neg'];
    case 'ammeter': return ['a', 'b'];
    default: return [];
  }
}

/** Gaussian elimination with partial pivoting */
function solveLinearSystem(A: Float64Array[], b: Float64Array, n: number): Float64Array | null {
  // Augmented matrix
  const aug = A.map((row, i) => {
    const r = new Float64Array(n + 1);
    r.set(row);
    r[n] = b[i];
    return r;
  });

  for (let col = 0; col < n; col++) {
    // Pivot
    let maxRow = col;
    let maxVal = Math.abs(aug[col][col]);
    for (let row = col + 1; row < n; row++) {
      if (Math.abs(aug[row][col]) > maxVal) {
        maxVal = Math.abs(aug[row][col]);
        maxRow = row;
      }
    }
    if (maxVal < 1e-12) continue; // singular, skip
    [aug[col], aug[maxRow]] = [aug[maxRow], aug[col]];

    // Eliminate
    for (let row = col + 1; row < n; row++) {
      const factor = aug[row][col] / aug[col][col];
      for (let j = col; j <= n; j++) {
        aug[row][j] -= factor * aug[col][j];
      }
    }
  }

  // Back substitution
  const x = new Float64Array(n);
  for (let row = n - 1; row >= 0; row--) {
    if (Math.abs(aug[row][row]) < 1e-12) {
      x[row] = 0;
      continue;
    }
    let sum = aug[row][n];
    for (let j = row + 1; j < n; j++) {
      sum -= aug[row][j] * x[j];
    }
    x[row] = sum / aug[row][row];
  }

  return x;
}