package config

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"time"
)

// Config holds runtime configuration for the AI gRPC gateway.
type Config struct {
	GRPCPort            string
	OllamaURL           string
	OllamaModel         string
	OllamaTimeout       time.Duration
	HAGatewayAddr       string
	HAGatewayServerName string
	TLSDir              string
	OTELEndpoint        string
	LogLevel            string
	LogFormat           string
	LightCacheTTL       time.Duration
}

// Load reads configuration from environment variables and applies defaults.
func Load() (*Config, error) {
	ollamaTimeout, err := parseDurationEnv("OLLAMA_TIMEOUT", 120*time.Second)
	if err != nil {
		return nil, err
	}
	cacheTTL, err := parseDurationEnv("LIGHT_CACHE_TTL", 60*time.Second)
	if err != nil {
		return nil, err
	}

	cfg := &Config{
		GRPCPort:            getenvDefault("GRPC_PORT", "50052"),
		OllamaURL:           getenvDefault("OLLAMA_URL", "http://192.168.7.96:11434"),
		OllamaModel:         getenvDefault("OLLAMA_MODEL", "llama3"),
		OllamaTimeout:       ollamaTimeout,
		HAGatewayAddr:       getenvDefault("HA_GATEWAY_ADDR", "ha-gateway.home-services.svc.cluster.local:50051"),
		HAGatewayServerName: getenvDefault("HA_GATEWAY_SERVER_NAME", "ha-gateway.home-services.svc.cluster.local"),
		TLSDir:              os.Getenv("TLS_DIR"),
		OTELEndpoint:        os.Getenv("OTEL_ENDPOINT"),
		LogLevel:            getenvDefault("LOG_LEVEL", "info"),
		LogFormat:           getenvDefault("LOG_FORMAT", "json"),
		LightCacheTTL:       cacheTTL,
	}
	if cfg.TLSDir != "" {
		if err := validateTLSDir(cfg.TLSDir); err != nil {
			return nil, err
		}
	}
	return cfg, nil
}

func getenvDefault(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func parseDurationEnv(key string, fallback time.Duration) (time.Duration, error) {
	if v := os.Getenv(key); v != "" {
		d, err := time.ParseDuration(v)
		if err != nil {
			return 0, fmt.Errorf("parse %s: %w", key, err)
		}
		return d, nil
	}
	return fallback, nil
}

func validateTLSDir(dir string) error {
	required := []string{"tls.crt", "tls.key", "ca.crt"}
	for _, name := range required {
		path := filepath.Join(dir, name)
		info, err := os.Stat(path)
		if err != nil {
			return fmt.Errorf("tls dir validation failed for %s: %w", path, err)
		}
		if info.IsDir() {
			return fmt.Errorf("tls dir validation failed for %s: %w", path, errors.New("expected file"))
		}
	}
	return nil
}