from __future__ import annotations

from dataclasses import dataclass
from datetime import date
from typing import Any

from django.utils.dateparse import parse_date

REQUIRED_RECORD_FIELDS = {
    "competition_external_id",
    "competition_name",
    "season",
    "team_external_id",
    "team_name",
    "player_external_id",
    "full_name",
    "games_played",
    "minutes_per_game",
    "points_per_game",
    "rebounds_per_game",
    "assists_per_game",
    "steals_per_game",
    "blocks_per_game",
    "turnovers_per_game",
    "fg_pct",
    "three_pt_pct",
    "ft_pct",
}

OPTIONAL_RECORD_FIELDS = {
    "first_name",
    "last_name",
    "birth_date",
    "nationality",
    "height_cm",
    "weight_kg",
    "position",
}

ALLOWED_TOP_LEVEL_FIELDS = {
    "source_name",
    "snapshot_date",
    "records",
    "source_metadata",
    "raw_payload",
}

ALLOWED_RECORD_FIELDS = REQUIRED_RECORD_FIELDS | OPTIONAL_RECORD_FIELDS | {
    "role",
    "source_metadata",
    "raw_payload",
}


@dataclass
class SnapshotValidationResult:
    source_name: str
    snapshot_date: date
    records: list[dict[str, Any]]


class SnapshotValidationError(ValueError):
    pass


class SnapshotSchemaValidator:
    """Strict JSON schema validator for HoopScout v2 player-season snapshots."""

    @staticmethod
    def _require_string(value: Any, field: str) -> str:
        if not isinstance(value, str) or not value.strip():
            raise SnapshotValidationError(f"{field} must be a non-empty string")
        return value.strip()

    @staticmethod
    def _optional_string(value: Any, field: str) -> str | None:
        if value in (None, ""):
            return None
        if not isinstance(value, str):
            raise SnapshotValidationError(f"{field} must be a string when provided")
        stripped = value.strip()
        return stripped or None

    @staticmethod
    def _require_non_negative_int(value: Any, field: str) -> int:
        if isinstance(value, bool):
            raise SnapshotValidationError(f"{field} must be a non-negative integer")
        try:
            parsed = int(value)
        except (TypeError, ValueError) as exc:
            raise SnapshotValidationError(f"{field} must be a non-negative integer") from exc
        if parsed < 0:
            raise SnapshotValidationError(f"{field} must be a non-negative integer")
        return parsed

    @classmethod
    def _optional_non_negative_int(cls, value: Any, field: str) -> int | None:
        if value in (None, ""):
            return None
        return cls._require_non_negative_int(value, field)

    @staticmethod
    def _require_float(value: Any, field: str) -> float:
        try:
            parsed = float(value)
        except (TypeError, ValueError) as exc:
            raise SnapshotValidationError(f"{field} must be numeric") from exc
        return parsed

    @classmethod
    def _validate_record(cls, record: dict[str, Any], index: int) -> dict[str, Any]:
        unknown = set(record.keys()) - ALLOWED_RECORD_FIELDS
        if unknown:
            raise SnapshotValidationError(
                f"record[{index}] contains unknown fields: {', '.join(sorted(unknown))}"
            )

        missing = REQUIRED_RECORD_FIELDS - set(record.keys())
        if missing:
            raise SnapshotValidationError(
                f"record[{index}] missing required fields: {', '.join(sorted(missing))}"
            )

        normalized = dict(record)
        for field in (
            "competition_external_id",
            "competition_name",
            "season",
            "team_external_id",
            "team_name",
            "player_external_id",
            "full_name",
        ):
            normalized[field] = cls._require_string(record.get(field), f"record[{index}].{field}")

        for field in ("first_name", "last_name", "nationality", "position"):
            normalized[field] = cls._optional_string(record.get(field), f"record[{index}].{field}")

        if record.get("role") is not None:
            normalized["role"] = cls._require_string(record.get("role"), f"record[{index}].role")

        birth_date_raw = record.get("birth_date")
        if birth_date_raw in (None, ""):
            normalized["birth_date"] = None
        else:
            birth_date = parse_date(str(birth_date_raw))
            if not birth_date:
                raise SnapshotValidationError(f"record[{index}].birth_date must be YYYY-MM-DD")
            normalized["birth_date"] = birth_date.isoformat()

        normalized["height_cm"] = cls._optional_non_negative_int(record.get("height_cm"), f"record[{index}].height_cm")
        normalized["weight_kg"] = cls._optional_non_negative_int(record.get("weight_kg"), f"record[{index}].weight_kg")
        normalized["games_played"] = cls._require_non_negative_int(record.get("games_played"), f"record[{index}].games_played")

        for field in (
            "minutes_per_game",
            "points_per_game",
            "rebounds_per_game",
            "assists_per_game",
            "steals_per_game",
            "blocks_per_game",
            "turnovers_per_game",
            "fg_pct",
            "three_pt_pct",
            "ft_pct",
        ):
            normalized[field] = cls._require_float(record.get(field), f"record[{index}].{field}")

        return normalized

    @classmethod
    def validate(cls, payload: dict[str, Any]) -> SnapshotValidationResult:
        if not isinstance(payload, dict):
            raise SnapshotValidationError("Snapshot root must be an object")

        unknown = set(payload.keys()) - ALLOWED_TOP_LEVEL_FIELDS
        if unknown:
            raise SnapshotValidationError(
                f"Snapshot contains unknown top-level fields: {', '.join(sorted(unknown))}"
            )

        source_name = cls._require_string(payload.get("source_name"), "source_name")

        snapshot_date_raw = payload.get("snapshot_date")
        snapshot_date = parse_date(str(snapshot_date_raw))
        if not snapshot_date:
            raise SnapshotValidationError("snapshot_date must be YYYY-MM-DD")

        records = payload.get("records")
        if not isinstance(records, list) or not records:
            raise SnapshotValidationError("records must be a non-empty array")

        normalized_records: list[dict[str, Any]] = []
        for index, record in enumerate(records):
            if not isinstance(record, dict):
                raise SnapshotValidationError(f"record[{index}] must be an object")
            normalized_records.append(cls._validate_record(record, index=index))

        return SnapshotValidationResult(
            source_name=source_name,
            snapshot_date=snapshot_date,
            records=normalized_records,
        )