from __future__ import annotations

from dataclasses import dataclass
from datetime import timezone
from functools import partial
from typing import Callable, Iterable, Iterator, Sequence

from .export_query import ProjectExportFilters, ScenarioExportFilters

__all__ = [
    "CSVExportColumn",
    "CSVExportRowFactory",
    "build_project_row_factory",
    "build_scenario_row_factory",
]

CSVValueFormatter = Callable[[object | None], str]
RowExtractor = Callable[[object], Sequence[object | None]]


@dataclass(slots=True, frozen=True)
class CSVExportColumn:
    """Describe how a field is rendered into CSV output."""

    header: str
    accessor: str
    formatter: CSVValueFormatter | None = None


@dataclass(slots=True, frozen=True)
class CSVExportRowFactory:
    """Builds row values for CSV serialization."""

    columns: tuple[CSVExportColumn, ...]

    def headers(self) -> tuple[str, ...]:
        return tuple(column.header for column in self.columns)

    def to_row(self, entity: object) -> tuple[str, ...]:
        values: list[str] = []
        for column in self.columns:
            value = getattr(entity, column.accessor, None)
            formatter = column.formatter or _default_formatter
            values.append(formatter(value))
        return tuple(values)


def build_project_row_factory(
    *,
    include_timestamps: bool = True,
    include_description: bool = True,
) -> CSVExportRowFactory:
    columns: list[CSVExportColumn] = [
        CSVExportColumn(header="name", accessor="name"),
        CSVExportColumn(header="location", accessor="location"),
        CSVExportColumn(header="operation_type", accessor="operation_type"),
    ]
    if include_description:
        columns.append(
            CSVExportColumn(header="description", accessor="description")
        )
    if include_timestamps:
        columns.extend(
            (
                CSVExportColumn(
                    header="created_at",
                    accessor="created_at",
                    formatter=_format_datetime,
                ),
                CSVExportColumn(
                    header="updated_at",
                    accessor="updated_at",
                    formatter=_format_datetime,
                ),
            )
        )
    return CSVExportRowFactory(columns=tuple(columns))


def build_scenario_row_factory(
    *,
    include_description: bool = True,
    include_timestamps: bool = True,
) -> CSVExportRowFactory:
    columns: list[CSVExportColumn] = [
        CSVExportColumn(header="project_name", accessor="project_name"),
        CSVExportColumn(header="name", accessor="name"),
        CSVExportColumn(header="status", accessor="status"),
        CSVExportColumn(
            header="start_date",
            accessor="start_date",
            formatter=_format_date,
        ),
        CSVExportColumn(
            header="end_date",
            accessor="end_date",
            formatter=_format_date,
        ),
        CSVExportColumn(header="discount_rate",
                        accessor="discount_rate", formatter=_format_number),
        CSVExportColumn(header="currency", accessor="currency"),
        CSVExportColumn(header="primary_resource",
                        accessor="primary_resource"),
    ]
    if include_description:
        columns.append(
            CSVExportColumn(header="description", accessor="description")
        )
    if include_timestamps:
        columns.extend(
            (
                CSVExportColumn(
                    header="created_at",
                    accessor="created_at",
                    formatter=_format_datetime,
                ),
                CSVExportColumn(
                    header="updated_at",
                    accessor="updated_at",
                    formatter=_format_datetime,
                ),
            )
        )
    return CSVExportRowFactory(columns=tuple(columns))


def stream_projects_to_csv(
    projects: Sequence[object],
    *,
    row_factory: CSVExportRowFactory | None = None,
) -> Iterator[str]:
    factory = row_factory or build_project_row_factory()
    yield _join_row(factory.headers())
    for project in projects:
        yield _join_row(factory.to_row(project))


def stream_scenarios_to_csv(
    scenarios: Sequence[object],
    *,
    row_factory: CSVExportRowFactory | None = None,
) -> Iterator[str]:
    factory = row_factory or build_scenario_row_factory()
    yield _join_row(factory.headers())
    for scenario in scenarios:
        yield _join_row(factory.to_row(scenario))


def _join_row(values: Iterable[str]) -> str:
    return ",".join(values)


def _default_formatter(value: object | None) -> str:
    if value is None:
        return ""
    return str(value)


def _format_datetime(value: object | None) -> str:
    from datetime import datetime

    if not isinstance(value, datetime):
        return ""
    return value.astimezone(timezone.utc).replace(tzinfo=timezone.utc).isoformat().replace("+00:00", "Z")


def _format_date(value: object | None) -> str:
    from datetime import date

    if not isinstance(value, date):
        return ""
    return value.isoformat()


def _format_number(value: object | None) -> str:
    if value is None:
        return ""
    return f"{value:.2f}"