refactoring, support for storing feature photos

* errors put into separate package
* added table to store feature photos
* added API endpoints for serving photos
* POST /data extended to accept photos using a multipart/form-data body

errs/errors.go

@@ -0,0 +1,63 @@
+package errs
+
+import "fmt"
+
+type ConstError string
+
+func (e ConstError) Error() string {
+	return string(e)
+}
+
+const (
+	ErrUserNotExists               = ConstError("user does not exist")
+	ErrUserAlreadyExists           = ConstError("user already exists")
+	ErrPhotoNotExists              = ConstError("photo does not exist (for the given feature)")
+	ErrAttemptedSystemUser         = ConstError("attempted to associate with system user")
+	ErrUnsupportedImageFormat      = ConstError("unsupported image format")
+	ErrUnsupportedImageContentType = ConstError("unsupported image content type")
+	ErrNonUniqueCreatedFeatureIDs  = ConstError("created features do not have unique IDs")
+)
+
+type EErrPhotoNotProvided *ErrPhotoNotProvided
+
+type ErrPhotoNotProvided struct {
+	Reference string
+}
+
+func NewErrPhotoNotProvided(reference string) *ErrPhotoNotProvided {
+	return &ErrPhotoNotProvided{
+		Reference: reference,
+	}
+}
+
+func (e *ErrPhotoNotProvided) Error() string {
+	return fmt.Sprintf("referenced photo %s which was not provided", e.Reference)
+}
+
+type ErrFeatureForPhotoNotExists struct {
+	PhotoFeatureReference int64
+}
+
+func NewErrFeatureForPhotoNotExists(reference int64) *ErrFeatureForPhotoNotExists {
+	return &ErrFeatureForPhotoNotExists{
+		PhotoFeatureReference: reference,
+	}
+}
+
+func (e *ErrFeatureForPhotoNotExists) Error() string {
+	return fmt.Sprintf("photos were referenced for feature with local ID %d which does not exist in posted created features", e.PhotoFeatureReference)
+}
+
+type ErrUnsupportedContentType struct {
+	Reference string
+}
+
+func NewErrUnsupportedContentType(reference string) *ErrUnsupportedContentType {
+	return &ErrUnsupportedContentType{
+		Reference: reference,
+	}
+}
+
+func (e *ErrUnsupportedContentType) Error() string {
+	return fmt.Sprintf("photo %s has an unsupported Content-Type", e.Reference)
+}

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"os"
 	"os/signal"
 	"syscall"
@@ -18,6 +19,12 @@ func main() {
 
 	flag.Parse()
 
+	if *tilepackFileArg == "" {
+		fmt.Fprintln(os.Stderr, "Tile pack not specified.")
+		flag.Usage()
+		os.Exit(1)
+	}
+
 	s := server.New(*dbFileArg, *tilepackFileArg, *apkFileArg)
 
 	sigs := make(chan os.Signal, 1)

models/models.go

@@ -1,11 +1,16 @@
 package models
 
-import geojson "github.com/paulmach/go.geojson"
+import (
+	"io"
+
+	geojson "github.com/paulmach/go.geojson"
+)
 
 // core objects
 
-type UserID int
-type FeatureID int
+type UserID int64
+type FeatureID int64
+type FeaturePhotoID int64
 
 type User struct {
 	ID   UserID `json:"id"`
@@ -13,20 +18,29 @@ type User struct {
 }
 
 type Feature struct {
+	// ID is an ID of the feature.
+	// When the feature is submitted by a client for creation (i.e. in Update.Create) it is considered a 'local' ID which must be unique across all submitted features.
 	ID          FeatureID        `json:"id"`
 	OwnerID     *UserID          `json:"owner_id"`
 	Name        string           `json:"name"`
 	Description *string          `json:"description"`
 	Category    *string          `json:"category"`
 	Geometry    geojson.Geometry `json:"geometry"`
+	// PhotoIDs contains a list IDs of photos associated with the feature.
+	// When the feature is retrieved from the server, the IDs can be used to retrieve the photos.
+	// When the feature is submitted by a client (created or updated, i.e. in Update.Create or Update.Update), this list is ignored (as photos are managed through Update.CreatePhotos and Update.DeletePhotos fields).
+	PhotoIDs []FeaturePhotoID `json:"photo_ids"`
 }
 
 // transport objects
 
 type Update struct {
-	Create []Feature   `json:"create"`
-	Update []Feature   `json:"update"`
-	Delete []FeatureID `json:"delete"`
+	Create        []Feature              `json:"create"`
+	CreatedPhotos map[FeatureID][]string `json:"created_photos"`
+	AddPhotos     map[FeatureID][]string `json:"add_photos"`
+	Update        []Feature              `json:"update"`
+	Delete        []FeatureID            `json:"delete"`
+	DeletePhotos  []FeaturePhotoID       `json:"delete_photos"`
 }
 
 type HandshakeChallenge struct {
@@ -44,3 +58,9 @@ type Data struct {
 	Users    []User    `json:"users"`
 	Features []Feature `json:"features"`
 }
+
+type Photo struct {
+	ContentType string
+	File        io.ReadCloser
+	Size        int64
+}

server/errors.go

@@ -1,13 +0,0 @@
-package server
-
-type ConstError string
-
-func (e ConstError) Error() string {
-	return string(e)
-}
-
-const (
-	ErrUserNotExists       = ConstError("user does not exist")
-	ErrUserAlreadyExists   = ConstError("user already exists")
-	ErrAttemptedSystemUser = ConstError("attepted to associate with system user")
-)

server/handling.go

@@ -1,13 +1,17 @@
 package server
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"math"
 	"net/http"
 	"os"
+	"strconv"
 	"time"
 
+	"cernobor.cz/oko-server/errs"
 	"cernobor.cz/oko-server/models"
 	"github.com/gin-gonic/gin"
 	"github.com/sirupsen/logrus"
@@ -90,6 +94,7 @@ func (s *Server) setupRouter() *gin.Engine {
 	router.POST(URIData, s.handlePOSTData)
 	router.GET(URIDataPeople, s.handleGETDataPeople)
 	router.GET(URIDataFeatures, s.handleGETDataFeatures)
+	router.GET(URIDataFeaturesPhoto, s.handleGETDataFeaturesPhoto)
 
 	// tileserver
 	router.GET(URITileserver, gin.WrapH(s.tileserverSvSet.Handler()))
@@ -111,11 +116,11 @@ func (s *Server) handlePOSTHandshake(gc *gin.Context) {
 
 	id, err := s.handshake(hs)
 	if err != nil {
-		if errors.Is(err, ErrUserAlreadyExists) {
+		if errors.Is(err, errs.ErrUserAlreadyExists) {
 			gc.Status(http.StatusConflict)
-		} else if errors.Is(err, ErrUserNotExists) {
+		} else if errors.Is(err, errs.ErrUserNotExists) {
 			gc.Status(http.StatusNotFound)
-		} else if errors.Is(err, ErrAttemptedSystemUser) {
+		} else if errors.Is(err, errs.ErrAttemptedSystemUser) {
 			gc.Status(http.StatusForbidden)
 		} else {
 			internalError(gc, err)
@@ -140,6 +145,17 @@ func (s *Server) handleGETData(gc *gin.Context) {
 }
 
 func (s *Server) handlePOSTData(gc *gin.Context) {
+	switch gc.ContentType() {
+	case "application/json":
+		s.handlePOSTDataJSON(gc)
+	case "multipart/form-data":
+		s.handlePOSTDataMultipart(gc)
+	default:
+		gc.String(http.StatusBadRequest, "unsupported Content-Type")
+	}
+}
+
+func (s *Server) handlePOSTDataJSON(gc *gin.Context) {
 	var data models.Update
 	err := gc.ShouldBindJSON(&data)
 	if err != nil {
@@ -147,7 +163,17 @@ func (s *Server) handlePOSTData(gc *gin.Context) {
 		return
 	}
 
-	err = s.update(data)
+	if !isUniqueFeatureID(data.Create) {
+		gc.String(http.StatusBadRequest, "created features do not have unique IDs")
+		return
+	}
+
+	if data.CreatedPhotos != nil || data.AddPhotos != nil {
+		gc.String(http.StatusBadRequest, "created_photos and/or add_photos present, but Content-Type is application/json")
+		return
+	}
+
+	err = s.update(data, nil)
 	if err != nil {
 		internalError(gc, fmt.Errorf("failed to update data: %w", err))
 		return
@@ -155,6 +181,84 @@ func (s *Server) handlePOSTData(gc *gin.Context) {
 	gc.Status(http.StatusNoContent)
 }
 
+func (s *Server) handlePOSTDataMultipart(gc *gin.Context) {
+	form, err := gc.MultipartForm()
+	if err != nil {
+		gc.String(http.StatusBadRequest, "malformed multipart/form-data content")
+		return
+	}
+
+	dataStr, ok := form.Value["data"]
+	if !ok {
+		dataFile, ok := form.File["data"]
+		if !ok {
+			gc.String(http.StatusBadRequest, "value 'data' is missing from the content")
+			return
+		}
+		if len(dataFile) != 1 {
+			gc.String(http.StatusBadRequest, "value 'data' does not contain exactly 1 item")
+			return
+		}
+		df, err := dataFile[0].Open()
+		if err != nil {
+			internalError(gc, fmt.Errorf("failed to open 'data' 'file': %w", err))
+			return
+		}
+		dataBytes, err := ioutil.ReadAll(df)
+		if err != nil {
+			internalError(gc, fmt.Errorf("failed to open 'data' 'file': %w", err))
+			return
+		}
+		dataStr = []string{string(dataBytes)}
+	}
+	if len(dataStr) != 1 {
+		gc.String(http.StatusBadRequest, "value 'data' does not contain exactly 1 item")
+		return
+	}
+
+	var data models.Update
+	err = json.Unmarshal([]byte(dataStr[0]), &data)
+	if err != nil {
+		gc.String(http.StatusBadRequest, "malformed 'data' value: %v", err)
+		return
+	}
+
+	if !isUniqueFeatureID(data.Create) {
+		gc.String(http.StatusBadRequest, "created features do not have unique IDs")
+		return
+	}
+
+	photos := make(map[string]models.Photo, len(form.File))
+	for name, fh := range form.File {
+		if len(fh) != 1 {
+			gc.String(http.StatusBadRequest, "file item %s does not contain exactly 1 file", name)
+			return
+		}
+		var photo models.Photo
+		f := fh[0]
+		photo.ContentType = f.Header.Get("Content-Type")
+		photo.Size = f.Size
+		photo.File, err = f.Open()
+		if err != nil {
+			internalError(gc, fmt.Errorf("failed to open provided photo file: %w", err))
+		}
+		defer photo.File.Close()
+		photos[name] = photo
+	}
+	err = s.update(data, photos)
+	if err != nil {
+		var e *errs.ErrUnsupportedContentType
+		if errors.As(err, &e) {
+			gc.String(http.StatusBadRequest, e.Error())
+			return
+		}
+		internalError(gc, fmt.Errorf("failed to update data: %w", err))
+		return
+	}
+
+	gc.Status(http.StatusNoContent)
+}
+
 func (s *Server) handleGETDataPeople(gc *gin.Context) {
 	people, err := s.getPeople(nil)
 	if err != nil {
@@ -172,3 +276,28 @@ func (s *Server) handleGETDataFeatures(gc *gin.Context) {
 	}
 	gc.JSON(http.StatusOK, pois)
 }
+
+func (s *Server) handleGETDataFeaturesPhoto(gc *gin.Context) {
+	reqFeatureID, err := strconv.Atoi(gc.Param("feature"))
+	if err != nil {
+		gc.String(http.StatusBadRequest, "malformed feature ID")
+		return
+	}
+	reqPhotoID, err := strconv.Atoi(gc.Param("photo"))
+	if err != nil {
+		gc.String(http.StatusBadRequest, "malformed photo ID")
+		return
+	}
+
+	photoBytes, contentType, err := s.getPhoto(models.FeatureID(reqFeatureID), models.FeaturePhotoID(reqPhotoID))
+	if err != nil {
+		if errors.Is(err, errs.ErrPhotoNotExists) {
+			gc.String(http.StatusNotFound, "%v", err)
+		} else {
+			internalError(gc, fmt.Errorf("failed to retrieve photo: %w", err))
+		}
+		return
+	}
+
+	gc.Data(http.StatusOK, contentType, photoBytes)
+}

server/initdb.sql

@@ -8,10 +8,17 @@ INSERT INTO users(id, name) VALUES(0, 'system');
 DROP TABLE IF EXISTS features;
 CREATE TABLE IF NOT EXISTS features (
   id integer PRIMARY KEY AUTOINCREMENT,
-  owner_id integer,
+  owner_id integer REFERENCES users(id) ON DELETE CASCADE,
   name text NOT NULL,
   description text,
   category text,
-  geom text NOT NULL,
-  FOREIGN KEY(owner_id) REFERENCES users(id) ON DELETE CASCADE
+  geom text NOT NULL
+);
+
+DROP TABLE IF EXISTS feature_photos;
+CREATE TABLE IF NOT EXISTS feature_photos (
+  id integer PRIMARY KEY AUTOINCREMENT,
+  feature_id integer NOT NULL REFERENCES features(id) ON DELETE CASCADE,
+  content_type text NOT NULL,
+  file_contents blob NOT NULL
 );

server/server.go

@@ -4,12 +4,14 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
 	"time"
 
 	_ "embed"
 
+	"cernobor.cz/oko-server/errs"
 	"cernobor.cz/oko-server/models"
 	"crawshaw.io/sqlite"
 	"crawshaw.io/sqlite/sqlitex"
@@ -144,10 +146,10 @@ func (s *Server) handshake(hc models.HandshakeChallenge) (models.UserID, error)
 				return 0, err
 			}
 			if id == nil {
-				return 0, ErrUserNotExists
+				return 0, errs.ErrUserNotExists
 			}
 			if *id == 0 {
-				return 0, ErrAttemptedSystemUser
+				return 0, errs.ErrAttemptedSystemUser
 			}
 		} else {
 			err = sqlitex.Exec(conn, "insert into users(name) values(?) returning id", func(stmt *sqlite.Stmt) error {
@@ -155,7 +157,7 @@ func (s *Server) handshake(hc models.HandshakeChallenge) (models.UserID, error)
 				return nil
 			}, hc.Name)
 			if sqlite.ErrCode(err) == sqlite.SQLITE_CONSTRAINT_UNIQUE {
-				return 0, ErrUserAlreadyExists
+				return 0, errs.ErrUserAlreadyExists
 			}
 			if sqlite.ErrCode(err) != sqlite.SQLITE_OK {
 				return 0, err
@@ -193,20 +195,32 @@ func (s *Server) getData() (models.Data, error) {
 	}()
 }
 
-func (s *Server) update(data models.Update) error {
+func (s *Server) update(data models.Update, photos map[string]models.Photo) error {
 	conn := s.getDbConn()
 	defer s.dbpool.Put(conn)
 
 	return func() (err error) {
 		defer sqlitex.Save(conn)(&err)
 
+		var createdIDMapping map[models.FeatureID]models.FeatureID
 		if data.Create != nil {
-			err = s.addFeatures(conn, data.Create)
+			createdIDMapping, err = s.addFeatures(conn, data.Create)
 			if err != nil {
 				err = fmt.Errorf("failed to add features: %w", err)
 				return
 			}
 		}
+		if data.CreatedPhotos != nil || data.AddPhotos != nil {
+			if photos == nil {
+				err = fmt.Errorf("photo assignment present but no photos provided")
+				return
+			}
+			err = s.addPhotos(conn, data.CreatedPhotos, data.AddPhotos, createdIDMapping, photos)
+			if err != nil {
+				err = fmt.Errorf("failed to add photos: %w", err)
+				return
+			}
+		}
 		if data.Update != nil {
 			err = s.updateFeatures(conn, data.Update)
 			if err != nil {
@@ -221,6 +235,13 @@ func (s *Server) update(data models.Update) error {
 				return
 			}
 		}
+		if data.DeletePhotos != nil {
+			err = s.deletePhotos(conn, data.DeletePhotos)
+			if err != nil {
+				err = fmt.Errorf("failed to delete photos: %w", err)
+				return
+			}
+		}
 
 		return nil
 	}()
@@ -253,29 +274,44 @@ func (s *Server) getFeatures(conn *sqlite.Conn) ([]models.Feature, error) {
 	}
 
 	features := make([]models.Feature, 0, 100)
-	err := sqlitex.Exec(conn, "select id, owner_id, name, description, category, geom from features", func(stmt *sqlite.Stmt) error {
-		id := stmt.ColumnInt(0)
-		var ownerID *int
+	err := sqlitex.Exec(conn, `select f.id, f.owner_id, f.name, f.description, f.category, f.geom, '[' || coalesce(group_concat(p.id, ', '), '') || ']'
+		from features f
+		left join feature_photos p on f.id = p.feature_id
+		group by f.id, f.owner_id, f.name, f.description, f.category, f.geom`, func(stmt *sqlite.Stmt) error {
+
+		id := stmt.ColumnInt64(0)
+
+		var ownerID *int64
 		if stmt.ColumnType(1) != sqlite.SQLITE_NULL {
-			ownerID = ptrInt(stmt.ColumnInt(1))
+			ownerID = ptrInt64(stmt.ColumnInt64(1))
 		}
+
 		name := stmt.ColumnText(2)
+
 		var description *string
 		if stmt.ColumnType(3) != sqlite.SQLITE_NULL {
 			description = ptrString(stmt.ColumnText(3))
 		}
+
 		var category *string
 		if stmt.ColumnType(4) != sqlite.SQLITE_NULL {
 			category = ptrString(stmt.ColumnText(4))
 		}
-		geomRaw := stmt.ColumnText(5)
 
+		geomRaw := stmt.ColumnText(5)
 		var geom geojson.Geometry
 		err := json.Unmarshal([]byte(geomRaw), &geom)
 		if err != nil {
 			return fmt.Errorf("failed to parse geometry for point id=%d: %w", id, err)
 		}
 
+		photosRaw := stmt.ColumnText(6)
+		var photos []models.FeaturePhotoID
+		err = json.Unmarshal([]byte(photosRaw), &photos)
+		if err != nil {
+			return fmt.Errorf("failed to parse list of photo IDs: %w", err)
+		}
+
 		feature := models.Feature{
 			ID:          models.FeatureID(id),
 			OwnerID:     (*models.UserID)(ownerID),
@@ -283,6 +319,7 @@ func (s *Server) getFeatures(conn *sqlite.Conn) ([]models.Feature, error) {
 			Description: description,
 			Category:    category,
 			Geometry:    geom,
+			PhotoIDs:    photos,
 		}
 
 		features = append(features, feature)
@@ -294,21 +331,25 @@ func (s *Server) getFeatures(conn *sqlite.Conn) ([]models.Feature, error) {
 	return features, nil
 }
 
-func (s *Server) addFeatures(conn *sqlite.Conn, features []models.Feature) error {
+func (s *Server) addFeatures(conn *sqlite.Conn, features []models.Feature) (map[models.FeatureID]models.FeatureID, error) {
 	stmt, err := conn.Prepare("insert into features(owner_id, name, description, category, geom) values(?, ?, ?, ?, ?)")
 	if err != nil {
-		return fmt.Errorf("failed to prepare statement: %w", err)
+		return nil, fmt.Errorf("failed to prepare statement: %w", err)
 	}
 	defer stmt.Finalize()
 
+	localIDMapping := make(map[models.FeatureID]models.FeatureID, len(features))
 	for _, feature := range features {
+		if _, ok := localIDMapping[feature.ID]; ok {
+			return nil, errs.ErrNonUniqueCreatedFeatureIDs
+		}
 		err := stmt.Reset()
 		if err != nil {
-			return fmt.Errorf("failed to reset prepared statement: %w", err)
+			return nil, fmt.Errorf("failed to reset prepared statement: %w", err)
 		}
 		err = stmt.ClearBindings()
 		if err != nil {
-			return fmt.Errorf("failed to clear bindings of prepared statement: %w", err)
+			return nil, fmt.Errorf("failed to clear bindings of prepared statement: %w", err)
 		}
 
 		if feature.OwnerID == nil {
@@ -329,13 +370,87 @@ func (s *Server) addFeatures(conn *sqlite.Conn, features []models.Feature) error
 		}
 		geomBytes, err := json.Marshal(feature.Geometry)
 		if err != nil {
-			return fmt.Errorf("failed to marshal geometry of feature ID %d: %w", feature.ID, err)
+			return nil, fmt.Errorf("failed to marshal geometry of feature ID %d: %w", feature.ID, err)
 		}
 		stmt.BindText(5, string(geomBytes))
 
 		_, err = stmt.Step()
 		if err != nil {
-			return fmt.Errorf("failed to evaluate prepared statement: %w", err)
+			return nil, fmt.Errorf("failed to evaluate prepared statement: %w", err)
+		}
+
+		localIDMapping[feature.ID] = models.FeatureID(conn.LastInsertRowID())
+	}
+	return localIDMapping, nil
+}
+
+func (s *Server) addPhotos(conn *sqlite.Conn, createdFeatureMapping, addedFeatureMapping map[models.FeatureID][]string, createdIDMapping map[models.FeatureID]models.FeatureID, photos map[string]models.Photo) error {
+	stmt, err := conn.Prepare("insert into feature_photos(feature_id, content_type, file_contents) values(?, ?, ?)")
+	if err != nil {
+		return fmt.Errorf("failed to prepare statement: %w", err)
+	}
+	defer stmt.Finalize()
+
+	uploadPhotos := func(featureID models.FeatureID, photoNames []string) error {
+		for _, photoName := range photoNames {
+			photo, ok := photos[photoName]
+			if !ok {
+				return errs.NewErrPhotoNotProvided(photoName)
+			}
+			if !checkImageContentType(photo.ContentType) {
+				return errs.NewErrUnsupportedContentType(photoName)
+			}
+
+			err := stmt.Reset()
+			if err != nil {
+				return fmt.Errorf("failed to reset prepared statement: %w", err)
+			}
+			err = stmt.ClearBindings()
+			if err != nil {
+				return fmt.Errorf("failed to clear bindings of prepared statement: %w", err)
+			}
+
+			stmt.BindInt64(1, int64(featureID))
+			stmt.BindText(2, photo.ContentType)
+			stmt.BindZeroBlob(3, photo.Size)
+
+			_, err = stmt.Step()
+			if err != nil {
+				return fmt.Errorf("failed to evaluate prepared statement: %w", err)
+			}
+
+			blob, err := conn.OpenBlob("", "feature_photos", "file_contents", conn.LastInsertRowID(), true)
+			if err != nil {
+				return fmt.Errorf("failed to open photo content blob: %w", err)
+			}
+			err = func() error {
+				defer blob.Close()
+				defer photo.File.Close()
+
+				_, err := io.Copy(blob, photo.File)
+				return err
+			}()
+			if err != nil {
+				return fmt.Errorf("failed to write to photo content blob: %w", err)
+			}
+		}
+		return nil
+	}
+
+	for localFeatureID, photoNames := range createdFeatureMapping {
+		featureID, ok := createdIDMapping[localFeatureID]
+		if !ok {
+			return errs.NewErrFeatureForPhotoNotExists(int64(localFeatureID))
+		}
+		err = uploadPhotos(featureID, photoNames)
+		if err != nil {
+			return fmt.Errorf("failed to upload photos for created features: %w", err)
+		}
+	}
+	for featureID, photoNames := range addedFeatureMapping {
+		err = uploadPhotos(featureID, photoNames)
+		if err != nil {
+			return fmt.Errorf("failed to upload photos for existing features: %w", err)
 		}
 	}
 	return nil
@@ -415,3 +530,58 @@ func (s *Server) deleteFeatures(conn *sqlite.Conn, featureIDs []models.FeatureID
 	}
 	return nil
 }
+
+func (s *Server) deletePhotos(conn *sqlite.Conn, photoIDs []models.FeaturePhotoID) error {
+	stmt, err := conn.Prepare("delete from feature_photos where id = ?")
+	if err != nil {
+		return fmt.Errorf("failed to prepare statement: %w", err)
+	}
+	defer stmt.Finalize()
+
+	for _, photoID := range photoIDs {
+		err := stmt.Reset()
+		if err != nil {
+			return fmt.Errorf("failed to reset prepared statement: %w", err)
+		}
+		err = stmt.ClearBindings()
+		if err != nil {
+			return fmt.Errorf("failed to clear bindings of prepared statement: %w", err)
+		}
+
+		stmt.BindInt64(1, int64(photoID))
+
+		_, err = stmt.Step()
+		if err != nil {
+			return fmt.Errorf("failed to evaluate prepared statement: %w", err)
+		}
+	}
+	return nil
+}
+
+func (s *Server) getPhoto(featureID models.FeatureID, photoID models.FeaturePhotoID) ([]byte, string, error) {
+	conn := s.getDbConn()
+	defer s.dbpool.Put(conn)
+
+	var contentType *string = nil
+	var data []byte = nil
+	found := false
+	err := sqlitex.Exec(conn, "select content_type, file_contents from feature_photos where id = ? and feature_id = ?", func(stmt *sqlite.Stmt) error {
+		if found {
+			return fmt.Errorf("multiple photos returned for feature id %d, photo id %d", featureID, photoID)
+		}
+		contentType = ptrString(stmt.ColumnText(0))
+		data = make([]byte, stmt.ColumnLen(1))
+		stmt.ColumnBytes(1, data)
+		found = true
+		return nil
+	}, photoID, featureID)
+	if err != nil {
+		return nil, "", fmt.Errorf("photo db query failed: %w", err)
+	}
+
+	if !found {
+		return nil, "", errs.ErrPhotoNotExists
+	}
+
+	return data, *contentType, nil
+}

server/uris.go

@@ -1,15 +1,16 @@
 package server
 
 const (
-	URIPing           = "/ping"
-	URIHardFail       = "/hard-fail"
-	URISoftFail       = "/soft-fail"
-	URITilepack       = "/tilepack"
-	URIHandshake      = "/handshake"
-	URIData           = "/data"
-	URIDataPeople     = "/data/people"
-	URIDataExtra      = "/data/extra"
-	URIDataFeatures   = "/data/features"
-	URITileserverRoot = "/tileserver"
-	URITileserver     = URITileserverRoot + "/*x"
+	URIPing              = "/ping"
+	URIHardFail          = "/hard-fail"
+	URISoftFail          = "/soft-fail"
+	URITilepack          = "/tilepack"
+	URIHandshake         = "/handshake"
+	URIData              = "/data"
+	URIDataPeople        = "/data/people"
+	URIDataExtra         = "/data/extra"
+	URIDataFeatures      = "/data/features"
+	URIDataFeaturesPhoto = "/data/features/:feature/photos/:photo"
+	URITileserverRoot    = "/tileserver"
+	URITileserver        = URITileserverRoot + "/*x"
 )

server/utils.go

@@ -1,9 +1,34 @@
 package server
 
+import (
+	"cernobor.cz/oko-server/models"
+)
+
 func ptrInt(x int) *int {
 	return &x
 }
 
+func ptrInt64(x int64) *int64 {
+	return &x
+}
+
 func ptrString(x string) *string {
 	return &x
 }
+
+var contentTypes map[string]struct{} = map[string]struct{}{"image/jpeg": {}, "image/png": {}}
+
+func checkImageContentType(contentType string) bool {
+	_, ok := contentTypes[contentType]
+	return ok
+}
+
+func isUniqueFeatureID(features []models.Feature) bool {
+	ids := make(map[models.FeatureID]struct{}, len(features))
+	for _, f := range features {
+		if _, pres := ids[f.ID]; pres {
+			return false
+		}
+	}
+	return true
+}