/**
 * Unit tests for v1.7.0 T1: layered config loader (conf.d drop-ins).
 *
 * Exercises loadLayeredConfig() directly — no server.
 *
 * Test cases:
 *   1. Missing base + empty conf.d returns {}
 *   2. Base-only loads correctly
 *   3. Drop-in overrides base (deep merge preserves siblings)
 *   4. Drop-ins merged in lexicographic order (last wins)
 *   5. Arrays replace per RFC 7396 (not append)
 *   6. Invalid JSON in drop-in throws with filename in message
 *   7. Non-.json files in conf.d are ignored
 *   8. Missing conf.d directory is not an error
 */

#include "../service/src/config/config_loader.hpp"

#include <cassert>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
#include <unistd.h>

namespace fs = std::filesystem;
using smartbotic::database::loadLayeredConfig;

namespace {

fs::path makeTestDir(const std::string& name) {
    auto dir = fs::temp_directory_path() / ("conf-test-" + name + "-" + std::to_string(::getpid()));
    fs::remove_all(dir);
    fs::create_directories(dir);
    return dir;
}

void writeFile(const fs::path& p, const std::string& content) {
    std::ofstream f(p);
    f << content;
}

} // anonymous namespace

void test_no_base_no_dropins_returns_empty() {
    auto dir = makeTestDir("empty");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);

    auto cfg = loadLayeredConfig(base, confDir);
    assert(cfg.is_object());
    assert(cfg.empty());
    fs::remove_all(dir);
    std::cout << "PASS: missing base + empty conf.d returns {}\n";
}

void test_base_only() {
    auto dir = makeTestDir("base");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"log_level":"info","storage":{"rpc_port":9004}})");

    auto cfg = loadLayeredConfig(base, confDir);
    assert(cfg["log_level"] == "info");
    assert(cfg["storage"]["rpc_port"] == 9004);
    fs::remove_all(dir);
    std::cout << "PASS: base-only config loads correctly\n";
}

void test_dropin_overrides_base() {
    auto dir = makeTestDir("override");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"log_level":"info","storage":{"rpc_port":9004,"node_id":"base"}})");
    writeFile(confDir / "50-override.json", R"({"log_level":"debug","storage":{"node_id":"overridden"}})");

    auto cfg = loadLayeredConfig(base, confDir);
    assert(cfg["log_level"] == "debug");                    // overridden
    assert(cfg["storage"]["rpc_port"] == 9004);             // preserved from base
    assert(cfg["storage"]["node_id"] == "overridden");      // overridden
    fs::remove_all(dir);
    std::cout << "PASS: drop-in overrides base (deep merge preserves siblings)\n";
}

void test_lexicographic_order() {
    auto dir = makeTestDir("order");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"log_level":"info"})");
    writeFile(confDir / "50-middle.json", R"({"log_level":"debug"})");
    writeFile(confDir / "10-first.json",  R"({"log_level":"trace"})");
    writeFile(confDir / "99-last.json",   R"({"log_level":"warn"})");

    auto cfg = loadLayeredConfig(base, confDir);
    // Order: base -> 10-first -> 50-middle -> 99-last. Last wins.
    assert(cfg["log_level"] == "warn");
    fs::remove_all(dir);
    std::cout << "PASS: drop-ins merged in lexicographic order, last wins\n";
}

void test_arrays_replace_not_append() {
    auto dir = makeTestDir("arrays");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"sensitive_fields":["email","phone"]})");
    writeFile(confDir / "50-override.json", R"({"sensitive_fields":["ssn"]})");

    auto cfg = loadLayeredConfig(base, confDir);
    // RFC 7396: arrays replace, don't merge
    assert(cfg["sensitive_fields"].size() == 1);
    assert(cfg["sensitive_fields"][0] == "ssn");
    fs::remove_all(dir);
    std::cout << "PASS: arrays replace (RFC 7396), don't append\n";
}

void test_invalid_json_throws() {
    auto dir = makeTestDir("invalid");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"log_level":"info"})");
    writeFile(confDir / "50-bad.json", R"({this is not json)");

    bool threw = false;
    try {
        (void)loadLayeredConfig(base, confDir);
    } catch (const std::exception& e) {
        threw = true;
        std::string msg = e.what();
        // Error should mention the filename so the operator knows which file
        assert(msg.find("50-bad.json") != std::string::npos);
    }
    assert(threw);
    fs::remove_all(dir);
    std::cout << "PASS: invalid JSON in drop-in throws with filename\n";
}

void test_non_json_files_ignored() {
    auto dir = makeTestDir("nonjson");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";
    fs::create_directories(confDir);
    writeFile(base, R"({"log_level":"info"})");
    writeFile(confDir / "README.txt", "not a config file");
    writeFile(confDir / "backup.json.bak", R"({"log_level":"trace"})");
    writeFile(confDir / "50-real.json", R"({"log_level":"debug"})");

    auto cfg = loadLayeredConfig(base, confDir);
    assert(cfg["log_level"] == "debug");  // only 50-real.json should apply
    fs::remove_all(dir);
    std::cout << "PASS: non-json files in conf.d ignored\n";
}

void test_missing_confd_dir_is_ok() {
    auto dir = makeTestDir("nodir");
    auto base = dir / "config.json";
    auto confDir = dir / "conf.d";  // intentionally NOT created
    writeFile(base, R"({"log_level":"info"})");

    auto cfg = loadLayeredConfig(base, confDir);
    assert(cfg["log_level"] == "info");  // no drop-ins, base wins
    fs::remove_all(dir);
    std::cout << "PASS: missing conf.d directory is not an error\n";
}

int main() {
    test_no_base_no_dropins_returns_empty();
    test_base_only();
    test_dropin_overrides_base();
    test_lexicographic_order();
    test_arrays_replace_not_append();
    test_invalid_json_throws();
    test_non_json_files_ignored();
    test_missing_confd_dir_is_ok();
    std::cout << "\nAll config drop-in tests PASSED!\n";
    return 0;
}