"""Export an agent run as a portable, shareable trace (Sharing is Caring).

The activity bus (``server/events.py``) groups every event from one agent run
under a ``run_scope`` id. This module serializes such a run into a small,
self-contained JSON envelope that a user can download and (optionally) publish to
the Hugging Face Hub with ``training/share_trace.py``.

Privacy: the bus is structural by design — every ``emit(...)`` carries counts +
short status strings, never event titles or raw thread text. The *only* free-text
that can carry personal data is the chat-name suffix in the ingest message
(``app.py``: ``"N msg(s) from {chats}"``). With ``redact=True`` (the default) that
tail is dropped. Steps use a fixed key allowlist, so a future payload key can't
silently leak into a shared trace.
"""
from __future__ import annotations

import json
import os
import re
import tempfile
from datetime import datetime

from . import events as bus

TRACE_SCHEMA = "imessage-cal-trace"
TRACE_SCHEMA_VERSION = 1

# Only these keys ever appear in an exported step (allowlist, not denylist).
_STEP_KEYS = ("stage", "level", "ts", "latency_ms", "events", "conflicts", "images", "tokens")


def _scrub_message(stage: str, message: str, redact: bool) -> str:
    """All bus messages are structural except the ingest one, which appends
    ``" from {chats}"`` (chat names — PII). Drop that tail when redacting."""
    if redact and stage == "ingest":
        # "3 msg(s) from 3rd grade chat" -> "3 msg(s)"
        return re.sub(r"\s+from\s+.*$", "", message)
    return message


def _step(ev: dict, redact: bool) -> dict:
    step = {k: ev[k] for k in _STEP_KEYS if k in ev}
    step["message"] = _scrub_message(ev.get("stage", ""), ev.get("message", ""), redact)
    return step


def export_run(run_id: str | None = None, redact: bool = True) -> dict:
    """Serialize one agent run (newest by default) into a shareable envelope.

    Returns a valid empty envelope (``steps == []``) when there is no matching
    run, so callers don't need to handle exceptions.
    """
    runs = bus.recent_runs(n=50)  # newest first
    evs: list[dict] = []
    rid = run_id
    if run_id is None:
        if runs:
            rid, evs = runs[0]
    else:
        for r, e in runs:
            if r == run_id:
                evs = e
                break

    steps = [_step(e, redact) for e in evs]
    summary = {
        "steps": len(steps),
        "events": sum(s.get("events", 0) for s in steps),
        "conflicts": sum(s.get("conflicts", 0) for s in steps),
        "images": sum(s.get("images", 0) for s in steps),
        "model_calls": sum(1 for s in steps if s.get("latency_ms") is not None),
        "total_latency_ms": sum(s.get("latency_ms", 0) for s in steps),
    }
    return {
        "schema": TRACE_SCHEMA,
        "version": TRACE_SCHEMA_VERSION,
        "exported_at": datetime.now().isoformat(timespec="seconds"),
        "run_id": rid,
        # run ids look like "12:analyze" — the label is the part after ":".
        "run_label": (rid.split(":", 1)[1] if rid and ":" in rid else None),
        "redacted": redact,
        "steps": steps,
        "summary": summary,
    }


def write_trace(trace: dict, path: str | None = None) -> str:
    """Write a trace envelope to a JSON file and return the path (Gradio download).

    Mirrors ``calendar_out.ics.write_ics``. Deliberately does NOT emit a bus event
    — that would mutate the very run being exported.
    """
    if path is None:
        fd, path = tempfile.mkstemp(suffix=".json", prefix="trace_")
        os.close(fd)
    with open(path, "w", encoding="utf-8") as f:
        json.dump(trace, f, indent=2, ensure_ascii=False)
    return path