turnstone/app/services/diagnose/synthesizer.py

"""Stage 5: Summary Synthesizer — deterministic narrative from ranked hypotheses.

Streaming upgrade (async SSE chunks) is tracked as a follow-up enhancement.
This implementation is synchronous to match the rest of the pipeline.
"""
from __future__ import annotations

import logging

from app.context.retriever import RetrievedContext
from app.services.diagnose._llm_client import call_llm
from app.services.diagnose.models import RankedHypothesis, TimelineResult

logger = logging.getLogger(__name__)

_SYSTEM_PROMPT = (
    "You are a Linux sysadmin diagnosing a system incident. "
    "Write a concise, actionable incident diagnosis.\n\n"
    "Format your response exactly as:\n"
    "1. VERDICT: [CRITICAL|ERROR|WARN|INFO] — <what happened> (<X>% confidence)\n"
    "2. TIMELINE: <what the logs show in sequence, 2-3 sentences>\n"
    "3. ROOT CAUSES:\n"
    "   - <hypothesis 1 title> (<confidence>%)\n"
    "   - <hypothesis 2 title> (<confidence>%)\n"
    "4. RECOMMENDED ACTIONS:\n"
    "   - <action based on hypotheses>\n"
    "5. INVESTIGATE FURTHER: <open questions, if any>"
)


def _build_hypothesis_block(ranked: list[RankedHypothesis]) -> str:
    """Build the hypothesis block for the prompt (non-suppressed only, top 3)."""
    active = [rh for rh in ranked if not rh.suppress][:3]
    if not active:
        return "(none)"
    lines: list[str] = []
    for rh in active:
        h = rh.hypothesis
        conf_pct = int(h.confidence * 100)
        novelty = f"{rh.novelty_score:.2f}"
        lines.append(
            f"- [{h.severity}, {conf_pct}%] {h.title}\n"
            f"  Novelty: {novelty}"
        )
    return "\n".join(lines)


def _build_context_block(ctx: RetrievedContext) -> str:
    """Build the runbook context block for the prompt."""
    parts: list[str] = []
    for chunk in ctx.chunks[:5]:
        filename = chunk.get("filename", "unknown")
        text = chunk.get("text", "")[:300]
        parts.append(f"[{filename}] {text}")
    return "\n".join(parts) if parts else "(none)"


def _deterministic_fallback(
    ranked: list[RankedHypothesis],
    timeline: TimelineResult,
) -> str:
    """Build a deterministic fallback text when no LLM is available."""
    active = [rh for rh in ranked if not rh.suppress][:3]
    if active:
        top = active[0]
        verdict_severity = top.hypothesis.severity
        verdict_title = top.hypothesis.title
        verdict_conf = int(top.hypothesis.confidence * 100)
    elif ranked:
        top = ranked[0]
        verdict_severity = top.hypothesis.severity
        verdict_title = top.hypothesis.title
        verdict_conf = int(top.hypothesis.confidence * 100)
    else:
        verdict_severity = "UNKNOWN"
        verdict_title = "No hypotheses generated"
        verdict_conf = 0

    root_causes = ", ".join(
        rh.hypothesis.title for rh in (active or ranked[:3])
    ) or "None"

    return (
        f"VERDICT: {verdict_severity} — {verdict_title} ({verdict_conf}% confidence)\n"
        f"TIMELINE: {timeline.total_entries} entries across {len(timeline.clusters)} clusters.\n"
        f"ROOT CAUSES: {root_causes}"
    )


class SummarySynthesizer:
    """Stage 5 of the multi-agent diagnose pipeline.

    Synthesizes a human-readable incident narrative from ranked hypotheses,
    the reconstructed timeline, and RAG context. When no LLM is configured,
    returns a deterministic fallback built from the hypothesis data.
    """

    def synthesize(
        self,
        ranked: list[RankedHypothesis],
        timeline: TimelineResult,
        ctx: RetrievedContext,
        query: str,
        llm_url: str | None = None,
        llm_model: str | None = None,
        llm_api_key: str | None = None,
    ) -> str:
        """Return synthesis text (single string, synchronous).

        Falls back to a deterministic narrative when no LLM URL or model is
        provided, or when the LLM call fails.
        """
        fallback = _deterministic_fallback(ranked, timeline)

        if not llm_url or not llm_model:
            return fallback

        hypothesis_block = _build_hypothesis_block(ranked)
        context_block = _build_context_block(ctx)
        dominant = ", ".join(timeline.dominant_sources[:5]) or "none"

        user_message = (
            f"Query: {query}\n\n"
            f"Timeline summary:\n"
            f"- {len(timeline.clusters)} clusters, "
            f"{timeline.burst_count} bursts, "
            f"{timeline.gap_count} silence gaps\n"
            f"- Primary sources: {dominant}\n\n"
            f"Top hypotheses:\n{hypothesis_block}\n\n"
            f"Context from runbooks:\n{context_block}"
        )

        messages = [
            {"role": "system", "content": _SYSTEM_PROMPT},
            {"role": "user", "content": user_message},
        ]

        result = call_llm(
            llm_url=llm_url,
            llm_model=llm_model,
            llm_api_key=llm_api_key,
            messages=messages,
        )
        return result if result else fallback