Load vanilla feature stages and place ores

cmd/genfeatures/main.go

@@ -0,0 +1,128 @@
+// Command genfeatures extracts the vanilla feature datapack subset from the
+// Mojang bundler jar into one deterministic archive embedded by worldgen.
+package main
+
+import (
+	"archive/zip"
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+var prefixes = []string{
+	"data/minecraft/worldgen/configured_feature/",
+	"data/minecraft/worldgen/placed_feature/",
+	"data/minecraft/worldgen/biome/",
+	"data/minecraft/tags/block/",
+}
+
+func main() {
+	server := flag.String("server", "server.jar", "Mojang bundler server.jar")
+	output := flag.String("output", "internal/worldgen/feature_data.zip", "output archive")
+	flag.Parse()
+
+	outer, err := zip.OpenReader(*server)
+	if err != nil {
+		fatal(err)
+	}
+	defer outer.Close()
+	var innerBytes []byte
+	for _, file := range outer.File {
+		if strings.HasPrefix(file.Name, "META-INF/versions/") && strings.HasSuffix(file.Name, ".jar") {
+			innerBytes, err = readZipFile(file)
+			if err != nil {
+				fatal(err)
+			}
+			break
+		}
+	}
+	if len(innerBytes) == 0 {
+		fatal(fmt.Errorf("%s contains no inner server jar", *server))
+	}
+	inner, err := zip.NewReader(bytes.NewReader(innerBytes), int64(len(innerBytes)))
+	if err != nil {
+		fatal(err)
+	}
+	type entry struct {
+		name string
+		data []byte
+	}
+	entries := make([]entry, 0, 1024)
+	for _, file := range inner.File {
+		if file.FileInfo().IsDir() || !strings.HasSuffix(file.Name, ".json") || !selected(file.Name) {
+			continue
+		}
+		data, err := readZipFile(file)
+		if err != nil {
+			fatal(err)
+		}
+		entries = append(entries, entry{name: file.Name, data: data})
+	}
+	sort.Slice(entries, func(i, j int) bool { return entries[i].name < entries[j].name })
+	if len(entries) < 500 {
+		fatal(fmt.Errorf("only %d feature datapack files found; wrong server version", len(entries)))
+	}
+
+	if err := os.MkdirAll(filepath.Dir(*output), 0o755); err != nil {
+		fatal(err)
+	}
+	tmp := *output + ".tmp"
+	f, err := os.Create(tmp)
+	if err != nil {
+		fatal(err)
+	}
+	zw := zip.NewWriter(f)
+	for _, entry := range entries {
+		header := &zip.FileHeader{Name: entry.name, Method: zip.Deflate}
+		header.SetModTime(time.Unix(0, 0).UTC())
+		writer, err := zw.CreateHeader(header)
+		if err != nil {
+			fatal(err)
+		}
+		if _, err := writer.Write(entry.data); err != nil {
+			fatal(err)
+		}
+	}
+	if err := zw.Close(); err != nil {
+		fatal(err)
+	}
+	if err := f.Sync(); err != nil {
+		fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		fatal(err)
+	}
+	if err := os.Rename(tmp, *output); err != nil {
+		fatal(err)
+	}
+	fmt.Printf("wrote %s with %d vanilla datapack files\n", *output, len(entries))
+}
+
+func selected(name string) bool {
+	for _, prefix := range prefixes {
+		if strings.HasPrefix(name, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+func readZipFile(file *zip.File) ([]byte, error) {
+	r, err := file.Open()
+	if err != nil {
+		return nil, err
+	}
+	defer r.Close()
+	return io.ReadAll(r)
+}
+
+func fatal(err error) {
+	fmt.Fprintln(os.Stderr, "genfeatures:", err)
+	os.Exit(1)
+}