App version management.

* DB migration adds app_versions table for managing known app versions.
* /ping reads app version from User-Agent header and responds with latest version if the app is OKO and its version is older than the latest one stored.
* Added endpoint /app-versions which
  * lists all known versions via GET
  * adds/updates a version via POST

#3
Fix #4

go.mod

@@ -4,14 +4,15 @@ go 1.19
 
 require (
 	crawshaw.io/sqlite v0.3.2
-	github.com/consbio/mbtileserver v0.8.1
+	github.com/consbio/mbtileserver v0.8.2
 	github.com/gin-gonic/gin v1.7.7
 	github.com/paulmach/go.geojson v1.4.0
 	github.com/sirupsen/logrus v1.8.1
 )
 
 require (
-	github.com/brendan-ward/mbtiles-go v0.0.0-20211210015813-553bc514bbdf // indirect
+	github.com/brendan-ward/mbtiles-go v0.1.1-0.20220129145719-67a7dabdbaab // indirect
+	github.com/coreos/go-semver v0.3.0
 	github.com/gin-contrib/sse v0.1.0 // indirect
 	github.com/go-playground/locales v0.14.0 // indirect
 	github.com/go-playground/universal-translator v0.18.0 // indirect
@@ -22,6 +23,7 @@ require (
 	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/mssola/user_agent v0.5.3
 	github.com/ugorji/go/codec v1.2.6 // indirect
 	golang.org/x/crypto v0.0.0-20220112180741-5e0467b6c7ce // indirect
 	golang.org/x/image v0.0.0-20220722155232-062f8c9fd539

go.sum

@@ -68,8 +68,8 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bgentry/speakeasy v0.1.0/go.mod h1:+zsyZBPWlz7T6j88CTgSN5bM796AkVf0kBD4zp0CCIs=
-github.com/brendan-ward/mbtiles-go v0.0.0-20211210015813-553bc514bbdf h1:RT/qOIiM0yuaELiwbyli7g6bHFARWlU8B27Ff1r8K6g=
+github.com/brendan-ward/mbtiles-go v0.1.1-0.20220129145719-67a7dabdbaab h1:KC2TqbUmfkIrTwVpkH1ysJiZicPoSyb6chH3JxKHqBM=
-github.com/brendan-ward/mbtiles-go v0.0.0-20211210015813-553bc514bbdf/go.mod h1:rlKkU0/sjOysMB+dvVI+b90UyzmD5alQK7KlhJplVrg=
+github.com/brendan-ward/mbtiles-go v0.1.1-0.20220129145719-67a7dabdbaab/go.mod h1:rlKkU0/sjOysMB+dvVI+b90UyzmD5alQK7KlhJplVrg=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/census-instrumentation/opencensus-proto v0.3.0/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/certifi/gocertifi v0.0.0-20210507211836-431795d63e8d/go.mod h1:sGbDF6GwGcLpkNXPUTkMRoywsNa/ol15pxFe6ERfguA=
@@ -92,8 +92,9 @@ github.com/cncf/xds/go v0.0.0-20210922020428-25de7278fc84/go.mod h1:eXthEFrGJvWH
 github.com/cncf/xds/go v0.0.0-20211001041855-01bcc9b48dfe/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
 github.com/cncf/xds/go v0.0.0-20211011173535-cb28da3451f1/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
 github.com/cncf/xds/go v0.0.0-20211130200136-a8f946100490/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
-github.com/consbio/mbtileserver v0.8.1 h1:Q1x3Vf4Wbb92uNQ9ZAIn2bkS+nzMbcnH2qidq81lxOs=
+github.com/consbio/mbtileserver v0.8.2 h1:iXOBkCp4r/7Z7wC4sw6dYkFAJnuyVpQMu0dbT+RHSxE=
-github.com/consbio/mbtileserver v0.8.1/go.mod h1:efp5wvQOhIhElvcXrFhXUw+k43dwn9EfdACvXBwHy7o=
+github.com/consbio/mbtileserver v0.8.2/go.mod h1:lVBCXeAL6OzooRXWbQ/MZFGFtwm/0A1fkeNTf9T4gzA=
+github.com/coreos/go-semver v0.3.0 h1:wkHLiw0WNATZnSG7epLsujiMCgPAc9xhjJ4tgnAxmfM=
 github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
 github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
@@ -317,6 +318,8 @@ github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lN
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/modern-go/reflect2 v1.0.2 h1:xBagoLtFs94CBntxluKeaWgTMpvLxC4ur3nMaC9Gz0M=
 github.com/modern-go/reflect2 v1.0.2/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
+github.com/mssola/user_agent v0.5.3 h1:lBRPML9mdFuIZgI2cmlQ+atbpJdLdeVl2IDodjBR578=
+github.com/mssola/user_agent v0.5.3/go.mod h1:TTPno8LPY3wAIEKRpAtkdMT0f8SE24pLRGPahjCH4uw=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pascaldekloe/goe v0.1.0/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=

models/models.go

@@ -4,6 +4,7 @@ import (
 	"io"
 	"time"
 
+	"github.com/coreos/go-semver/semver"
 	geojson "github.com/paulmach/go.geojson"
 )
 
@@ -40,6 +41,11 @@ type BuildInfo struct {
 
 // transport objects
 
+type AppVersionInfo struct {
+	Version semver.Version `json:"version"`
+	Address string         `json:"address"`
+}
+
 type Coords struct {
 	Lat float64 `json:"lat"`
 	Lng float64 `json:"lng"`

server/constants.go

@@ -5,6 +5,7 @@ const (
 	URIBuildInfo         = "/build-info"
 	URIHardFail          = "/hard-fail"
 	URISoftFail          = "/soft-fail"
+	URIAppVersions       = "/app-versions"
 	URIReinit            = "/reinit"
 	URIMapPack           = "/mappack"
 	URIHandshake         = "/handshake"
@@ -16,4 +17,6 @@ const (
 	URITileserverRoot    = "/tileserver"
 	URITileserver        = URITileserverRoot + "/*x"
 	URITileTemplate      = URITileserverRoot + "/map/tiles/{z}/{x}/{y}.pbf"
+
+	AppName = "OKO"
 )

server/handling.go

@@ -13,14 +13,22 @@ import (
 
 	"cernobor.cz/oko-server/errs"
 	"cernobor.cz/oko-server/models"
+	"github.com/coreos/go-semver/semver"
 	"github.com/gin-gonic/gin"
+	"github.com/mssola/user_agent"
 	"github.com/sirupsen/logrus"
 )
 
 func internalError(gc *gin.Context, err error) {
+	gc.Error(err)
 	gc.String(http.StatusInternalServerError, "%v", err)
 }
 
+func badRequest(gc *gin.Context, err error) {
+	gc.Error(err)
+	gc.String(http.StatusBadRequest, "%v", err)
+}
+
 func (s *Server) setupRouter() *gin.Engine {
 	gin.SetMode(gin.ReleaseMode)
 	router := gin.New()
@@ -77,10 +85,23 @@ func (s *Server) setupRouter() *gin.Engine {
 		}
 	})
 
+	// tileserver
+	router.GET(URITileserver, gin.WrapH(s.tileserverSvSet.Handler()))
+
+	/*** API ***/
+	router.GET(URIPing, s.handleGETPing)
+	router.POST(URIHandshake, s.handlePOSTHandshake)
+	router.GET(URIData, s.handleGETData)
+	router.POST(URIData, s.handlePOSTData)
+	router.GET(URIDataPeople, s.handleGETDataPeople)
+	router.GET(URIDataFeatures, s.handleGETDataFeatures)
+	router.GET(URIDataFeaturesPhoto, s.handleGETDataFeaturesPhoto)
+	router.GET(URIDataProposals, s.handleGETDataProposals)
+
+	// resources
+	router.GET(URIMapPack, s.handleGETTilepack)
+
 	// utility/debug paths
-	router.GET(URIPing, func(gc *gin.Context) {
-		gc.Status(http.StatusNoContent)
-	})
 	router.GET(URIBuildInfo, func(gc *gin.Context) {
 		gc.JSON(http.StatusOK, models.BuildInfo{
 			VersionHash: s.config.VersionHash,
@@ -93,26 +114,72 @@ func (s *Server) setupRouter() *gin.Engine {
 	router.GET(URISoftFail, func(gc *gin.Context) {
 		gc.JSON(http.StatusOK, map[string]string{"error": "artificial fail"})
 	})
+	router.GET(URIAppVersions, s.handleGETAppVersions)
+	router.POST(URIAppVersions, s.handlePOSTAppVersions)
 	router.POST(URIReinit, s.handlePOSTReset)
 
-	// resources
-	router.GET(URIMapPack, s.handleGETTilepack)
-
-	// API
-	router.POST(URIHandshake, s.handlePOSTHandshake)
-	router.GET(URIData, s.handleGETData)
-	router.POST(URIData, s.handlePOSTData)
-	router.GET(URIDataPeople, s.handleGETDataPeople)
-	router.GET(URIDataFeatures, s.handleGETDataFeatures)
-	router.GET(URIDataFeaturesPhoto, s.handleGETDataFeaturesPhoto)
-	router.GET(URIDataProposals, s.handleGETDataProposals)
-
-	// tileserver
-	router.GET(URITileserver, gin.WrapH(s.tileserverSvSet.Handler()))
-
 	return router
 }
 
+func extractAppVersion(gc *gin.Context) (*semver.Version, error) {
+	ua := user_agent.New(gc.Request.UserAgent())
+	n, v := ua.Browser()
+	if n != AppName {
+		return nil, nil
+	}
+
+	version, err := semver.NewVersion(v)
+	if err != nil {
+		return nil, fmt.Errorf("malformed version in User-Agent header: %w", err)
+	}
+	return version, nil
+}
+
+func (s *Server) handleGETPing(gc *gin.Context) {
+	version, err := extractAppVersion(gc)
+	if err != nil {
+		badRequest(gc, err)
+		return
+	}
+
+	res, err := s.getLatestVersion(version)
+	if err != nil {
+		internalError(gc, err)
+		return
+	}
+
+	if res == nil {
+		gc.Status(http.StatusNoContent)
+	} else {
+		gc.JSON(http.StatusOK, res)
+	}
+}
+
+func (s *Server) handleGETAppVersions(gc *gin.Context) {
+	versions, err := s.getAppVersions()
+	if err != nil {
+		internalError(gc, err)
+		return
+	}
+	gc.JSON(http.StatusOK, versions)
+}
+
+func (s *Server) handlePOSTAppVersions(gc *gin.Context) {
+	var versionInfo models.AppVersionInfo
+	err := gc.ShouldBindJSON(&versionInfo)
+	if err != nil {
+		badRequest(gc, fmt.Errorf("malformed version info: %w", err))
+		return
+	}
+
+	err = s.putAppVersion(&versionInfo)
+	if err != nil {
+		internalError(gc, err)
+		return
+	}
+	gc.Status(http.StatusNoContent)
+}
+
 func (s *Server) handlePOSTReset(gc *gin.Context) {
 	err := s.initDB(true)
 	if err != nil {
@@ -130,7 +197,7 @@ func (s *Server) handlePOSTHandshake(gc *gin.Context) {
 	var hs models.HandshakeChallenge
 	err := gc.ShouldBindJSON(&hs)
 	if err != nil {
-		gc.String(http.StatusBadRequest, fmt.Sprintf("malformed handshake challenge: %v", err))
+		badRequest(gc, fmt.Errorf("malformed handshake challenge: %w", err))
 		return
 	}
 
@@ -205,7 +272,7 @@ func (s *Server) handlePOSTData(gc *gin.Context) {
 	case "multipart/form-data":
 		s.handlePOSTDataMultipart(gc)
 	default:
-		gc.String(http.StatusBadRequest, "unsupported Content-Type")
+		badRequest(gc, fmt.Errorf("unsupported Content-Type"))
 	}
 }
 
@@ -213,17 +280,17 @@ func (s *Server) handlePOSTDataJSON(gc *gin.Context) {
 	var data models.Update
 	err := gc.ShouldBindJSON(&data)
 	if err != nil {
-		gc.String(http.StatusBadRequest, fmt.Sprintf("malformed data: %v", err))
+		badRequest(gc, fmt.Errorf("malformed data: %w", err))
 		return
 	}
 
 	if !isUniqueFeatureID(data.Create) {
-		gc.String(http.StatusBadRequest, "created features do not have unique IDs")
+		badRequest(gc, fmt.Errorf("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")
+		badRequest(gc, fmt.Errorf("created_photos and/or add_photos present, but Content-Type is application/json"))
 		return
 	}
 
@@ -238,7 +305,7 @@ func (s *Server) handlePOSTDataJSON(gc *gin.Context) {
 func (s *Server) handlePOSTDataMultipart(gc *gin.Context) {
 	form, err := gc.MultipartForm()
 	if err != nil {
-		gc.String(http.StatusBadRequest, "malformed multipart/form-data content")
+		badRequest(gc, fmt.Errorf("malformed multipart/form-data content"))
 		return
 	}
 
@@ -246,11 +313,11 @@ func (s *Server) handlePOSTDataMultipart(gc *gin.Context) {
 	if !ok {
 		dataFile, ok := form.File["data"]
 		if !ok {
-			gc.String(http.StatusBadRequest, "value 'data' is missing from the content")
+			badRequest(gc, fmt.Errorf("value 'data' is missing from the content"))
 			return
 		}
 		if len(dataFile) != 1 {
-			gc.String(http.StatusBadRequest, "value 'data' does not contain exactly 1 item")
+			badRequest(gc, fmt.Errorf("value 'data' does not contain exactly 1 item"))
 			return
 		}
 		df, err := dataFile[0].Open()
@@ -266,26 +333,26 @@ func (s *Server) handlePOSTDataMultipart(gc *gin.Context) {
 		dataStr = []string{string(dataBytes)}
 	}
 	if len(dataStr) != 1 {
-		gc.String(http.StatusBadRequest, "value 'data' does not contain exactly 1 item")
+		badRequest(gc, fmt.Errorf("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)
+		badRequest(gc, fmt.Errorf("malformed 'data' value: %w", err))
 		return
 	}
 
 	if !isUniqueFeatureID(data.Create) {
-		gc.String(http.StatusBadRequest, "created features do not have unique IDs")
+		badRequest(gc, fmt.Errorf("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)
+			badRequest(gc, fmt.Errorf("file item %s does not contain exactly 1 file", name))
 			return
 		}
 		var photo models.Photo
@@ -303,7 +370,7 @@ func (s *Server) handlePOSTDataMultipart(gc *gin.Context) {
 	if err != nil {
 		var e *errs.ErrUnsupportedContentType
 		if errors.As(err, &e) {
-			gc.String(http.StatusBadRequest, e.Error())
+			badRequest(gc, e)
 			return
 		}
 		internalError(gc, fmt.Errorf("failed to update data: %w", err))
@@ -334,12 +401,12 @@ func (s *Server) handleGETDataFeatures(gc *gin.Context) {
 func (s *Server) handleGETDataFeaturesPhoto(gc *gin.Context) {
 	reqFeatureID, err := strconv.Atoi(gc.Param("feature"))
 	if err != nil {
-		gc.String(http.StatusBadRequest, "malformed feature ID")
+		badRequest(gc, fmt.Errorf("malformed feature ID"))
 		return
 	}
 	reqPhotoID, err := strconv.Atoi(gc.Param("photo"))
 	if err != nil {
-		gc.String(http.StatusBadRequest, "malformed photo ID")
+		badRequest(gc, fmt.Errorf("malformed photo ID"))
 		return
 	}
 

server/server.go

@@ -4,30 +4,31 @@ import (
 	"archive/zip"
 	"bytes"
 	"context"
+	"embed"
 	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
 	"net/url"
 	"os"
+	"path"
+	"regexp"
+	"sort"
+	"strconv"
 	"time"
 
-	_ "embed"
-
 	"cernobor.cz/oko-server/errs"
 	"cernobor.cz/oko-server/models"
 	"crawshaw.io/sqlite"
 	"crawshaw.io/sqlite/sqlitex"
 	mbsh "github.com/consbio/mbtileserver/handlers"
+	"github.com/coreos/go-semver/semver"
 	geojson "github.com/paulmach/go.geojson"
 	"github.com/sirupsen/logrus"
 )
 
-//go:embed sql_schema/V1_init.sql
+//go:embed sql_schema/V*.sql
-var sql_v1 string
+var sqlSchema embed.FS
-
-//go:embed sql_schema/V2_proposals.sql
-var sql_v2 string
 
 type Server struct {
 	config           ServerConfig
@@ -240,7 +241,7 @@ func (s *Server) initDB(reinit bool) error {
 	defer s.requestCheckpoint()
 
 	if reinit {
-		s.log.Warn("REinitializing DB.")
+		s.log.Warn("Reinitializing DB.")
 		tables := []string{}
 		err := sqlitex.Exec(conn, "select name from sqlite_master where type = 'table'", func(stmt *sqlite.Stmt) error {
 			tables = append(tables, stmt.ColumnText(0))
@@ -262,6 +263,16 @@ func (s *Server) initDB(reinit bool) error {
 			return fmt.Errorf("failed to reset user version: %w", err)
 		}
 	}
+
+	err := s.migrateDb(conn)
+	if err != nil {
+		return fmt.Errorf("failed to migrate db: %w", err)
+	}
+
+	return nil
+}
+
+func (s *Server) migrateDb(conn *sqlite.Conn) error {
 	var version int
 	err := sqlitex.Exec(conn, "PRAGMA user_version", func(stmt *sqlite.Stmt) error {
 		version = stmt.ColumnInt(0)
@@ -270,23 +281,153 @@ func (s *Server) initDB(reinit bool) error {
 	if err != nil {
 		return fmt.Errorf("failed to get user version: %w", err)
 	}
-
 	s.log.Debugf("Current db version: %d", version)
-	if version <= 0 {
+
-		s.log.Debugf("Running db migration V1")
+	entries, err := sqlSchema.ReadDir("sql_schema")
-		err = sqlitex.ExecScript(conn, sql_v1)
+	if err != nil {
+		return fmt.Errorf("failed to read sql_schema migrations: %w", err)
+	}
+
+	type migration struct {
+		file    string
+		version int
+		name    string
+	}
+
+	pattern := regexp.MustCompile("^V([0-9]+)_(.*)[.][sS][qQ][lL]$")
+	migrations := []migration{}
+	for _, entry := range entries {
+		name := entry.Name()
+		if entry.IsDir() {
+			return fmt.Errorf("embedded sql migration '%s' is a directory", name)
+		}
+		matches := pattern.FindStringSubmatch(name)
+		if matches == nil {
+			return fmt.Errorf("embedded sql migration '%s' does not match the filename pattern", name)
+		}
+		if len(matches) != 3 {
+			return fmt.Errorf("embedded sql migration '%s' does not have the correct number of submatches", name)
+		}
+		version, err := strconv.Atoi(matches[1])
 		if err != nil {
-			return fmt.Errorf("failed to run V1 init script")
+			return fmt.Errorf("failed to parse version number of migration '%s': %w", name, err)
+		}
+		migName := matches[2]
+		file := path.Join("sql_schema", name)
+		migrations = append(migrations, migration{
+			file:    file,
+			version: version,
+			name:    migName,
+		})
+	}
+	sort.Slice(migrations, func(i, j int) bool {
+		return migrations[i].version < migrations[j].version
+	})
+
+	for _, migration := range migrations {
+		if version >= migration.version {
+			s.log.Debugf("Skipping migration version %d because current version %d is not smaller.", migration.version, version)
+			continue
+		}
+
+		migContent, err := sqlSchema.ReadFile(migration.file)
+		if err != nil {
+			return fmt.Errorf("failed to read embedded migration '%s': %w", migration.file, err)
+		}
+
+		err = func() (err error) {
+			rollback := sqlitex.Save(conn)
+			defer func() {
+				if err != nil {
+					s.log.Info("Rolling back last migration attempt.")
+				}
+				rollback(&err)
+			}()
+
+			s.log.Infof("Executing migration V%d - %s", migration.version, migration.name)
+			err = sqlitex.ExecScript(conn, string(migContent))
+			if err != nil {
+				return fmt.Errorf("failed to execute migration '%s': %w", migration.name, err)
+			}
+
+			err = sqlitex.Exec(conn, fmt.Sprintf("PRAGMA user_version = %d", migration.version), nil)
+			if err != nil {
+				return fmt.Errorf("failed to set user_version in db: %w", err)
+			}
+
+			err = sqlitex.Exec(conn, "PRAGMA user_version", func(stmt *sqlite.Stmt) error {
+				version = stmt.ColumnInt(0)
+				return nil
+			})
+			if err != nil {
+				return fmt.Errorf("failed to get user_version: %w", err)
+			}
+
+			s.log.Infof("Migrated db to version: %d", version)
+			return nil
+		}()
+		if err != nil {
+			return err
 		}
 	}
-	if version <= 1 {
+	return nil
-		s.log.Debugf("Running db migration V2")
+}
-		err = sqlitex.ExecScript(conn, sql_v2)
+
-		if err != nil {
+func (s *Server) getLatestVersion(v *semver.Version) (*models.AppVersionInfo, error) {
-			return fmt.Errorf("failed to run V2 init script")
+	conn := s.getDbConn()
+	defer s.dbpool.Put(conn)
+
+	var latest *models.AppVersionInfo
+	versions, err := s.getAppVersions()
+	if err != nil {
+		return nil, fmt.Errorf("failed to retrieve app versions from db: %w", err)
+	}
+
+	for _, ver := range versions {
+		if (v == nil || v.LessThan(ver.Version)) && (latest == nil || latest.Version.LessThan(ver.Version)) {
+			latest = ver
 		}
 	}
 
+	return latest, nil
+}
+
+func (s *Server) getAppVersions() ([]*models.AppVersionInfo, error) {
+	conn := s.getDbConn()
+	defer s.dbpool.Put(conn)
+
+	versions := []*models.AppVersionInfo{}
+	err := sqlitex.Exec(conn, "select version, address from app_versions", func(stmt *sqlite.Stmt) error {
+		verStr := stmt.ColumnText(0)
+		addr := stmt.ColumnText(1)
+
+		ver, err := semver.NewVersion(verStr)
+		if err != nil {
+			return fmt.Errorf("failed to parse version: %w", err)
+		}
+
+		versions = append(versions, &models.AppVersionInfo{
+			Version: *ver,
+			Address: addr,
+		})
+		return nil
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to insert/retrieve user from db: %w", err)
+	}
+
+	return versions, nil
+}
+
+func (s *Server) putAppVersion(versionInfo *models.AppVersionInfo) error {
+	conn := s.getDbConn()
+	defer s.dbpool.Put(conn)
+
+	err := sqlitex.Exec(conn, "insert into app_versions(version, address) values(?, ?) on conflict(version) do update set address = excluded.address", nil, versionInfo.Version.String(), versionInfo.Address)
+	if err != nil {
+		return fmt.Errorf("failed to insert app version into db: %w", err)
+	}
+
 	return nil
 }
 
@@ -300,7 +441,7 @@ func (s *Server) handshake(hc models.HandshakeChallenge) (models.UserID, error)
 		var id *int64
 		if hc.Exists {
 			err = sqlitex.Exec(conn, "select id from users where name = ?", func(stmt *sqlite.Stmt) error {
-				id = ptrInt64(stmt.ColumnInt64(0))
+				id = ptr(stmt.ColumnInt64(0))
 				return nil
 			}, hc.Name)
 			if sqlite.ErrCode(err) != sqlite.SQLITE_OK {
@@ -314,7 +455,7 @@ func (s *Server) handshake(hc models.HandshakeChallenge) (models.UserID, error)
 			}
 		} else {
 			err = sqlitex.Exec(conn, "insert into users(name) values(?)", func(stmt *sqlite.Stmt) error {
-				id = ptrInt64(stmt.ColumnInt64(0))
+				id = ptr(stmt.ColumnInt64(0))
 				return nil
 			}, hc.Name)
 			if sqlite.ErrCode(err) == sqlite.SQLITE_CONSTRAINT_UNIQUE {
@@ -323,7 +464,7 @@ func (s *Server) handshake(hc models.HandshakeChallenge) (models.UserID, error)
 			if sqlite.ErrCode(err) != sqlite.SQLITE_OK {
 				return 0, err
 			}
-			id = ptrInt64(conn.LastInsertRowID())
+			id = ptr(conn.LastInsertRowID())
 			s.requestCheckpoint()
 		}
 		return *id, nil
@@ -925,7 +1066,7 @@ func (s *Server) getPhoto(featureID models.FeatureID, photoID models.FeaturePhot
 		if found {
 			return fmt.Errorf("multiple photos returned for feature id %d, photo id %d", featureID, photoID)
 		}
-		contentType = ptrString(stmt.ColumnText(0))
+		contentType = ptr(stmt.ColumnText(0))
 		data = make([]byte, stmt.ColumnLen(1))
 		stmt.ColumnBytes(1, data)
 		found = true

server/sql_schema/V1_init.sql

@@ -21,5 +21,3 @@ CREATE TABLE feature_photos (
   thumbnail_contents blob NOT NULL,
   contents blob NOT NULL
 );
-
-PRAGMA user_version = 1;

server/sql_schema/V2_proposals.sql

@@ -3,5 +3,3 @@ CREATE TABLE proposals (
   description text NOT NULL,
   how text NOT NULL
 );
-
-PRAGMA user_version = 2;

server/sql_schema/V3_app_versions.sql

@@ -0,0 +1,4 @@
+CREATE TABLE app_versions (
+  version text NOT NULL PRIMARY KEY,
+  address text NOT NULL
+);

server/utils.go

@@ -13,15 +13,7 @@ import (
 	"cernobor.cz/oko-server/models"
 )
 
-func ptrInt(x int) *int {
+func ptr[T any](x T) *T {
-	return &x
-}
-
-func ptrInt64(x int64) *int64 {
-	return &x
-}
-
-func ptrString(x string) *string {
 	return &x
 }