"""OCR-vs-visual-retrieval degradation benchmark (issue #16, docs/prd.md sections
6, 8, and open risk #3).

Open risk #3, verbatim: "Whether visual retrieval actually beats a strong OCR
baseline on this specific corpus is an open question, not a known result."
This module is the harness to answer it -- it is explicitly NOT built to
confirm a foregone conclusion. It compares any number of named extraction
approaches on the *same* held-out set with the *same* metric (reusing
evaluation.field_accuracy, issue #15), split by a real corpus degradation
axis, and reports whichever way the numbers come out.

The two approaches the PRD contrasts:
  - baseline: OCR text -> LLM extraction (llm_extraction). Section 6 insists
    this be a *genuinely strong* baseline, not a strawman -- so it's the same
    schema-constrained tool-use extractor the product uses, not a weakened one.
  - visual: ColPali retrieves the relevant page -> multimodal LLM extraction
    from that page image (the combined pass from resolution.py, issue #10).
    Plugged in as one or more predictors so "zero-shot" and "lightly adapted"
    (section 9) are just two entries in the approaches map.

The degradation axis is REAL, not synthetic noise (acceptance criterion): it
reuses the exact OCR-damage text heuristic from
notebooks/01_dataset_exploration.ipynb -- a spurious mid-sentence period (a
lowercase letter, '.', whitespace, lowercase letter), which a real sentence
boundary, followed by a capital, wouldn't produce.

IMPORTANT caveat, surfaced by notebooks/02_colpali_retrieval_exploration.ipynb
(cell 22) and carried here so the benchmark can't quietly overclaim: this is a
TEXT-level degradation proxy. Text-level and image-level scan degradation are
different axes -- that notebook found a case flagged "clean" by this text
heuristic whose scanned image was visibly degraded (redaction block, faded
print). A clean/degraded split on this proxy measures robustness to *OCR text*
damage, which is exactly the axis where visual retrieval is hypothesized to
help; it does not claim to measure visual scan quality.

Blocked on real results until an LLM API key, ColPali compute, and a
ground-truth labeling pass (issue #15) all exist. The harness and the real
degraded-subset partition run today; the predictors are injected so the
comparison logic is tested without live models.
"""

from __future__ import annotations

import re
from dataclasses import dataclass, field
from pathlib import Path
from typing import Callable, Mapping, Optional

from endopath import colpali_retrieval, consensus, llm_extraction, resolution
from endopath.evaluation import (
    AccuracyReport,
    CasePredictions,
    FieldPrediction,
    GroundTruthCase,
    field_accuracy,
)

# The real OCR-damage heuristic from notebook 01: a spurious mid-sentence
# period. A genuine sentence boundary is followed by a capital letter; a
# lowercase letter after "word. word" is an OCR artifact.
#
# Measured over the real corpus, this binary flag fires on ~91% of reports
# (500/545 ingested UCEC image cases) -- one spurious period anywhere trips
# it, so as a binary split it separates "essentially all reports" from a tiny
# clean remainder, not worst-from-typical. ocr_damage_density() below grades
# severity (matches per 1000 chars) so the benchmark can select a genuinely
# *worst-N%* degraded subset -- still real corpus OCR damage, but a
# discriminating axis rather than a near-constant flag.
SPURIOUS_MID_SENTENCE_PERIOD = re.compile(r"[a-z]\.\s+[a-z]")

DEGRADATION_CAVEAT = (
    "Clean/degraded split is on a TEXT-level OCR-damage proxy (spurious "
    "mid-sentence periods). Text-level and image-level scan degradation are "
    "different axes (notebook 02 found a text-'clean' case with a visibly "
    "degraded image); this measures robustness to OCR text damage, not visual "
    "scan quality."
)

Predictor = Callable[[str], CasePredictions]  # case_barcode -> predictions


def has_ocr_text_damage(text: str) -> bool:
    return bool(SPURIOUS_MID_SENTENCE_PERIOD.search(text or ""))


def ocr_damage_density(text: str) -> float:
    """Graded OCR-damage severity: spurious-period matches per 1000 chars.
    The binary flag saturates (~91% of the corpus), so severity is what lets
    the benchmark rank reports and take the genuinely worst ones. Empty/short
    text scores 0.0 rather than dividing by zero."""
    text = text or ""
    if not text:
        return 0.0
    matches = len(SPURIOUS_MID_SENTENCE_PERIOD.findall(text))
    return matches / (len(text) / 1000.0)


def damage_flags_from_scores(
    scores: Mapping[str, float], *, top_fraction: float = 0.2
) -> dict[str, bool]:
    """Turn graded damage scores into a clean/degraded split by flagging the
    worst `top_fraction` of cases as degraded. Ties at the cutoff are all
    included on the degraded side, so the split never depends on dict order.
    This is how the benchmark gets a balanced, meaningfully-worst degraded
    subset out of a proxy that would otherwise flag almost everything."""
    if not 0.0 < top_fraction < 1.0:
        raise ValueError("top_fraction must be in (0, 1)")
    if not scores:
        return {}
    ordered = sorted(scores.values(), reverse=True)
    k = max(1, round(len(ordered) * top_fraction))
    cutoff = ordered[k - 1]
    return {barcode: score >= cutoff for barcode, score in scores.items()}


def load_ocr_damage_scores(reports_csv_path: Optional[Path | str] = None) -> dict[str, float]:
    """case_barcode -> graded OCR-damage density over the real corpus CSV."""
    import pandas as pd

    path = Path(reports_csv_path) if reports_csv_path else Path("data") / "raw" / "TCGA_Reports.csv"
    reports = pd.read_csv(path)
    return {
        str(row["patient_filename"]).split(".")[0]: ocr_damage_density(str(row["text"]))
        for _, row in reports.iterrows()
    }


def load_ocr_damage_flags(reports_csv_path: Optional[Path | str] = None) -> dict[str, bool]:
    """case_barcode -> whether its OCR text shows the spurious-period damage
    signal. Runs today against the real corpus CSV -- this is what makes the
    degraded subset real rather than synthetic. case_barcode is the part of
    patient_filename before the first '.', matching ingestion.py."""
    import pandas as pd

    path = Path(reports_csv_path) if reports_csv_path else Path("data") / "raw" / "TCGA_Reports.csv"
    reports = pd.read_csv(path)
    flags: dict[str, bool] = {}
    for _, row in reports.iterrows():
        case_barcode = str(row["patient_filename"]).split(".")[0]
        flags[case_barcode] = has_ocr_text_damage(str(row["text"]))
    return flags


@dataclass
class BenchmarkReport:
    # results[approach_name][subset] -> AccuracyReport; subset in {all, clean, degraded}
    results: dict[str, dict[str, AccuracyReport]]
    subset_case_counts: dict[str, int] = field(default_factory=dict)

    def degradation_gap(self, approach: str) -> Optional[float]:
        """clean accuracy minus degraded accuracy for one approach -- how much
        that approach loses on OCR-damaged reports. Positive = worse on
        degraded. None if either subset had nothing to score. Reported as a
        number, not a verdict; the point of the benchmark is that the sign and
        size are unknown until measured."""
        clean = self.results.get(approach, {}).get("clean")
        degraded = self.results.get(approach, {}).get("degraded")
        if clean is None or degraded is None:
            return None
        if clean.accuracy is None or degraded.accuracy is None:
            return None
        return clean.accuracy - degraded.accuracy


def run_benchmark(
    ground_truth: Mapping[str, GroundTruthCase],
    damage_by_case: Mapping[str, bool],
    approaches: Mapping[str, Predictor],
    *,
    numeric_tolerance: float = 0.0,
    numeric_tolerances: Optional[Mapping[str, float]] = None,
) -> BenchmarkReport:
    """Score every approach on the same held-out set with the same metric,
    split into all / clean / degraded subsets. A case whose damage flag is
    unknown lands only in 'all' -- it is not silently assumed clean."""
    barcodes = list(ground_truth)
    clean = [b for b in barcodes if damage_by_case.get(b) is False]
    degraded = [b for b in barcodes if damage_by_case.get(b) is True]
    subsets = {"all": barcodes, "clean": clean, "degraded": degraded}

    results: dict[str, dict[str, AccuracyReport]] = {}
    for name, predictor in approaches.items():
        preds = {b: predictor(b) for b in barcodes}
        results[name] = {}
        for subset_name, subset_barcodes in subsets.items():
            gt_subset = {b: ground_truth[b] for b in subset_barcodes}
            results[name][subset_name] = field_accuracy(
                preds,
                gt_subset,
                numeric_tolerance=numeric_tolerance,
                numeric_tolerances=numeric_tolerances,
            )

    return BenchmarkReport(
        results=results,
        subset_case_counts={k: len(v) for k, v in subsets.items()},
    )


def format_report(report: BenchmarkReport) -> str:
    """Plain, neutral rendering -- states the numbers for every approach and
    subset without framing a winner. Ends with the text-vs-image caveat so a
    reader can't mistake the degradation axis for visual scan quality."""
    lines: list[str] = []
    counts = report.subset_case_counts
    lines.append(
        f"cases: all={counts.get('all', 0)}, clean={counts.get('clean', 0)}, "
        f"degraded={counts.get('degraded', 0)}"
    )
    for approach, by_subset in report.results.items():
        lines.append(f"\n{approach}:")
        for subset in ("all", "clean", "degraded"):
            rep = by_subset.get(subset)
            if rep is None:
                continue
            acc = f"{rep.accuracy:.3f}" if rep.accuracy is not None else "n/a"
            rec = f"{rep.recall:.3f}" if rep.recall is not None else "n/a"
            lines.append(
                f"  {subset:8s} accuracy={acc} recall={rec} "
                f"(answered {rep.n_answered}/{rep.n_applicable})"
            )
        gap = report.degradation_gap(approach)
        if gap is not None:
            lines.append(f"  clean-minus-degraded accuracy gap: {gap:+.3f}")
    lines.append(f"\nCAVEAT: {DEGRADATION_CAVEAT}")
    return "\n".join(lines)


# --- Real predictor wirings (thin glue; the comparison logic above is the
# tested part). ------------------------------------------------------------


def make_ocr_llm_predictor(text_by_case: Mapping[str, str], *, client=None) -> Predictor:
    """The strong baseline: the same schema-constrained tool-use extractor the
    product uses, over OCR text. Not weakened -- section 7 requires the OCR
    baseline be genuinely strong before visual retrieval is trusted over it."""

    def predict(case_barcode: str) -> CasePredictions:
        text = text_by_case[case_barcode]
        raw = llm_extraction.extract_raw(text, client=client)
        fields = llm_extraction.build_checklist_fields(raw, text)
        return {
            name: FieldPrediction(value=f.value, confidence=f.confidence)
            for name, f in fields.items()
        }

    return predict


def _visual_predictions(
    text: str,
    image_paths: list[Path],
    probe_for: Callable[[str], Callable[[], object]],
    client,
) -> dict[str, FieldPrediction]:
    """Shared visual-pipeline loop: for each checklist field, run the field's
    embedding probe (which page does the retriever flag?) then the combined
    multimodal LLM extract on that page. `probe_for(name)` returns the field's
    probe callable -- the one thing that differs between the live-ColPali and
    precomputed-embeddings variants; everything downstream is identical."""
    preds: dict[str, FieldPrediction] = {}
    for name in colpali_retrieval.FIELD_QUERIES:
        hit = probe_for(name)()
        extracted = resolution._build_combined_extract(name, text, image_paths, client=client)(hit)
        if extracted is not None:
            preds[name] = FieldPrediction(value=extracted.value, confidence=extracted.confidence)
        else:
            preds[name] = FieldPrediction(value=None, confidence=None)
    return preds


def make_visual_llm_predictor(
    image_paths_by_case: Mapping[str, list[Path]],
    text_by_case: Mapping[str, str],
    *,
    client=None,
    margin_threshold: float = consensus.DEFAULT_VISUAL_MARGIN_THRESHOLD,
) -> Predictor:
    """The visual approach: ColPali retrieves the best page per field, then a
    multimodal LLM extracts from that page image (resolution.py's combined
    pass). Zero-shot as written; a lightly-adapted retriever would be a second
    predictor built the same way, not a change here.

    Embeds each case's pages live with ColPali (torch). When the corpus has
    already been embedded offline (issue #19), prefer
    make_precomputed_visual_llm_predictor, which scores the stored vectors in
    numpy and needs no GPU or model load."""

    def predict(case_barcode: str) -> CasePredictions:
        image_paths = list(image_paths_by_case.get(case_barcode, []))
        text = text_by_case.get(case_barcode, "")
        page_embeddings = resolution._embed_pages_if_available(image_paths)
        probe_for = lambda name: resolution._build_embedding_probe(  # noqa: E731
            name, page_embeddings, margin_threshold
        )
        return _visual_predictions(text, image_paths, probe_for, client)

    return predict


def make_precomputed_visual_llm_predictor(
    image_paths_by_case: Mapping[str, list[Path]],
    text_by_case: Mapping[str, str],
    page_embeddings_by_case: Mapping[str, list],
    query_embeddings: Mapping[str, object],
    *,
    client=None,
    margin_threshold: float = consensus.DEFAULT_VISUAL_MARGIN_THRESHOLD,
) -> Predictor:
    """Same visual pipeline as make_visual_llm_predictor, but the retrieval half
    scores precomputed page + query vectors (issue #19/#21) in numpy instead of
    embedding pages live. This is what makes the benchmark runnable on a corpus
    that was embedded offline: no torch, no ~6GB model load, no per-case GPU
    time. The combined multimodal LLM extraction still runs live (that is the
    approach under test); only the page-retrieval step reads stored vectors.

    `page_embeddings_by_case` maps case_barcode -> the case's per-page vectors
    (precomputed_retrieval.load_case_page_embeddings); `query_embeddings` maps
    field name -> query vector (precomputed_retrieval.load_query_embeddings). A
    case absent from page_embeddings_by_case falls back to a skipped embedding
    pass (probe returns None), exactly as a missing image would live."""

    def predict(case_barcode: str) -> CasePredictions:
        image_paths = list(image_paths_by_case.get(case_barcode, []))
        text = text_by_case.get(case_barcode, "")
        page_embs = page_embeddings_by_case.get(case_barcode)
        probe_for = lambda name: resolution._build_precomputed_embedding_probe(  # noqa: E731
            name, page_embs, query_embeddings, margin_threshold
        )
        return _visual_predictions(text, image_paths, probe_for, client)

    return predict