"""Shared wire schema. Semantic storage validation belongs to the worker."""
import json
import math

STRING_FIELDS = ("raw_id", "device_id", "caller_num", "svc", "lac", "ci")
INTEGER_FIELDS = ("rat", "epoch_start", "epoch_end", "up_bytes", "down_bytes")
REQUIRED_FIELDS = STRING_FIELDS + INTEGER_FIELDS


class PayloadError(ValueError):
    def __init__(self, reason, detail, field=None):
        super().__init__(detail)
        self.reason = reason
        self.field = field


def parse_payload(data):
    def reject_constant(value):
        raise ValueError(f"Non-finite number: {value}")
    def finite_float(value):
        number = float(value)
        if not math.isfinite(number):
            raise ValueError(f"Non-finite number: {value}")
        return number
    try:
        payload = json.loads(data.decode("utf-8"), parse_constant=reject_constant, parse_float=finite_float)
    except (UnicodeError, ValueError, RecursionError) as exc:
        raise PayloadError("invalid_json", str(exc)) from exc
    if not isinstance(payload, dict):
        raise PayloadError("invalid_payload", "Expected a JSON object")
    return payload


def validate_structure(payload):
    for field in REQUIRED_FIELDS:
        if payload.get(field) is None:
            raise PayloadError("missing_required_field", f"Field {field} is required", field)
    for field in STRING_FIELDS:
        if not isinstance(payload[field], str) or not payload[field].strip():
            raise PayloadError("invalid_payload", f"Field {field} must be a nonempty string", field)
        try:
            payload[field].encode("utf-8")
        except UnicodeError as exc:
            raise PayloadError("invalid_payload", f"Field {field} contains invalid Unicode", field) from exc
    for field in INTEGER_FIELDS:
        if type(payload[field]) is not int:
            raise PayloadError("invalid_payload", f"Field {field} must be an integer", field)
    if payload.get("src_ip") is not None and not isinstance(payload["src_ip"], str):
        raise PayloadError("invalid_payload", "Field src_ip must be a string or null", "src_ip")