Implement get_history command (WIP)

Author: rowanseymour

Diff for: README.md

@@ -52,6 +52,23 @@ Creates a new incoming message from the client:
 }
 ```
 
+### `get_history`
+
+Requests message history for the current contact:
+
+```json
+{
+    "type": "get_history"
+}
+```
+
+```json
+{
+    "type": "get_history",
+    "before": "2024-05-01T17:15:30.123456Z"
+}
+```
+
 ### `set_email`
 
 Updates the email address for the current contact:
@@ -105,6 +122,17 @@ A new outgoing message has been created and should be displayed in the client:
     "type": "msg_created",
     "text": "How can we help?",
     "origin": "chat",
-    "origin": "bob@nyaruka.com"
+    "user": "bob@nyaruka.com"
+}
+```
+
+### `history_fetched`
+
+A new outgoing message has been created and should be displayed in the client:
+
+```json
+{
+    "type": "history_fetched",
+    "history": []
 }
-```
+```

Diff for: web/client.go

@@ -117,6 +117,20 @@ func (c *Client) onCommand(cmd commands.Command) error {
 			return errors.Wrap(err, "error notifying courier")
 		}
 
+	case *commands.GetHistory:
+		if c.contact == nil {
+			log.Debug("chat not started, command ignored")
+			return nil
+		}
+
+		msgs, err := models.LoadContactMessages(ctx, c.server.rt, c.contact.ID, typed.Before, 10)
+		if err != nil {
+			return errors.Wrap(err, "error loading contact messages")
+
+		}
+
+		c.Send(events.NewHistoryFetched(msgs))
+
 	case *commands.SetEmail:
 		if c.contact == nil {
 			log.Debug("chat not started, command ignored")

Diff for: web/commands/get_history.go

@@ -0,0 +1,15 @@
+package commands
+
+import "time"
+
+func init() {
+	registerType(TypeGetHistory, func() Command { return &GetHistory{} })
+}
+
+const TypeGetHistory string = "get_history"
+
+type GetHistory struct {
+	baseCommand
+
+	Before *time.Time `json:"before"`
+}

Diff for: web/events/history_fetched.go

@@ -0,0 +1,17 @@
+package events
+
+import "github.com/nyaruka/tembachat/core/models"
+
+const TypeHistoryFetched string = "history_fetched"
+
+type HistoryFetched struct {
+	baseEvent
+
+	History []any `json:"history"`
+}
+
+func NewHistoryFetched(msgs []*models.Msg) *HistoryFetched {
+	// TODO convert messages to something
+
+	return &HistoryFetched{baseEvent: baseEvent{Type_: TypeHistoryFetched}, History: []any{}}
+}