#!/usr/bin/env node
/**
 * answer-picker — a standalone clickable "answer picker" for a running pi agent.
 *
 * Runs in its OWN terminal pane and talks to the pi process over a unix socket.
 * Click a button (or press its number) and the corresponding preset prompt is
 * sent to the agent as a real user message.
 *
 *   usage: answer-picker <socket-path> [--selftest]
 *          PI_ANSWER_PICKER_SOCKET=<path> answer-picker
 *
 * WHY THIS IS A SEPARATE PROCESS
 * Terminal mouse reporting is per-terminal, not per-region: the moment an app
 * enables it, that terminal stops doing native wheel scrolling and click-drag
 * selection, because the wheel is just another button in the protocol. Running
 * the buttons inside pi therefore cost pi's pane its scrollback scrolling. Here
 * the tracking is confined to THIS pane, which has nothing worth scrolling, so
 * pi's pane keeps native scrolling and selection untouched.
 *
 * A second benefit: we render our own alt-screen canvas, so we know exactly
 * which row every button is on. Hit-testing is direct arithmetic instead of
 * trying to locate ourselves inside somebody else's frame.
 *
 * PROTOCOL (newline-delimited JSON, both directions)
 *   pi -> picker  {"t":"hello","nudges":[{"label":"continue"},...],"title":"..."}
 *                 {"t":"state","running":true,"turn":7}
 *   picker -> pi  {"t":"pick","idx":3}
 * The preset list is owned by the pi extension and pushed on connect, so this
 * process holds no copy of it and the two can never disagree.
 *
 * TERMINAL STATE
 * We enter the alt screen, hide the cursor, and enable SGR mouse reporting with
 * all-motion (?1003h) so buttons can highlight on hover. Every one of those is
 * reversed on exit, including on SIGINT/SIGTERM/SIGHUP and on an uncaught
 * exception, so a crash cannot leave the pane in raw mouse mode.
 */

"use strict";

const net = require("node:net");
const os = require("node:os");

// ── terminal control ────────────────────────────────────────────────────────
const ALT_ON = "\x1b[?1049h";
const ALT_OFF = "\x1b[?1049l";
const CURSOR_HIDE = "\x1b[?25l";
const CURSOR_SHOW = "\x1b[?25h";
// 1000=click 1002=button-drag 1003=any-motion (for hover) 1006=SGR encoding
const MOUSE_ON = "\x1b[?1000h\x1b[?1002h\x1b[?1003h\x1b[?1006h";
const MOUSE_OFF = "\x1b[?1003l\x1b[?1002l\x1b[?1000l\x1b[?1006l";
const CLEAR = "\x1b[H\x1b[2J";

const C = {
  reset: "\x1b[0m",
  dim: "\x1b[38;5;244m",
  muted: "\x1b[38;5;245m",
  accent: "\x1b[38;5;208m",
  bold: "\x1b[1m",
  hotFg: "\x1b[1;38;5;16m",
  hotBg: "\x1b[48;5;208m",
  hoverBg: "\x1b[48;5;238m",
  ok: "\x1b[38;5;114m",
  warn: "\x1b[38;5;214m",
};

// Layout geometry. Buttons begin at PILL_ROW0 (1-based screen row) and we own
// the whole canvas, so a click's row maps to a button row by subtraction.
const PILL_ROW0 = 3;
const INDENT = 2;
const GAP = 2;

const SGR_MOUSE = /^\x1b\[<(\d+);(\d+);(\d+)([Mm])$/;

/**
 * Lay presets out into rows of pills, wrapping to the pane width.
 * Returns [{ row, spans:[{start,end,idx}] }] with 1-based inclusive columns.
 * Pure function — exercised by --selftest.
 */
function layout(nudges, width) {
  const usable = Math.max(1, width - 1);
  const rows = [];
  let cur = { row: PILL_ROW0, spans: [], len: INDENT };
  for (let idx = 0; idx < nudges.length; idx++) {
    const text = `[${idx + 1} ${nudges[idx].label}]`;
    const pad = cur.spans.length === 0 ? 0 : GAP;
    if (cur.len + pad + text.length > usable && cur.spans.length > 0) {
      rows.push(cur);
      cur = { row: cur.row + 1, spans: [], len: INDENT };
    }
    // Still too wide on a fresh row: skip it (number key remains available).
    if (INDENT + text.length > usable) continue;
    const start = (cur.spans.length === 0 ? INDENT : cur.len + GAP) + 1;
    cur.len = start - 1 + text.length;
    cur.spans.push({ start, end: start + text.length - 1, idx, text });
  }
  if (cur.spans.length > 0) rows.push(cur);
  return rows;
}

/** Which preset is at 1-based (col,row)? undefined if none. Pure. */
function hit(rows, col, row) {
  for (const r of rows) {
    if (r.row !== row) continue;
    for (const s of r.spans) if (col >= s.start && col <= s.end) return s.idx;
  }
  return undefined;
}

// ── selftest (no TTY required) ───────────────────────────────────────────────
if (process.argv.includes("--selftest")) {
  const nudges = ["continue", "yes", "no", "explain", "tests", "commit"].map((label) => ({ label }));
  let fails = 0;
  const check = (cond, msg) => {
    if (!cond) {
      console.error("FAIL:", msg);
      fails++;
    }
  };
  for (const w of [200, 120, 80, 60, 40, 30, 20, 12, 8]) {
    const rows = layout(nudges, w);
    for (const r of rows) {
      check(r.spans.length > 0, `w=${w} empty row emitted`);
      const last = r.spans[r.spans.length - 1];
      check(last.end <= w, `w=${w} row overflows: end=${last.end}`);
      for (const s of r.spans) {
        check(hit(rows, s.start, r.row) === s.idx, `w=${w} miss at start col ${s.start}`);
        check(hit(rows, s.end, r.row) === s.idx, `w=${w} miss at end col ${s.end}`);
        check(hit(rows, s.start - 1, r.row) !== s.idx, `w=${w} false hit left of ${s.idx}`);
        check(hit(rows, s.end + 1, r.row) !== s.idx, `w=${w} false hit right of ${s.idx}`);
      }
    }
    // no row may claim a column twice
    for (const r of rows) {
      for (let c = 1; c <= w; c++) {
        const owners = r.spans.filter((s) => c >= s.start && c <= s.end);
        check(owners.length <= 1, `w=${w} col ${c} claimed by ${owners.length} pills`);
      }
    }
    check(hit(rows, 1, PILL_ROW0 - 1) === undefined, `w=${w} hit above button rows`);
    check(hit(rows, 1, PILL_ROW0 + 99) === undefined, `w=${w} hit below button rows`);
  }
  // mouse sequence parsing
  const parse = (d) => {
    const m = SGR_MOUSE.exec(d);
    return m ? { b: +m[1], col: +m[2], row: +m[3], press: m[4] === "M" } : undefined;
  };
  check(parse("\x1b[<0;5;3M").press === true, "press not parsed");
  check(parse("\x1b[<0;5;3m").press === false, "release not parsed");
  check(parse("\x1b[<35;5;3M").b === 35, "motion button not parsed");
  check(parse("hello") === undefined, "plain text parsed as mouse");
  console.log(fails === 0 ? "answer-picker selftest: ALL PASS" : `answer-picker selftest: ${fails} FAILURE(S)`);
  process.exit(fails === 0 ? 0 : 1);
}

// ── runtime ─────────────────────────────────────────────────────────────────
const sockPath = process.argv[2] || process.env.PI_ANSWER_PICKER_SOCKET;
if (!sockPath) {
  console.error("answer-picker: no socket path given (argv[1] or PI_ANSWER_PICKER_SOCKET)");
  process.exit(2);
}

let nudges = [];
let title = "answers";
let running = false;
let turn = 0;
let hover;
let flash;
let flashTimer;
let rows = [];
let restored = false;
let connected = false;

const out = (s) => {
  try {
    process.stdout.write(s);
  } catch {}
};

function restore() {
  if (restored) return;
  restored = true;
  out(MOUSE_OFF + CURSOR_SHOW + ALT_OFF);
  try {
    if (process.stdin.isTTY) process.stdin.setRawMode(false);
  } catch {}
}

function bail(code, msg) {
  restore();
  if (msg) process.stderr.write(msg + "\n");
  process.exit(code);
}

function pad(s, n) {
  return s.length >= n ? s : s + " ".repeat(n - s.length);
}

function render() {
  const width = process.stdout.columns || 80;
  rows = layout(nudges, width);

  const status = !connected
    ? `${C.dim}connecting…${C.reset}`
    : running
      ? `${C.warn}● working${C.reset}`
      : `${C.ok}● idle${C.reset}`;
  const head =
    " ".repeat(INDENT) +
    `${C.accent}◈ ${C.bold}${title}${C.reset}` +
    (turn ? `${C.dim} #${turn}${C.reset}` : "") +
    "   " +
    status;

  const lines = [head, ""];
  const maxRow = rows.length ? rows[rows.length - 1].row : PILL_ROW0 - 1;
  for (let r = PILL_ROW0; r <= maxRow; r++) {
    const row = rows.find((x) => x.row === r);
    if (!row) {
      lines.push("");
      continue;
    }
    let line = " ".repeat(INDENT);
    let col = INDENT + 1;
    for (const s of row.spans) {
      if (s.start > col) line += " ".repeat(s.start - col);
      const isFlash = flash === s.idx;
      const isHover = hover === s.idx;
      if (isFlash) line += `${C.hotBg}${C.hotFg}${s.text}${C.reset}`;
      else if (isHover) line += `${C.hoverBg}${C.bold}${s.text}${C.reset}`;
      else {
        const n = String(s.idx + 1);
        const label = s.text.slice(3 + n.length - 1, -1);
        line += `${C.muted}[${C.reset}${C.dim}${n}${C.reset} ${C.accent}${label}${C.reset}${C.muted}]${C.reset}`;
      }
      col = s.end + 1;
    }
    lines.push(line);
  }
  lines.push("");
  lines.push(`${" ".repeat(INDENT)}${C.dim}click · 1-9 · q quit${C.reset}`);

  out(CLEAR + lines.map((l) => pad(l, 0)).join("\r\n"));
}

// ── socket ──────────────────────────────────────────────────────────────────
const sock = net.createConnection(sockPath);
let rx = "";

sock.on("connect", () => {
  connected = true;
  render();
});

sock.on("data", (chunk) => {
  rx += chunk.toString("utf8");
  let nl;
  while ((nl = rx.indexOf("\n")) >= 0) {
    const line = rx.slice(0, nl);
    rx = rx.slice(nl + 1);
    if (!line.trim()) continue;
    let msg;
    try {
      msg = JSON.parse(line);
    } catch {
      continue;
    }
    if (msg.t === "hello") {
      nudges = Array.isArray(msg.nudges) ? msg.nudges : [];
      if (msg.title) title = msg.title;
      if (typeof msg.running === "boolean") running = msg.running;
      if (typeof msg.turn === "number") turn = msg.turn;
      render();
    } else if (msg.t === "state") {
      if (typeof msg.running === "boolean") running = msg.running;
      if (typeof msg.turn === "number") turn = msg.turn;
      render();
    } else if (msg.t === "bye") {
      bail(0);
    }
  }
});

// pi went away (exit or /reload): nothing left to drive, so close the pane.
sock.on("close", () => bail(0));
sock.on("error", (err) => bail(1, `answer-picker: cannot reach pi at ${sockPath}\n${err.message}`));

function pick(idx) {
  if (idx < 0 || idx >= nudges.length) return;
  flash = idx;
  render();
  clearTimeout(flashTimer);
  flashTimer = setTimeout(() => {
    flash = undefined;
    render();
  }, 160);
  try {
    sock.write(JSON.stringify({ t: "pick", idx }) + "\n");
  } catch {}
}

// ── input ───────────────────────────────────────────────────────────────────
if (!process.stdin.isTTY) bail(2, "answer-picker: stdin is not a TTY (run me in a terminal pane)");
process.stdin.setRawMode(true);
process.stdin.resume();

process.stdin.on("data", (buf) => {
  const data = buf.toString("utf8");

  const m = SGR_MOUSE.exec(data);
  if (m) {
    const b = +m[1];
    const col = +m[2];
    const row = +m[3];
    const press = m[4] === "M";
    const idx = hit(rows, col, row);
    // motion (bit 5) with no button: hover only
    if (b & 32 || !press) {
      if (idx !== hover) {
        hover = idx;
        render();
      }
      return;
    }
    if (b & 64) return; // wheel: nothing to scroll here
    if ((b & 3) !== 0) return; // not the left button
    if (idx !== undefined) pick(idx);
    return;
  }

  if (data === "\x03" || data === "q" || data === "\x1b") bail(0); // ctrl+c / q / esc
  const n = data.charCodeAt(0) - 48;
  if (n >= 1 && n <= 9) pick(n - 1);
});

process.stdout.on("resize", render);
for (const sig of ["SIGINT", "SIGTERM", "SIGHUP"]) process.on(sig, () => bail(0));
process.on("uncaughtException", (e) => bail(1, "answer-picker: " + (e && e.message)));
process.on("exit", restore);

out(ALT_ON + CURSOR_HIDE + MOUSE_ON);
render();