"""Unit tests for `undercooked.config` (PLAN.md A17): defaults, overrides, validation.

Everything here calls `load_settings({...})` with an explicit mapping wherever
possible, so a developer's local `.env` can never change what a test asserts.
The `.env` / cache behaviour is exercised separately, in an isolated directory.
"""

from __future__ import annotations

import dataclasses
import os
import subprocess
import sys
from collections.abc import Callable, Iterator
from pathlib import Path

import pytest

from undercooked import config
from undercooked.config import (
    ENV_KEYS,
    ConfigError,
    Settings,
    apply_cli_overrides,
    get_settings,
    load_settings,
    reset_settings_cache,
)

pytestmark = pytest.mark.unit

REPO_ROOT = Path(__file__).resolve().parents[2]


@pytest.fixture(autouse=True)
def pristine_env() -> Iterator[None]:
    """Undo env/cache side effects - `load_dotenv` mutates `os.environ` in place."""
    saved = dict(os.environ)
    reset_settings_cache()
    yield
    os.environ.clear()
    os.environ.update(saved)
    reset_settings_cache()


# ----------------------------------------------------------------------------- defaults


def test_defaults_match_the_documented_table() -> None:
    settings = load_settings({})
    assert settings == Settings()
    assert settings.host == "127.0.0.1"
    assert settings.port == 8000
    assert settings.tick_hz == 20
    assert settings.snapshot_hz == 20
    assert settings.max_players == 4
    assert settings.max_rooms == 200
    assert settings.levels_dir == Path("levels")
    assert settings.static_dir is None  # derived from the package layout, see server.app
    assert settings.lobby_idle_timeout_s == 900.0
    assert settings.guest_idle_timeout_s == 45.0
    assert settings.max_message_bytes == 4096
    assert settings.max_inputs_per_s == 40
    assert settings.sim_latency_ms == 0
    assert settings.debugpy is False
    assert settings.debugpy_port == 5678
    assert settings.allowed_origins == ()


def test_env_keys_cover_exactly_the_settings_fields() -> None:
    assert set(ENV_KEYS) == {field.name for field in dataclasses.fields(Settings)}


def test_settings_is_frozen_and_uses_slots() -> None:
    settings = Settings()
    with pytest.raises(dataclasses.FrozenInstanceError):
        settings.port = 1234  # type: ignore[misc]
    assert not hasattr(settings, "__dict__")


def test_config_error_is_a_value_error() -> None:
    assert issubclass(ConfigError, ValueError)


# ----------------------------------------------------------------------------- overrides


@pytest.mark.parametrize(
    ("field", "raw", "expected"),
    [
        ("host", "localhost", "localhost"),
        ("port", "8123", 8123),
        ("tick_hz", "30", 30),
        ("snapshot_hz", "15", 15),
        ("max_players", "2", 2),
        ("max_rooms", "1", 1),
        ("lobby_idle_timeout_s", "60", 60.0),
        ("guest_idle_timeout_s", "7.5", 7.5),
        ("max_message_bytes", "8192", 8192),
        ("max_inputs_per_s", "60", 60),
        ("sim_latency_ms", "150", 150),
        ("debugpy_port", "5679", 5679),
    ],
)
def test_single_variable_override(field: str, raw: str, expected: object) -> None:
    settings = load_settings({ENV_KEYS[field]: raw})
    assert getattr(settings, field) == expected
    assert settings.levels_dir == Path("levels")  # untouched fields keep their default


@pytest.mark.parametrize("raw", ["1", "true", "TRUE", "yes", "on"])
def test_debugpy_truthy_values(raw: str) -> None:
    assert load_settings({"DEBUGPY": raw}).debugpy is True


@pytest.mark.parametrize("raw", ["0", "false", "False", "no", "off"])
def test_debugpy_falsy_values(raw: str) -> None:
    assert load_settings({"DEBUGPY": raw}).debugpy is False


@pytest.mark.parametrize(
    ("raw", "expected"),
    [
        ("", ()),
        ("   ", ()),
        ("http://localhost:3000", ("http://localhost:3000",)),
        ("http://a , http://b", ("http://a", "http://b")),
        ("http://a,,http://b,", ("http://a", "http://b")),
        (",,", ()),
    ],
)
def test_allowed_origins_is_comma_split(raw: str, expected: tuple[str, ...]) -> None:
    assert load_settings({ENV_KEYS["allowed_origins"]: raw}).allowed_origins == expected


@pytest.mark.parametrize(
    ("raw", "expected"),
    [
        ("levels", Path("levels")),
        ("levels/", Path("levels")),
        ("/srv/undercooked/levels", Path("/srv/undercooked/levels")),
        ("~/kitchens", Path.home() / "kitchens"),
        ("./kitchens", Path("kitchens")),
    ],
)
def test_levels_dir_path_handling(raw: str, expected: Path) -> None:
    assert load_settings({ENV_KEYS["levels_dir"]: raw}).levels_dir == expected


@pytest.mark.parametrize(
    ("raw", "expected"),
    [
        ("/app/app/static", Path("/app/app/static")),
        ("~/static", Path.home() / "static"),
        ("static/", Path("static")),
        ("", None),
        ("   ", None),
    ],
)
def test_static_dir_is_optional_and_expanded(raw: str, expected: Path | None) -> None:
    """An unset `UNDERCOOKED_STATIC_DIR` means "derive it from the package"."""
    assert load_settings({ENV_KEYS["static_dir"]: raw}).static_dir == expected


@pytest.mark.parametrize(
    "field", ["port", "tick_hz", "lobby_idle_timeout_s", "host", "allowed_origins"]
)
@pytest.mark.parametrize("blank", ["", "   ", "\t"])
def test_blank_value_counts_as_unset(field: str, blank: str) -> None:
    assert load_settings({ENV_KEYS[field]: blank}) == Settings()


def test_surrounding_whitespace_is_tolerated() -> None:
    settings = load_settings({ENV_KEYS["port"]: " 8123 ", ENV_KEYS["host"]: "\nlocalhost\t"})
    assert (settings.port, settings.host) == (8123, "localhost")


def test_snapshot_hz_may_equal_tick_hz_but_not_exceed_it() -> None:
    both_ten = load_settings({ENV_KEYS["tick_hz"]: "10", ENV_KEYS["snapshot_hz"]: "10"})
    assert both_ten.snapshot_hz == 10
    with pytest.raises(ConfigError, match=r"UNDERCOOKED_SNAPSHOT_HZ.*must be >= 1, <= 10"):
        load_settings({ENV_KEYS["tick_hz"]: "10", ENV_KEYS["snapshot_hz"]: "20"})


# ----------------------------------------------------------------------------- validation errors


@pytest.mark.parametrize(
    ("field", "raw", "message"),
    [
        ("port", "http", "UNDERCOOKED_PORT='http' is not an integer"),
        ("port", "8.5", "UNDERCOOKED_PORT='8.5' is not an integer"),
        ("port", "0", "UNDERCOOKED_PORT=0 is invalid: must be >= 1, <= 65535"),
        ("port", "65536", "UNDERCOOKED_PORT=65536 is invalid: must be >= 1, <= 65535"),
        ("tick_hz", "4", "UNDERCOOKED_TICK_HZ=4 is invalid: must be >= 5, <= 60"),
        ("tick_hz", "99", "UNDERCOOKED_TICK_HZ=99 is invalid: must be >= 5, <= 60"),
        ("tick_hz", "twenty", "UNDERCOOKED_TICK_HZ='twenty' is not an integer"),
        ("snapshot_hz", "0", "UNDERCOOKED_SNAPSHOT_HZ=0 is invalid: must be >= 1, <= 20"),
        ("max_players", "0", "UNDERCOOKED_MAX_PLAYERS=0 is invalid: must be >= 1, <= 4"),
        ("max_players", "5", "UNDERCOOKED_MAX_PLAYERS=5 is invalid: must be >= 1, <= 4"),
        ("max_rooms", "0", "UNDERCOOKED_MAX_ROOMS=0 is invalid: must be >= 1"),
        ("max_rooms", "-3", "UNDERCOOKED_MAX_ROOMS=-3 is invalid: must be >= 1"),
        (
            "lobby_idle_timeout_s",
            "-1",
            "UNDERCOOKED_LOBBY_IDLE_TIMEOUT_S=-1.0 is invalid: must be >= 0.0",
        ),
        ("lobby_idle_timeout_s", "soon", "UNDERCOOKED_LOBBY_IDLE_TIMEOUT_S='soon' is not a number"),
        (
            "guest_idle_timeout_s",
            "-0.5",
            "UNDERCOOKED_GUEST_IDLE_TIMEOUT_S=-0.5 is invalid: must be >= 0.0",
        ),
        (
            "max_message_bytes",
            "255",
            "UNDERCOOKED_MAX_MESSAGE_BYTES=255 is invalid: must be >= 256",
        ),
        ("max_inputs_per_s", "0", "UNDERCOOKED_MAX_INPUTS_PER_S=0 is invalid: must be >= 1"),
        ("sim_latency_ms", "-1", "UNDERCOOKED_SIM_LATENCY_MS=-1 is invalid: must be >= 0"),
        ("debugpy_port", "0", "DEBUGPY_PORT=0 is invalid: must be >= 1, <= 65535"),
        (
            "debugpy",
            "maybe",
            "DEBUGPY='maybe' is not a boolean (use 1/0, true/false, yes/no, on/off)",
        ),
    ],
)
def test_invalid_values_raise_config_error(field: str, raw: str, message: str) -> None:
    with pytest.raises(ConfigError) as excinfo:
        load_settings({ENV_KEYS[field]: raw})
    assert str(excinfo.value) == message


def test_out_of_range_tick_hz_fails_from_the_real_environment() -> None:
    """The documented criterion: `UNDERCOOKED_TICK_HZ=99` fails loudly at startup."""
    env = {
        key: value
        for key, value in os.environ.items()
        if not key.startswith(("UNDERCOOKED_", "DEBUGPY"))
    }
    env["UNDERCOOKED_TICK_HZ"] = "99"
    result = subprocess.run(  # fixed argv, repo's own interpreter
        [sys.executable, "-c", "from undercooked.config import load_settings; load_settings()"],
        cwd=REPO_ROOT,
        env=env,
        capture_output=True,
        text=True,
        check=False,
        timeout=120,
    )
    assert result.returncode != 0
    assert "ConfigError" in result.stderr
    assert "UNDERCOOKED_TICK_HZ=99" in result.stderr


# ----------------------------------------------------------------------------- cached accessor


def test_get_settings_caches_until_reset(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
    monkeypatch.chdir(tmp_path)
    monkeypatch.setenv("UNDERCOOKED_PORT", "8123")
    first = get_settings()
    assert first.port == 8123
    monkeypatch.setenv("UNDERCOOKED_PORT", "9999")
    assert get_settings() is first  # still the cached object
    reset_settings_cache()
    assert get_settings().port == 9999


def test_get_settings_applies_defaults_with_an_empty_environment(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    for key in list(os.environ):
        if key.startswith(("UNDERCOOKED_", "DEBUGPY")):
            monkeypatch.delenv(key, raising=False)
    monkeypatch.setenv("PYTHON_DOTENV_DISABLED", "true")
    assert get_settings() == Settings()


# ----------------------------------------------------------------------------- .env loading


def test_dotenv_file_is_read_from_the_current_directory(
    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
) -> None:
    monkeypatch.delenv("UNDERCOOKED_PORT", raising=False)
    monkeypatch.delenv("UNDERCOOKED_MAX_ROOMS", raising=False)
    (tmp_path / ".env").write_text(
        "UNDERCOOKED_PORT=8123\nUNDERCOOKED_MAX_ROOMS=7\n", encoding="utf-8"
    )
    monkeypatch.chdir(tmp_path)
    settings = load_settings()
    assert (settings.port, settings.max_rooms) == (8123, 7)


def test_dotenv_is_found_in_a_parent_directory(
    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
) -> None:
    monkeypatch.delenv("UNDERCOOKED_PORT", raising=False)
    (tmp_path / ".env").write_text("UNDERCOOKED_PORT=8245\n", encoding="utf-8")
    nested = tmp_path / "src" / "undercooked"
    nested.mkdir(parents=True)
    monkeypatch.chdir(nested)
    assert load_settings().port == 8245


def test_dotenv_never_overrides_an_exported_variable(
    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
) -> None:
    monkeypatch.setenv("UNDERCOOKED_PORT", "7000")
    (tmp_path / ".env").write_text("UNDERCOOKED_PORT=8123\n", encoding="utf-8")
    monkeypatch.chdir(tmp_path)
    assert load_settings().port == 7000


def test_dotenv_is_read_once_until_the_cache_is_reset(
    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
) -> None:
    loaded: list[str] = []
    (tmp_path / ".env").write_text("UNDERCOOKED_PORT=8123\n", encoding="utf-8")
    monkeypatch.chdir(tmp_path)
    def fake_load_dotenv(path: object, **_kwargs: object) -> bool:
        loaded.append(str(path))
        return True

    monkeypatch.setattr(config, "load_dotenv", fake_load_dotenv)
    load_settings()
    load_settings()
    assert len(loaded) == 1  # one `.env` read per process, not one per call
    reset_settings_cache()
    load_settings()
    assert len(loaded) == 2


def test_missing_dotenv_file_is_not_an_error(
    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
) -> None:
    monkeypatch.delenv("UNDERCOOKED_PORT", raising=False)
    monkeypatch.chdir(tmp_path)
    assert load_settings().port == 8000


def test_explicit_env_mapping_skips_dotenv(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
    monkeypatch.chdir(tmp_path)
    def never_find(**_kwargs: object) -> str:
        pytest.fail("dotenv must not be read when an explicit env mapping is given")

    monkeypatch.setattr(config, "find_dotenv", never_find)
    assert load_settings({"UNDERCOOKED_PORT": "8123"}).port == 8123


# ----------------------------------------------------------------------------- .env.example


def parse_env_example(path: Path) -> dict[str, str]:
    """Read `KEY=value` lines from an env template, ignoring comments."""
    values: dict[str, str] = {}
    for line in path.read_text(encoding="utf-8").splitlines():
        stripped = line.strip()
        if not stripped or stripped.startswith("#") or "=" not in stripped:
            continue
        key, _, value = stripped.partition("=")
        values[key.strip()] = value.strip()
    return values


def test_env_example_documents_every_variable_with_its_default() -> None:
    example = parse_env_example(REPO_ROOT / ".env.example")
    assert set(example) == set(ENV_KEYS.values())
    assert load_settings(example) == Settings()


@pytest.mark.parametrize("forbidden", ["token", "password", "secret", "api_key", "reese", ".com"])
def test_env_example_values_carry_no_secrets_or_hostnames(forbidden: str) -> None:
    """The template is committed, so its values must stay placeholders (A16/A17)."""
    for key, value in parse_env_example(REPO_ROOT / ".env.example").items():
        assert forbidden not in value.lower(), f"{key} looks like it holds a secret or a real host"
        assert len(value) <= 40, f"{key} is too long to be a default"


# ----------------------------------------------------------------------------- README table


def parse_readme_config_table(path: Path) -> dict[str, str]:
    """Read the VAR / default / meaning rows of the README configuration table.

    A default written as *(empty)* means "no value", i.e. an empty string.
    """
    lines = path.read_text(encoding="utf-8").splitlines()
    try:
        start = lines.index("## Configuration")
    except ValueError:  # pragma: no cover - fails loudly if the section is renamed
        pytest.fail("README.md has no '## Configuration' section")
    table: dict[str, str] = {}
    for line in lines[start + 1 :]:
        if line.startswith("## "):
            break
        stripped = line.strip()
        if not stripped.startswith("|"):
            continue
        cells = [cell.strip() for cell in stripped.strip("|").split("|")]
        key = cells[0].strip("`")
        if not key.isupper():
            continue  # header and separator rows
        default = cells[1].strip("`")
        table[key] = "" if default.startswith("*") else default
    return table


def test_readme_documents_every_variable_with_its_default() -> None:
    table = parse_readme_config_table(REPO_ROOT / "README.md")
    assert set(table) == set(ENV_KEYS.values())
    assert load_settings(table) == Settings()


# ----------------------------------------------------------------------------- CLI overrides


def test_apply_cli_overrides_publishes_env_and_rebuilds(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    monkeypatch.delenv("UNDERCOOKED_LEVELS_DIR", raising=False)
    settings = apply_cli_overrides(levels_dir=Path("kitchens"), port=9123)
    assert settings.levels_dir == Path("kitchens")
    assert settings.port == 9123
    assert os.environ["UNDERCOOKED_LEVELS_DIR"] == "kitchens"
    assert get_settings() == settings  # a later get_settings() sees the same thing


def test_apply_cli_overrides_beats_an_existing_environment_value(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    monkeypatch.setenv("UNDERCOOKED_PORT", "8123")
    assert apply_cli_overrides(port=9200).port == 9200


def test_apply_cli_overrides_validates_the_values_it_writes() -> None:
    with pytest.raises(ConfigError, match=r"UNDERCOOKED_PORT=0 is invalid"):
        apply_cli_overrides(port=0)


def test_apply_cli_overrides_rejects_an_unknown_field() -> None:
    with pytest.raises(ConfigError, match="'nonsense' is not a configuration field"):
        apply_cli_overrides(**{"nonsense": 1})


def test_apply_cli_overrides_renders_booleans_as_env_flags() -> None:
    assert apply_cli_overrides(debugpy=True).debugpy is True
    assert os.environ["DEBUGPY"] == "1"
    assert apply_cli_overrides(debugpy=False).debugpy is False
    assert os.environ["DEBUGPY"] == "0"


def test_apply_cli_overrides_with_nothing_still_validates_the_environment(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    monkeypatch.setenv("UNDERCOOKED_TICK_HZ", "99")
    with pytest.raises(ConfigError, match="UNDERCOOKED_TICK_HZ=99"):
        apply_cli_overrides()


# ----------------------------------------------------------------------------- conftest factory


def test_make_settings_fixture_builds_settings(make_settings: Callable[..., Settings]) -> None:
    settings = make_settings(tick_hz=30, snapshot_hz=15, debugpy=True, allowed_origins=["http://a", "http://b"])
    assert (settings.tick_hz, settings.snapshot_hz) == (30, 15)
    assert settings.debugpy is True
    assert settings.allowed_origins == ("http://a", "http://b")
    assert settings.levels_dir == Path("levels")