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
	TLSEnabled    bool
	// Секреты инстанса (генерируются установщиком, AGENT.md §10.3).
	SessionPepper     string
	MasterKey         string
	TOTPEncryptionKey string
	SessionTTLHours   int
	Argon2MemoryKiB   int
	Argon2Iterations  int
	Argon2Parallelism int
	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),
		TLSEnabled:        envBool("TLS_ENABLED", true),
		SessionPepper:     env("SESSION_PEPPER", ""),
		MasterKey:         env("MASTER_KEY", ""),
		TOTPEncryptionKey: env("TOTP_ENCRYPTION_KEY", ""),
		SessionTTLHours:   envInt("SESSION_TTL_HOURS", 720),
		Argon2MemoryKiB:   envInt("ARGON2_MEMORY_KIB", 19456),
		Argon2Iterations:  envInt("ARGON2_ITERATIONS", 2),
		Argon2Parallelism: envInt("ARGON2_PARALLELISM", 1),
		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
}

// Scheme выбирается установщиком: при установке без TLS (--skip-tls,
// например стенд без домена) клиент должен получать http/ws, а не https/wss.
func (c Config) Scheme() string {
	if c.TLSEnabled {
		return "https"
	}
	return "http"
}

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

func (c Config) GatewayURL() string {
	scheme := "ws"
	if c.TLSEnabled {
		scheme = "wss"
	}
	return scheme + "://" + c.Domain + "/gateway"
}

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 envBool(key string, fallback bool) bool {
	v, ok := os.LookupEnv(key)
	if !ok || v == "" {
		return fallback
	}
	parsed, err := strconv.ParseBool(v)
	if err != nil {
		return fallback
	}
	return parsed
}

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
}