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package message
import (
"bytes"
"crypto/sha256"
"encoding/json"
"fmt"
"math/bits"
"time"
ipfs "github.com/ipfs/go-ipfs-api"
)
var IPFSGateway = "http://localhost:5001" // IPFS Gateway used to connect to the IPFS daemon
// Set up an IPFS instance based on the IPFSGateway
func InitIPFS() *ipfs.Shell {
return ipfs.NewShell(IPFSGateway)
}
// Messages on Infodump use a "stamp" using the hashcash algorithm to prevent spam and enable storing messages by importance
// The Message type contains the message itself and a nonce that is used to verify the stamp
type Message struct {
Message string
Timestamp int64
Nonce int
}
// String method for Message: "Message *hash* sent at *human readable timestamp* with nonce *nonce*:\n*message*"
func (m *Message) String() string {
return fmt.Sprintf("Message %x sent at %s with nonce %d:\n%s", m.Hash(), time.Unix(m.Timestamp, 0).Format(time.RFC3339), m.Nonce, m.Message)
}
// Proof of Work: Find the nonce for a message by hashing the message and checking for at least n initial zeroes in the binary representation of the resulting hash
func (msg *Message) ProofOfWork(n int) {
// Create a local copy of the message and start counting
m := *msg
m.Nonce = 0
// Loop until we find a nonce that satisfies the proof of work
for {
// Increment the nonce and hash the message
m.Nonce++
hash := m.Hash()
// If the hash has at least n initial zeroes, we have found a valid nonce
if CountLeadingZeroes(hash) >= n {
break
}
}
// Set the message to the local copy
*msg = m
}
// Get the SHA256 hash of a message plus the timestamp plus the nonce as a byte slice
func (m *Message) Hash() [32]byte {
hash := sha256.Sum256([]byte(m.Message + fmt.Sprintf("%d", m.Timestamp) + fmt.Sprintf("%d", m.Nonce)))
return hash
}
// Bitwise count leading zeroes in a byte slice
func CountLeadingZeroes(b [32]byte) int {
count := 0
for _, v := range b {
// If the byte is zero, that means there are 8 leading zeroes and we need to continue counting
if v == 0 {
count += 8
} else { // Otherwise, we add the number of leading zeroes in the byte and stop counting
// Bitwise count leading zeroes in the byte
count += bits.LeadingZeros8(v)
// If the byte is not zero, we can stop counting
break
}
}
return count
}
// Get the stamp of the message
func (m *Message) Stamp() string {
return fmt.Sprintf("%x", m.Hash())
}
// Lead is a method that returns the number of leading zeroes in the hash of a message plus its nonce
func (m *Message) Lead() int {
return CountLeadingZeroes(m.Hash())
}
func New(msg string, n int, timestamp int64) *Message {
m := Message{Message: msg, Timestamp: timestamp}
m.ProofOfWork(n)
return &m
}
// Map Messages maps the stamp of the message to the message itself
type Messages map[string]*Message
// Add a message to the Messages map
func (m *Messages) Add(msg *Message) {
(*m)[msg.Stamp()] = msg
}
// Remove a message from the Messages map by stamp
func (m *Messages) Remove(stamp string) {
delete(*m, stamp)
}
// Return a JSON representation of the Messages map
func (m *Messages) JSON() ([]byte, error) {
return json.Marshal(m)
}
// Add the messages as a JSON object to IPFS
func (m *Messages) AddToIPFS() (string, error) {
json, err := m.JSON()
if err != nil {
return "", err
}
return AddJSONToIPFS(json)
}
func AddJSONToIPFS(json []byte) (string, error) {
// Create an IPFS instance based on the IPFSGateway
myIPFS := ipfs.NewShell(IPFSGateway)
// Turn the JSON into a Reader and add it to IPFS
cid, err := myIPFS.Add(bytes.NewReader(json))
if err != nil {
return "", err
}
return cid, nil
}
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