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package main
import (
"crypto/ed25519"
"crypto/sha256"
"encoding/hex"
"flag"
"fmt"
"io"
"log"
"net/http"
"sort"
"strings"
"sync"
)
type user struct {
pubkey []byte
}
var mu sync.Mutex
var me string
var myHash string
var myPos int
var hashToDomain map[string]string
var peerHashes []string
var kvstore map[string]string
// Get the sha256sum of string as a hex string
func sha256sum(s string) string {
b := sha256.Sum256([]byte(s))
return hex.EncodeToString(b[:])
}
// 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
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
}
// 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)
fmt.Println(key, keyHash)
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" {
b, err := io.ReadAll(r.Body)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
}
if keyPos - myPos < 5 {
mu.Lock()
kvstore[key] = string(b)
}
} else {
w.WriteHeader(http.StatusMethodNotAllowed)
}
}
// Handle storage requests
func storageHandler(w http.ResponseWriter, r *http.Request) {
filename := r.URL.String()[5:]
if r.Method == "GET" {
} else if r.Method == "PUT" {
} else if r.Method == "DELETE" {
} else {
w.WriteHeader(http.StatusMethodNotAllowed)
}
}
func main() {
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
myHash = sha256sum(me)
myPos = 0
peerHashes = append(peerHashes, sha256sum(me))
hashToDomain = map[string]string{peerHashes[0]: me}
if *peer != "" {
go addPeer(*peer)
}
http.HandleFunc("/peer", peerHandler)
http.HandleFunc("/dht", dhtHandler)
http.HandleFunc("/storage", storageHandler)
log.Fatal(http.ListenAndServe(*bindAddr, nil))
}
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