// steamcache/service.go
package steamcache

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"net/http"
	"regexp"
	"strings"
	"sync"
)

// ServiceConfig defines configuration for a cacheable service
type ServiceConfig struct {
	Name       string           `json:"name"`        // Service name (e.g., "steam", "epic", "origin")
	Prefix     string           `json:"prefix"`      // Cache key prefix (e.g., "steam", "epic")
	UserAgents []string         `json:"user_agents"` // User-Agent patterns to match
	compiled   []*regexp.Regexp // Compiled regex patterns (internal use)
}

// ServiceManager manages service configurations
type ServiceManager struct {
	services map[string]*ServiceConfig
	mutex    sync.RWMutex
}

// NewServiceManager creates a new service manager with default Steam configuration
func NewServiceManager() *ServiceManager {
	sm := &ServiceManager{
		services: make(map[string]*ServiceConfig),
	}

	// Add default Steam service configuration
	steamConfig := &ServiceConfig{
		Name:   "steam",
		Prefix: "steam",
		UserAgents: []string{
			`Valve/Steam HTTP Client 1\.0`,
			`SteamClient`,
			`Steam`,
		},
	}
	_ = sm.AddService(steamConfig) // error impossible: hardcoded patterns are valid regexes (user-provided services validated in AddService)

	return sm
}

// AddService adds or updates a service configuration
func (sm *ServiceManager) AddService(config *ServiceConfig) error {
	sm.mutex.Lock()
	defer sm.mutex.Unlock()

	// Compile regex patterns
	compiled := make([]*regexp.Regexp, 0, len(config.UserAgents))
	for _, pattern := range config.UserAgents {
		regex, err := regexp.Compile(pattern)
		if err != nil {
			return fmt.Errorf("invalid regex pattern %q for service %s: %w", pattern, config.Name, err)
		}
		compiled = append(compiled, regex)
	}

	config.compiled = compiled
	sm.services[config.Name] = config

	return nil
}

// GetService returns a service configuration by name
func (sm *ServiceManager) GetService(name string) (*ServiceConfig, bool) {
	sm.mutex.RLock()
	defer sm.mutex.RUnlock()

	service, exists := sm.services[name]
	return service, exists
}

// DetectService detects which service a request belongs to based on User-Agent
func (sm *ServiceManager) DetectService(userAgent string) (*ServiceConfig, bool) {
	sm.mutex.RLock()
	defer sm.mutex.RUnlock()

	for _, service := range sm.services {
		for _, regex := range service.compiled {
			if regex.MatchString(userAgent) {
				return service, true
			}
		}
	}

	return nil, false
}

// ListServices returns all configured services
func (sm *ServiceManager) ListServices() []*ServiceConfig {
	sm.mutex.RLock()
	defer sm.mutex.RUnlock()

	services := make([]*ServiceConfig, 0, len(sm.services))
	for _, service := range sm.services {
		services = append(services, service)
	}

	return services
}

// detectService is a one-line delegation to ServiceManager (per Phase 2).
// Empty User-Agent yields no match (identical to prior behavior).
func (sc *SteamCache) detectService(r *http.Request) (*ServiceConfig, bool) {
	return sc.serviceManager.DetectService(r.Header.Get("User-Agent"))
}

// --- Cache key / hash helpers (service-related) ---

func generateURLHash(urlPath string) (string, error) {
	if urlPath == "" {
		return "", fmt.Errorf("empty URL path")
	}
	// Additional validation for suspicious patterns (kept for backward compat with prior behavior)
	if strings.Contains(urlPath, "..") || strings.Contains(urlPath, "//") {
		return "", fmt.Errorf("generateURLHash: invalid URL path")
	}
	hash := sha256.Sum256([]byte(urlPath))
	return hex.EncodeToString(hash[:]), nil
}

func calculateSHA256(data []byte) string {
	hasher := sha256.New()
	hasher.Write(data)
	return hex.EncodeToString(hasher.Sum(nil))
}

// validateURLPath validates URL path for security concerns (used early in request handling).
func validateURLPath(urlPath string) error {
	if urlPath == "" {
		return fmt.Errorf("validateURLPath: invalid URL path")
	}
	if strings.Contains(urlPath, "..") {
		return fmt.Errorf("validateURLPath: invalid URL path")
	}
	if strings.Contains(urlPath, "//") {
		return fmt.Errorf("validateURLPath: invalid URL path")
	}
	if strings.ContainsAny(urlPath, "<>\"'&") {
		return fmt.Errorf("validateURLPath: invalid URL path")
	}
	if len(urlPath) > 2048 {
		return fmt.Errorf("validateURLPath: invalid URL path")
	}
	return nil
}

// generateServiceCacheKey creates a cache key from the URL path using SHA256
// The prefix indicates which service the request came from (detected via User-Agent)
func generateServiceCacheKey(urlPath string, servicePrefix string) (string, error) {
	if servicePrefix == "" {
		return "", fmt.Errorf("generateServiceCacheKey: unsupported service")
	}
	hash, err := generateURLHash(urlPath)
	if err != nil {
		return "", err
	}
	return servicePrefix + "/" + hash, nil
}