frontend/src/engine/traces.ts

// Trace records: the day's surfaced decisions + how the user reacted,
// snapshotted with the fairy/taste/bias state that produced them.
// This is the molt's training data — exported at Night Bloom, appended
// to server/data/traces.jsonl by the daemon.

import { sourceBias } from "./learning";
import type { FairyState, FeedItem, Profile, SurfaceOutcome, Taste } from "./types";

export interface TraceRecord {
  v: 1;
  ts: string;
  event: Pick<FeedItem, "id" | "source" | "say" | "tier" | "decision"> & {
    channel: FeedItem["channel"] | null;
  };
  /** the dials that shaped this decision, at export time */
  fairy: Pick<FairyState, "mischief" | "protectiveness" | "chattiness" | "curiosity" | "energy">;
  taste: Taste;
  sourceBias: number;
  outcome: SurfaceOutcome | null;
}

/** Snapshot the day's feed as training traces. Pure — caller decides when/where to ship. */
export function buildTraces(
  feed: FeedItem[],
  fs: FairyState,
  taste: Taste,
  profile: Profile,
  now: Date = new Date(),
): TraceRecord[] {
  const ts = now.toISOString();
  const fairy = {
    mischief: fs.mischief,
    protectiveness: fs.protectiveness,
    chattiness: fs.chattiness,
    curiosity: fs.curiosity,
    energy: fs.energy,
  };
  return feed.map((e) => ({
    v: 1 as const,
    ts,
    event: {
      id: e.id,
      source: e.source,
      say: e.say,
      tier: e.tier,
      decision: e.decision,
      channel: e.channel ?? null,
    },
    fairy,
    taste,
    sourceBias: sourceBias(profile, e.source),
    outcome: e.outcome ?? null,
  }));
}