/**
 * Line shopping — for each unique prop (game/player/stat), find the best
 * line per side across books.
 *
 * Best Over = lowest line + best odds at that line.
 * Best Under = highest line + best odds at that line.
 *
 * We also flag "outlier" books — a book that's 1+ points off the median.
 */

function propKey(p) {
  return `${p.game_id}|${p.player_id ?? p.player_name}|${p.stat_type}`;
}

function americanToImplied(odds) {
  if (typeof odds !== 'number' || !Number.isFinite(odds)) return null;
  return odds > 0 ? 100 / (odds + 100) : -odds / (-odds + 100);
}

function median(values) {
  if (!values.length) return null;
  const sorted = [...values].sort((a, b) => a - b);
  const mid = Math.floor(sorted.length / 2);
  return sorted.length % 2 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2;
}

function process(props) {
  const grouped = new Map();
  for (const p of props || []) {
    const key = propKey(p);
    if (!grouped.has(key)) grouped.set(key, []);
    grouped.get(key).push(p);
  }

  const out = [];
  for (const [key, rows] of grouped.entries()) {
    if (rows.length === 1) {
      out.push({ ...rows[0], best_over: rows[0], best_under: rows[0], line_outliers: [] });
      continue;
    }
    const lines = rows.map((r) => r.line).filter((n) => typeof n === 'number');
    const med = median(lines);

    const overs = rows.filter((r) => r.odds_over != null);
    const unders = rows.filter((r) => r.odds_under != null);

    // Best Over = lowest line, then best (highest implied prob) odds at that line.
    let bestOver = null;
    for (const r of overs) {
      if (!bestOver) { bestOver = r; continue; }
      if (r.line < bestOver.line) bestOver = r;
      else if (r.line === bestOver.line) {
        const a = americanToImplied(r.odds_over);
        const b = americanToImplied(bestOver.odds_over);
        if (a != null && b != null && a < b) bestOver = r;
      }
    }
    let bestUnder = null;
    for (const r of unders) {
      if (!bestUnder) { bestUnder = r; continue; }
      if (r.line > bestUnder.line) bestUnder = r;
      else if (r.line === bestUnder.line) {
        const a = americanToImplied(r.odds_under);
        const b = americanToImplied(bestUnder.odds_under);
        if (a != null && b != null && a < b) bestUnder = r;
      }
    }

    const outliers = (med != null)
      ? rows.filter((r) => Math.abs(r.line - med) >= 1).map((r) => ({ book: r.book, line: r.line, delta: r.line - med }))
      : [];

    out.push({
      key,
      median_line: med,
      books: rows,
      best_over: bestOver,
      best_under: bestUnder,
      line_outliers: outliers,
    });
  }
  return out;
}

module.exports = { process, americanToImplied };