1 files changed, 139 insertions, 0 deletions
diff --git a/server/dht.go b/server/dht.go
new file mode 100644
index 0000000..e5d96f1
--- /dev/null
+++ b/server/dht.go
@@ -0,0 +1,139 @@
+package main
+
+import (
+	"crypto/ed25519"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"sort"
+	"strings"
+)
+
+// Try to peer with another server
+func addPeer(peer string) error {
+	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()
+	i := sort.SearchStrings(peerHashes, peerHash)
+	peerHashes = append(peerHashes, "")
+	copy(peerHashes[i+1:], peerHashes[i:])
+	peerHashes[i] = peerHash
+	myPos = sort.SearchStrings(peerHashes, me)
+	mu.Unlock()
+	// Read response body
+	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
+}
+
+// Handle incoming peer requests
+func peerHandler(w http.ResponseWriter, r *http.Request) {
+	r.ParseForm()
+	peer := r.Form.Get("peer")
+	if peer == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	for _, p := range hashToDomain {
+		fmt.Fprintf(w, "%s\n", p)
+	}
+	go addPeer(peer)
+}
+
+// Handle DHT requests
+func dhtHandler(w http.ResponseWriter, r *http.Request) {
+	key := r.URL.String()[5:]
+	keyHash := sha256sum(key)
+	pubKey := asPubKey(key)
+	fmt.Println(key, keyHash, pubKey)
+	mu.Lock()
+	keyPos := sort.SearchStrings(peerHashes, keyHash)
+	if keyPos < myPos {
+		keyPos += len(peerHashes)
+	}
+	mu.Unlock()
+	if r.Method == "GET" {
+		if keyPos - myPos < 5 {
+			mu.Lock()
+			if val, ok := kvstore[key]; ok {
+				w.Write([]byte(val))
+			} else {
+				w.WriteHeader(http.StatusNotFound)
+			}
+			mu.Unlock()
+		} else {
+			for i := 0; i < 5 && i < len(peerHashes); i++ {
+				j := hashToDomain[peerHashes[(keyPos+i)%len(peerHashes)]]
+				go func() string {
+					resp, err := http.Get(j + r.URL.String())
+					if err != nil {
+						return ""
+					}
+					b, err := io.ReadAll(resp.Body)
+					if err != nil {
+						return ""
+					}
+					return string(b)
+				}()
+
+			}
+
+
+		}
+	} else if r.Method == "PUT" {
+		// Read request body
+		b, err := io.ReadAll(r.Body)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		// Extract signature
+		valSplit := strings.Split(string(b), "\n")
+		sig := valSplit[len(valSplit)-1]
+		// Verify signature
+		if !ed25519.Verify(pubKey, b[:len(b)-len(sig)-1], []byte(sig)) {
+			w.WriteHeader(http.StatusUnauthorized)
+			return
+		}
+		if keyPos - myPos < 5 {
+			mu.Lock()
+			kvstore[key] = string(b[:len(b)-len(sig)-1])
+			mu.Unlock()
+		} else {
+
+		}
+	} else {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+	}
+}