/**
 * @file Per-hour token usage (`token_usage_hourly`): written from a Claude
 * transcript's `tokensByHour` (`server/lib/transcript-cache.js`) by the hook
 * writer, back-filled once for sessions recorded before the table existed, and
 * read only by the daily cost split in `GET /api/pricing/cost` — so a session
 * that runs for days books each day's spend to that day instead of its start.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const { db, stmts } = require("../db");
const TranscriptCache = require("./transcript-cache");

/** Write every hour of one transcript parse (MAX per hour, see the statement). */
function writeHourly(sessionId, tokensByHour) {
  // ponytail: rewrites every hour of the session on each hook — ~1 row per
  // active hour per model, cheap; write only the newest hours if it ever shows.
  for (const t of Object.values(tokensByHour || {})) {
    stmts.upsertHourlyUsage.run(
      sessionId,
      t.hour,
      t.model,
      t.speed,
      t.geo,
      t.tier,
      t.input,
      t.output,
      t.cacheRead,
      t.cacheWrite,
      t.cacheWrite1h,
      t.webSearch,
      t.webFetch,
      t.codeExec
    );
  }
}

/**
 * Fill the table for Claude sessions that have tokens but no hourly rows yet,
 * one transcript per tick so a large history never blocks the event loop.
 * Resolves with the number of sessions written.
 */
function backfillHourly() {
  const rows = db
    .prepare(
      `SELECT s.id, s.transcript_path FROM sessions s
       WHERE s.transcript_path IS NOT NULL AND s.transcript_path != ''
         AND EXISTS (SELECT 1 FROM token_usage tu WHERE tu.session_id = s.id)
         AND NOT EXISTS (SELECT 1 FROM token_usage_hourly h WHERE h.session_id = s.id)`
    )
    .all();
  const cache = new TranscriptCache(1);
  let written = 0;
  return new Promise((resolve) => {
    const next = (i) => {
      if (i >= rows.length) return resolve(written);
      const { id, transcript_path } = rows[i];
      try {
        const result = cache.extract(transcript_path);
        if (result?.tokensByHour && Object.keys(result.tokensByHour).length > 0) {
          db.transaction(() => writeHourly(id, result.tokensByHour))();
          written++;
        }
      } catch {
        /* an unreadable transcript keeps its start-date booking */
      }
      setImmediate(() => next(i + 1));
    };
    next(0);
  });
}

module.exports = { writeHourly, backfillHourly };