Implement server peering

2 files changed, 113 insertions, 5 deletions

diff --git a/server/server.go b/server/server.go
index 709888b..e84b4e0 100644
--- a/server/server.go
+++ b/server/server.go
@@ -1,17 +1,115 @@
 package main
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
+	"flag"
 	"fmt"
-	"html"
+	"io"
 	"log"
 	"net/http"
+	"sort"
+	"strings"
+	"sync"
 )
 
-func handler(w http.ResponseWriter, r *http.Request) {
-	fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
+var mu sync.Mutex
+var me string
+var hashToDomain map[string]string
+var peerHashes []string
+var kvstore map[string]string
+
+func sha256sum(s string) string {
+	// Get the sha256sum of string as a hex string
+	b := sha256.Sum256([]byte(s))
+	return hex.EncodeToString(b[:])
+}
+
+func addPeer(peer string) error {
+	// Try to peer with another server
+	peerHash := sha256sum(peer)
+	// Check if already peered
+	mu.Lock()
+	_, ok := hashToDomain[peerHash]
+	mu.Unlock()
+	if ok {
+		return nil
+	}
+	mu.Lock()
+	hashToDomain[peerHash] = peer
+	mu.Unlock()
+
+	// Try request to peer
+	log.Printf("%s trying to peer with %s", me, peer)
+	resp, err := http.Get(peer + "/peer?peer=" + me)
+	if err != nil {
+		// Request failed, delete peer
+		mu.Lock()
+		delete(hashToDomain, peerHash)
+		mu.Unlock()
+		return err
+	}
+
+	log.Printf("%s successfully peered with %s", me, peer)
+	mu.Lock()
+	peerHashes = append(peerHashes, peerHash)
+	sort.Sort(sort.StringSlice(peerHashes))
+	mu.Unlock()
+	// Read response body
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	// Try adding all peers of this peer
+	newPeers := strings.Split(string(body), "\n")
+	for _, newPeer := range newPeers[:len(newPeers)-1] {
+		go addPeer(newPeer)
+	}
+	return nil
+}
+
+func peerHandler(w http.ResponseWriter, r *http.Request) {
+	// Handle incoming peer requests
+	r.ParseForm()
+	peer := r.Form.Get("peer")
+	if peer == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	go addPeer(peer)
+	for _, p := range hashToDomain {
+		fmt.Fprintf(w, "%s\n", p)
+	}
+}
+
+func getHandler(w http.ResponseWriter, r *http.Request) {
+
+}
+
+func setHandler(w http.ResponseWriter, r *http.Request) {
+
 }
 
 func main() {
-	http.HandleFunc("/", handler)
-	log.Fatal(http.ListenAndServe(":8080", nil))
+	bindAddr := flag.String("b", ":4200", "bind address")
+	domain := flag.String("d", "http://localhost:4200", "full domain name")
+	peer := flag.String("i", "", "initial peer")
+	flag.Parse()
+
+	log.Printf("Starting %s %s %s", *bindAddr, *domain, *peer)
+
+	// Record myself
+	me = *domain
+	peerHashes = append(peerHashes, sha256sum(me))
+	hashToDomain = map[string]string{peerHashes[0]: me}
+
+	if *peer != "" {
+		go addPeer(*peer)
+	}
+
+	http.HandleFunc("/peer", peerHandler)
+	http.HandleFunc("/get", getHandler)
+	http.HandleFunc("/set", setHandler)
+	log.Fatal(http.ListenAndServe(*bindAddr, nil))
 }
diff --git a/server/test.sh b/server/test.sh
new file mode 100755
index 0000000..8ca1d42
--- /dev/null
+++ b/server/test.sh
@@ -0,0 +1,10 @@
+#!/bin/bash
+trap "kill 0" EXIT
+go build
+./server -b :4200 -d http://localhost:4200 &
+for i in $(seq 1 9)
+do
+    sleep 0.1
+	./server -b :420$i -d http://localhost:420$i -i http://localhost:420$((i-1)) &
+done
+wait