package config

import (
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

const (
	DefaultListenAddr = "127.0.0.1:8080"
	DefaultDataDir    = "/opt/glchat/data"
	DefaultLogLevel   = "info"
)

type Config struct {
	Domain        string
	FilesDomain   string
	InstanceName  string
	ListenAddr    string
	DataDir       string
	WebRoot       string
	DatabasePath  string
	SQLiteCache   string
	SQLiteMmap    string
	LogLevel      string
	LogFormat     string
	ReadPoolSize  int
	MaxUploadSize int64
	Version       string
	Commit        string
	BuildDate     string
	ShutdownTTL   time.Duration
	Maintenance   time.Duration
}

func Load() (Config, error) {
	cfg := Config{
		Domain:        env("DOMAIN", "localhost"),
		FilesDomain:   env("FILES_DOMAIN", ""),
		InstanceName:  env("INSTANCE_NAME", "glchat"),
		ListenAddr:    env("LISTEN_ADDR", DefaultListenAddr),
		DataDir:       env("DATA_DIR", DefaultDataDir),
		WebRoot:       env("WEB_ROOT", "/app/web"),
		DatabasePath:  env("DATABASE_PATH", ""),
		SQLiteCache:   env("SQLITE_CACHE_SIZE", "-8000"),
		SQLiteMmap:    env("SQLITE_MMAP_SIZE", "134217728"),
		LogLevel:      strings.ToLower(env("LOG_LEVEL", DefaultLogLevel)),
		LogFormat:     strings.ToLower(env("LOG_FORMAT", "json")),
		ReadPoolSize:  envInt("SQLITE_READ_POOL", 4),
		MaxUploadSize: envInt64("MAX_UPLOAD_SIZE", 26214400),
		Version:       env("APP_VERSION", "dev"),
		Commit:        env("APP_COMMIT", "none"),
		BuildDate:     env("APP_BUILD_DATE", "unknown"),
		ShutdownTTL:   time.Duration(envInt("SHUTDOWN_TIMEOUT_SECONDS", 20)) * time.Second,
		Maintenance:   time.Duration(envInt("DB_MAINTENANCE_INTERVAL_SECONDS", 21600)) * time.Second,
	}
	if cfg.FilesDomain == "" {
		cfg.FilesDomain = "files." + cfg.Domain
	}
	if cfg.DatabasePath == "" {
		cfg.DatabasePath = cfg.DataDir + "/db/glchat.db"
	}
	if cfg.ReadPoolSize < 1 {
		return Config{}, fmt.Errorf("SQLITE_READ_POOL must be >= 1, got %d", cfg.ReadPoolSize)
	}
	if _, err := parseLogLevel(cfg.LogLevel); err != nil {
		return Config{}, err
	}
	if cfg.LogFormat != "json" && cfg.LogFormat != "text" {
		return Config{}, fmt.Errorf("LOG_FORMAT must be json or text, got %q", cfg.LogFormat)
	}
	return cfg, nil
}

func (c Config) BaseURL() string  { return "https://" + c.Domain }
func (c Config) FilesURL() string { return "https://" + c.FilesDomain }

func (c Config) LogLevelNumeric() int {
	level, err := parseLogLevel(c.LogLevel)
	if err != nil {
		return 0
	}
	return level
}

func parseLogLevel(level string) (int, error) {
	switch level {
	case "debug":
		return -4, nil
	case "info":
		return 0, nil
	case "warn", "warning":
		return 4, nil
	case "error":
		return 8, nil
	default:
		return 0, fmt.Errorf("unknown LOG_LEVEL %q", level)
	}
}

func env(key, fallback string) string {
	if v, ok := os.LookupEnv(key); ok && v != "" {
		return v
	}
	return fallback
}

func envInt(key string, fallback int) int {
	v, ok := os.LookupEnv(key)
	if !ok || v == "" {
		return fallback
	}
	n, err := strconv.Atoi(v)
	if err != nil {
		return fallback
	}
	return n
}

func envInt64(key string, fallback int64) int64 {
	v, ok := os.LookupEnv(key)
	if !ok || v == "" {
		return fallback
	}
	n, err := strconv.ParseInt(v, 10, 64)
	if err != nil {
		return fallback
	}
	return n
}