# topology_api/routes/snapshot.py
from datetime import datetime

from flask import Blueprint, request, jsonify
from topology_api.queries.snapshot_queries import (
    resolve_snapshot_time, fetch_snapshot, fetch_layout, fetch_missions,
)

snapshot_bp = Blueprint("snapshot", __name__)
GHC06_LAYOUT_START = datetime.fromisoformat("2025-02-15T00:00:00+00:00")


def _layout_key_for_snapshot(requested_mission, snapshot_at):
    """Keep historical mission views pinned to their contemporary layout.

    GHC-05 overlaps GHC-06 chronologically, so timestamp-only selection would
    incorrectly redraw the GHC-05 terminal snapshot with the later expansion
    layout. Explicit mission views therefore take precedence over time.
    """
    if requested_mission:
        try:
            mission_number = int(requested_mission.rsplit("-", 1)[-1])
        except (TypeError, ValueError):
            mission_number = None
        return (
            "engineering_overview_ghc06_v1"
            if mission_number is not None and mission_number >= 6
            else None
        )

    snapshot_dt = datetime.fromisoformat(snapshot_at.replace("Z", "+00:00"))
    return (
        "engineering_overview_ghc06_v1"
        if snapshot_dt >= GHC06_LAYOUT_START
        else None
    )


def _parse_iso_timestamp(value):
    if value is None:
        return None
    try:
        parsed = datetime.fromisoformat(value.replace("Z", "+00:00"))
    except ValueError:
        return None
    if parsed.tzinfo is None:
        return None
    return parsed.isoformat()


@snapshot_bp.route("/api/v1/bases/<base_code>/missions")
def get_missions(base_code):
    if base_code != "guanghan":
        return jsonify({
            "error": "base_not_found",
            "message": f"Base '{base_code}' not found.",
        }), 404
    return jsonify({"missions": fetch_missions(base_code)})


@snapshot_bp.route("/api/v1/bases/<base_code>/snapshot")
def get_snapshot(base_code):
    if base_code != "guanghan":
        return jsonify({
            "error": "base_not_found",
            "message": f"Base '{base_code}' not found. Only 'guanghan' is available.",
        }), 404

    requested_mission = request.args.get("mission")
    requested_at = request.args.get("at")
    normalized_at = _parse_iso_timestamp(requested_at)

    if requested_at is not None and normalized_at is None:
        return jsonify({
            "error": "invalid_time",
            "message": (
                "Parameter 'at' must be an ISO 8601 timestamp with a timezone."
            ),
        }), 400

    snapshot_at, anchor_source = resolve_snapshot_time(
        requested_mission=requested_mission,
        requested_at=normalized_at,
    )

    if anchor_source == "mission_not_found":
        return jsonify({
            "error": "mission_not_found",
            "message": f"Mission '{requested_mission}' not found.",
        }), 404

    if anchor_source == "mission_has_no_timed_event":
        return jsonify({
            "error": "mission_has_no_timed_event",
            "message": f"Mission '{requested_mission}' has no timed events.",
        }), 409

    if anchor_source == "no_events":
        return jsonify({
            "base": {"code": "guanghan", "name": "广寒基地"},
            "query": {
                "requestedAt": requested_at,
                "requestedMission": requested_mission,
                "snapshotAt": None,
                "anchorSource": "no_events",
            },
            "components": [],
            "connections": [],
        })

    data = fetch_snapshot(snapshot_at)
    layout_key = _layout_key_for_snapshot(requested_mission, snapshot_at)
    layout = fetch_layout(layout_key=layout_key)

    return jsonify({
        "base": data["base"],
        "query": {
            "requestedAt": requested_at,
            "requestedMission": requested_mission,
            "snapshotAt": snapshot_at,
            "anchorSource": anchor_source,
        },
        "components": data["components"],
        "connections": data["connections"],
        "layout": layout,
    })