"""Tests for configuration loading, merging, and ENV overrides."""

import os
from pathlib import Path

import pytest
import yaml

from kb_search.config import (
    DEFAULTS,
    _deep_merge,
    _get_nested,
    _set_nested,
    config_with_sources,
    load_config,
    save_config_value,
)


def test_deep_merge_basic():
    base = {"a": 1, "b": {"c": 2, "d": 3}}
    override = {"b": {"c": 99}}
    result = _deep_merge(base, override)
    assert result == {"a": 1, "b": {"c": 99, "d": 3}}


def test_deep_merge_new_keys():
    base = {"a": 1}
    override = {"b": 2}
    result = _deep_merge(base, override)
    assert result == {"a": 1, "b": 2}


def test_deep_merge_does_not_mutate():
    base = {"a": {"b": 1}}
    override = {"a": {"b": 2}}
    _deep_merge(base, override)
    assert base["a"]["b"] == 1


def test_set_nested():
    d = {}
    _set_nested(d, "a.b.c", 42)
    assert d == {"a": {"b": {"c": 42}}}


def test_get_nested():
    d = {"a": {"b": {"c": 42}}}
    assert _get_nested(d, "a.b.c") == 42
    assert _get_nested(d, "a.b.x", "missing") == "missing"
    assert _get_nested(d, "x.y.z") is None


def test_load_config_defaults(tmp_path):
    """With no config file, returns defaults."""
    cfg = load_config(tmp_path / "nonexistent.yaml")
    assert cfg["embedding"]["model"] == "all-MiniLM-L6-v2"
    assert cfg["search"]["default_top"] == 10
    assert cfg["chunking"]["pdf"]["strategy"] == "hierarchy"


def test_load_config_yaml_override(tmp_path):
    """YAML values override defaults."""
    config_path = tmp_path / "config.yaml"
    config_path.write_text(yaml.dump({"embedding": {"model": "nomic-embed-text"}}))
    cfg = load_config(config_path)
    assert cfg["embedding"]["model"] == "nomic-embed-text"
    # Other defaults preserved
    assert cfg["search"]["default_top"] == 10


def test_load_config_env_override(tmp_path, monkeypatch):
    """ENV overrides both YAML and defaults."""
    config_path = tmp_path / "config.yaml"
    config_path.write_text(yaml.dump({"search": {"default_top": 20}}))
    monkeypatch.setenv("KB_DEFAULT_TOP", "50")
    cfg = load_config(config_path)
    assert cfg["search"]["default_top"] == 50


def test_load_config_env_model(tmp_path, monkeypatch):
    monkeypatch.setenv("KB_MODEL", "bge-small-en-v1.5")
    cfg = load_config(tmp_path / "nonexistent.yaml")
    assert cfg["embedding"]["model"] == "bge-small-en-v1.5"


def test_save_config_value(tmp_path):
    config_path = tmp_path / "config.yaml"
    save_config_value(config_path, "chunking.pdf.max_tokens", "2048")
    with open(config_path) as f:
        data = yaml.safe_load(f)
    assert data["chunking"]["pdf"]["max_tokens"] == 2048


def test_save_config_value_bool(tmp_path):
    config_path = tmp_path / "config.yaml"
    save_config_value(config_path, "chunking.code.include_context", "false")
    with open(config_path) as f:
        data = yaml.safe_load(f)
    assert data["chunking"]["code"]["include_context"] is False


def test_save_config_preserves_existing(tmp_path):
    config_path = tmp_path / "config.yaml"
    config_path.write_text(yaml.dump({"embedding": {"model": "custom"}}))
    save_config_value(config_path, "search.default_top", "20")
    with open(config_path) as f:
        data = yaml.safe_load(f)
    assert data["embedding"]["model"] == "custom"
    assert data["search"]["default_top"] == 20


def test_config_with_sources_defaults(tmp_path, monkeypatch):
    entries = config_with_sources(tmp_path / "nonexistent.yaml")
    sources = {k: s for k, _, s in entries}
    assert sources["embedding.model"] == "default"


def test_config_with_sources_yaml(tmp_path):
    config_path = tmp_path / "config.yaml"
    config_path.write_text(yaml.dump({"embedding": {"model": "custom"}}))
    entries = config_with_sources(config_path)
    sources = {k: s for k, _, s in entries}
    assert sources["embedding.model"] == "config.yaml"


def test_config_with_sources_env(tmp_path, monkeypatch):
    monkeypatch.setenv("KB_MODEL", "from-env")
    entries = config_with_sources(tmp_path / "nonexistent.yaml")
    sources = {k: s for k, _, s in entries}
    assert sources["embedding.model"] == "env (KB_MODEL)"