"""Snapshot regression tests against fixtures in this directory.

Discovery: every <name>.expected.json under fixtures/ pairs with a sibling
<name>.input.<ext>. The runner parses the input, then asserts each tolerance
in the expected file. Tolerance keys are documented in fixtures/README.md.

Performance baselines are opt-in per fixture via a `performance` block in
the expected file. They run only when ZSGDP_REGRESSION_PERF=1 (or when the
performance block has `always_enforce: true`) so a slow CI runner does not
fail on transient noise. When enabled, the parse is run twice and the
median elapsed time is compared against the floor.
"""

from __future__ import annotations

import json
import os
import statistics
import tempfile
import time
import unittest
import unittest.mock
from pathlib import Path
from typing import Any

from zsgdp.pipeline import parse_document

FIXTURE_DIR = Path(__file__).parent / "fixtures"


def _discover_fixtures() -> list[tuple[str, Path, Path]]:
    pairs: list[tuple[str, Path, Path]] = []
    if not FIXTURE_DIR.exists():
        return pairs
    for expected in sorted(FIXTURE_DIR.glob("*.expected.json")):
        name = expected.name[: -len(".expected.json")]
        candidates = sorted(FIXTURE_DIR.glob(f"{name}.input.*"))
        if not candidates:
            continue
        pairs.append((name, candidates[0], expected))
    return pairs


def _check_int_or_range(actual: int, exact: Any, range_value: Any, label: str) -> str | None:
    if exact is not None and int(exact) != actual:
        return f"{label}: expected {exact}, got {actual}"
    if isinstance(range_value, (list, tuple)) and len(range_value) == 2:
        lo, hi = int(range_value[0]), int(range_value[1])
        if not (lo <= actual <= hi):
            return f"{label}: expected in [{lo}, {hi}], got {actual}"
    return None


def _evaluate(parsed, tolerances: dict[str, Any]) -> list[str]:
    failures: list[str] = []
    score = float(parsed.quality_report.score)
    if "quality_score_min" in tolerances and score < float(tolerances["quality_score_min"]):
        failures.append(f"quality_score: {score:.3f} < {tolerances['quality_score_min']}")
    if "quality_score_max" in tolerances and score > float(tolerances["quality_score_max"]):
        failures.append(f"quality_score: {score:.3f} > {tolerances['quality_score_max']}")

    for label, count, exact_key, range_key in (
        ("element_count", len(parsed.elements), "element_count", "element_count_range"),
        ("table_count", len(parsed.tables), "table_count", "table_count_range"),
        ("figure_count", len(parsed.figures), "figure_count", "figure_count_range"),
    ):
        message = _check_int_or_range(count, tolerances.get(exact_key), tolerances.get(range_key), label)
        if message:
            failures.append(message)

    chunk_count = len(parsed.chunks)
    if "chunk_count_min" in tolerances and chunk_count < int(tolerances["chunk_count_min"]):
        failures.append(f"chunk_count: {chunk_count} < {tolerances['chunk_count_min']}")
    if "chunk_count_max" in tolerances and chunk_count > int(tolerances["chunk_count_max"]):
        failures.append(f"chunk_count: {chunk_count} > {tolerances['chunk_count_max']}")

    if "blocking_failures" in tolerances:
        actual = parsed.quality_report.has_blocking_failures
        expected = bool(tolerances["blocking_failures"])
        if actual != expected:
            failures.append(f"blocking_failures: expected {expected}, got {actual}")

    md = parsed.to_markdown()
    for needle in tolerances.get("must_contain_markdown", []) or []:
        if str(needle) not in md:
            failures.append(f"must_contain_markdown: {needle!r} not found")
    for needle in tolerances.get("must_not_contain_markdown", []) or []:
        if str(needle) in md:
            failures.append(f"must_not_contain_markdown: {needle!r} present")

    metrics = parsed.quality_report.metrics
    for key in tolerances.get("must_contain_quality_metrics", []) or []:
        if key not in metrics:
            failures.append(f"must_contain_quality_metrics: {key!r} missing")

    if "parser_disagreement_rate_max" in tolerances:
        rate = float(metrics.get("parser_disagreement_rate", 0.0))
        if rate > float(tolerances["parser_disagreement_rate_max"]):
            failures.append(
                f"parser_disagreement_rate: {rate:.3f} > {tolerances['parser_disagreement_rate_max']}"
            )
    if "repair_resolution_rate_min" in tolerances:
        rate = float(metrics.get("repair_resolution_rate", 1.0))
        if rate < float(tolerances["repair_resolution_rate_min"]):
            failures.append(
                f"repair_resolution_rate: {rate:.3f} < {tolerances['repair_resolution_rate_min']}"
            )

    return failures


def _perf_enforcement_enabled(performance: dict[str, Any]) -> bool:
    if performance.get("always_enforce"):
        return True
    return os.environ.get("ZSGDP_REGRESSION_PERF", "").strip().lower() in {"1", "true", "yes"}


def _measure_parse(input_path: Path, *, config_path: Path | None, selected_parsers, repeats: int) -> tuple[Any, list[float]]:
    """Parse the input N times, returning (last_parsed, list_of_elapsed_seconds).

    Uses a fresh temp output directory for each run so disk caching effects
    are roughly equal across runs. The last parsed document is returned for
    tolerance evaluation; per-run elapsed times feed the perf assertion.
    """

    elapsed: list[float] = []
    parsed = None
    for _ in range(max(1, repeats)):
        with tempfile.TemporaryDirectory() as tmp:
            started = time.perf_counter()
            parsed = parse_document(
                input_path,
                Path(tmp) / "out",
                config_path=config_path if config_path else None,
                selected_parsers=selected_parsers,
            )
            elapsed.append(time.perf_counter() - started)
    return parsed, elapsed


def _evaluate_performance(parsed, performance: dict[str, Any], elapsed_seconds: list[float]) -> list[str]:
    failures: list[str] = []
    if not elapsed_seconds:
        return failures

    median_elapsed = statistics.median(elapsed_seconds)
    page_count = max(len(parsed.pages), 1)
    median_pages_per_second = page_count / median_elapsed if median_elapsed > 0 else float("inf")

    max_elapsed = performance.get("max_elapsed_seconds")
    if max_elapsed is not None and median_elapsed > float(max_elapsed):
        failures.append(
            f"performance.max_elapsed_seconds: median {median_elapsed:.2f}s > {max_elapsed}s "
            f"(runs={len(elapsed_seconds)})"
        )

    min_pps = performance.get("min_pages_per_second")
    if min_pps is not None and median_pages_per_second < float(min_pps):
        failures.append(
            f"performance.min_pages_per_second: median {median_pages_per_second:.2f} < {min_pps} "
            f"(runs={len(elapsed_seconds)})"
        )

    return failures


class RegressionFixturesTest(unittest.TestCase):
    def test_regression_fixtures_match_snapshots(self):
        fixtures = _discover_fixtures()
        if not fixtures:
            self.skipTest("No regression fixtures present.")

        all_failures: list[str] = []
        for name, input_path, expected_path in fixtures:
            with self.subTest(fixture=name):
                expected = json.loads(expected_path.read_text(encoding="utf-8"))
                tolerances = expected.get("tolerances") or {}
                performance = expected.get("performance") or {}
                config_rel = expected.get("config")
                config_path = Path(config_rel) if config_rel else None
                if config_path and not config_path.is_absolute():
                    config_path = Path(__file__).resolve().parents[2] / config_path
                selected_parsers = expected.get("selected_parsers")

                perf_enabled = bool(performance) and _perf_enforcement_enabled(performance)
                repeats = int(performance.get("repeats", 2)) if perf_enabled else 1

                parsed, elapsed = _measure_parse(
                    input_path,
                    config_path=config_path,
                    selected_parsers=selected_parsers,
                    repeats=repeats,
                )

                failures = _evaluate(parsed, tolerances)
                if perf_enabled:
                    failures.extend(_evaluate_performance(parsed, performance, elapsed))
                if failures:
                    all_failures.append(f"[{name}] " + "; ".join(failures))

        if all_failures:
            self.fail("\n".join(all_failures))


class PerformanceEvaluatorTests(unittest.TestCase):
    """Unit tests for the perf-evaluation helpers, separate from fixture discovery."""

    def test_max_elapsed_floor_fires_when_too_slow(self):
        from types import SimpleNamespace

        parsed = SimpleNamespace(pages=[{"page_num": 1}])
        failures = _evaluate_performance(parsed, {"max_elapsed_seconds": 0.1}, [0.5, 0.5])
        self.assertEqual(len(failures), 1)
        self.assertIn("max_elapsed_seconds", failures[0])

    def test_min_pages_per_second_fires_when_too_slow(self):
        from types import SimpleNamespace

        parsed = SimpleNamespace(pages=[{"page_num": 1}])
        # 1 page in 10s => 0.1 pps, floor 1.0 => fail.
        failures = _evaluate_performance(parsed, {"min_pages_per_second": 1.0}, [10.0, 10.0])
        self.assertEqual(len(failures), 1)
        self.assertIn("min_pages_per_second", failures[0])

    def test_passing_floors_yield_no_failures(self):
        from types import SimpleNamespace

        parsed = SimpleNamespace(pages=[{"page_num": 1}, {"page_num": 2}])
        # 2 pages in 0.5s => 4 pps; floor 1.0 pps and max 2s.
        failures = _evaluate_performance(
            parsed,
            {"max_elapsed_seconds": 2.0, "min_pages_per_second": 1.0},
            [0.5, 0.5, 0.5],
        )
        self.assertEqual(failures, [])

    def test_median_strips_cold_outlier(self):
        from types import SimpleNamespace

        parsed = SimpleNamespace(pages=[{"page_num": 1}])
        # First run cold (5s), next two warm (0.1s). Median = 0.1s; floor 1s passes.
        failures = _evaluate_performance(parsed, {"max_elapsed_seconds": 1.0}, [5.0, 0.1, 0.1])
        self.assertEqual(failures, [])

    def test_perf_enforcement_gating(self):
        with unittest.mock.patch.dict("os.environ", {"ZSGDP_REGRESSION_PERF": "0"}, clear=False):
            self.assertFalse(_perf_enforcement_enabled({"max_elapsed_seconds": 1.0}))
            self.assertTrue(_perf_enforcement_enabled({"always_enforce": True}))

        with unittest.mock.patch.dict("os.environ", {"ZSGDP_REGRESSION_PERF": "1"}, clear=False):
            self.assertTrue(_perf_enforcement_enabled({"max_elapsed_seconds": 1.0}))


if __name__ == "__main__":
    unittest.main()