"""Shared upload serializers and response helpers for form upload endpoints."""

from __future__ import annotations

from datetime import datetime
from typing import Any
from uuid import uuid4

from django.utils import timezone
from rest_framework import serializers, status
from rest_framework.response import Response

MAX_UPLOAD_SIZE_BYTES = 50 * 1024 * 1024
ALLOWED_UPLOAD_EXTENSIONS = (".xlsx", ".xls")

_ROMAN_NUMBERS = {
    1: "I",
    2: "II",
    3: "III",
    4: "IV",
}


def _normalize_extension(name: str) -> str:
    return name.rsplit(".", 1)[-1].lower() if "." in name else ""


def _validate_uploaded_file(value: Any) -> None:
    if not hasattr(value, "name") or not value.name:
        raise serializers.ValidationError("Файл не выбран")

    extension = "." + _normalize_extension(value.name)
    if extension not in ALLOWED_UPLOAD_EXTENSIONS:
        raise serializers.ValidationError("Неподдерживаемый формат файла")

    if value.size > MAX_UPLOAD_SIZE_BYTES:
        raise serializers.ValidationError("Размер файла превышает 50MB")


def report_quarter_display(report_year: int, report_quarter: int) -> str:
    return f"{_ROMAN_NUMBERS.get(report_quarter, report_quarter)} квартал {report_year}"


def report_half_year_display(report_year: int, report_half_year: int) -> str:
    return f"{_ROMAN_NUMBERS.get(report_half_year, report_half_year)} полугодие {report_year}"


def report_annual_display(report_year: int) -> str:
    return f"{report_year} год"


def build_upload_success_payload(
    *,
    form: str,
    report_year: int,
    status: str,
    report_quarter: int | None = None,
    report_half_year: int | None = None,
    result: dict[str, Any] | None = None,
    job_id: str | None = None,
    created_at: datetime | None = None,
) -> dict[str, Any]:
    created = created_at or timezone.now()
    payload: dict[str, Any] = {
        "upload_id": str(uuid4()),
        "form": form,
        "report_year": report_year,
        "status": status,
        "created_at": created.isoformat(),
    }

    if report_half_year is not None:
        payload["report_half_year"] = report_half_year
        payload["report_period_display"] = report_half_year_display(
            report_year=report_year,
            report_half_year=report_half_year,
        )
    elif report_quarter is not None:
        payload["report_quarter"] = report_quarter
        payload["report_period_display"] = report_quarter_display(
            report_year=report_year,
            report_quarter=report_quarter,
        )
    else:
        payload["report_period_display"] = report_annual_display(
            report_year=report_year
        )

    if result is not None:
        payload["result"] = result

    if job_id is not None:
        payload["job_id"] = job_id

    return payload


def build_upload_validation_payload(errors: dict[str, Any]) -> dict[str, Any]:
    details: list[dict[str, Any]] = []

    def _collect(field: str, value: Any) -> None:
        if isinstance(value, dict):
            for nested_field, nested_value in value.items():
                nested_name = f"{field}.{nested_field}" if field else nested_field
                _collect(nested_name, nested_value)
            return

        if isinstance(value, list):
            for item in value:
                _collect(field, item)
            return

        code = getattr(value, "code", None) or "invalid"
        details.append(
            {
                "field": field,
                "code": code,
                "message": str(value),
            }
        )

    for field, value in errors.items():
        target_field = "non_field_errors" if field == "non_field_errors" else field
        _collect(target_field, value)

    return {
        "error_code": "validation_error",
        "error_message": "Validation failed",
        "details": details,
    }


def build_upload_error_payload(
    *,
    error_code: str,
    error_message: str,
    details: list[dict[str, Any]] | None = None,
) -> dict[str, Any]:
    return {
        "error_code": error_code,
        "error_message": error_message,
        "details": details or [],
    }


def build_upload_error_response(
    *,
    error_code: str,
    error_message: str,
    details: list[dict[str, Any]] | None = None,
    status_code: int = status.HTTP_400_BAD_REQUEST,
) -> Response:
    return Response(
        build_upload_error_payload(
            error_code=error_code,
            error_message=error_message,
            details=details,
        ),
        status=status_code,
    )


def build_upload_validation_response(errors: dict[str, Any]) -> Response:
    return Response(
        build_upload_validation_payload(errors),
        status=status.HTTP_400_BAD_REQUEST,
    )


class BaseUploadSerializer(serializers.Serializer):
    file = serializers.FileField(help_text="Excel файл (.xlsx, .xls)")
    report_year = serializers.IntegerField(min_value=2000, help_text="Отчетный год")

    def validate_file(self, value):
        _validate_uploaded_file(value)
        return value


class UploadQuarterSerializer(BaseUploadSerializer):
    report_quarter = serializers.IntegerField(
        min_value=1,
        max_value=4,
        required=True,
        help_text="Отчетный квартал от 1 до 4",
    )


class UploadHalfYearSerializer(BaseUploadSerializer):
    report_half_year = serializers.IntegerField(
        min_value=1,
        max_value=2,
        required=True,
        help_text="Полугодие отчета: 1 или 2",
    )


class UploadAnnualSerializer(BaseUploadSerializer):
    """Upload payload without period quarter (годовая форма)."""


class FieldErrorSerializer(serializers.Serializer):
    field = serializers.CharField()
    message = serializers.CharField()


class RowValidationErrorSerializer(serializers.Serializer):
    row = serializers.IntegerField()
    inn = serializers.CharField(allow_null=True)
    kpp = serializers.CharField(allow_null=True)
    organization_name = serializers.CharField(allow_null=True)
    errors = FieldErrorSerializer(many=True)


class UploadParseResultSerializer(serializers.Serializer):
    batch_id = serializers.IntegerField()
    loaded_count = serializers.IntegerField()
    skipped_count = serializers.IntegerField()
    errors = RowValidationErrorSerializer(many=True)