"""Validation harness — does the engine actually predict? Receipts, not claims.

The glass-box thesis lives or dies on this: every score we surface is framed
as a prediction to verify, so we owe the user proof the predictions track
reality. This harness correlates the engine's zero-shot ESM-2 ΔLL ranking
against measured deep-mutational-scanning (DMS) fitness from published studies
(e.g. ProteinGym) and reports the two numbers a protein engineer actually
cares about:

  * Spearman ρ — does the ranking order match measured fitness order?
  * top-decile precision — of the variants we rank in the top 10%, what
    fraction are genuinely high-fitness (top quartile measured)? i.e. "if I
    only make the picks you put on top, how often are they real?"

Pure numpy, predictions injected — so it's unit-testable without ESM. The
reproducible CLI (scripts/run_benchmarks.py) runs it against real DMS with the
live model where the weights exist; the app only ever serves results a real
run produced. No number is fabricated here.
"""
from __future__ import annotations

import re
from dataclasses import dataclass
from typing import List, Optional, Sequence

import numpy as np

_LABEL_RE = re.compile(r"^([A-Za-z])(\d+)([A-Za-z*])$")


def predict_additive(scores_df, labels: Sequence[str]) -> List[float]:
    """Sum-of-single-site ESM-2 ΔLL for each (possibly multi-site) DMS label
    ('A1C', 'A1C:D5E', or 'A1C,D5E') — the SAME additive scoring the design
    engine itself uses (dee.optimizer.search), so this validates exactly what
    we ship rather than a different metric. ``scores_df`` is the long-format
    output of ``ESM2Scorer.score_all_substitutions`` (columns: position
    0-indexed, mut_aa, delta_ll).

    Single source of truth for both the reproducible CLI
    (scripts/run_benchmarks.py) and the admin in-Space endpoint — never
    duplicated, so they can't silently drift apart.

    A label with any unparseable or out-of-table site becomes NaN (never
    silently coerced to 0) — spearman()/top_decile_precision() mask NaNs out
    via ``np.isfinite``, so a bad label reduces the effective N rather than
    corrupting the correlation."""
    lut = {(int(r.position), str(r.mut_aa)): float(r.delta_ll)
           for r in scores_df.itertuples(index=False)}
    out: List[float] = []
    for lab in labels:
        total, ok = 0.0, True
        for tok in re.split(r"[:,]", str(lab).strip()):
            m = _LABEL_RE.match(tok.strip())
            if not m:
                ok = False
                break
            pos, mut = int(m.group(2)) - 1, m.group(3).upper()
            key = (pos, mut)
            if key not in lut:
                ok = False
                break
            total += lut[key]
        out.append(total if ok else float("nan"))
    return out


def _average_ranks(x: np.ndarray) -> np.ndarray:
    """Ranks with ties resolved to the average rank (proper Spearman ties)."""
    order = np.argsort(x, kind="mergesort")
    ranks = np.empty(len(x), dtype=np.float64)
    sx = x[order]
    i = 0
    n = len(x)
    while i < n:
        j = i
        while j + 1 < n and sx[j + 1] == sx[i]:
            j += 1
        avg = (i + j) / 2.0 + 1.0          # 1-indexed average rank over the tie block
        ranks[order[i:j + 1]] = avg
        i = j + 1
    return ranks


def spearman(a: Sequence[float], b: Sequence[float]) -> Optional[float]:
    """Spearman rank correlation. None if <3 points or no variance."""
    a = np.asarray(a, dtype=np.float64)
    b = np.asarray(b, dtype=np.float64)
    mask = np.isfinite(a) & np.isfinite(b)
    a, b = a[mask], b[mask]
    if len(a) < 3:
        return None
    ra, rb = _average_ranks(a), _average_ranks(b)
    if ra.std() < 1e-9 or rb.std() < 1e-9:
        return None
    return float(np.corrcoef(ra, rb)[0, 1])


def top_decile_precision(
    predicted: Sequence[float], measured: Sequence[float],
    *, pred_frac: float = 0.10, true_frac: float = 0.25,
) -> Optional[float]:
    """Of the top ``pred_frac`` by prediction, the fraction that land in the
    top ``true_frac`` by measured fitness. The 'are your top picks real?' number.
    None if too few points to form a meaningful top set."""
    p = np.asarray(predicted, dtype=np.float64)
    m = np.asarray(measured, dtype=np.float64)
    mask = np.isfinite(p) & np.isfinite(m)
    p, m = p[mask], m[mask]
    n = len(p)
    k = int(round(n * pred_frac))
    if n < 10 or k < 1:
        return None
    top_pred_idx = np.argsort(-p)[:k]
    true_cut = np.quantile(m, 1.0 - true_frac)
    hits = int(np.sum(m[top_pred_idx] >= true_cut))
    return float(hits / k)


@dataclass
class DatasetResult:
    """One DMS assay's validation result."""
    name: str
    protein: str            # e.g. UniProt/DMS id
    n: int                  # variants scored
    spearman: Optional[float]
    top_decile_precision: Optional[float]
    source: str = ""        # citation / DOI / dataset id (provenance)

    def as_dict(self) -> dict:
        return {
            "name": self.name, "protein": self.protein, "n": self.n,
            "spearman": None if self.spearman is None else round(self.spearman, 4),
            "top_decile_precision": None if self.top_decile_precision is None
                else round(self.top_decile_precision, 4),
            "source": self.source,
        }


def evaluate_dataset(
    name: str, protein: str,
    predicted: Sequence[float], measured: Sequence[float],
    *, source: str = "",
) -> DatasetResult:
    """Score one aligned (predicted, measured) DMS assay."""
    p = np.asarray(predicted, dtype=np.float64)
    m = np.asarray(measured, dtype=np.float64)
    mask = np.isfinite(p) & np.isfinite(m)
    return DatasetResult(
        name=name, protein=protein, n=int(mask.sum()),
        spearman=spearman(p, m),
        top_decile_precision=top_decile_precision(p, m),
        source=source,
    )


def summarize(results: Sequence[DatasetResult]) -> dict:
    """Headline across datasets: median Spearman, median top-decile precision,
    dataset + variant counts. Medians (robust to a couple of hard assays)."""
    rhos = [r.spearman for r in results if r.spearman is not None]
    precs = [r.top_decile_precision for r in results if r.top_decile_precision is not None]
    return {
        "n_datasets": len(results),
        "n_variants": int(sum(r.n for r in results)),
        "median_spearman": None if not rhos else round(float(np.median(rhos)), 4),
        "median_top_decile_precision": None if not precs
            else round(float(np.median(precs)), 4),
    }