/**
 * One line of advice, in the player's own words.
 *
 * A pure function of the snapshot the server sent plus two things the client
 * works out from the map it was given: whether you are standing on a site,
 * and whether you are within reach of the spike. Never more than one prompt —
 * the most urgent thing wins, because two instructions at once is none.
 */

/** Within this many units the server lets you pick up, plant or defuse. */
export const REACH = 46;

const secs = (n) => Math.max(0, Math.ceil(n));

/** "Spike defused" the way the log says it, lower-cased to sit mid-sentence. */
export const lower = (text) => String(text).charAt(0).toLowerCase() + String(text).slice(1);

/**
 * How the round just ended, from the viewer's side of it. The server says who
 * took it and why; a person wants to know whether that was them. A viewer
 * with no team (watching) is told the team.
 */
export function roundOutcome(snap) {
  const last = snap && snap.last;
  if (!last) return null;
  const team = snap.me && snap.me.team;
  const title = team ? (last.winner === team ? "Round won" : "Round lost") : `${last.winner} take the round`;
  return { title, why: lower(last.why), winner: last.winner };
}

export function choosePrompt(snap, world = {}) {
  if (!snap) return "";
  const me = snap.me;
  const spike = snap.spike;
  const onSite = world.onSite === true;
  const nearSpike = world.nearSpike === true;
  // The page is played with a mouse and the terminal with keys; one line
  // names the input, so it says the thing the reader can actually do.
  const buyWith = world.input === "keys" ? "Press b and buy a gun you can afford." : "Click a gun you can afford.";

  if (snap.phase === "over")
    return `Match over — ${snap.result ?? "done"} · a new match starts in ${secs(snap.clock)}s`;
  if (me.blind > 0.05) return "You are blind — back off until it clears";
  if (snap.phase === "end") {
    const outcome = roundOutcome(snap);
    const next = `next round in ${secs(snap.clock)}s`;
    return outcome ? `${outcome.title} — ${outcome.why} · ${next}` : `Round over · ${next}`;
  }
  if (!me.alive)
    return snap.phase === "buy"
      ? "Buy phase — you are back next round"
      : "Waiting for the next round — you're in it";
  if (snap.phase === "buy") {
    const side = me.side === "atk" ? "You attack: plant the spike on A or B." : "You defend: hold A and B.";
    return `Buy phase — ${secs(snap.clock)}s left. ${side} ${buyWith}`;
  }

  if (me.planting > 0) return `Planting — hold F for ${secs(4 - me.planting)}s more`;
  if (spike.planted) {
    if (me.side === "def") {
      if (spike.defuse > 0) return `Defusing — keep holding F, ${secs(7 - spike.defuse)}s`;
      return nearSpike
        ? `Spike down, ${secs(spike.fuse)}s — hold F to defuse`
        : `Spike down, ${secs(spike.fuse)}s — get to it and hold F`;
    }
    return `Spike down, ${secs(spike.fuse)}s — keep them off it`;
  }

  if (me.side === "atk") {
    if (me.spike) return onSite ? "Hold F to plant" : "You have the spike — get to site A or B";
    if (spike.carried) return "Your team has the spike — go with them and take a site";
    if (nearSpike) return "Walk onto the spike to pick it up";
    return "Somebody has to carry the spike — it is on the ground";
  }
  return `Defending — hold A and B, ${secs(snap.clock)}s`;
}