Have got session creation working

models/errors.go

@@ -8,3 +8,4 @@ var NotFoundError = errors.New("not found")
 var SiteRequiredError = errors.New("site required")
 var DeleteDebounceError = errors.New("permanent delete too soon, try again in a few seconds")
 var SlugConflictError = errors.New("a record with this slug already exists")
+var UnsupportedImageFormat = errors.New("unsupported image format")

models/imgedit.go

@@ -0,0 +1,59 @@
+package models
+
+import (
+	"crypto/md5"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+)
+
+type ImageEditSession struct {
+	GUID         string               `json:"guid"`
+	SiteID       int64                `json:"siteId"`
+	UserID       int64                `json:"userId"`
+	BaseUploadID int64                `json:"baseUploadId"`
+	ImageExt     string               `json:"imageExt"`
+	CreatedAt    time.Time            `json:"createdAt"`
+	UpdatedAt    time.Time            `json:"updatedAt"`
+	Processors   []ImageEditProcessor `json:"processors"`
+}
+
+func (ieh ImageEditSession) PreviewURL() string {
+	return fmt.Sprintf("/sites/%v/imageedit/%v/preview/%v", ieh.SiteID, ieh.GUID, ieh.Processors[len(ieh.Processors)-1].VersionID)
+}
+
+func (ieh *ImageEditSession) RecalcVersionIDs() {
+	for i, p := range ieh.Processors {
+		if i == 0 {
+			p.SetVersionID("")
+		} else {
+			p.SetVersionID(ieh.Processors[i-1].VersionID)
+		}
+
+		ieh.Processors[i] = p
+	}
+}
+
+type ImageEditProcessor struct {
+	Type  string          `json:"type"`
+	Props json.RawMessage `json:"props"`
+
+	// VersionID is a unique hash of the particular processor. This includes the version ID of the previous processor,
+	// thereby causing a change of one processor to affect the version IDs of processors down the line.
+	VersionID string `json:"versionId"`
+}
+
+func (ieh *ImageEditProcessor) SetVersionID(previousVersionID string) {
+	var sb strings.Builder
+	sb.WriteString(previousVersionID)
+	sb.WriteString("-")
+	sb.WriteString(ieh.Type)
+	sb.WriteString("-")
+	sb.WriteString(string(ieh.Props))
+	ieh.VersionID = fmt.Sprintf("%x", md5.Sum([]byte(sb.String())))
+}
+
+type CopyUploadProps struct {
+	UploadID int64 `json:"uploadId"`
+}