import { db } from '../db.js';

function todayISO() {
  return new Date().toISOString().slice(0, 10);
}

function goalProgress(goal) {
  let current = 0;
  if (goal.kind === 'session_count') {
    current = goal.scope === 'overall'
      ? db.prepare('SELECT COUNT(*) AS n FROM entries').get().n
      : db.prepare('SELECT COUNT(*) AS n FROM entries WHERE category_id = ?').get(goal.category_id).n;
  } else if (goal.kind === 'metric_best' && goal.metric_id) {
    current = db.prepare('SELECT COALESCE(MAX(value), 0) AS v FROM entry_values WHERE metric_id = ?')
      .get(goal.metric_id).v;
  } else if (goal.kind === 'metric_total' && goal.metric_id) {
    current = db.prepare('SELECT COALESCE(SUM(value), 0) AS v FROM entry_values WHERE metric_id = ?')
      .get(goal.metric_id).v;
  }
  const pct = goal.target > 0 ? Math.min(100, Math.round((current / goal.target) * 100)) : 0;
  return { ...goal, current, pct };
}

function streaks(days) {
  // days: ISO strings sorted ascending, distinct
  if (!days.length) return { current: 0, longest: 0 };
  const set = new Set(days);
  let longest = 0;
  for (const d of days) {
    const prev = new Date(d); prev.setDate(prev.getDate() - 1);
    if (!set.has(prev.toISOString().slice(0, 10))) {
      // start of a run
      let len = 0; const cur = new Date(d);
      while (set.has(cur.toISOString().slice(0, 10))) { len++; cur.setDate(cur.getDate() + 1); }
      if (len > longest) longest = len;
    }
  }
  // current streak ending today or yesterday
  let current = 0; const cur = new Date(todayISO());
  if (!set.has(cur.toISOString().slice(0, 10))) cur.setDate(cur.getDate() - 1);
  while (set.has(cur.toISOString().slice(0, 10))) { current++; cur.setDate(cur.getDate() - 1); }
  return { current, longest };
}

export default async function statsRoutes(app) {
  app.get('/api/stats', async () => {
    const totalSessions = db.prepare('SELECT COUNT(*) AS n FROM entries').get().n;
    const dayRows = db.prepare('SELECT DISTINCT day FROM entries ORDER BY day').all().map((r) => r.day);
    const totalDays = dayRows.length;

    // Heatmap: entries per day.
    const heatmap = db.prepare(
      'SELECT day, COUNT(*) AS count FROM entries GROUP BY day ORDER BY day'
    ).all();

    // Radar: sessions per category (all-time + last 30 days).
    const since = new Date(); since.setDate(since.getDate() - 30);
    const since30 = since.toISOString().slice(0, 10);
    const radar = db.prepare(
      `SELECT c.id AS category_id, c.name, c.emoji, c.color,
              COUNT(e.id) AS sessions,
              SUM(CASE WHEN e.day >= ? THEN 1 ELSE 0 END) AS sessions30
         FROM categories c LEFT JOIN entries e ON e.category_id = c.id
        WHERE c.archived = 0
        GROUP BY c.id ORDER BY c.sort_order, c.id`
    ).all(since30);

    // Per-metric time series for line charts.
    const seriesRows = db.prepare(
      `SELECT ev.metric_id, e.day, ev.value, e.id AS entry_id
         FROM entry_values ev JOIN entries e ON e.id = ev.entry_id
        ORDER BY e.day, e.id`
    ).all();
    const series = {};
    for (const r of seriesRows) {
      (series[r.metric_id] ||= []).push({ day: r.day, value: r.value, entry_id: r.entry_id });
    }

    const goals = db.prepare('SELECT * FROM goals ORDER BY is_main DESC, sort_order, id').all()
      .map(goalProgress);

    return {
      totalSessions,
      totalDays,
      ...streaks(dayRows),
      today: todayISO(),
      heatmap,
      radar,
      series,
      goals,
    };
  });
}