"""Validate pipeline outputs before Make stamps are touched."""

from __future__ import annotations

import argparse
import json
import sys
import zipfile
from pathlib import Path

import polars as pl


def _failures_for_file(path: Path) -> list[str]:
    if not path.exists():
        return [f"{path}: missing"]
    if not path.is_file():
        return [f"{path}: not a file"]
    try:
        size = path.stat().st_size
    except OSError as exc:
        return [f"{path}: unreadable metadata: {exc}"]
    if size <= 0:
        return [f"{path}: empty file"]
    return []


def _failures_for_dir(path: Path) -> list[str]:
    if not path.exists():
        return [f"{path}: missing"]
    if not path.is_dir():
        return [f"{path}: not a directory"]
    try:
        if not any(not child.name.startswith(".") for child in path.iterdir()):
            return [f"{path}: empty directory"]
    except OSError as exc:
        return [f"{path}: unreadable directory: {exc}"]
    return []


def _failures_for_parquet(path: Path) -> list[str]:
    failures = _failures_for_file(path)
    if failures:
        return failures
    try:
        row_count = pl.scan_parquet(path).select(pl.len()).collect().item()
    except Exception as exc:
        return [f"{path}: unreadable parquet: {exc}"]
    if row_count <= 0:
        return [f"{path}: parquet has no rows"]
    return []


def _failures_for_zip(path: Path) -> list[str]:
    failures = _failures_for_file(path)
    if failures:
        return failures
    if not zipfile.is_zipfile(path):
        return [f"{path}: unreadable zip"]
    try:
        with zipfile.ZipFile(path) as archive:
            if not archive.namelist():
                return [f"{path}: zip has no members"]
    except Exception as exc:
        return [f"{path}: unreadable zip: {exc}"]
    return []


def _split_glob(spec: str) -> tuple[Path, str]:
    if "::" not in spec:
        raise argparse.ArgumentTypeError(
            f"{spec!r} must use BASE::PATTERN, for example data::**/*.csv"
        )
    base, pattern = spec.split("::", 1)
    if not base or not pattern:
        raise argparse.ArgumentTypeError(f"{spec!r} must include BASE and PATTERN")
    return Path(base), pattern


def _split_pair(spec: str, label: str) -> tuple[Path, Path]:
    if "::" not in spec:
        raise argparse.ArgumentTypeError(
            f"{spec!r} must use LEFT::RIGHT for {label}"
        )
    left, right = spec.split("::", 1)
    if not left or not right:
        raise argparse.ArgumentTypeError(f"{spec!r} must include both paths")
    return Path(left), Path(right)


def _canonical_postcode(value: object) -> str:
    compact = "".join(str(value).split()).upper()
    if len(compact) >= 5:
        return f"{compact[:-3]} {compact[-3:]}"
    return compact


def _matched_files(spec: str) -> tuple[Path, str, list[Path]]:
    base, pattern = _split_glob(spec)
    if not base.exists():
        return base, pattern, []
    return base, pattern, sorted(path for path in base.glob(pattern) if path.is_file())


def _failures_for_glob(spec: str) -> list[str]:
    base, pattern, paths = _matched_files(spec)
    if not paths:
        return [f"{base}: no files matched {pattern!r}"]

    failures: list[str] = []
    for path in paths:
        failures.extend(_failures_for_file(path))
    return failures


def _failures_for_zip_glob(spec: str) -> list[str]:
    base, pattern, paths = _matched_files(spec)
    if not paths:
        return [f"{base}: no zip files matched {pattern!r}"]

    failures: list[str] = []
    for path in paths:
        failures.extend(_failures_for_zip(path))
    return failures


def _postcode_column(columns: list[str]) -> str | None:
    for name in ("postcode", "Postcode", "pcds", "PCDS"):
        if name in columns:
            return name
    return None


def _parquet_postcodes(path: Path) -> set[str]:
    schema = pl.scan_parquet(path).collect_schema()
    column = _postcode_column(schema.names())
    if column is None:
        raise ValueError(f"{path}: missing postcode column")
    values = (
        pl.scan_parquet(path)
        .select(pl.col(column).drop_nulls().unique())
        .collect()
        .get_column(column)
        .to_list()
    )
    return {_canonical_postcode(value) for value in values if _canonical_postcode(value)}


def _boundary_postcodes(path: Path) -> set[str]:
    units_dir = path / "units" if (path / "units").is_dir() else path
    postcodes: set[str] = set()
    for geojson_path in sorted(units_dir.glob("*.geojson")):
        with geojson_path.open("r", encoding="utf-8") as handle:
            data = json.load(handle)
        for feature in data.get("features", []):
            properties = feature.get("properties") or {}
            value = properties.get("postcodes")
            if value is not None:
                postcode = _canonical_postcode(value)
                if postcode:
                    postcodes.add(postcode)
    return postcodes


def _sample(values: set[str]) -> str:
    return ", ".join(sorted(values)[:10])


def _failures_for_postcode_boundary_match(spec: str) -> list[str]:
    parquet_path, boundaries_path = _split_pair(spec, "postcode boundary matching")
    failures = _failures_for_parquet(parquet_path) + _failures_for_dir(boundaries_path)
    if failures:
        return failures

    try:
        parquet_postcodes = _parquet_postcodes(parquet_path)
        boundary_postcodes = _boundary_postcodes(boundaries_path)
    except Exception as exc:
        return [f"{parquet_path} / {boundaries_path}: postcode match check failed: {exc}"]

    failures = []
    if not boundary_postcodes:
        failures.append(f"{boundaries_path}: no boundary postcodes found")

    missing_boundaries = parquet_postcodes - boundary_postcodes
    orphan_boundaries = boundary_postcodes - parquet_postcodes
    if missing_boundaries:
        failures.append(
            f"{boundaries_path}: {len(missing_boundaries):,} postcodes from {parquet_path} "
            f"are missing boundaries; sample: {_sample(missing_boundaries)}"
        )
    if orphan_boundaries:
        failures.append(
            f"{boundaries_path}: {len(orphan_boundaries):,} boundary postcodes are absent from "
            f"{parquet_path}; sample: {_sample(orphan_boundaries)}"
        )
    return failures


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--file", action="append", default=[], type=Path)
    parser.add_argument("--dir", action="append", default=[], type=Path)
    parser.add_argument("--parquet", action="append", default=[], type=Path)
    parser.add_argument("--zip", action="append", default=[], type=Path)
    parser.add_argument(
        "--glob",
        action="append",
        default=[],
        help="Require at least one non-empty file matching BASE::PATTERN",
    )
    parser.add_argument(
        "--zip-glob",
        action="append",
        default=[],
        help="Require at least one readable zip matching BASE::PATTERN",
    )
    parser.add_argument(
        "--postcode-boundary-match",
        action="append",
        default=[],
        help="Require postcode parquet keys to exactly match boundary GeoJSON postcodes: PARQUET::DIR",
    )
    args = parser.parse_args()

    failures: list[str] = []
    for path in args.file:
        failures.extend(_failures_for_file(path))
    for path in args.dir:
        failures.extend(_failures_for_dir(path))
    for path in args.parquet:
        failures.extend(_failures_for_parquet(path))
    for path in args.zip:
        failures.extend(_failures_for_zip(path))
    for spec in args.glob:
        failures.extend(_failures_for_glob(spec))
    for spec in args.zip_glob:
        failures.extend(_failures_for_zip_glob(spec))
    for spec in args.postcode_boundary_match:
        failures.extend(_failures_for_postcode_boundary_match(spec))

    if failures:
        print("Output validation failed:", file=sys.stderr)
        for failure in failures:
            print(f"  - {failure}", file=sys.stderr)
        return 1

    return 0


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