package config

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/spf13/viper"
)

type Config struct {
	App      AppConfig      `mapstructure:"app"`
	OAuth    OAuthConfig    `mapstructure:"oauth"`
	Google   GoogleConfig   `mapstructure:"google"`
	Server   ServerConfig   `mapstructure:"server"`
	API      APIConfig      `mapstructure:"api"`
	MCP      MCPConfig      `mapstructure:"mcp"`
	Security SecurityConfig `mapstructure:"security"`
	Output   OutputConfig   `mapstructure:"output"`
}

type AppConfig struct {
	Name     string `mapstructure:"name"`
	Env      string `mapstructure:"env"`
	LogLevel string `mapstructure:"log_level"`
	DataDir  string `mapstructure:"data_dir"`
}

type OAuthConfig struct {
	ClientCredentialsFile string `mapstructure:"client_credentials_file"`
	TokenStoreFile        string `mapstructure:"token_store_file"`
	DefaultPort           int    `mapstructure:"default_port"`
	OpenBrowser           bool   `mapstructure:"open_browser"`
	ManualFallback        bool   `mapstructure:"manual_fallback"`
	CallbackPath          string `mapstructure:"callback_path"`
}

type GoogleConfig struct {
	Scopes            []string `mapstructure:"scopes"`
	DefaultCalendarID string   `mapstructure:"default_calendar_id"`
}

type ServerConfig struct {
	Bind            string        `mapstructure:"bind"`
	Port            int           `mapstructure:"port"`
	ReadTimeout     time.Duration `mapstructure:"read_timeout"`
	WriteTimeout    time.Duration `mapstructure:"write_timeout"`
	ShutdownTimeout time.Duration `mapstructure:"shutdown_timeout"`
}

type APIConfig struct {
	Enabled  bool    `mapstructure:"enabled"`
	BasePath string  `mapstructure:"base_path"`
	Auth     AuthCfg `mapstructure:"auth"`
}

type AuthCfg struct {
	OAuthBearerEnabled bool `mapstructure:"oauth_bearer_enabled"`
	APIKeyEnabled      bool `mapstructure:"api_key_enabled"`
}

type MCPConfig struct {
	Enabled         bool   `mapstructure:"enabled"`
	Stdio           bool   `mapstructure:"stdio"`
	HTTP            bool   `mapstructure:"http"`
	HTTPPath        string `mapstructure:"http_path"`
	ProtocolVersion string `mapstructure:"protocol_version"`
	SessionRequired bool   `mapstructure:"session_required"`
}

type SecurityConfig struct {
	APIKeysFile         string `mapstructure:"api_keys_file"`
	RedactSecretsInLogs bool   `mapstructure:"redact_secrets_in_logs"`
	RequireTLSForRemote bool   `mapstructure:"require_tls_for_remote_http"`
}

type OutputConfig struct {
	Format   string `mapstructure:"format"`
	Timezone string `mapstructure:"timezone"`
}

func Load(cfgFile, profile string) (*Config, error) {
	v := viper.New()
	setDefaults(v)

	v.SetEnvPrefix("GOCALGOO")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	v.AutomaticEnv()

	if cfgFile != "" {
		v.SetConfigFile(cfgFile)
	} else {
		home, err := os.UserHomeDir()
		if err != nil {
			return nil, fmt.Errorf("get home dir: %w", err)
		}
		cfgName := "config"
		if profile != "" {
			cfgName = "config." + profile
		}
		v.SetConfigName(cfgName)
		v.SetConfigType("yaml")
		v.AddConfigPath(filepath.Join(home, ".config", "gocalgoo"))
		v.AddConfigPath(".")
		v.AddConfigPath("./configs")
	}

	if err := v.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			return nil, fmt.Errorf("read config: %w", err)
		}
	}

	var cfg Config
	if err := v.Unmarshal(&cfg); err != nil {
		return nil, fmt.Errorf("unmarshal config: %w", err)
	}

	cfg.OAuth.ClientCredentialsFile = expandHome(cfg.OAuth.ClientCredentialsFile)
	cfg.OAuth.TokenStoreFile = expandHome(cfg.OAuth.TokenStoreFile)
	cfg.Security.APIKeysFile = expandHome(cfg.Security.APIKeysFile)
	cfg.App.DataDir = expandHome(cfg.App.DataDir)

	return &cfg, nil
}

func Validate(cfg *Config) error {
	if cfg.OAuth.ClientCredentialsFile == "" {
		return fmt.Errorf("oauth.client_credentials_file is required")
	}
	if cfg.OAuth.TokenStoreFile == "" {
		return fmt.Errorf("oauth.token_store_file is required")
	}
	if len(cfg.Google.Scopes) == 0 {
		return fmt.Errorf("google.scopes must not be empty")
	}
	if cfg.Server.Port < 1 || cfg.Server.Port > 65535 {
		return fmt.Errorf("server.port must be 1-65535")
	}
	return nil
}

func setDefaults(v *viper.Viper) {
	home, _ := os.UserHomeDir()

	v.SetDefault("app.name", "GoCalGoo")
	v.SetDefault("app.env", "development")
	v.SetDefault("app.log_level", "info")
	v.SetDefault("app.data_dir", filepath.Join(home, ".local", "share", "gocalgoo"))

	v.SetDefault("oauth.client_credentials_file", filepath.Join(home, ".config", "gocalgoo", "credentials.json"))
	v.SetDefault("oauth.token_store_file", filepath.Join(home, ".config", "gocalgoo", "tokens.json"))
	v.SetDefault("oauth.default_port", 53682)
	v.SetDefault("oauth.open_browser", true)
	v.SetDefault("oauth.manual_fallback", true)
	v.SetDefault("oauth.callback_path", "/oauth/callback")

	v.SetDefault("google.scopes", []string{
		"https://www.googleapis.com/auth/calendar",
		"https://www.googleapis.com/auth/contacts",
	})
	v.SetDefault("google.default_calendar_id", "primary")

	v.SetDefault("server.bind", "127.0.0.1")
	v.SetDefault("server.port", 8080)
	v.SetDefault("server.read_timeout", "15s")
	v.SetDefault("server.write_timeout", "30s")
	v.SetDefault("server.shutdown_timeout", "10s")

	v.SetDefault("api.enabled", true)
	v.SetDefault("api.base_path", "/api/v1")
	v.SetDefault("api.auth.oauth_bearer_enabled", true)
	v.SetDefault("api.auth.api_key_enabled", true)

	v.SetDefault("mcp.enabled", true)
	v.SetDefault("mcp.stdio", true)
	v.SetDefault("mcp.http", true)
	v.SetDefault("mcp.http_path", "/mcp")
	v.SetDefault("mcp.protocol_version", "2025-06-18")
	v.SetDefault("mcp.session_required", true)

	v.SetDefault("security.api_keys_file", filepath.Join(home, ".config", "gocalgoo", "api-keys.yaml"))
	v.SetDefault("security.redact_secrets_in_logs", true)
	v.SetDefault("security.require_tls_for_remote_http", false)

	v.SetDefault("output.format", "table")
	v.SetDefault("output.timezone", "UTC")
}

func expandHome(path string) string {
	if path == "" {
		return path
	}
	if strings.HasPrefix(path, "~/") {
		home, err := os.UserHomeDir()
		if err != nil {
			return path
		}
		return filepath.Join(home, path[2:])
	}
	return path
}