"""Definitions for persisted precomputed historical snapshots."""

from __future__ import annotations

from datetime import datetime, timezone
from pathlib import Path

from .historical_storage import (
    list_historical_server_summaries,
    list_historical_servers,
    list_recent_historical_matches,
    list_weekly_leaderboard,
)

SNAPSHOT_TYPE_SERVER_SUMMARY = "server-summary"
SNAPSHOT_TYPE_WEEKLY_LEADERBOARD = "weekly-leaderboard"
SNAPSHOT_TYPE_RECENT_MATCHES = "recent-matches"

SUPPORTED_SNAPSHOT_TYPES = frozenset(
    {
        SNAPSHOT_TYPE_SERVER_SUMMARY,
        SNAPSHOT_TYPE_WEEKLY_LEADERBOARD,
        SNAPSHOT_TYPE_RECENT_MATCHES,
    }
)

SUPPORTED_LEADERBOARD_METRICS = frozenset(
    {
        "kills",
        "deaths",
        "support",
        "matches_over_100_kills",
    }
)
SNAPSHOT_LEADERBOARD_METRICS = (
    "kills",
    "deaths",
    "matches_over_100_kills",
    "support",
)

DEFAULT_SNAPSHOT_WINDOW = "all-time"
DEFAULT_WEEKLY_SNAPSHOT_WINDOW = "7d"
DEFAULT_WEEKLY_LEADERBOARD_LIMIT = 10
DEFAULT_RECENT_MATCHES_LIMIT = 20


def validate_snapshot_identity(
    *,
    snapshot_type: str,
    metric: str | None = None,
) -> None:
    """Validate the persisted snapshot selectors accepted by the storage layer."""
    if snapshot_type not in SUPPORTED_SNAPSHOT_TYPES:
        raise ValueError(f"Unsupported historical snapshot type: {snapshot_type}")

    if snapshot_type == SNAPSHOT_TYPE_WEEKLY_LEADERBOARD:
        if metric not in SUPPORTED_LEADERBOARD_METRICS:
            raise ValueError(f"Unsupported historical snapshot metric: {metric}")
        return

    if metric is not None:
        raise ValueError(f"Metric is only supported for {SNAPSHOT_TYPE_WEEKLY_LEADERBOARD}.")


def list_snapshot_server_keys(*, db_path: Path | None = None) -> list[str]:
    """Return the historical server slugs that should receive persisted snapshots."""
    return [
        str(item["slug"])
        for item in list_historical_servers(db_path=db_path)
        if item.get("slug")
    ]


def build_historical_server_snapshots(
    *,
    server_key: str,
    generated_at: datetime | None = None,
    leaderboard_limit: int = DEFAULT_WEEKLY_LEADERBOARD_LIMIT,
    recent_matches_limit: int = DEFAULT_RECENT_MATCHES_LIMIT,
    db_path: Path | None = None,
) -> list[dict[str, object]]:
    """Build all precomputed historical snapshots required for one server."""
    generated_at_value = _as_utc(generated_at or datetime.now(timezone.utc))
    snapshots = [_build_server_summary_snapshot(server_key, generated_at_value, db_path=db_path)]

    for metric in SNAPSHOT_LEADERBOARD_METRICS:
        snapshots.append(
            _build_weekly_leaderboard_snapshot(
                server_key,
                metric,
                generated_at_value,
                limit=leaderboard_limit,
                db_path=db_path,
            )
        )

    snapshots.append(
        _build_recent_matches_snapshot(
            server_key,
            generated_at_value,
            limit=recent_matches_limit,
            db_path=db_path,
        )
    )
    return snapshots


def build_all_historical_snapshots(
    *,
    server_key: str | None = None,
    generated_at: datetime | None = None,
    leaderboard_limit: int = DEFAULT_WEEKLY_LEADERBOARD_LIMIT,
    recent_matches_limit: int = DEFAULT_RECENT_MATCHES_LIMIT,
    db_path: Path | None = None,
) -> list[dict[str, object]]:
    """Build the full snapshot set for one server or for all configured servers."""
    target_server_keys = [server_key] if server_key else list_snapshot_server_keys(db_path=db_path)
    snapshots: list[dict[str, object]] = []
    for target_server_key in target_server_keys:
        snapshots.extend(
            build_historical_server_snapshots(
                server_key=target_server_key,
                generated_at=generated_at,
                leaderboard_limit=leaderboard_limit,
                recent_matches_limit=recent_matches_limit,
                db_path=db_path,
            )
        )
    return snapshots


def _build_server_summary_snapshot(
    server_key: str,
    generated_at: datetime,
    *,
    db_path: Path | None = None,
) -> dict[str, object]:
    summary_items = list_historical_server_summaries(server_slug=server_key, db_path=db_path)
    summary_item = summary_items[0] if summary_items else {}
    time_range = summary_item.get("time_range") if isinstance(summary_item, dict) else {}
    return {
        "server_key": server_key,
        "snapshot_type": SNAPSHOT_TYPE_SERVER_SUMMARY,
        "metric": None,
        "window": DEFAULT_SNAPSHOT_WINDOW,
        "generated_at": generated_at,
        "source_range_start": _parse_optional_timestamp(time_range.get("start")),
        "source_range_end": _parse_optional_timestamp(time_range.get("end")),
        "is_stale": False,
        "payload": {
            "server_key": server_key,
            "generated_at": _to_iso(generated_at),
            "item": summary_item,
        },
    }


def _build_weekly_leaderboard_snapshot(
    server_key: str,
    metric: str,
    generated_at: datetime,
    *,
    limit: int,
    db_path: Path | None = None,
) -> dict[str, object]:
    leaderboard_result = list_weekly_leaderboard(
        limit=limit,
        server_id=server_key,
        metric=metric,
        db_path=db_path,
    )
    return {
        "server_key": server_key,
        "snapshot_type": SNAPSHOT_TYPE_WEEKLY_LEADERBOARD,
        "metric": metric,
        "window": DEFAULT_WEEKLY_SNAPSHOT_WINDOW,
        "generated_at": generated_at,
        "source_range_start": _parse_optional_timestamp(leaderboard_result.get("window_start")),
        "source_range_end": _parse_optional_timestamp(leaderboard_result.get("window_end")),
        "is_stale": False,
        "payload": {
            "server_key": server_key,
            "metric": metric,
            "limit": limit,
            "generated_at": _to_iso(generated_at),
            **leaderboard_result,
        },
    }


def _build_recent_matches_snapshot(
    server_key: str,
    generated_at: datetime,
    *,
    limit: int,
    db_path: Path | None = None,
) -> dict[str, object]:
    items = list_recent_historical_matches(
        limit=limit,
        server_slug=server_key,
        db_path=db_path,
    )
    closed_points = [
        _parse_optional_timestamp(item.get("closed_at"))
        for item in items
        if isinstance(item, dict) and item.get("closed_at")
    ]
    return {
        "server_key": server_key,
        "snapshot_type": SNAPSHOT_TYPE_RECENT_MATCHES,
        "metric": None,
        "window": DEFAULT_SNAPSHOT_WINDOW,
        "generated_at": generated_at,
        "source_range_start": min(closed_points) if closed_points else None,
        "source_range_end": max(closed_points) if closed_points else None,
        "is_stale": False,
        "payload": {
            "server_key": server_key,
            "limit": limit,
            "generated_at": _to_iso(generated_at),
            "items": items,
        },
    }


def _parse_optional_timestamp(value: object) -> datetime | None:
    if not isinstance(value, str) or not value.strip():
        return None
    normalized = value.strip().replace("Z", "+00:00")
    parsed = datetime.fromisoformat(normalized)
    if parsed.tzinfo is None:
        return parsed.replace(tzinfo=timezone.utc)
    return parsed.astimezone(timezone.utc)


def _as_utc(value: datetime) -> datetime:
    if value.tzinfo is None:
        return value.replace(tzinfo=timezone.utc)
    return value.astimezone(timezone.utc)


def _to_iso(value: datetime) -> str:
    return _as_utc(value).isoformat().replace("+00:00", "Z")