splatter-tennis/gameplay.js

// Game logic: ballistics, swings, serves, rules/scoring, AI, and the per-frame update.

import { TUNE, COURT, CONTACT, ZONE_DEPTH, HOME, P_BOUNDS, TOSS, SHOT_DEPTH, POSE_TIME, BOUNCE_IDLE } from './config.js';
import { P, O, ball, score, crowd, G, other, deuceSide, setupPoint, sendBoy } from './state.js';
import { audio, pock, swish, applause, voice } from './audio.js';
import { axisX, axisZ, takeFlickAim } from './input.js';

// ------------------------------------------------------------- ballistics ----
// Launch ball from (x0,y0,z0) so it lands at (tx, tz) with horizontal speed s under gravity g.
export function solveShot(x0, y0, z0, tx, tz, s, g = TUNE.gravity) {
  const dx = tx - x0, dz = tz - z0, dist = Math.hypot(dx, dz), T = dist / s;
  return { vx: dx / T, vz: dz / T, vy: (0.08 - y0 + 0.5 * g * T * T) / T };
}

export function predictLanding() { // first-bounce point, closed form — exact, so the ring never jitters
  const g = ball.g || TUNE.gravity;
  const disc = ball.vy * ball.vy + 2 * g * ball.y;
  if (disc < 0) return null;
  const t = (ball.vy + Math.sqrt(disc)) / g; // time until y = 0
  return { x: ball.x + ball.vx * t, z: ball.z + ball.vz * t };
}

function doHit(ch, quality, aim) {
  // aim: {ax: -1|0|1, az: -1|0|1} from held keys / flick at contact (az -1 = deep, 1 = short)
  const toFar = ch.side === 'P';
  // snap the ball to the racket at the contact frame so the hit visually connects
  ball.x = ch.x + ch.facing * 0.5;
  ball.z = ch.z + (toFar ? -0.3 : 0.3);
  const err = () => (Math.random() * 2 - 1) * TUNE.aimError * (1 - quality);
  let tx = aim.ax * (toFar ? 3.3 : 2.7) + err(); // your aimed shots go properly wide
  const tzBase = aim.az < 0 ? SHOT_DEPTH.deep : aim.az > 0 ? SHOT_DEPTH.short : SHOT_DEPTH.mid;
  const tz = (toFar ? tzBase : COURT.L - tzBase) + err() * 0.8;
  tx = Math.max(-5, Math.min(5, tx));
  let s = TUNE.baseShotSpeed + quality * TUNE.qualityShotSpeed;
  // topspin: quality shots dive under extra effective gravity, which is what lets real
  // pace arc over the net and still land in — the core tennis trade-off
  const g = TUNE.gravity * (1 + quality * TUNE.spinFactor);
  let v = solveShot(ball.x, ball.y, ball.z, tx, tz, s, g);
  // low contact → trade pace for loft until the net is cleared; good timing gets a
  // comfortable margin, sloppy timing keeps some tape risk
  const margin = 0.06 + 0.22 * quality;
  for (let i = 0; i < 8; i++) {
    const tN = (COURT.netZ - ball.z) / v.vz;
    const yN = ball.y + v.vy * tN - 0.5 * g * tN * tN;
    if (tN <= 0 || yN >= COURT.netH + margin) break;
    s *= 0.9; v = solveShot(ball.x, ball.y, ball.z, tx, tz, s, g);
  }
  ball.g = g;
  ball.vx = v.vx; ball.vy = v.vy; ball.vz = v.vz;
  ball.lastHit = ch.side; ball.bounces = 0; ball.firstLand = null;
  if (ch.side === 'P') { // shot marker: where this will land — red means it's going out
    const ok = Math.abs(tx) <= COURT.W / 2 + 0.02 && tz >= -0.02 && tz <= COURT.netZ;
    G.outMarker = { x: tx, z: tz, out: !ok, t: 1.3 };
    G.aiReactT = 0; // CPU hasn't read the shot yet
  }
  pock(0.9, 950);
  if (quality > 0.999) { G.hitstop = 0.05; G.flash = { text: 'PERFECT', t: 0.7 }; pock(0.5, 1600); }
  ch.pose = 'swing'; ch.poseT = 0;
}

// ----------------------------------------------------------------- serve ----
function tossBall(sv) {
  ball.active = true; ball.bounces = 0; ball.firstLand = null; ball.collected = false;
  ball.x = sv.x + 0.35 * (sv.side === 'P' ? 1 : -1); ball.z = sv.z; ball.y = TOSS.y0;
  ball.vx = 0; ball.vz = 0; ball.vy = TOSS.vy; ball.g = TUNE.gravity;
  G.phase = 'toss';
}
export function serveApexY() { return TOSS.y0 + TOSS.vy * TOSS.vy / (2 * TUNE.gravity); } // ~2.95

function hitServe(sv, quality) {
  const toFar = sv.side === 'P';
  // target: diagonal service box. Serving from deuce side → target box is across.
  const boxX = (deuceSide() ? -1 : 1) * (toFar ? 1 : -1) * 2.0 + (Math.random() * 2 - 1) * TUNE.aimError * 0.8 * (1 - quality);
  const boxZ = toFar ? COURT.svcFar + 1.6 : COURT.svcNear - 1.6;
  const s = TUNE.serveSpeed + quality * TUNE.serveQualitySpeed;
  const tzs = boxZ + (Math.random() * 2 - 1) * (1 - quality) * 1.5;
  const g = TUNE.gravity * (1 + quality * 0.35); // kick serves dip a little too
  const v = solveShot(ball.x, ball.y, ball.z, boxX, tzs, s, g);
  ball.g = g;
  ball.vx = v.vx; ball.vy = v.vy; ball.vz = v.vz;
  ball.lastHit = sv.side; ball.bounces = 0;
  if (sv.side === 'P') G.outMarker = { x: boxX, z: tzs, out: !inServeBox(boxX, tzs), t: 1.3 };
  G.phase = 'rally'; pock(1, 1100);
  sv.pose = 'serve'; sv.poseT = 0;
  if (quality > 0.999) { G.flash = { text: 'PERFECT', t: 0.7 }; G.hitstop = 0.05; }
}

// ---------------------------------------------------------------- scoring ----
function scoreKey() {
  const N = ['love', 'fifteen', 'thirty', 'forty'];
  const s = score.server === 'P' ? [score.pts[0], score.pts[1]] : [score.pts[1], score.pts[0]];
  if (s[0] >= 3 && s[1] >= 3) {
    if (s[0] === s[1]) return 'deuce';
    return (s[0] > s[1]) === (score.server === 'P') ? 'advantage_player' : 'advantage_receiver';
  }
  if (s[0] === s[1]) return N[s[0]] + '_all';
  return N[s[0]] + '_' + N[s[1]];
}

function cheer(seconds, vol) {
  applause(seconds, vol);
  crowd.cheer = Math.max(crowd.cheer, seconds);
}

function pointTo(side, reason) {
  const i = side === 'P' ? 0 : 1, j = 1 - i;
  score.pts[i]++;
  let gameOver = false;
  if (score.pts[i] >= 4 && score.pts[i] - score.pts[j] >= 2) {
    score.games[i]++; score.pts = [0, 0]; gameOver = true;
  }
  G.phase = 'over'; G.overT = gameOver ? 3.2 : 2.2;
  sendBoy();
  if (reason) voice(reason);
  if (gameOver) {
    voice(side === 'P' ? 'game_player' : 'game_opponent', 0.7);
    cheer(2.8, 0.6);
    score.server = other(score.server);
  } else {
    voice(scoreKey(), 0.7);
    if (side === 'P') cheer(1.2, 0.3);
  }
  G.serveNum = 1;
}

function fault() {
  if (G.serveNum === 1) { G.serveNum = 2; voice('fault'); G.phase = 'over'; G.overT = 1.4; sendBoy(); }
  else pointTo(other(score.server), 'double_fault');
}

export function inCourt(x, z) { return Math.abs(x) <= COURT.W / 2 + 0.02 && z >= -0.02 && z <= COURT.L + 0.02; }
export function inServeBox(x, z) {
  const toFar = score.server === 'P';
  const xOK = deuceSide() ? (toFar ? x <= 0.02 : x >= -0.02) : (toFar ? x >= -0.02 : x <= 0.02);
  const zOK = toFar ? (z >= COURT.svcFar - 0.02 && z <= COURT.netZ) : (z >= COURT.netZ && z <= COURT.svcNear + 0.02);
  return xOK && Math.abs(x) <= COURT.W / 2 + 0.02 && zOK;
}

function onBounce() {
  ball.bounces++;
  pock(0.35, 500);
  if (ball.bounces === 1) {
    ball.firstLand = { x: ball.x, z: ball.z };
    const wasServe = G.wasServe; G.wasServe = false;
    if (wasServe) {
      if (!inServeBox(ball.x, ball.z)) { ball.active = false; fault(); }
      return;
    }
    // must land on the side opposite the hitter
    const okSide = ball.lastHit === 'P' ? ball.z < COURT.netZ : ball.z > COURT.netZ;
    if (!inCourt(ball.x, ball.z) || !okSide) {
      ball.active = false; pointTo(other(ball.lastHit), 'out');
    }
  } else if (ball.bounces === 2) {
    ball.active = false; pointTo(ball.lastHit, null);
  }
}

// -------------------------------------------------------------- movement ----
// Where should a player run to? Simulate the ball forward and take the first point in
// their half at hitting height that they can actually REACH IN TIME; otherwise chase the
// deepest hittable point. This is the "every ball is catchable, timing is the skill" contract.
function intercept(side) {
  const ch = side === 'O' ? O : P;
  const spd = side === 'O' ? TUNE.aiSpeed : TUNE.playerSpeed * TUNE.autoAssist;
  let { x, y, z, vx, vy, vz } = ball;
  const g = ball.g || TUNE.gravity, dt = 0.01;
  const inZone = side === 'O' ? zz => zz <= ZONE_DEPTH : zz => zz >= COURT.L - ZONE_DEPTH;
  const home = HOME[side];
  let fallback = null, deepest = null;
  for (let i = 0; i < 300; i++) {
    vy -= g * dt; x += vx * dt; y += vy * dt; z += vz * dt;
    if (y <= 0 && vy < 0) { y = 0; vy = -vy * TUNE.bounceY; vx *= TUNE.bounceXZ; vz *= TUNE.bounceXZ; }
    if (i > 5 && inZone(z) && y < 1.6 && y > 0.3) {
      const pt = { x, z: side === 'O' ? Math.max(0.8, z) : Math.min(24.5, z) };
      const reachable = Math.hypot(pt.x - ch.x, pt.z - ch.z) / spd <= i * dt;
      if (y > 0.7 && reachable) return pt;          // waist-high AND arrivable in time
      if (reachable && !fallback) fallback = pt;    // low but arrivable
      deepest = pt;                                 // last resort: run at the deepest hittable point
    }
  }
  return fallback || deepest || home;
}

function trySwing(ch, isAI) {
  // Contact happens if the ball is inside reach while the swing window is open.
  const reach = isAI ? TUNE.aiReach : TUNE.reach;
  const t = ch.swingT;
  if (t < TUNE.swingWindup || t > TUNE.swingWindup + TUNE.swingWindow) return;
  if (!ball.active || G.phase !== 'rally') return;
  if (ball.lastHit === ch.side) return;
  const dx = ball.x - ch.x, dz = ball.z - ch.z;
  if (Math.hypot(dx, dz * 0.8) > reach || ball.y > CONTACT.maxY) return;
  if (ball.y < CONTACT.minY) return; // below the ankles the ball is past you — no grass-scraping saves
  // quality: how centered in the window the contact lands
  const center = TUNE.swingWindup + TUNE.swingWindow / 2;
  const off = Math.abs(t - center) / (TUNE.swingWindow / 2);
  let q = Math.max(0.05, 1 - off);
  if (Math.abs(t - center) * 1000 < TUNE.perfectMs) q = 1;
  ch.facing = dx >= 0 ? 1 : -1; // forehand right (righty), backhand left → mirrored sprite
  const flick = isAI ? null : takeFlickAim();
  const aim = isAI
    ? { ax: [ -1, 0, 1 ][Math.floor(Math.random() * 3)], az: Math.random() < 0.25 ? -1 : 0 }
    : flick || { ax: axisX(), az: axisZ() * (ch.side === 'P' ? 1 : -1) };
  if (isAI) q = Math.min(q, TUNE.aiQualityMin + Math.random() * (TUNE.aiQualityMax - TUNE.aiQualityMin));
  doHit(ch, q, aim);
  ch.swingT = -1;
}

export function keyPressed(code) {
  if (code !== 'Space') return;
  audio(); // unlock on first gesture
  if (G.phase === 'pretoss' && score.server === 'P') { tossBall(P); return; }
  if (G.phase === 'toss' && score.server === 'P') {
    // serve timing: distance from apex = quality
    const dy = Math.abs(ball.y - serveApexY());
    if (ball.y < 2.0) return; // too low, let it drop (re-toss)
    let q = Math.max(0.05, 1 - dy / 0.9);
    if (dy < 0.12) q = 1;
    G.wasServe = true;
    hitServe(P, q);
    return;
  }
  if (G.phase === 'rally' && P.swingT < 0) { P.swingT = 0; P.pose = 'swing'; P.poseT = 0; }
}

function expirePose(ch, dt) {
  if (ch.pose === 'swing' || ch.pose === 'serve') { ch.poseT += dt; if (ch.poseT > POSE_TIME) ch.pose = 'idle'; }
}

// ---------------------------------------------------------------- update ----
export function update(dt) {
  if (G.hitstop > 0) { G.hitstop -= dt; return; }
  if (G.flash) { G.flash.t -= dt; if (G.flash.t <= 0) G.flash = null; }
  crowd.cheer = Math.max(0, crowd.cheer - dt);
  G.idleT += dt;
  const w = BOUNCE_IDLE.tempo;
  if (G.phase === 'pretoss' && Math.sin(G.idleT * w) * Math.sin((G.idleT - dt) * w) < 0) pock(0.12, 420); // ball bounce
  if (G.phase === 'toss') { const sv = score.server === 'P' ? P : O; sv.pose = 'serve'; sv.poseT = 0; }

  // --- player movement (near half only, generous margins)
  if (G.phase === 'rally') {
    const slow = P.swingT >= 0 ? 0.35 : 1;
    const mx = axisX(), mz = axisZ();
    P.x += mx * TUNE.playerSpeed * slow * dt;
    P.z += mz * TUNE.playerSpeed * slow * dt;
    let assist = 0;
    if (!mx && !mz && TUNE.autoAssist > 0 && ball.active) {
      const chasing = ball.lastHit === 'O';
      // no `slow` here: tapping must not freeze your legs, or anticipating a shot loses it
      const rate = TUNE.playerSpeed * TUNE.autoAssist * dt * (chasing ? 1 : 0.55);
      const tgt = chasing ? intercept('P') : HOME.P; // run to the ball, then recover home
      const dx = tgt.x - P.x, dz = tgt.z - P.z, d = Math.hypot(dx, dz);
      if (d > 0.35) { // deadzone: stand ready near the spot instead of dithering over it
        P.x += dx / d * Math.min(rate, d);
        P.z += dz / d * Math.min(rate, d);
        assist = dx;
      }
    }
    P.x = Math.max(-P_BOUNDS.x, Math.min(P_BOUNDS.x, P.x));
    P.z = Math.max(P_BOUNDS.zMin, Math.min(P_BOUNDS.zMax, P.z));
    const moving = mx || mz || assist !== 0;
    P.runT += moving ? dt : 0;
    if (P.pose !== 'swing' && P.pose !== 'serve') P.pose = moving ? 'run' : 'idle';
    if (mx) P.facing = mx > 0 ? 1 : -1;
    else if (Math.abs(assist) > 0.25) P.facing = assist > 0 ? 1 : -1; // hysteresis: small corrections don't flip facing
  }
  if (P.swingT >= 0) {
    P.swingT += dt; trySwing(P, false); // a contact resets swingT to -1 inside trySwing
    if (P.swingT > TUNE.swingWindup + TUNE.swingWindow + 0.02) { P.swingT = -1; if (G.phase === 'rally') swish(); }
  }
  expirePose(P, dt);

  // --- AI
  if (score.server === 'O' && G.phase === 'pretoss') {
    G.aiServeT -= dt;
    if (G.aiServeT <= 0) tossBall(O);
  } else if (score.server === 'O' && G.phase === 'toss') {
    if (ball.vy < 0 && ball.y < serveApexY() - 0.1) { G.wasServe = true; hitServe(O, 0.6 + Math.random() * 0.35); }
  }
  if (G.phase === 'rally') {
    G.aiReactT += dt;
    const incoming = ball.active && ball.lastHit === 'P' && G.aiReactT >= TUNE.aiReaction;
    const tgt = incoming ? intercept('O') : HOME.O;
    const spd = TUNE.aiSpeed * (incoming ? 1 : 0.5); // slow recovery: wrong-footing wins points
    const dx = tgt.x - O.x, dz = tgt.z - O.z, d = Math.hypot(dx, dz);
    if (d > 0.1) {
      O.x += dx / d * Math.min(spd * dt, d);
      O.z += dz / d * Math.min(spd * dt, d);
      O.pose = O.pose === 'swing' ? 'swing' : 'run'; O.runT += dt;
      if (Math.abs(dx) > 0.25) O.facing = dx > 0 ? 1 : -1;
    } else if (O.pose === 'run') O.pose = 'idle';
    G.aiSwingCool -= dt;
    if (incoming && G.aiSwingCool <= 0 && O.swingT < 0) {
      // same radius trySwing uses for contact, so an armed swing actually connects
      const near = Math.hypot(ball.x - O.x, (ball.z - O.z) * 0.8) < TUNE.aiReach
        && ball.y < CONTACT.maxY && ball.y > CONTACT.minY && ball.vz < 0;
      if (near) {
        if (Math.random() < TUNE.aiFlub) G.aiSwingCool = 0.5; // whiff: hesitates and misses
        else {
          O.swingT = TUNE.swingWindup + TUNE.swingWindow / 2;
          trySwing(O, true); O.swingT = -1;
          G.aiSwingCool = ball.lastHit === 'O' ? 0.4 : 0.12;
        }
      }
    }
  }
  expirePose(O, dt);

  // --- ball physics
  if (ball.active) {
    ball.vy -= (ball.g || TUNE.gravity) * dt;
    const oldZ = ball.z;
    ball.x += ball.vx * dt; ball.y += ball.vy * dt; ball.z += ball.vz * dt;
    // net: plane at netZ, only during rally flight
    if (G.phase === 'rally' && (oldZ - COURT.netZ) * (ball.z - COURT.netZ) < 0 && Math.abs(ball.x) < COURT.netW / 2) {
      const tCross = (COURT.netZ - oldZ) / (ball.z - oldZ);
      const yAt = ball.y - ball.vy * dt * (1 - tCross); // approx height at crossing
      if (yAt < COURT.netH) {
        ball.z = COURT.netZ + (oldZ < COURT.netZ ? -0.05 : 0.05);
        ball.vz *= -0.08; ball.vx *= 0.3; ball.vy = Math.min(ball.vy, 0);
        pock(0.4, 300);
      }
    }
    if (ball.y <= 0 && ball.vy < 0) {
      ball.y = 0; ball.vy = -ball.vy * TUNE.bounceY;
      ball.vx *= TUNE.bounceXZ; ball.vz *= TUNE.bounceXZ;
      onBounce();
      if (ball.active && Math.abs(ball.vy) < 0.8) { // rolled out — dead ball
        ball.active = false;
        if (ball.bounces === 1) pointTo(ball.lastHit, null);
      }
    }
    if (G.phase === 'toss' && ball.y <= 1.4 && ball.vy < 0) { // uncaught toss → retoss
      ball.active = false; G.phase = 'pretoss';
      if (score.server === 'O') G.aiServeT = 0.8;
    }
  }

  // ball boy: sprint across, scoop the ball in passing, despawn off the far side
  const boy = G.boy;
  if (boy) {
    boy.x += boy.dir * 7.5 * dt; boy.runT += dt;
    if (!ball.collected && !ball.active) {
      const dz = ball.z - boy.z;
      boy.z += Math.sign(dz) * Math.min(Math.abs(dz), 3 * dt); // track the rolling ball a little
      if (Math.abs(boy.x - ball.x) < 0.4 && Math.abs(dz) < 1.2) ball.collected = true;
    }
    if (Math.abs(boy.x) > 13.5) G.boy = null;
  }
  if (G.outMarker && (G.outMarker.t -= dt) <= 0) G.outMarker = null;

  if (G.phase === 'over') { G.overT -= dt; if (G.overT <= 0) setupPoint(); }
}