"""
Compare two VDM runtime run directories.

This is a smoke/parity aid, not a model-quality validator. It compares emitted
runtime artifacts while ignoring external clock fields by default.
"""

from __future__ import annotations

import argparse
import json
import math
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Dict, Iterable, List, Sequence, Tuple

import zstandard as zstd


DEFAULT_STREAMS = ("events.jsonl.zst", "motor_traces.jsonl.zst")
DEFAULT_IGNORE_FIELDS = frozenset({"wall_time_s", "ts", "run_elapsed_s"})

RecordKey = Tuple[Any, ...]


@dataclass(frozen=True)
class FieldDiff:
    record_key: RecordKey
    field: str
    baseline: Any
    candidate: Any

    def to_dict(self) -> Dict[str, Any]:
        return {
            "record_key": list(self.record_key),
            "field": self.field,
            "baseline": self.baseline,
            "candidate": self.candidate,
        }


@dataclass
class StreamComparison:
    stream: str
    baseline_rows: int
    candidate_rows: int
    matched_records: int
    baseline_only_records: List[RecordKey] = field(default_factory=list)
    candidate_only_records: List[RecordKey] = field(default_factory=list)
    added_fields: List[str] = field(default_factory=list)
    removed_fields: List[str] = field(default_factory=list)
    common_field_diff_count: int = 0
    first_diffs: List[FieldDiff] = field(default_factory=list)
    baseline_tick_range: Tuple[int, int] | None = None
    candidate_tick_range: Tuple[int, int] | None = None
    missing_baseline_stream: bool = False
    missing_candidate_stream: bool = False

    def has_unexpected_changes(
        self,
        *,
        allowed_added_fields: Iterable[str] = (),
        allowed_removed_fields: Iterable[str] = (),
    ) -> bool:
        allowed_added = set(allowed_added_fields)
        allowed_removed = set(allowed_removed_fields)
        if self.baseline_only_records or self.candidate_only_records:
            return True
        if set(self.added_fields) - allowed_added:
            return True
        if set(self.removed_fields) - allowed_removed:
            return True
        return self.common_field_diff_count > 0

    def to_dict(self) -> Dict[str, Any]:
        return {
            "stream": self.stream,
            "baseline_rows": self.baseline_rows,
            "candidate_rows": self.candidate_rows,
            "matched_records": self.matched_records,
            "baseline_only_records": [list(k) for k in self.baseline_only_records],
            "candidate_only_records": [list(k) for k in self.candidate_only_records],
            "added_fields": self.added_fields,
            "removed_fields": self.removed_fields,
            "common_field_diff_count": self.common_field_diff_count,
            "first_diffs": [diff.to_dict() for diff in self.first_diffs],
            "baseline_tick_range": list(self.baseline_tick_range) if self.baseline_tick_range else None,
            "candidate_tick_range": list(self.candidate_tick_range) if self.candidate_tick_range else None,
            "missing_baseline_stream": self.missing_baseline_stream,
            "missing_candidate_stream": self.missing_candidate_stream,
        }


@dataclass
class RunComparison:
    baseline_dir: str
    candidate_dir: str
    streams: List[StreamComparison]

    def has_unexpected_changes(
        self,
        *,
        allowed_added_fields: Iterable[str] = (),
        allowed_removed_fields: Iterable[str] = (),
    ) -> bool:
        return any(
            stream.has_unexpected_changes(
                allowed_added_fields=allowed_added_fields,
                allowed_removed_fields=allowed_removed_fields,
            )
            for stream in self.streams
        )

    def to_dict(self) -> Dict[str, Any]:
        return {
            "baseline_dir": self.baseline_dir,
            "candidate_dir": self.candidate_dir,
            "streams": [stream.to_dict() for stream in self.streams],
        }


def read_jsonl_zst(path: Path) -> List[Dict[str, Any]]:
    if not path.exists():
        return []
    dctx = zstd.ZstdDecompressor()
    with path.open("rb") as fh:
        try:
            reader = dctx.stream_reader(fh, read_across_frames=True)
        except TypeError:
            reader = dctx.stream_reader(fh)
        with reader:
            text = reader.read().decode("utf-8")
    rows: List[Dict[str, Any]] = []
    for line in text.splitlines():
        if not line.strip():
            continue
        item = json.loads(line)
        if isinstance(item, dict):
            rows.append(item)
    return rows


def _base_record_key(stream: str, row: Dict[str, Any], index: int) -> RecordKey:
    if row.get("msg") == "tick" and "tick" in row:
        try:
            return ("tick", int(row["tick"]))
        except Exception:
            pass
    if "tick" in row:
        try:
            tick = int(row["tick"])
        except Exception:
            tick = row["tick"]
        kind = row.get("trace_kind", row.get("msg", "row"))
        return ("tick-kind", tick, str(kind))
    return ("row", stream, index)


def keyed_rows(stream: str, rows: Sequence[Dict[str, Any]]) -> Dict[RecordKey, Dict[str, Any]]:
    counts: Dict[RecordKey, int] = {}
    keyed: Dict[RecordKey, Dict[str, Any]] = {}
    for index, row in enumerate(rows):
        base = _base_record_key(stream, row, index)
        ordinal = counts.get(base, 0)
        counts[base] = ordinal + 1
        keyed[base + (ordinal,)] = row
    return keyed


def tick_range(rows: Sequence[Dict[str, Any]]) -> Tuple[int, int] | None:
    ticks: List[int] = []
    for row in rows:
        if "tick" not in row:
            continue
        try:
            ticks.append(int(row["tick"]))
        except Exception:
            continue
    if not ticks:
        return None
    return (min(ticks), max(ticks))


def _values_equal(left: Any, right: Any, *, abs_tol: float) -> bool:
    if isinstance(left, bool) or isinstance(right, bool):
        return left == right
    if isinstance(left, (int, float)) or isinstance(right, (int, float)):
        try:
            return math.isclose(float(left), float(right), rel_tol=0.0, abs_tol=float(abs_tol))
        except Exception:
            return left == right
    return left == right


def compare_rows(
    stream: str,
    baseline_rows: Sequence[Dict[str, Any]],
    candidate_rows: Sequence[Dict[str, Any]],
    *,
    ignore_fields: Iterable[str] = DEFAULT_IGNORE_FIELDS,
    abs_tol: float = 1e-12,
    max_diffs: int = 20,
    missing_baseline_stream: bool = False,
    missing_candidate_stream: bool = False,
) -> StreamComparison:
    ignored = set(ignore_fields)
    baseline_keyed = keyed_rows(stream, baseline_rows)
    candidate_keyed = keyed_rows(stream, candidate_rows)
    baseline_keys = set(baseline_keyed)
    candidate_keys = set(candidate_keyed)
    common_keys = sorted(baseline_keys & candidate_keys)
    added_fields: set[str] = set()
    removed_fields: set[str] = set()
    diff_count = 0
    first_diffs: List[FieldDiff] = []

    for key in common_keys:
        baseline = {k: v for k, v in baseline_keyed[key].items() if k not in ignored}
        candidate = {k: v for k, v in candidate_keyed[key].items() if k not in ignored}
        baseline_fields = set(baseline)
        candidate_fields = set(candidate)
        added_fields.update(candidate_fields - baseline_fields)
        removed_fields.update(baseline_fields - candidate_fields)
        for field_name in sorted(baseline_fields & candidate_fields):
            left = baseline[field_name]
            right = candidate[field_name]
            if _values_equal(left, right, abs_tol=abs_tol):
                continue
            diff_count += 1
            if len(first_diffs) < int(max(0, max_diffs)):
                first_diffs.append(
                    FieldDiff(
                        record_key=key,
                        field=field_name,
                        baseline=left,
                        candidate=right,
                    )
                )

    return StreamComparison(
        stream=stream,
        baseline_rows=len(baseline_rows),
        candidate_rows=len(candidate_rows),
        matched_records=len(common_keys),
        baseline_only_records=sorted(baseline_keys - candidate_keys),
        candidate_only_records=sorted(candidate_keys - baseline_keys),
        added_fields=sorted(added_fields),
        removed_fields=sorted(removed_fields),
        common_field_diff_count=diff_count,
        first_diffs=first_diffs,
        baseline_tick_range=tick_range(baseline_rows),
        candidate_tick_range=tick_range(candidate_rows),
        missing_baseline_stream=missing_baseline_stream,
        missing_candidate_stream=missing_candidate_stream,
    )


def compare_run_dirs(
    baseline_dir: Path | str,
    candidate_dir: Path | str,
    *,
    streams: Sequence[str] = DEFAULT_STREAMS,
    ignore_fields: Iterable[str] = DEFAULT_IGNORE_FIELDS,
    abs_tol: float = 1e-12,
    max_diffs: int = 20,
) -> RunComparison:
    baseline = Path(baseline_dir)
    candidate = Path(candidate_dir)
    comparisons: List[StreamComparison] = []
    for stream in streams:
        baseline_path = baseline / stream
        candidate_path = candidate / stream
        baseline_rows = read_jsonl_zst(baseline_path)
        candidate_rows = read_jsonl_zst(candidate_path)
        comparisons.append(
            compare_rows(
                stream,
                baseline_rows,
                candidate_rows,
                ignore_fields=ignore_fields,
                abs_tol=abs_tol,
                max_diffs=max_diffs,
                missing_baseline_stream=not baseline_path.exists(),
                missing_candidate_stream=not candidate_path.exists(),
            )
        )
    return RunComparison(
        baseline_dir=str(baseline),
        candidate_dir=str(candidate),
        streams=comparisons,
    )


def format_text_report(
    comparison: RunComparison,
    *,
    allowed_added_fields: Iterable[str] = (),
    allowed_removed_fields: Iterable[str] = (),
) -> str:
    lines = [
        f"baseline: {comparison.baseline_dir}",
        f"candidate: {comparison.candidate_dir}",
    ]
    for stream in comparison.streams:
        unexpected = stream.has_unexpected_changes(
            allowed_added_fields=allowed_added_fields,
            allowed_removed_fields=allowed_removed_fields,
        )
        lines.append("")
        lines.append(f"[{stream.stream}] {'DIFF' if unexpected else 'OK'}")
        lines.append(f"rows: baseline={stream.baseline_rows} candidate={stream.candidate_rows}")
        lines.append(f"matched_records: {stream.matched_records}")
        lines.append(
            f"tick_range: baseline={stream.baseline_tick_range} candidate={stream.candidate_tick_range}"
        )
        if stream.baseline_only_records:
            lines.append(f"baseline_only_records: {len(stream.baseline_only_records)}")
        if stream.candidate_only_records:
            lines.append(f"candidate_only_records: {len(stream.candidate_only_records)}")
        if stream.added_fields:
            lines.append(f"added_fields: {', '.join(stream.added_fields)}")
        if stream.removed_fields:
            lines.append(f"removed_fields: {', '.join(stream.removed_fields)}")
        lines.append(f"common_field_diff_count: {stream.common_field_diff_count}")
        for diff in stream.first_diffs:
            lines.append(
                "diff "
                f"{diff.record_key} {diff.field}: "
                f"baseline={diff.baseline!r} candidate={diff.candidate!r}"
            )
    return "\n".join(lines)


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Compare VDM runtime run artifacts.")
    parser.add_argument("baseline_dir", type=Path)
    parser.add_argument("candidate_dir", type=Path)
    parser.add_argument("--stream", action="append", dest="streams", default=None)
    parser.add_argument("--ignore-field", action="append", default=[])
    parser.add_argument("--allow-added-field", action="append", default=[])
    parser.add_argument("--allow-removed-field", action="append", default=[])
    parser.add_argument("--abs-tol", type=float, default=1e-12)
    parser.add_argument("--max-diffs", type=int, default=20)
    parser.add_argument("--json", action="store_true", dest="json_output")
    parser.add_argument("--no-fail", action="store_true")
    return parser


def main(argv: Sequence[str] | None = None) -> int:
    args = build_parser().parse_args(argv)
    ignore_fields = set(DEFAULT_IGNORE_FIELDS)
    ignore_fields.update(args.ignore_field or [])
    comparison = compare_run_dirs(
        args.baseline_dir,
        args.candidate_dir,
        streams=tuple(args.streams or DEFAULT_STREAMS),
        ignore_fields=ignore_fields,
        abs_tol=float(args.abs_tol),
        max_diffs=int(args.max_diffs),
    )
    if args.json_output:
        print(json.dumps(comparison.to_dict(), indent=2, sort_keys=True))
    else:
        print(
            format_text_report(
                comparison,
                allowed_added_fields=args.allow_added_field,
                allowed_removed_fields=args.allow_removed_field,
            )
        )
    if args.no_fail:
        return 0
    return 1 if comparison.has_unexpected_changes(
        allowed_added_fields=args.allow_added_field,
        allowed_removed_fields=args.allow_removed_field,
    ) else 0


if __name__ == "__main__":
    raise SystemExit(main())