package config

import (
	"strings"
	"time"

	"git.yuntuo.hk/k2safe/go-omni/httpx"
	"git.yuntuo.hk/k2safe/go-omni/logx"
)

const defaultRequestIDHeader = "X-Request-ID"

// Config controls the default runtime behavior of an App.
type Config struct {
	Address         string
	RequestIDHeader string
	EnableLogger    bool
	TrustedProxies  []string
	ShutdownTimeout time.Duration
	Log             logx.Config
}

func Default() Config {
	return Config{
		Address:         ":8080",
		RequestIDHeader: defaultRequestIDHeader,
		ShutdownTimeout: 10 * time.Second,
		Log:             logx.Default(),
	}
}

// Validate checks configuration values before an application starts.
func (c Config) Validate() error {
	if strings.TrimSpace(c.Address) == "" {
		return &ConfigError{Field: "address", Message: "is required"}
	}
	if strings.TrimSpace(c.RequestIDHeader) == "" {
		return &ConfigError{Field: "request_id_header", Message: "is required"}
	}
	if c.ShutdownTimeout <= 0 {
		return &ConfigError{Field: "shutdown_timeout", Message: "must be positive"}
	}
	if _, err := httpx.NewClientIPResolver(c.TrustedProxies...); err != nil {
		return &ConfigError{Field: "trusted_proxies", Message: err.Error()}
	}
	return nil
}

// ConfigError describes an invalid application configuration field.
type ConfigError struct {
	Field   string
	Message string
}

func (e *ConfigError) Error() string { return "config " + e.Field + " " + e.Message }

// Option changes an App's configuration.
type Option func(*Config)

// WithRequestIDHeader changes the header used to read and return request IDs.
func WithRequestIDHeader(header string) Option {
	return func(cfg *Config) {
		if value := strings.TrimSpace(header); value != "" {
			cfg.RequestIDHeader = value
		}
	}
}

// WithLogger enables GoOmni's structured access logger.
func WithLogger(enabled bool) Option {
	return func(cfg *Config) { cfg.EnableLogger = enabled }
}

// WithTrustedProxies allows only these IPs/CIDRs to supply X-Forwarded-For.
// An empty list disables forwarding-header trust. Invalid entries are rejected
// by Config.Validate and panic when passed directly to App.New.
func WithTrustedProxies(proxies ...string) Option {
	proxies = append([]string(nil), proxies...)
	return func(cfg *Config) { cfg.TrustedProxies = append([]string(nil), proxies...) }
}

// WithConfig applies a complete configuration loaded from a file or
// environment. Later options can still override individual fields.
func WithConfig(settings Config) Option {
	settings.TrustedProxies = append([]string(nil), settings.TrustedProxies...)
	return func(cfg *Config) {
		*cfg = settings
		cfg.TrustedProxies = append([]string(nil), settings.TrustedProxies...)
	}
}

// WithLogConfig configures the logger used by the application runtime.
func WithLogConfig(settings logx.Config) Option {
	return func(cfg *Config) { cfg.Log = settings }
}

// WithShutdownTimeout controls how long RunContext waits for active requests.
func WithShutdownTimeout(timeout time.Duration) Option {
	return func(cfg *Config) {
		if timeout > 0 {
			cfg.ShutdownTimeout = timeout
		}
	}
}