feat: initial open-source release of Pipely

OTA update server designed for high-concurrency, low-bandwidth deployments.
GORM-backed PostgreSQL, JWT auth, device management, artefact versioning,
deployment rollout with gated rate-limited downloads, and a React admin panel.

internal/delta/handler.go

@@ -0,0 +1,85 @@
+package delta
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+
+	"github.com/gin-gonic/gin"
+)
+
+// Handler provides delta patch generation for JAR artefacts.
+type Handler struct {
+	artefactDir string
+}
+
+func NewHandler(artefactDir string) *Handler {
+	return &Handler{artefactDir: artefactDir}
+}
+
+// GenerateDelta creates a delta patch between two artefact versions.
+// POST /api/v1/delta/generate
+// Form fields: oldVersion, newVersion
+func (h *Handler) GenerateDelta(c *gin.Context) {
+	oldVersion := c.PostForm("oldVersion")
+	newVersion := c.PostForm("newVersion")
+	if oldVersion == "" || newVersion == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "oldVersion and newVersion are required"})
+		return
+	}
+
+	oldDir := filepath.Join(h.artefactDir, oldVersion)
+	newDir := filepath.Join(h.artefactDir, newVersion)
+
+	if _, err := os.Stat(oldDir); os.IsNotExist(err) {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Old version not found: " + oldVersion})
+		return
+	}
+	if _, err := os.Stat(newDir); os.IsNotExist(err) {
+		c.JSON(http.StatusNotFound, gin.H{"error": "New version not found: " + newVersion})
+		return
+	}
+
+	// Find JAR files in each version directory
+	oldJar, err := findJarInDir(oldDir)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "No JAR found in old version: " + err.Error()})
+		return
+	}
+	newJar, err := findJarInDir(newDir)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "No JAR found in new version: " + err.Error()})
+		return
+	}
+
+	patchPath := filepath.Join(h.artefactDir, "patches", oldVersion+"-to-"+newVersion+".patch")
+	if err := os.MkdirAll(filepath.Dir(patchPath), 0755); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create patch directory"})
+		return
+	}
+
+	if err := GenerateJarDelta(oldJar, newJar, patchPath); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Delta generation failed: " + err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"status":     "generated",
+		"patchPath":  patchPath,
+		"oldVersion": oldVersion,
+		"newVersion": newVersion,
+	})
+}
+
+func findJarInDir(dir string) (string, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return "", err
+	}
+	for _, e := range entries {
+		if !e.IsDir() && filepath.Ext(e.Name()) == ".jar" {
+			return filepath.Join(dir, e.Name()), nil
+		}
+	}
+	return "", os.ErrNotExist
+}