package platform

import (
	"fmt"
	"log/slog"
	"os"
	"strings"
)

const (
	DatabaseModePostgres = "postgres"
	DatabaseModeMemory   = "memory"
)

type Config struct {
	HTTPAddress  string
	DatabaseMode string
	DatabaseURL  string
	StaticDir    string
	LogLevelName string
}

func LoadConfig() (Config, error) {
	cfg := Config{
		HTTPAddress:  valueOrDefault("SENSE_HTTP_ADDRESS", "127.0.0.1:18080"),
		DatabaseMode: strings.ToLower(valueOrDefault("SENSE_DATABASE_MODE", DatabaseModePostgres)),
		DatabaseURL:  strings.TrimSpace(os.Getenv("SENSE_DATABASE_URL")),
		StaticDir:    strings.TrimSpace(os.Getenv("SENSE_UI_STATIC_DIR")),
		LogLevelName: strings.ToLower(valueOrDefault("SENSE_LOG_LEVEL", "info")),
	}

	switch cfg.DatabaseMode {
	case DatabaseModePostgres:
		if cfg.DatabaseURL == "" {
			return Config{}, fmt.Errorf("SENSE_DATABASE_URL is required when SENSE_DATABASE_MODE=postgres")
		}
	case DatabaseModeMemory:
		// Explicitly limited to local smoke tests and automated tests.
	default:
		return Config{}, fmt.Errorf("unsupported SENSE_DATABASE_MODE %q", cfg.DatabaseMode)
	}
	return cfg, nil
}

func (c Config) LogLevel() slog.Level {
	switch c.LogLevelName {
	case "debug":
		return slog.LevelDebug
	case "warn":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}

func valueOrDefault(key, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		return value
	}
	return fallback
}