package config

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// Regression: config.Load used plain yaml.Unmarshal, so an unknown/misspelled
// key (e.g. telnet_listen) was silently discarded and the default applied.
// It now uses KnownFields(true), matching the data loaders, while
// SaveDefault's output must still round-trip through Load.

func writeConfig(t *testing.T, body string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "config.yaml")
	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	return path
}

func TestLoadRejectsUnknownKey(t *testing.T) {
	path := writeConfig(t, "tick_length: 700\ntelnet_listen: 4000\n")
	if _, err := Load(path); err == nil {
		t.Fatal("expected an error for unknown key telnet_listen, got nil")
	} else if !strings.Contains(err.Error(), "telnet_listen") {
		t.Fatalf("error should name the offending key, got: %v", err)
	}
}

func TestLoadKnownKeysOverrideDefaults(t *testing.T) {
	path := writeConfig(t, "tick_length: 700\nstarting_room: 2002\nstartup_validation:\n  root_rooms: [2002]\n")
	cfg, err := Load(path)
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if cfg.TickLength != 700 {
		t.Errorf("TickLength = %d, want 700", cfg.TickLength)
	}
	if cfg.StartingRoom != 2002 {
		t.Errorf("StartingRoom = %d, want 2002", cfg.StartingRoom)
	}
	if len(cfg.StartupValidation.RootRooms) != 1 || cfg.StartupValidation.RootRooms[0] != 2002 {
		t.Errorf("RootRooms = %v, want [2002]", cfg.StartupValidation.RootRooms)
	}
	// Unset values keep their defaults.
	if cfg.Telnet.Port != Default().Telnet.Port {
		t.Errorf("unset Telnet.Port = %d, want default %d", cfg.Telnet.Port, Default().Telnet.Port)
	}
}

func TestSaveDefaultRoundTrips(t *testing.T) {
	path := filepath.Join(t.TempDir(), "config.yaml")
	if err := SaveDefault(path); err != nil {
		t.Fatalf("SaveDefault: %v", err)
	}
	cfg, err := Load(path)
	if err != nil {
		t.Fatalf("Load(SaveDefault output): %v", err)
	}
	if cfg.TickLength != Default().TickLength {
		t.Errorf("TickLength = %d, want %d", cfg.TickLength, Default().TickLength)
	}
}