Make the home page's AS name search work (closes #151)

The AS Name Search card on the home page said the search was coming
soon. It now asks the new GET /api/v1/search/as?q=<text>, which
searches the AS list built into asinfo, and lists the matches as links
to their AS pages. An empty q answers 400. asinfo.Search now ignores
case and returns its matches in AS number order. asinfo puts each
handle and description in lower case once, when the list loads.

A match can be an AS that the database has no record of. Its AS page
and /api/v1/as/{asn} then take its handle and description from asinfo
and still list its prefixes. They answer 404 only for an AS with no
record, no asinfo entry and no prefix. Empty prefix lists in that JSON
answer are [] rather than null.

Model: opus-5-5

pkg/asinfo/asinfo.go

@@ -2,10 +2,13 @@ package asinfo
 
 import (
 	"bytes"
+	"cmp"
 	"compress/gzip"
 	_ "embed"
 	"encoding/json"
 	"io"
+	"slices"
+	"strings"
 	"sync"
 )
 
@@ -23,6 +26,17 @@ type Info struct {
 type Registry struct {
 	mu    sync.RWMutex
 	byASN map[int]*Info
+	// searchEntries holds every entry in AS number order, for Search.
+	searchEntries []searchEntry
+}
+
+// searchEntry is an entry with its handle and description in lower case. They
+// are put in lower case once, when the data loads, so that Search only
+// compares.
+type searchEntry struct {
+	info             *Info
+	lowerHandle      string
+	lowerDescription string
 }
 
 var (
@@ -59,9 +73,21 @@ func initRegistry() {
 		panic("failed to unmarshal embedded AS data: " + err.Error())
 	}
 
+	slices.SortFunc(asInfos, func(a, b Info) int {
+		return cmp.Compare(a.ASN, b.ASN)
+	})
+
+	defaultRegistry.searchEntries = make([]searchEntry, 0, len(asInfos))
+
 	for i := range asInfos {
 		info := &asInfos[i]
 		defaultRegistry.byASN[info.ASN] = info
+		defaultRegistry.searchEntries = append(defaultRegistry.searchEntries,
+			searchEntry{
+				info:             info,
+				lowerHandle:      strings.ToLower(info.Handle),
+				lowerDescription: strings.ToLower(info.Description),
+			})
 	}
 }
 
@@ -129,36 +155,28 @@ func All() []Info {
 	return result
 }
 
-// Search searches for AS entries where the handle or description contains the query
-// This is a simple case-sensitive substring search
+// Search returns the AS entries whose handle or description contains query,
+// ignoring case, in AS number order. An empty query matches nothing.
 func Search(query string) []Info {
 	once.Do(initRegistry)
 
+	if query == "" {
+		return nil
+	}
+
+	query = strings.ToLower(query)
+
 	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)
+	for _, entry := range defaultRegistry.searchEntries {
+		if strings.Contains(entry.lowerHandle, query) ||
+			strings.Contains(entry.lowerDescription, query) {
+			results = append(results, *entry.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
-}