feat: implement CSV export functionality with customizable columns and formatters

tests/test_export_serializers.py

@@ -0,0 +1,166 @@
+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([])