#!/usr/bin/env node

/**
 * A stand-in for the SteelSeries GameSense server.
 *
 * It speaks enough of the real API to exercise the client, and it resolves the
 * bound handlers against each incoming frame to render the keyboard as ANSI
 * colour in the terminal. That makes the lighting logic verifiable without an
 * Apex 7 (or Windows) in front of you.
 *
 *   npm run stub -- --port 51000
 *   node bin/apex7-scale.js --address 127.0.0.1:51000 --root D --scale dorian
 */

import http from 'http';

import { errorMessage } from '../src/errors';
import { HID } from '../src/hid';
import type { Frame, Handler, Rgb } from '../src/protocol';

const args = process.argv.slice(2);
const portArg = args.indexOf('--port');
const PORT = portArg >= 0 ? Number(args[portArg + 1]) : 51000;
const QUIET = args.includes('--quiet');
const ONCE = args.includes('--once'); // exit after the first rendered frame

/** A printable key, or a gap in the row. */
type Cell = readonly [label: string, hid: number] | null;

const LAYOUT: readonly (readonly Cell[])[] = [
  [['esc', HID.escape], null, ['f1', HID.f1], ['f2', HID.f2], ['f3', HID.f3], ['f4', HID.f4], null,
   ['f5', HID.f5], ['f6', HID.f6], ['f7', HID.f7], ['f8', HID.f8], null,
   ['f9', HID.f9], ['f10', HID.f10], ['f11', HID.f11], ['f12', HID.f12], null,
   ['prt', HID.printScreen], ['scr', HID.scrollLock], ['brk', HID.pause]],

  [['`', HID.backquote], ['1', HID[1]], ['2', HID[2]], ['3', HID[3]], ['4', HID[4]],
   ['5', HID[5]], ['6', HID[6]], ['7', HID[7]], ['8', HID[8]], ['9', HID[9]],
   ['0', HID[0]], ['-', HID.minus], ['=', HID.equal], ['bsp', HID.backspace], null,
   ['ins', HID.insert], ['hom', HID.home], ['pup', HID.pageUp], null,
   ['num', HID.numLock], ['/', HID.numpadDivide], ['*', HID.numpadMultiply], ['-', HID.numpadSubtract]],

  [['tab', HID.tab], ['q', HID.q], ['w', HID.w], ['e', HID.e], ['r', HID.r], ['t', HID.t],
   ['y', HID.y], ['u', HID.u], ['i', HID.i], ['o', HID.o], ['p', HID.p],
   ['[', HID.bracketLeft], [']', HID.bracketRight], ['\\', HID.backslash], null,
   ['del', HID.delete], ['end', HID.end], ['pdn', HID.pageDown], null,
   ['7', HID.numpad7], ['8', HID.numpad8], ['9', HID.numpad9], ['+', HID.numpadAdd]],

  [['cap', HID.capsLock], ['a', HID.a], ['s', HID.s], ['d', HID.d], ['f', HID.f], ['g', HID.g],
   ['h', HID.h], ['j', HID.j], ['k', HID.k], ['l', HID.l], [';', HID.semicolon],
   ["'", HID.quote], ['ent', HID.enter], null, null, null, null, null, null,
   ['4', HID.numpad4], ['5', HID.numpad5], ['6', HID.numpad6]],

  [['sft', HID.shiftLeft], ['z', HID.z], ['x', HID.x], ['c', HID.c], ['v', HID.v], ['b', HID.b],
   ['n', HID.n], ['m', HID.m], [',', HID.comma], ['.', HID.period], ['/', HID.slash],
   ['sft', HID.shiftRight], null, null, null, null, ['up', HID.arrowUp], null, null,
   ['1', HID.numpad1], ['2', HID.numpad2], ['3', HID.numpad3], ['ent', HID.numpadEnter]],

  [['ctl', HID.controlLeft], ['win', HID.metaLeft], ['alt', HID.altLeft],
   ['spc', HID.space], ['alt', HID.altRight], ['win', HID.metaRight],
   ['men', HID.application], ['ctl', HID.controlRight], null, null, null, null, null,
   ['lft', HID.arrowLeft], ['dn', HID.arrowDown], ['rgt', HID.arrowRight], null,
   ['0', HID.numpad0], ['.', HID.numpadDecimal]],
];

interface GameEntry {
  metadata: unknown;
  events: Map<string, readonly Handler[]>;
}

const state = {
  games: new Map<string, GameEntry>(),
  lastColors: new Map<number, Rgb>(),
};

/**
 * Request bodies are whatever the client POSTs. This stub only ever talks to
 * our own client on localhost, so it reads the fields it cares about rather
 * than validating the whole shape.
 */
interface GameSenseRequest {
  game?: string;
  event?: string;
  handlers?: readonly Handler[];
  data?: { value?: number; frame?: Frame };
  game_display_name?: string;
  developer?: string;
}

function cell(label: string, color: Rgb | undefined): string {
  const text = ` ${String(label).slice(0, 3).padEnd(3)} `;
  if (!color) return `\x1b[2m${text}\x1b[0m`;
  const { red, green, blue } = color;
  // Relative luminance, to keep the label readable on any background.
  const luma = 0.2126 * red + 0.7152 * green + 0.0722 * blue;
  const fg = luma > 140 ? '30' : '97';
  return `\x1b[48;2;${red};${green};${blue}m\x1b[${fg}m${text}\x1b[0m`;
}

function render(): void {
  const lines = LAYOUT.map((row) =>
    row.map((key) => (key ? cell(key[0], state.lastColors.get(key[1])) : '     ')).join('')
  );
  console.log(`\n${lines.join('\n')}\n`);
}

/** Resolve bound handlers against an incoming frame -> hid => color. */
function applyFrame(handlers: readonly Handler[], frame: Frame): Map<number, Rgb> {
  const colors = new Map<number, Rgb>();
  for (const handler of handlers) {
    if (handler['device-type'] !== 'rgb-per-key-zones') continue;
    if (handler.mode !== 'context-color') continue;

    const color = frame[handler['context-frame-key']];
    if (!color) continue;

    for (const hid of handler['custom-zone-keys'] || []) colors.set(hid, color);
  }
  return colors;
}

function readBody(req: http.IncomingMessage): Promise<GameSenseRequest> {
  return new Promise((resolve, reject) => {
    const chunks: Buffer[] = [];
    req.on('data', (c: Buffer) => chunks.push(c));
    req.on('end', () => {
      const text = Buffer.concat(chunks).toString('utf8');
      try {
        resolve(text ? (JSON.parse(text) as GameSenseRequest) : {});
      } catch (err) {
        reject(err instanceof Error ? err : new Error(String(err)));
      }
    });
    req.on('error', reject);
  });
}

function log(...parts: unknown[]): void {
  if (!QUIET) console.log(...parts);
}

const server = http.createServer((req, res) => {
  const reply = (code: number, payload: unknown): void => {
    res.writeHead(code, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify(payload));
  };

  void (async () => {
    let body: GameSenseRequest;
    try {
      body = await readBody(req);
    } catch (err) {
      reply(400, { error: `bad JSON: ${errorMessage(err)}` });
      return;
    }

    const game = body.game;
    const entry = (name: string): GameEntry => {
      let found = state.games.get(name);
      if (!found) {
        found = { metadata: null, events: new Map() };
        state.games.set(name, found);
      }
      return found;
    };

    switch (req.url) {
      case '/game_metadata':
        if (!game) return reply(400, { error: 'missing game' });
        entry(game).metadata = body;
        log(`[metadata] ${game} "${body.game_display_name}" by ${body.developer}`);
        return reply(200, { game });

      case '/bind_game_event': {
        if (!game || !body.event) return reply(400, { error: 'missing game or event' });
        const handlers = body.handlers || [];
        entry(game).events.set(body.event, handlers);
        const zoneKeys = handlers.reduce(
          (n, h) => n + (h['custom-zone-keys'] || []).length,
          0
        );
        log(
          `[bind]     ${game}/${body.event}: ${handlers.length} handlers, ${zoneKeys} keys addressed`
        );
        return reply(200, { game, event: body.event });
      }

      case '/game_event': {
        const known = game !== undefined ? state.games.get(game) : undefined;
        const handlers = known && body.event ? known.events.get(body.event) : undefined;
        if (!handlers) return reply(404, { error: `no handler for ${game}/${body.event}` });

        const frame = body.data?.frame ?? {};
        const missing = handlers
          .filter((h) => h.mode === 'context-color' && !(h['context-frame-key'] in frame))
          .map((h) => h['context-frame-key']);
        if (missing.length) {
          log(`[warn]     frame is missing keys: ${missing.join(', ')}`);
        }

        state.lastColors = applyFrame(handlers, frame);
        log(`[event]    ${game}/${body.event} value=${body.data?.value}`);
        render();
        if (ONCE) setTimeout(() => process.exit(0), 50);
        return reply(200, { game, event: body.event });
      }

      case '/game_heartbeat':
        log(`[heartbeat] ${game}`);
        return reply(200, { game });

      case '/remove_game':
        if (game !== undefined) state.games.delete(game);
        state.lastColors = new Map();
        log(`[remove]   ${game}`);
        return reply(200, { game });

      default:
        return reply(404, { error: `unhandled endpoint ${req.url}` });
    }
  })();
});

server.listen(PORT, '127.0.0.1', () => {
  console.log(`fake GameSense server on 127.0.0.1:${PORT}`);
  console.log(`  GAMESENSE_ADDRESS=127.0.0.1:${PORT} node bin/apex7-scale.js --root C --scale major\n`);
});