From 0d99789a54e289ba6d5a96f4091a33d0006641d9 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Tue, 6 May 2025 00:15:45 -0300
Subject: [PATCH] khatru/blossom: implement bud-04 mirror.

---
 khatru/blossom/handlers.go | 91 ++++++++++++++++++++++++++++++++++++++
 khatru/blossom/server.go   |  5 +++
 2 files changed, 96 insertions(+)

diff --git a/khatru/blossom/handlers.go b/khatru/blossom/handlers.go
index 8bbf3ec..cdfe937 100644
--- a/khatru/blossom/handlers.go
+++ b/khatru/blossom/handlers.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"mime"
 	"net/http"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
@@ -15,6 +16,10 @@ import (
 	"github.com/liamg/magic"
 )
 
+type mirrorRequest struct {
+	URL string `json:"url"`
+}
+
 func (bs BlossomServer) handleUploadCheck(w http.ResponseWriter, r *http.Request) {
 	auth, err := readAuthorization(r)
 	if err != nil {
@@ -355,6 +360,92 @@ func (bs BlossomServer) handleReport(w http.ResponseWriter, r *http.Request) {
 }
 
 func (bs BlossomServer) handleMirror(w http.ResponseWriter, r *http.Request) {
+	auth, err := readAuthorization(r)
+	if err != nil {
+		blossomError(w, "invalid \"Authorization\": "+err.Error(), 400)
+		return
+	}
+	if auth == nil {
+		blossomError(w, "missing \"Authorization\" header", 401)
+		return
+	}
+	if auth.Tags.FindWithValue("t", "upload") == nil {
+		blossomError(w, "invalid \"Authorization\" event \"t\" tag", 403)
+		return
+	}
+
+	var req mirrorRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		blossomError(w, "invalid request body: "+err.Error(), 400)
+		return
+	}
+
+	// download the blob
+	resp, err := http.Get(req.URL)
+	if err != nil {
+		blossomError(w, "failed to download from url: "+err.Error(), 503)
+		return
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		blossomError(w, "failed to read response body: "+err.Error(), 503)
+		return
+	}
+
+	// calculate sha256
+	hash := sha256.Sum256(body)
+	hhash := hex.EncodeToString(hash[:])
+
+	// verify hash against x tag
+	if auth.Tags.FindWithValue("x", hhash) == nil {
+		blossomError(w, "blob hash does not match any \"x\" tag in authorization event", 403)
+		return
+	}
+
+	// determine content type and extension
+	var ext string
+	contentType := resp.Header.Get("Content-Type")
+	if contentType != "" {
+		ext = getExtension(contentType)
+	} else {
+		// try to detect from url
+		ext = filepath.Ext(req.URL)
+	}
+
+	// run reject hook if defined
+	if bs.RejectUpload != nil {
+		reject, reason, code := bs.RejectUpload(r.Context(), auth, len(body), ext)
+		if reject {
+			blossomError(w, reason, code)
+			return
+		}
+	}
+
+	// keep track of the blob descriptor
+	bd := BlobDescriptor{
+		URL:      bs.ServiceURL + "/" + hhash + ext,
+		SHA256:   hhash,
+		Size:     len(body),
+		Type:     contentType,
+		Uploaded: nostr.Now(),
+	}
+	if err := bs.Store.Keep(r.Context(), bd, auth.PubKey); err != nil {
+		blossomError(w, "failed to save event: "+err.Error(), 400)
+		return
+	}
+
+	// save actual blob
+	if bs.StoreBlob != nil {
+		if err := bs.StoreBlob(r.Context(), hhash, body); err != nil {
+			blossomError(w, "failed to save: "+err.Error(), 500)
+			return
+		}
+	}
+
+	// return response
+	json.NewEncoder(w).Encode(bd)
 }
 
 func (bs BlossomServer) handleNegentropy(w http.ResponseWriter, r *http.Request) {
diff --git a/khatru/blossom/server.go b/khatru/blossom/server.go
index f2b9f0e..af94cd1 100644
--- a/khatru/blossom/server.go
+++ b/khatru/blossom/server.go
@@ -44,6 +44,11 @@ func New(rl *khatru.Relay, serviceURL string) *BlossomServer {
 			}
 		}
 
+		if r.URL.Path == "/mirror" && r.Method == "PUT" {
+			bs.handleMirror(w, r)
+			return
+		}
+
 		if strings.HasPrefix(r.URL.Path, "/list/") && r.Method == "GET" {
 			bs.handleList(w, r)
 			return