import { solveWalker } from './kinematics.js';
import { TAU, normalizeAngleRad } from './math.js';
import { renderScene } from './renderer.js';
import { create3DRenderer } from './renderer3d.js';
import { clearTrace, createTraceBuffer, pushTrace } from './trace.js';
import { updateDiagnostics, wireUI } from './ui.js';
import { BASE_DIMENSIONS_CM } from './geometry.js';

const PRESET_STORAGE_KEY = 'walkerSim.presets.v1';

const DEFAULT_LENGTH_CM = {
  crank: BASE_DIMENSIONS_CM.crank,
  leg: BASE_DIMENSIONS_CM.leg,
  tendon: BASE_DIMENSIONS_CM.tendon,
  body: BASE_DIMENSIONS_CM.body,
};

const BUILTIN_PRESET_NAME = 'Default 45cm leg';

const canvas = document.getElementById('sim-canvas');
const view3dPanelEl = document.getElementById('view-3d-panel');
const view3dEl = document.getElementById('sim-3d');
const viewsWrapEl = document.querySelector('.views-wrap');
const diagEl = document.getElementById('diag');

const state = {
  theta: 0,
  speedRps: 0.3,
  playing: true,
  showNear: true,
  showFar: true,
  showTrace: true,
  showAnnotations: false,
  show3d: true,
  lengthCm: { ...DEFAULT_LENGTH_CM },
  fallbackCount: 0,
  pose: null,
  ground: {
    floorY: null,
    bodyYOffset: 0,
    groundedFoot: null,
    minFootY: NaN,
    onFloor: false,
    verticalVel: 0,
  },
  trace: {
    nearF: createTraceBuffer(1200),
    nearG: createTraceBuffer(1200),
    farF: createTraceBuffer(1200),
    farG: createTraceBuffer(1200),
  },
};

const renderer3d = create3DRenderer(view3dEl);

function resize2DCanvasToDisplaySize() {
  const dpr = Math.min(window.devicePixelRatio || 1, 2);
  const width = Math.max(1, Math.floor(canvas.clientWidth * dpr));
  const height = Math.max(1, Math.floor(canvas.clientHeight * dpr));
  if (canvas.width !== width || canvas.height !== height) {
    canvas.width = width;
    canvas.height = height;
  }
}

function apply3DVisibility() {
  if (view3dPanelEl) {
    view3dPanelEl.style.display = state.show3d ? '' : 'none';
  }
  if (viewsWrapEl) {
    viewsWrapEl.style.gridTemplateRows = state.show3d ? '1fr 1fr' : '1fr';
  }
  renderer3d.setVisible(state.show3d);
}

function resizeViews() {
  resize2DCanvasToDisplaySize();
  if (state.show3d) {
    renderer3d.resize();
  }
}

const FOOT_KEYS = ['nearF', 'nearG', 'farF', 'farG'];

function mapSideWithYOffset(side, yOffset) {
  return {
    ...side,
    A: { x: side.A.x, y: side.A.y + yOffset },
    B: { x: side.B.x, y: side.B.y + yOffset },
    O: { x: side.O.x, y: side.O.y + yOffset },
    C: { x: side.C.x, y: side.C.y + yOffset },
    D: { x: side.D.x, y: side.D.y + yOffset },
    E: { x: side.E.x, y: side.E.y + yOffset },
    F: { x: side.F.x, y: side.F.y + yOffset },
    G: { x: side.G.x, y: side.G.y + yOffset },
  };
}

function getFootPoint(pose, key) {
  switch (key) {
    case 'nearF':
      return pose.near.F;
    case 'nearG':
      return pose.near.G;
    case 'farF':
      return pose.far.F;
    case 'farG':
      return pose.far.G;
    default:
      return null;
  }
}

function footCandidates(pose) {
  return [
    { key: 'nearF', point: pose.near.F },
    { key: 'nearG', point: pose.near.G },
    { key: 'farF', point: pose.far.F },
    { key: 'farG', point: pose.far.G },
  ];
}

function lowestFootCandidate(pose) {
  const feet = footCandidates(pose);
  let best = feet[0];
  for (let i = 1; i < feet.length; i += 1) {
    if (feet[i].point.y > best.point.y) {
      best = feet[i];
    }
  }
  return best;
}

function applyGrounding(rawPose) {
  const best = lowestFootCandidate(rawPose);

  if (state.ground.floorY == null) {
    state.ground.floorY = best.point.y;
  }

  let groundedFoot = state.ground.groundedFoot;
  if (!FOOT_KEYS.includes(groundedFoot)) {
    groundedFoot = best.key;
  }

  groundedFoot = best.key;

  const contact = getFootPoint(rawPose, groundedFoot) ?? best.point;
  const bodyYOffset = state.ground.floorY - contact.y;

  const groundedPose = {
    ...rawPose,
    near: mapSideWithYOffset(rawPose.near, bodyYOffset),
    far: mapSideWithYOffset(rawPose.far, bodyYOffset),
  };

  state.ground.groundedFoot = groundedFoot;
  state.ground.bodyYOffset = bodyYOffset;

  const lowestShifted = lowestFootCandidate(groundedPose);
  state.ground.minFootY = lowestShifted.point.y;
  state.ground.onFloor = Math.abs(lowestShifted.point.y - state.ground.floorY) < 1e-4;

  return groundedPose;
}

function clearAllTraces() {
  clearTrace(state.trace.nearF);
  clearTrace(state.trace.nearG);
  clearTrace(state.trace.farF);
  clearTrace(state.trace.farG);
}

function setTheta(theta) {
  state.theta = normalizeAngleRad(theta);
}

function currentLengthScale() {
  return {
    crank: state.lengthCm.crank / BASE_DIMENSIONS_CM.crank,
    leg: state.lengthCm.leg / BASE_DIMENSIONS_CM.leg,
    tendon: state.lengthCm.tendon / BASE_DIMENSIONS_CM.tendon,
    body: state.lengthCm.body / BASE_DIMENSIONS_CM.body,
  };
}

function sanitizePresetName(name) {
  if (typeof name !== 'string') return '';
  return name.trim().slice(0, 40);
}

function resetSimulation({ clearLengths = false } = {}) {
  if (clearLengths) {
    state.lengthCm = { ...DEFAULT_LENGTH_CM };
  }

  setTheta(0);
  state.fallbackCount = 0;
  state.ground.floorY = null;
  state.ground.groundedFoot = null;
  state.ground.bodyYOffset = 0;
  state.ground.minFootY = NaN;
  state.ground.onFloor = false;
  state.ground.verticalVel = 0;
  clearAllTraces();

  const raw = solveWalker(state.theta, null, currentLengthScale());
  state.pose = applyGrounding(raw);
}

function loadPersistedPresets() {
  const presets = {
    [BUILTIN_PRESET_NAME]: { ...DEFAULT_LENGTH_CM },
  };

  let parsed = null;
  try {
    parsed = JSON.parse(localStorage.getItem(PRESET_STORAGE_KEY) ?? 'null');
  } catch {
    parsed = null;
  }

  if (parsed && typeof parsed === 'object' && !Array.isArray(parsed)) {
    for (const [rawName, rawPreset] of Object.entries(parsed)) {
      const name = sanitizePresetName(rawName);
      if (!name || !rawPreset || typeof rawPreset !== 'object') continue;

      const crank = Number(rawPreset.crank);
      const leg = Number(rawPreset.leg);
      const tendon = Number(rawPreset.tendon);
      const body = Number(rawPreset.body);

      if ([crank, leg, tendon, body].every(Number.isFinite)) {
        presets[name] = { crank, leg, tendon, body };
      }
    }
  }

  return presets;
}

function persistPresets() {
  const serializable = {};
  for (const [name, preset] of Object.entries(state.presets)) {
    if (name === BUILTIN_PRESET_NAME) continue;
    serializable[name] = {
      crank: preset.crank,
      leg: preset.leg,
      tendon: preset.tendon,
      body: preset.body,
    };
  }
  localStorage.setItem(PRESET_STORAGE_KEY, JSON.stringify(serializable));
}

state.presets = loadPersistedPresets();

const ui = wireUI(state, {
  setTheta,
  reset() {
    resetSimulation({ clearLengths: true });
  },
  refresh() {
    resetSimulation({ clearLengths: false });
  },
  savePreset(name) {
    const presetName = sanitizePresetName(name);
    if (!presetName) return null;
    state.presets[presetName] = { ...state.lengthCm };
    persistPresets();
    return presetName;
  },
  loadPreset(name) {
    const presetName = sanitizePresetName(name);
    const preset = state.presets[presetName];
    if (!preset) return false;
    state.lengthCm = { ...preset };
    resetSimulation({ clearLengths: false });
    return true;
  },
  listPresets() {
    return Object.keys(state.presets);
  },
  set3DVisible(visible) {
    state.show3d = Boolean(visible);
    apply3DVisibility();
    resizeViews();
  },
  reset3DCamera() {
    renderer3d.resetCamera();
  },
});

state.pose = applyGrounding(solveWalker(state.theta, null, currentLengthScale()));
apply3DVisibility();
resizeViews();
renderScene(canvas, state);
if (state.show3d) renderer3d.render(state);
updateDiagnostics(diagEl, state);

window.addEventListener('resize', resizeViews);

const fixedDt = 1 / 240;
let acc = 0;
let lastT = performance.now() / 1000;

function step(dt) {
  if (state.playing) {
    state.theta = normalizeAngleRad(state.theta + TAU * state.speedRps * dt);
  }

  const prev = state.pose;
  const nextRaw = solveWalker(state.theta, prev, currentLengthScale());
  const next = applyGrounding(nextRaw);
  state.pose = next;

  if (nextRaw.near.fallbackUsed || nextRaw.far.fallbackUsed) {
    state.fallbackCount += 1;
  }

  pushTrace(state.trace.nearF, next.near.F);
  pushTrace(state.trace.nearG, next.near.G);
  pushTrace(state.trace.farF, next.far.F);
  pushTrace(state.trace.farG, next.far.G);
}

function frame() {
  const now = performance.now() / 1000;
  let dt = now - lastT;
  lastT = now;
  if (dt > 0.1) dt = 0.1;

  acc += dt;
  while (acc >= fixedDt) {
    step(fixedDt);
    acc -= fixedDt;
  }

  ui.syncAngle(state.theta);
  ui.syncPlay();
  renderScene(canvas, state);
  if (state.show3d) renderer3d.render(state);
  updateDiagnostics(diagEl, state);

  requestAnimationFrame(frame);
}

requestAnimationFrame(frame);