"""Tests for configuration loading and merging."""

import copy
from pathlib import Path

import pytest

from derp.config import DEFAULTS, _merge, load, resolve_config


class TestMerge:
    """Test deep merge logic."""

    def test_flat_override(self):
        base = {"a": 1, "b": 2}
        result = _merge(base, {"b": 99})
        assert result == {"a": 1, "b": 99}

    def test_nested_merge(self):
        base = {"server": {"host": "a", "port": 1}}
        result = _merge(base, {"server": {"port": 2}})
        assert result == {"server": {"host": "a", "port": 2}}

    def test_list_replacement(self):
        base = {"channels": ["#old"]}
        result = _merge(base, {"channels": ["#new"]})
        assert result == {"channels": ["#new"]}

    def test_empty_override(self):
        base = {"a": 1, "b": 2}
        result = _merge(base, {})
        assert result == {"a": 1, "b": 2}

    def test_new_keys(self):
        base = {"a": 1}
        result = _merge(base, {"b": 2})
        assert result == {"a": 1, "b": 2}

    def test_base_not_mutated(self):
        base = {"server": {"host": "original"}}
        original = copy.deepcopy(base)
        _merge(base, {"server": {"host": "changed"}})
        assert base == original


class TestLoad:
    """Test TOML file loading."""

    def test_minimal_toml(self, tmp_path: Path):
        config_file = tmp_path / "test.toml"
        config_file.write_text('[server]\nnick = "testbot"\n')
        result = load(config_file)
        # Overridden value
        assert result["server"]["nick"] == "testbot"
        # Default preserved
        assert result["server"]["host"] == "irc.libera.chat"
        assert result["server"]["port"] == 6697

    def test_full_override(self, tmp_path: Path):
        config_file = tmp_path / "test.toml"
        config_file.write_text(
            '[server]\nhost = "custom.irc"\nport = 6667\n'
            '[bot]\nprefix = "."\n'
        )
        result = load(config_file)
        assert result["server"]["host"] == "custom.irc"
        assert result["server"]["port"] == 6667
        assert result["bot"]["prefix"] == "."
        # Unset defaults still present
        assert result["bot"]["channels"] == ["#test"]


class TestChannelConfig:
    """Test channel-level configuration merging."""

    def test_channel_config_loaded(self, tmp_path: Path):
        config_file = tmp_path / "test.toml"
        config_file.write_text(
            '[channels."#ops"]\nplugins = ["core", "dns"]\n'
        )
        result = load(config_file)
        assert "#ops" in result["channels"]
        assert result["channels"]["#ops"]["plugins"] == ["core", "dns"]

    def test_default_channels_empty(self):
        assert DEFAULTS["channels"] == {}

    def test_default_logging_format(self):
        assert DEFAULTS["logging"]["format"] == "text"


class TestResolveConfig:
    """Test config path resolution and fallback."""

    def test_explicit_path(self, tmp_path: Path):
        config_file = tmp_path / "explicit.toml"
        config_file.write_text('[server]\nnick = "explicit"\n')
        result = resolve_config(str(config_file))
        assert result["server"]["nick"] == "explicit"

    def test_no_file_fallback(self, tmp_path: Path, monkeypatch: "pytest.MonkeyPatch"):
        # Run from tmp_path so config/derp.toml isn't found
        monkeypatch.chdir(tmp_path)
        result = resolve_config(str(tmp_path / "nonexistent.toml"))
        # Should fall back to DEFAULTS
        assert result["server"]["host"] == DEFAULTS["server"]["host"]
        assert result["bot"]["prefix"] == DEFAULTS["bot"]["prefix"]

    def test_defaults_not_mutated(self):
        original = copy.deepcopy(DEFAULTS)
        resolve_config(None)
        assert DEFAULTS == original