Add generic event

data/packetid/gen/gen_packetIDs.go

@@ -0,0 +1,184 @@
+// gen_packetIDs.go generates the enumeration of packet IDs used on the wire.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"strconv"
+	"text/template"
+
+	"github.com/iancoleman/strcase"
+)
+
+const (
+	protocolURL  = "https://raw.githubusercontent.com/PrismarineJS/minecraft-data/master/data/pc/1.16.2/protocol.json"
+	packetidTmpl = `// This file is automatically generated by gen_packetIDs.go. DO NOT EDIT.
+
+package packetid
+
+// Login state
+const (
+	// Clientbound
+{{range $ID, $Name := .Login.Clientbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+	// Serverbound
+{{range $ID, $Name := .Login.Serverbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+)
+
+// Ping state
+const (
+	// Clientbound
+{{range $ID, $Name := .Status.Clientbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+	// Serverbound
+{{range $ID, $Name := .Status.Serverbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+)
+
+// Play state
+const (
+	// Clientbound
+{{range $ID, $Name := .Play.Clientbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+	// Serverbound
+{{range $ID, $Name := .Play.Serverbound}}	{{$Name}} = {{$ID | printf "%#x"}}
+{{end}}
+)
+`
+)
+
+// unnest is a utility function to unpack a value from a nested map, given
+// an arbitrary set of keys to reach through.
+func unnest(input map[string]interface{}, keys ...string) (map[string]interface{}, error) {
+	for _, k := range keys {
+		sub, ok := input[k]
+		if !ok {
+			return nil, fmt.Errorf("key %q not found", k)
+		}
+		next, ok := sub.(map[string]interface{})
+		if !ok {
+			return nil, fmt.Errorf("key %q was %T, expected a string map", k, sub)
+		}
+		input = next
+	}
+	return input, nil
+}
+
+type duplexMappings struct {
+	Clientbound map[int32]string
+	Serverbound map[int32]string
+}
+
+func (m *duplexMappings) EnsureUniqueNames() {
+	// Assemble a slice of keys to check across both maps, because we cannot
+	// mutate a map while iterating it.
+	clientBounds := make(map[string]int32)
+	for sk, sv := range m.Clientbound {
+		clientBounds[sv] = sk
+	}
+	for sk, sv := range m.Serverbound {
+		if ck, ok := clientBounds[sv]; ok {
+			m.Clientbound[ck] = sv + "Clientbound"
+			m.Serverbound[sk] = sv + "Serverbound"
+		}
+	}
+}
+
+// unpackMapping returns the set of packet IDs and their names for a given
+// game state.
+func unpackMapping(data map[string]interface{}, gameState string) (duplexMappings, error) {
+	out := duplexMappings{
+		Clientbound: make(map[int32]string),
+		Serverbound: make(map[int32]string),
+	}
+
+	info, err := unnest(data, gameState, "toClient", "types")
+	if err != nil {
+		return duplexMappings{}, err
+	}
+	pType := info["packet"].([]interface{})[1].([]interface{})[0].(map[string]interface{})["type"]
+	mappings := pType.([]interface{})[1].(map[string]interface{})["mappings"].(map[string]interface{})
+	for k, v := range mappings {
+		out.Clientbound[mustAtoi(k)] = strcase.ToCamel(v.(string))
+	}
+	info, err = unnest(data, gameState, "toServer", "types")
+	if err != nil {
+		return duplexMappings{}, err
+	}
+	pType = info["packet"].([]interface{})[1].([]interface{})[0].(map[string]interface{})["type"]
+	mappings = pType.([]interface{})[1].(map[string]interface{})["mappings"].(map[string]interface{})
+	for k, v := range mappings {
+		out.Serverbound[mustAtoi(k)] = strcase.ToCamel(v.(string))
+	}
+
+	return out, nil
+}
+
+func mustAtoi(num string) int32 {
+	if n, err := strconv.ParseInt(num, 0, 32); err != nil {
+		panic(err)
+	} else {
+		return int32(n)
+	}
+}
+
+type protocolIDs struct {
+	Login  duplexMappings
+	Play   duplexMappings
+	Status duplexMappings
+	// Handshake state has no packets
+}
+
+func downloadInfo() (*protocolIDs, error) {
+	resp, err := http.Get(protocolURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	var data map[string]interface{}
+	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
+		return nil, err
+	}
+
+	var out protocolIDs
+	if out.Login, err = unpackMapping(data, "login"); err != nil {
+		return nil, fmt.Errorf("login: %v", err)
+	}
+	out.Login.EnsureUniqueNames()
+	if out.Play, err = unpackMapping(data, "play"); err != nil {
+		return nil, fmt.Errorf("play: %v", err)
+	}
+	out.Play.EnsureUniqueNames()
+	if out.Status, err = unpackMapping(data, "status"); err != nil {
+		return nil, fmt.Errorf("play: %v", err)
+	}
+	out.Status.EnsureUniqueNames()
+
+	return &out, nil
+}
+
+//go:generate go run $GOFILE
+//go:generate go fmt ../packetid.go
+func main() {
+	pIDs, err := downloadInfo()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+
+	f, err := os.Create("../packetid.go")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
+	tmpl := template.Must(template.New("packetIDs").Parse(packetidTmpl))
+	if err := tmpl.Execute(f, pIDs); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+}