from __future__ import annotations

from dataclasses import dataclass
from datetime import date, datetime, timezone
from decimal import Decimal
from typing import Any, Iterable

import pytest

from services.export_serializers import (
    CSVExportColumn,
    CSVExporter,
    default_formatter,
    default_project_columns,
    default_scenario_columns,
    format_date_iso,
    format_datetime_utc,
    format_decimal,
    stream_projects_to_csv,
    stream_scenarios_to_csv,
)


@dataclass(slots=True)
class DummyProject:
    name: str
    location: str | None = None
    operation_type: str = "open_pit"
    description: str | None = None
    created_at: datetime | None = None
    updated_at: datetime | None = None


@dataclass(slots=True)
class DummyScenario:
    project: DummyProject | None
    name: str
    status: str = "draft"
    start_date: date | None = None
    end_date: date | None = None
    discount_rate: Decimal | None = None
    currency: str | None = None
    primary_resource: str | None = None
    description: str | None = None
    created_at: datetime | None = None
    updated_at: datetime | None = None


def collect_csv_bytes(chunks: Iterable[bytes]) -> list[str]:
    return [chunk.decode("utf-8") for chunk in chunks]


def test_csv_exporter_writes_header_and_rows() -> None:
    exporter = CSVExporter(
        [
            CSVExportColumn("Name", "name"),
            CSVExportColumn("Location", "location"),
        ]
    )

    project = DummyProject(name="Alpha", location="Nevada")

    chunks = collect_csv_bytes(exporter.iter_bytes([project]))

    assert chunks[0] == "Name,Location\n"
    assert chunks[1] == "Alpha,Nevada\n"


def test_csv_exporter_handles_optional_values_and_default_formatter() -> None:
    exporter = CSVExporter(
        [
            CSVExportColumn("Name", "name"),
            CSVExportColumn("Description", "description"),
        ]
    )

    project = DummyProject(name="Bravo")

    chunks = collect_csv_bytes(exporter.iter_bytes([project]))

    assert chunks[-1] == "Bravo,\n"


def test_stream_projects_uses_default_columns() -> None:
    projects = [
        DummyProject(
            name="Alpha",
            location="Nevada",
            operation_type="open_pit",
            description="Primary",
            created_at=datetime(2025, 1, 1, tzinfo=timezone.utc),
            updated_at=datetime(2025, 1, 2, tzinfo=timezone.utc),
        )
    ]

    chunks = collect_csv_bytes(stream_projects_to_csv(projects))

    assert chunks[0].startswith("name,location,operation_type")
    assert any("Alpha" in chunk for chunk in chunks)


def test_stream_scenarios_resolves_project_name_accessor() -> None:
    project = DummyProject(name="Project X")
    scenario = DummyScenario(project=project, name="Scenario A")

    chunks = collect_csv_bytes(stream_scenarios_to_csv([scenario]))

    assert "Project X" in chunks[-1]
    assert "Scenario A" in chunks[-1]


def test_custom_formatter_applies() -> None:
    def uppercase(value: Any) -> str:
        return str(value).upper() if value is not None else ""

    exporter = CSVExporter([
        CSVExportColumn("Name", "name", formatter=uppercase),
    ])

    chunks = collect_csv_bytes(
        exporter.iter_bytes([DummyProject(name="alpha")]))

    assert chunks[-1] == "ALPHA\n"


def test_default_formatter_handles_multiple_types() -> None:
    assert default_formatter(None) == ""
    assert default_formatter(True) == "true"
    assert default_formatter(False) == "false"
    assert default_formatter(Decimal("1.234")) == "1.23"
    assert default_formatter(
        datetime(2025, 1, 1, tzinfo=timezone.utc)).endswith("Z")
    assert default_formatter(date(2025, 1, 1)) == "2025-01-01"


def test_format_helpers() -> None:
    assert format_date_iso(date(2025, 5, 1)) == "2025-05-01"
    assert format_date_iso("not-a-date") == ""

    ts = datetime(2025, 5, 1, 12, 0, tzinfo=timezone.utc)
    assert format_datetime_utc(ts) == "2025-05-01T12:00:00Z"

    assert format_datetime_utc("nope") == ""
    assert format_decimal(None) == ""
    assert format_decimal(Decimal("12.345")) == "12.35"
    assert format_decimal(10) == "10.00"


def test_default_project_columns_includes_required_fields() -> None:
    columns = default_project_columns()
    headers = [column.header for column in columns]
    assert headers[:3] == ["name", "location", "operation_type"]


def test_default_scenario_columns_handles_missing_project() -> None:
    scenario = DummyScenario(project=None, name="Orphan Scenario")

    exporter = CSVExporter(default_scenario_columns())
    chunks = collect_csv_bytes(exporter.iter_bytes([scenario]))

    assert chunks[-1].startswith(",Orphan Scenario")


def test_csv_exporter_requires_columns() -> None:
    with pytest.raises(ValueError):
        CSVExporter([])