Made of little things.

import type { Controller, ControllerFrame } from '../docs/examples/gamepad.js';
import { idleInput, type Driver, type Input } from './physics.js';

export type InputMethod = 'wasd' | 'arrows' | 'controller' | 'touch';
export type LocalPlayer = {
  id: string;
  name: string;
  car: number;
  method: InputMethod;
  controller: number | null;
};
export const inputMethods: Record<InputMethod, string> = {
  wasd: 'WASD', arrows: 'Arrow keys', controller: 'Controller', touch: 'Touch',
};
export const inputHints: Record<InputMethod, string> = {
  wasd: 'WASD drive · Space drift · Left Shift boost · R recover',
  arrows: 'Arrows drive · Enter drift · Right Shift boost · Backspace recover',
  controller: 'Stick steer · RT / LT gas / brake · B / ○ drift · X / □ boost · Y / △ recover',
  touch: 'Steering + pedals · hold Boost · Recover at the top',
};
export function keyboardDriving(keys: Set<string>, method: InputMethod, solo = false): Input {
  const input = idleInput();
  if (method !== 'wasd' && method !== 'arrows') return input;
  const wasd = method === 'wasd' || solo, arrows = method === 'arrows' || solo;
  const down = (a: string, b: string) => (wasd && keys.has(a)) || (arrows && keys.has(b));
  input.throttle = Number(down('KeyW', 'ArrowUp')) - Number(down('KeyS', 'ArrowDown'));
  input.steer = Number(down('KeyA', 'ArrowLeft')) - Number(down('KeyD', 'ArrowRight'));
  input.brake = down('Space', 'Enter') || (wasd && keys.has('ControlLeft')) || (arrows && keys.has('ControlRight'));
  input.boost = down('ShiftLeft', 'ShiftRight');
  return input;
}
export function controllerDriving(pad?: Controller): Input {
  if (!pad?.mapped) return idleInput();
  const a = pad.actions;
  return {
    throttle: (a.gas?.value || 0) - (a.serviceBrake?.value || 0),
    steer: a.steer?.value || 0,
    brake: !!a.drift?.down,
    boost: !!a.boost?.down,
    reset: false,
  };
}
// Browser indices can have gaps. A disconnected/replaced slot requires a new
// button edge before it controls its previous player's car again.
export function assignControllers(players: LocalPlayer[], frame: Pick<ControllerFrame, 'players' | 'disconnected'>) {
  const lost: string[] = [], joined: string[] = [];
  for (const player of players) {
    if (player.controller !== null && frame.disconnected.includes(player.controller)) {
      player.controller = null;
      lost.push(player.id);
    }
  }
  for (const pad of frame.players) {
    if (!pad.mapped || !pad.actions.confirm?.pressed || players.some(p => p.controller === pad.index)) continue;
    const waiting = players.find(p => p.method === 'controller' && p.controller === null);
    if (waiting) {
      waiting.controller = pad.index;
      joined.push(waiting.id);
    }
  }
  return { lost, joined };
}
export function localRoster(players: LocalPlayer[], count: number): Driver[] {
  const roster: Driver[] = players.map(p => ({ id: p.id, name: p.name, car: p.car, ai: false }));
  const names = ['Pip', 'Mochi', 'Rivet', 'Nori', 'Bolt'];
  for (let i = roster.length; i < Math.max(players.length, count); i++) {
    roster.push({ id: `ai-${i}`, name: names[i - players.length], car: (i + players[0].car) % 4, ai: true });
  }
  return roster;
}