Add asinfo package for AS number information lookups

- Created pkg/asinfo with embedded AS data from ipverse/asn-info
- Provides fast lookups by ASN with GetDescription() and GetHandle()
- Includes Search() functionality for finding AS by name/handle
- Added asinfo-gen tool to fetch and convert CSV data to JSON
- Added 'make asupdate' target to refresh AS data
- Embedded JSON data contains 130k+ AS entries
- Added comprehensive tests and examples

pkg/asinfo/asinfo.go

@@ -0,0 +1,139 @@
+// Package asinfo provides information about Autonomous Systems (AS)
+package asinfo
+
+import (
+	_ "embed"
+	"encoding/json"
+	"sync"
+)
+
+//go:embed asdata.json
+var asDataJSON []byte
+
+// Info represents information about an Autonomous System
+type Info struct {
+	ASN         int    `json:"asn"`
+	Handle      string `json:"handle"`
+	Description string `json:"description"`
+}
+
+// Registry provides access to AS information
+type Registry struct {
+	mu    sync.RWMutex
+	byASN map[int]*Info
+}
+
+var (
+	defaultRegistry *Registry
+	once            sync.Once
+)
+
+// initRegistry initializes the default registry with embedded data
+func initRegistry() {
+	defaultRegistry = &Registry{
+		byASN: make(map[int]*Info),
+	}
+	
+	var asInfos []Info
+	if err := json.Unmarshal(asDataJSON, &asInfos); err != nil {
+		panic("failed to unmarshal embedded AS data: " + err.Error())
+	}
+	
+	for i := range asInfos {
+		info := &asInfos[i]
+		defaultRegistry.byASN[info.ASN] = info
+	}
+}
+
+// Get returns AS information for the given ASN
+func Get(asn int) (*Info, bool) {
+	once.Do(initRegistry)
+	
+	defaultRegistry.mu.RLock()
+	defer defaultRegistry.mu.RUnlock()
+	
+	info, ok := defaultRegistry.byASN[asn]
+	if !ok {
+		return nil, false
+	}
+	
+	// Return a copy to prevent mutation
+	copy := *info
+	return &copy, true
+}
+
+// GetDescription returns just the description for an ASN
+func GetDescription(asn int) string {
+	info, ok := Get(asn)
+	if !ok {
+		return ""
+	}
+	return info.Description
+}
+
+// GetHandle returns just the handle for an ASN
+func GetHandle(asn int) string {
+	info, ok := Get(asn)
+	if !ok {
+		return ""
+	}
+	return info.Handle
+}
+
+// Total returns the total number of AS entries in the registry
+func Total() int {
+	once.Do(initRegistry)
+	
+	defaultRegistry.mu.RLock()
+	defer defaultRegistry.mu.RUnlock()
+	
+	return len(defaultRegistry.byASN)
+}
+
+// All returns all AS information as a slice
+// Note: This creates a copy of all data, use sparingly
+func All() []Info {
+	once.Do(initRegistry)
+	
+	defaultRegistry.mu.RLock()
+	defer defaultRegistry.mu.RUnlock()
+	
+	result := make([]Info, 0, len(defaultRegistry.byASN))
+	for _, info := range defaultRegistry.byASN {
+		result = append(result, *info)
+	}
+	
+	return result
+}
+
+// Search searches for AS entries where the handle or description contains the query
+// This is a simple case-sensitive substring search
+func Search(query string) []Info {
+	once.Do(initRegistry)
+	
+	defaultRegistry.mu.RLock()
+	defer defaultRegistry.mu.RUnlock()
+	
+	var results []Info
+	for _, info := range defaultRegistry.byASN {
+		if contains(info.Handle, query) || contains(info.Description, query) {
+			results = append(results, *info)
+		}
+	}
+	
+	return results
+}
+
+// contains is a simple substring search
+func contains(s, substr string) bool {
+	return len(substr) > 0 && len(s) >= len(substr) && containsImpl(s, substr)
+}
+
+func containsImpl(s, substr string) bool {
+	for i := 0; i <= len(s)-len(substr); i++ {
+		if s[i:i+len(substr)] == substr {
+			return true
+		}
+	}
+	return false
+}