"""Era rollups: per-month "what was happening" digests (consolidation step 3).

Groups session gists by the calendar month the session occurred (from real
exchange timestamps) and map-reduces each month into one digest. These are the
temporal memory tier — they answer "what was going on last December" and feed
the narrative engine. Runs on the consolidation backend (MI50 in steady state).
"""
from __future__ import annotations


from lyra import config, llm, logbus, memory
from lyra.llm import Backend, Message

BATCH_CHARS = 18000

_PROMPT = """You are writing a monthly memory digest about Brian from the session \
summaries below (all from the same month). Capture: what he was focused on (poker \
and otherwise), notable events/results/decisions, recurring themes, and his mood \
and arc across the month. Third person, referring to him as "Brian". 5-10 \
sentences. This is a memory record, not a reply. No preamble."""

_MERGE_PROMPT = """Merge these partial monthly digests (same month) into one \
coherent digest about Brian for that month. Keep it tight, 5-10 sentences, no \
repetition. Third person."""


def _batch_texts(texts: list[str], budget: int) -> list[str]:
    blocks, buf, size = [], [], 0
    for t in texts:
        if size + len(t) > budget and buf:
            blocks.append("\n\n".join(buf))
            buf, size = [], 0
        buf.append(t)
        size += len(t)
    if buf:
        blocks.append("\n\n".join(buf))
    return blocks


def _call(prompt: str, body: str, backend: Backend) -> str:
    messages: list[Message] = [
        {"role": "system", "content": prompt},
        {"role": "user", "content": body},
    ]
    return llm.complete(messages, backend=backend)


def _digest_month(gists: list[str], backend: Backend) -> str:
    """Map-reduce a month's session gists into one digest."""
    blocks = _batch_texts(gists, BATCH_CHARS)
    partials = [_call(_PROMPT, b, backend) for b in blocks]
    while len(partials) > 1:
        partials = [_call(_MERGE_PROMPT, g, backend) for g in _batch_texts(partials, BATCH_CHARS)]
    return partials[0]


def rebuild_eras(backend: Backend | None = None) -> dict:
    """(Re)build a digest for every month that has session gists."""
    backend = backend or config.load().summary_backend
    by_month = memory.summaries_by_month()
    months = 0
    for month in sorted(by_month):
        digest = _digest_month(by_month[month], backend)
        memory.store_era(month, digest, len(by_month[month]))
        months += 1
        logbus.log("info", "era built", month=month, sessions=len(by_month[month]))
    report = {"months": months}
    logbus.log("info", "eras complete", **report)
    return report


def main() -> int:
    report = rebuild_eras()
    if not report["months"]:
        print("No summaries yet — run lyra-summarize first.")
        return 1
    for era in memory.list_eras():
        print(f"\n## {era.month}  ({era.session_count} sessions)\n{era.content}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())