Start gen refactor

Signed-off-by: jolheiser <john.olheiser@gmail.com>

data/entity/gen_entity.go

@@ -0,0 +1,153 @@
+//+build ignore
+
+// gen_entity.go generates entity information.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/token"
+	"net/http"
+	"os"
+	"reflect"
+	"strconv"
+
+	"github.com/iancoleman/strcase"
+)
+
+const (
+	infoURL = "https://raw.githubusercontent.com/PrismarineJS/minecraft-data/master/data/pc/1.17/entities.json"
+)
+
+type Entity struct {
+	ID          uint32 `json:"id"`
+	InternalID  uint32 `json:"internalId"`
+	DisplayName string `json:"displayName"`
+	Name        string `json:"name"`
+
+	Width  float64 `json:"width"`
+	Height float64 `json:"height"`
+
+	Type string `json:"type"`
+}
+
+func downloadInfo() ([]Entity, error) {
+	resp, err := http.Get(infoURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	var data []Entity
+	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
+		return nil, err
+	}
+	return data, nil
+}
+
+func makeEntityDeclaration(entities []Entity) *ast.DeclStmt {
+	out := &ast.DeclStmt{Decl: &ast.GenDecl{Tok: token.VAR}}
+
+	for _, e := range entities {
+		t := reflect.TypeOf(e)
+		fields := make([]ast.Expr, t.NumField())
+
+		for i := 0; i < t.NumField(); i++ {
+			ft := t.Field(i)
+
+			var val ast.Expr
+			switch ft.Type.Kind() {
+			case reflect.Uint32, reflect.Int:
+				val = &ast.BasicLit{Kind: token.INT, Value: fmt.Sprint(reflect.ValueOf(e).Field(i))}
+			case reflect.Float64:
+				val = &ast.BasicLit{Kind: token.FLOAT, Value: fmt.Sprint(reflect.ValueOf(e).Field(i))}
+			case reflect.String:
+				val = &ast.BasicLit{Kind: token.STRING, Value: strconv.Quote(reflect.ValueOf(e).Field(i).String())}
+			case reflect.Bool:
+				val = &ast.BasicLit{Kind: token.IDENT, Value: fmt.Sprint(reflect.ValueOf(e).Field(i).Bool())}
+
+			case reflect.Slice:
+				val = &ast.CompositeLit{
+					Type: &ast.ArrayType{
+						Elt: &ast.BasicLit{Kind: token.IDENT, Value: ft.Type.Elem().Name()},
+					},
+				}
+				v := reflect.ValueOf(e).Field(i)
+				switch ft.Type.Elem().Kind() {
+				case reflect.Uint32, reflect.Int:
+					for x := 0; x < v.Len(); x++ {
+						val.(*ast.CompositeLit).Elts = append(val.(*ast.CompositeLit).Elts, &ast.BasicLit{
+							Kind:  token.INT,
+							Value: fmt.Sprint(v.Index(x)),
+						})
+					}
+				}
+			}
+
+			fields[i] = &ast.KeyValueExpr{
+				Key:   &ast.Ident{Name: ft.Name},
+				Value: val,
+			}
+		}
+
+		out.Decl.(*ast.GenDecl).Specs = append(out.Decl.(*ast.GenDecl).Specs, &ast.ValueSpec{
+			Names: []*ast.Ident{{Name: strcase.ToCamel(e.Name)}},
+			Values: []ast.Expr{
+				&ast.CompositeLit{
+					Type: &ast.Ident{Name: reflect.TypeOf(e).Name()},
+					Elts: fields,
+				},
+			},
+		})
+	}
+
+	return out
+}
+
+//go:generate go run $GOFILE
+//go:generate go fmt entity.go
+func main() {
+	entities, err := downloadInfo()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+
+	f, err := os.Create("entity.go")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
+	fmt.Fprintln(f, `// Code generated by gen_entity.go DO NOT EDIT.
+// Package entity stores information about entities in Minecraft.
+package entity
+// ID describes the numeric ID of an entity.
+type ID uint32
+
+// Entity describes information about a type of entity.
+type Entity struct {
+	ID          ID
+	InternalID  uint32
+	DisplayName string
+	Name        string
+	Width  float64
+	Height float64
+	Type     string
+}`)
+	format.Node(f, token.NewFileSet(), makeEntityDeclaration(entities))
+
+	fmt.Fprintln(f)
+	fmt.Fprintln(f)
+	fmt.Fprintln(f, "// ByID is an index of minecraft entities by their ID.")
+	fmt.Fprintln(f, "var ByID = map[ID]*Entity{")
+	for _, e := range entities {
+		fmt.Fprintf(f, "  %d: &%s,\n", e.ID, strcase.ToCamel(e.Name))
+	}
+	fmt.Fprintln(f, "}")
+
+	fmt.Fprintln(f)
+}