"""Control Room observability summary.

Projects the live :class:`~app.observability.local_store.LocalObservationStore`
-- the canonical, ordinary-product-traffic observation log built in Tasks 1-4
-- into the compact shape the Control Room endpoint returns under the
``observability`` key. This module only reads already-recorded observations
and aggregates them; it never recomputes timings from ``ProjectActivity`` and
it never emits a span, metric, log, or telemetry write of its own.

Status vocabulary (checked in this priority order, matching the plan's
"never silently convert missing data to zero" constraint):

1. ``not_instrumented`` -- telemetry itself is off (`bootstrap` mode is
   ``"disabled"``); there is no store to read at all.
2. ``not_observed`` -- telemetry is on but nothing has been recorded yet
   (store missing or empty).
3. ``degraded`` -- telemetry itself had trouble (one or more suppressed
   export/store failures were counted), even though some data did land.
4. ``observed`` -- real data present, nothing degraded.
"""

from __future__ import annotations

from typing import Any

from app.observability import bootstrap

# Maps a recorded `operation` name (see call sites across app/rag,
# app/websockets/handlers.py, app/agents/cerebras_client.py, and
# app/services/student_memory.py) to the one canonical stage-duration name
# from the plan preamble's "Operational measures" table. More than one
# operation name can share a canonical stage (e.g. both "embedding.query" and
# "embedding.batch" measure `embedding_ms`, and all three memory operations
# measure `memory_ms`); their durations are pooled before computing
# percentiles so the Control Room projection stays keyed by the one canonical
# name, not by the internal call-site name.
_OPERATION_TO_STAGE: dict[str, str] = {
    "pdf.page_extraction": "page_extraction_ms",
    "rag.chunking": "chunking_ms",
    "rag.ingestion": "ingestion_ms",
    "embedding.query": "embedding_ms",
    "embedding.batch": "embedding_ms",
    "chroma.collection_lookup": "collection_lookup_ms",
    "chroma.vector_search": "vector_search_ms",
    "rag.retrieval": "retrieval_ms",
    "context.assembly": "context_assembly_ms",
    "memory.push": "memory_ms",
    "memory.flush": "memory_ms",
    "memory.recall": "memory_ms",
    "llm.generate": "llm_ms",
    "citation.attach": "citation_attachment_ms",
}


def _percentile(sorted_values: list[float], fraction: float) -> float:
    """Nearest-rank-with-interpolation percentile over an already-sorted list."""
    if len(sorted_values) == 1:
        return sorted_values[0]
    index = fraction * (len(sorted_values) - 1)
    lower = int(index)
    upper = min(lower + 1, len(sorted_values) - 1)
    weight = index - lower
    return sorted_values[lower] + (sorted_values[upper] - sorted_values[lower]) * weight


def _stage_summary(rows: list[dict[str, Any]]) -> dict[str, dict[str, float | int]]:
    """p50/p95/count per canonical stage, over rows with a real duration only.

    A row whose `duration_ms` is `None` is skipped entirely for that stage --
    never treated as a zero-duration sample.
    """
    durations_by_stage: dict[str, list[float]] = {}
    for row in rows:
        stage = _OPERATION_TO_STAGE.get(row.get("operation"))
        if stage is None:
            continue
        duration = row.get("duration_ms")
        if duration is None:
            continue
        durations_by_stage.setdefault(stage, []).append(float(duration))

    summary: dict[str, dict[str, float | int]] = {}
    for stage, durations in durations_by_stage.items():
        ordered = sorted(durations)
        summary[stage] = {
            "p50": round(_percentile(ordered, 0.50), 3),
            "p95": round(_percentile(ordered, 0.95), 3),
            "count": len(ordered),
        }
    return summary


def _retrieval_summary(rows: list[dict[str, Any]]) -> dict[str, int]:
    """success/empty/error counts from every row carrying a retrieval outcome.

    Only rows where the call site attached a `RetrievalOutcome` (currently
    `rag.retrieval`, plus the benchmark harness's `rag.benchmark_query`) carry
    a `retrieval` field; every other row is silently skipped, not counted as
    a zero.
    """
    success = 0
    empty = 0
    error = 0
    for row in rows:
        retrieval = row.get("retrieval")
        if not retrieval:
            continue
        status = retrieval.get("status")
        if status == "success":
            success += 1
        elif status == "success_empty":
            empty += 1
        elif status == "error_fallback":
            error += 1
    return {"success_count": success, "empty_count": empty, "error_count": error}


def _latest_trace_id(rows: list[dict[str, Any]]) -> str | None:
    for row in reversed(rows):
        trace_id = row.get("trace_id")
        if trace_id:
            return trace_id
    return None


def _latest_pipeline_version(rows: list[dict[str, Any]]) -> str | None:
    for row in reversed(rows):
        experiment = row.get("experiment")
        if experiment and experiment.get("pipeline_version"):
            return experiment["pipeline_version"]
    return None


def _empty_projection() -> dict[str, Any]:
    return {
        "latest_trace_id": None,
        "pipeline_version": None,
        "stages": {},
        "retrieval": {"success_count": 0, "empty_count": 0, "error_count": 0},
    }


def observability_summary() -> dict[str, Any]:
    """Build the Control Room `observability` projection from live state.

    Always returns the same top-level shape regardless of status, so the
    frontend never has to branch on which keys exist:

    ```json
    {
      "status": "observed",
      "latest_trace_id": "...",
      "pipeline_version": "rag-naive-v1",
      "stages": {"retrieval_ms": {"p50": 1.0, "p95": 2.0, "count": 3}},
      "retrieval": {"success_count": 1, "empty_count": 0, "error_count": 0},
      "exporter": {"mode": "local", "suppressed_failures": 0},
      "signoz_url": null
    }
    ```
    """
    state = bootstrap.get_state()
    suppressed_failures = bootstrap.get_suppressed_failure_count()
    exporter = {"mode": state.mode, "suppressed_failures": suppressed_failures}
    signoz_url = state.config.signoz_ui_url if state.mode == "full" else None

    if state.mode == "disabled":
        return {
            "status": "not_instrumented",
            "exporter": exporter,
            "signoz_url": signoz_url,
            **_empty_projection(),
        }

    store = state.local_store
    rows = store.all() if store is not None else []

    if not rows:
        return {
            "status": "not_observed",
            "exporter": exporter,
            "signoz_url": signoz_url,
            **_empty_projection(),
        }

    status = "degraded" if suppressed_failures > 0 else "observed"

    return {
        "status": status,
        "latest_trace_id": _latest_trace_id(rows),
        "pipeline_version": _latest_pipeline_version(rows),
        "stages": _stage_summary(rows),
        "retrieval": _retrieval_summary(rows),
        "exporter": exporter,
        "signoz_url": signoz_url,
    }