from __future__ import annotations

import unittest

from fastapi import HTTPException

from govoplan_access.backend.api.v1.routes import (
    _decode_full_delta_cursor,
    _encode_full_delta_cursor,
    _full_delta_page,
    _page_query,
)


class FakeQuery:
    def __init__(self, rows: list[int]) -> None:
        self._rows = rows
        self._offset = 0
        self._limit: int | None = None

    def order_by(self, *_args: object) -> FakeQuery:
        return self

    def count(self) -> int:
        return len(self._rows)

    def offset(self, value: int) -> FakeQuery:
        clone = FakeQuery(self._rows)
        clone._offset = value
        clone._limit = self._limit
        return clone

    def limit(self, value: int) -> FakeQuery:
        clone = FakeQuery(self._rows)
        clone._offset = self._offset
        clone._limit = value
        return clone

    def all(self) -> list[int]:
        end = None if self._limit is None else self._offset + self._limit
        return self._rows[self._offset:end]


class AdminPaginationTests(unittest.TestCase):
    def test_page_query_returns_page_and_metadata(self) -> None:
        rows, metadata = _page_query(FakeQuery(list(range(7))), page=2, page_size=3)

        self.assertEqual(rows, [3, 4, 5])
        self.assertEqual(metadata, {"total": 7, "page": 2, "page_size": 3, "pages": 3})

    def test_full_delta_page_returns_cursor_until_last_page(self) -> None:
        rows, metadata, watermark, has_more = _full_delta_page(
            FakeQuery(list(range(7))),
            page=2,
            page_size=3,
            scope="users",
            snapshot_sequence=42,
        )

        self.assertEqual(rows, [3, 4, 5])
        self.assertEqual(metadata, {"total": 7, "page": 2, "page_size": 3, "pages": 3})
        self.assertEqual(watermark, "full:users:3:42")
        self.assertTrue(has_more)

    def test_full_delta_page_returns_sequence_watermark_on_last_page(self) -> None:
        rows, metadata, watermark, has_more = _full_delta_page(
            FakeQuery(list(range(7))),
            page=3,
            page_size=3,
            scope="users",
            snapshot_sequence=42,
        )

        self.assertEqual(rows, [6])
        self.assertEqual(metadata, {"total": 7, "page": 3, "page_size": 3, "pages": 3})
        self.assertEqual(watermark, "seq:42")
        self.assertFalse(has_more)

    def test_full_delta_cursor_round_trips_and_rejects_wrong_scope(self) -> None:
        cursor = _encode_full_delta_cursor("users", page=3, snapshot_sequence=42)

        self.assertEqual(_decode_full_delta_cursor(cursor, scope="users"), (3, 42))
        self.assertIsNone(_decode_full_delta_cursor("seq:42", scope="users"))
        with self.assertRaises(HTTPException):
            _decode_full_delta_cursor(cursor, scope="groups")


if __name__ == "__main__":
    unittest.main()