TileJSON support for pmtiles serve (#55)

* refactor metadata endpoint

* pmtiles serve implements TileJSON

* add --public-hostname option, required for TileJSON to work

main.go

@@ -58,11 +58,12 @@ var cli struct {
 	} `cmd:"" help:"Verifies that a local archive is valid."`
 
 	Serve struct {
-		Path      string `arg:"" help:"Local path or bucket prefix"`
-		Port      int    `default:8080`
-		Cors      string `help:"Value of HTTP CORS header."`
-		CacheSize int    `default:64 help:"Size of cache in Megabytes."`
-		Bucket    string `help:"Remote bucket"`
+		Path           string `arg:"" help:"Local path or bucket prefix"`
+		Port           int    `default:8080`
+		Cors           string `help:"Value of HTTP CORS header."`
+		CacheSize      int    `default:64 help:"Size of cache in Megabytes."`
+		Bucket         string `help:"Remote bucket"`
+		PublicHostname string `help:"Public hostname of tile endpoint e.g. https://example.com"`
 	} `cmd:"" help:"Run an HTTP proxy server for Z/X/Y tiles."`
 
 	Upload struct {
@@ -96,7 +97,7 @@ func main() {
 			logger.Fatalf("Failed to show database, %v", err)
 		}
 	case "serve <path>":
-		server, err := pmtiles.NewServer(cli.Serve.Bucket, cli.Serve.Path, logger, cli.Serve.CacheSize, cli.Serve.Cors)
+		server, err := pmtiles.NewServer(cli.Serve.Bucket, cli.Serve.Path, logger, cli.Serve.CacheSize, cli.Serve.Cors, cli.Serve.PublicHostname)
 
 		if err != nil {
 			logger.Fatalf("Failed to create new server, %v", err)

pmtiles/directory.go

@@ -76,6 +76,23 @@ func headerContentType(header HeaderV3) (string, bool) {
 	}
 }
 
+func headerExt(header HeaderV3) string {
+	switch header.TileType {
+	case Mvt:
+		return ".mvt"
+	case Png:
+		return ".png"
+	case Jpeg:
+		return ".jpg"
+	case Webp:
+		return ".webp"
+	case Avif:
+		return ".avif"
+	default:
+		return ""
+	}
+}
+
 func headerContentEncoding(compression Compression) (string, bool) {
 	switch compression {
 	case Gzip:

pmtiles/server.go

@@ -2,8 +2,11 @@ package pmtiles
 
 import (
 	"bytes"
+	"compress/gzip"
 	"container/list"
 	"context"
+	"encoding/json"
+	"errors"
 	"fmt"
 	"gocloud.dev/blob"
 	"io"
@@ -61,14 +64,15 @@ type Response struct {
 // }
 
 type Server struct {
-	reqs      chan Request
-	bucket    *blob.Bucket
-	logger    *log.Logger
-	cacheSize int
-	cors      string
+	reqs           chan Request
+	bucket         *blob.Bucket
+	logger         *log.Logger
+	cacheSize      int
+	cors           string
+	publicHostname string
 }
 
-func NewServer(bucketURL string, prefix string, logger *log.Logger, cacheSize int, cors string) (*Server, error) {
+func NewServer(bucketURL string, prefix string, logger *log.Logger, cacheSize int, cors string, publicHostname string) (*Server, error) {
 	if bucketURL == "" {
 		if strings.HasPrefix(prefix, "/") {
 			bucketURL = "file:///"
@@ -92,11 +96,12 @@ func NewServer(bucketURL string, prefix string, logger *log.Logger, cacheSize in
 	}
 
 	l := &Server{
-		reqs:      reqs,
-		bucket:    bucket,
-		logger:    logger,
-		cacheSize: cacheSize,
-		cors:      cors,
+		reqs:           reqs,
+		bucket:         bucket,
+		logger:         logger,
+		cacheSize:      cacheSize,
+		cors:           cors,
+		publicHostname: publicHostname,
 	}
 
 	return l, nil
@@ -210,32 +215,90 @@ func (server *Server) Start() {
 	}()
 }
 
-func (server *Server) get_metadata(ctx context.Context, http_headers map[string]string, name string) (int, map[string]string, []byte) {
+func (server *Server) get_header_metadata(ctx context.Context, name string) (error, bool, HeaderV3, []byte) {
 	root_req := Request{key: CacheKey{name: name, offset: 0, length: 0}, value: make(chan CachedValue, 1)}
 	server.reqs <- root_req
 	root_value := <-root_req.value
 	header := root_value.header
 
 	if !root_value.ok {
-		return 404, http_headers, []byte("Archive not found")
+		return nil, false, HeaderV3{}, nil
 	}
 
 	r, err := server.bucket.NewRangeReader(ctx, name+".pmtiles", int64(header.MetadataOffset), int64(header.MetadataLength), nil)
 	if err != nil {
-		return 404, http_headers, []byte("Archive not found")
+		return nil, false, HeaderV3{}, nil
 	}
 	defer r.Close()
-	b, err := io.ReadAll(r)
+
+	var metadata_bytes []byte
+	if header.InternalCompression == Gzip {
+		metadata_reader, _ := gzip.NewReader(r)
+		defer metadata_reader.Close()
+		metadata_bytes, err = io.ReadAll(metadata_reader)
+	} else if header.InternalCompression == NoCompression {
+		metadata_bytes, err = io.ReadAll(r)
+	} else {
+		return errors.New("Unknown compression"), true, HeaderV3{}, nil
+	}
+
+	return nil, true, header, metadata_bytes
+}
+
+func (server *Server) get_tilejson(ctx context.Context, http_headers map[string]string, name string) (int, map[string]string, []byte) {
+	err, found, header, metadata_bytes := server.get_header_metadata(ctx, name)
+
 	if err != nil {
 		return 500, http_headers, []byte("I/O Error")
 	}
 
-	if header_val, ok := headerContentEncoding(header.InternalCompression); ok {
-		http_headers["Content-Encoding"] = header_val
+	if !found {
+		return 404, http_headers, []byte("Archive not found")
+	}
+
+	var metadata_map map[string]interface{}
+	json.Unmarshal(metadata_bytes, &metadata_map)
+
+	tilejson := make(map[string]interface{})
+
+	if server.publicHostname == "" {
+		return 501, http_headers, []byte("PUBLIC_HOSTNAME must be set for TileJSON")
 	}
+
 	http_headers["Content-Type"] = "application/json"
+	tilejson["tilejson"] = "3.0.0"
+	tilejson["scheme"] = "xyz"
+	tilejson["tiles"] = []string{server.publicHostname + "/" + name + "/{z}/{x}/{y}" + headerExt(header)}
+	tilejson["vector_layers"] = metadata_map["vector_layers"]
+	tilejson["attribution"] = metadata_map["attribution"]
+	tilejson["description"] = metadata_map["description"]
+	tilejson["name"] = metadata_map["name"]
+	tilejson["version"] = metadata_map["version"]
+
+	E7 := 10000000.0
+	tilejson["bounds"] = []float64{float64(header.MinLonE7) / E7, float64(header.MinLatE7) / E7, float64(header.MaxLonE7) / E7, float64(header.MaxLatE7) / E7}
+	tilejson["center"] = []interface{}{float64(header.CenterLonE7) / E7, float64(header.CenterLatE7) / E7, header.CenterZoom}
+	tilejson["minzoom"] = header.MinZoom
+	tilejson["maxzoom"] = header.MaxZoom
+
+	tilejson_bytes, err := json.Marshal(tilejson)
+
+	return 200, http_headers, tilejson_bytes
+}
 
-	return 200, http_headers, b
+func (server *Server) get_metadata(ctx context.Context, http_headers map[string]string, name string) (int, map[string]string, []byte) {
+	err, found, _, metadata_bytes := server.get_header_metadata(ctx, name)
+
+	if err != nil {
+		return 500, http_headers, []byte("I/O Error")
+	}
+
+	if !found {
+		return 404, http_headers, []byte("Archive not found")
+	}
+
+	http_headers["Content-Type"] = "application/json"
+	return 200, http_headers, metadata_bytes
 }
 
 func (server *Server) get_tile(ctx context.Context, http_headers map[string]string, name string, z uint8, x uint32, y uint32, ext string) (int, map[string]string, []byte) {
@@ -318,6 +381,7 @@ func (server *Server) get_tile(ctx context.Context, http_headers map[string]stri
 
 var tilePattern = regexp.MustCompile(`^\/([-A-Za-z0-9_\/!-_\.\*'\(\)']+)\/(\d+)\/(\d+)\/(\d+)\.([a-z]+)$`)
 var metadataPattern = regexp.MustCompile(`^\/([-A-Za-z0-9_\/!-_\.\*'\(\)']+)\/metadata$`)
+var tileJSONPattern = regexp.MustCompile(`^\/([-A-Za-z0-9_\/!-_\.\*'\(\)']+)\.json$`)
 
 func parse_tile_path(path string) (bool, string, uint8, uint32, uint32, string) {
 	if res := tilePattern.FindStringSubmatch(path); res != nil {
@@ -331,6 +395,14 @@ func parse_tile_path(path string) (bool, string, uint8, uint32, uint32, string)
 	return false, "", 0, 0, 0, ""
 }
 
+func parse_tilejson_path(path string) (bool, string) {
+	if res := tileJSONPattern.FindStringSubmatch(path); res != nil {
+		name := res[1]
+		return true, name
+	}
+	return false, ""
+}
+
 func parse_metadata_path(path string) (bool, string) {
 	if res := metadataPattern.FindStringSubmatch(path); res != nil {
 		name := res[1]
@@ -348,6 +420,9 @@ func (server *Server) Get(ctx context.Context, path string) (int, map[string]str
 	if ok, key, z, x, y, ext := parse_tile_path(path); ok {
 		return server.get_tile(ctx, http_headers, key, z, x, y, ext)
 	}
+	if ok, key := parse_tilejson_path(path); ok {
+		return server.get_tilejson(ctx, http_headers, key)
+	}
 	if ok, key := parse_metadata_path(path); ok {
 		return server.get_metadata(ctx, http_headers, key)
 	}

pmtiles/server_test.go

@@ -33,4 +33,7 @@ func TestRegex(t *testing.T) {
 	ok, key = parse_metadata_path("/!-_.*'()/metadata")
 	assert.True(t, ok)
 	assert.Equal(t, key, "!-_.*'()")
+	ok, key = parse_tilejson_path("/!-_.*'().json")
+	assert.True(t, ok)
+	assert.Equal(t, key, "!-_.*'()")
 }