1 files changed, 85 insertions, 0 deletions
diff --git a/message/message.go b/message/message.go
index 14e9cac..c50310e 100644
--- a/message/message.go
+++ b/message/message.go
@@ -1,9 +1,15 @@
 package message
 
 import (
+	"context"
 	"crypto/sha256"
+	"database/sql"
+	"encoding/json"
 	"fmt"
 	"math/bits"
+
+	ipfs "github.com/ipfs/go-ipfs-api"
+	pubsub "github.com/libp2p/go-libp2p-pubsub"
 )
 
 // Messages on Infodump use a "stamp" using the hashcash algorithm to prevent spam and enable storing messages by importance
@@ -70,3 +76,82 @@ func New(msg string, n int) *Message {
 	m.ProofOfWork(n)
 	return &m
 }
+
+// Datatype Messages that contains a slice of message.Message that is to be stored on IPFS as JSON
+type Messages struct {
+	Messages []message.Message `json:"messages"`
+}
+
+// JSON encodes the Messages struct into a JSON string
+func (m *Messages) JSON() string {
+	json, _ := json.Marshal(m)
+	return string(json)
+}
+
+// Push the JSON string to IPFS and return the hash
+func (m *Messages) Push(ipfs *ipfs.IpfsApi) (string, error) {
+	hash, err := ipfs.BlockPut(m.JSON())
+	return hash, err
+}
+
+// Read the JSON string from IPFS and return the Messages struct
+func (m *Messages) Read(ipfs *ipfs.IpfsApi, hash string) error {
+	json, err := ipfs.BlockGet(hash)
+	if err != nil {
+		return err
+	}
+	err = json.Unmarshal([]byte(json), &m)
+	return err
+}
+
+// Save the Messages struct to the database
+func (m *Messages) Save(db *sql.DB) error {
+	stmt, err := db.Prepare("INSERT INTO messages (hash) VALUES (?)")
+	if err != nil {
+		return err
+	}
+	_, err = stmt.Exec(m.JSON())
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Push the Messages struct to IPFS and send the hash to the PubSub topic
+func (m *Messages) Publish(ipfs *ipfs.IpfsApi, ps *pubsub.PubSub, topic string) error {
+	hash, err := m.Push(ipfs)
+	if err != nil {
+		return err
+	}
+	err = ps.Publish(topic, []byte(hash))
+	return err
+}
+
+// ListenAndSave takes an IPFS instance, a PubSub instance, a database and a topic
+// Listen on the PubSub topic, look up the hash and read the Messages struct
+// On first receipt, save the Messages struct to the database
+func ListenAndSave(ipfs *ipfs.IpfsApi, ps *pubsub.PubSub, db *sql.DB, topic string) error {
+	// Subscribe to the topic
+	sub, err := ps.Subscribe(topic)
+	if err != nil {
+		return err
+	}
+	// Listen for messages on the topic
+	for {
+		msg, err := sub.Next(context.Background())
+		if err != nil {
+			return err
+		}
+		// Read the Messages struct from IPFS
+		m := Messages{}
+		err = m.Read(ipfs, string(msg.Data))
+		if err != nil {
+			return err
+		}
+		// Save the Messages struct to the database
+		err = m.Save(db)
+		if err != nil {
+			return err
+		}
+	}
+}