cmd/wit-bindgen-go: add new describe subcommand

cmd/wit-bindgen-go/cmd/describe/describe.go

@@ -2,10 +2,13 @@ package describe
 
 import (
 	"fmt"
+	"io"
+	"os"
+	"strings"
 
-	"github.com/k0kubun/pp/v3"
 	"github.com/urfave/cli/v3"
 	"github.com/ydnar/wasm-tools-go/internal/witcli"
+	"github.com/ydnar/wasm-tools-go/wit"
 )
 
 // Command is the CLI command for describe.
@@ -21,11 +24,96 @@ func action(ctx *cli.Context) error {
 		return err
 	}
 
-	fmt.Printf("// %d worlds(s), %d packages(s), %d interfaces(s), %d types(s)\n",
-		len(res.Worlds), len(res.Packages), len(res.Interfaces), len(res.TypeDefs))
-	p := pp.New()
-	p.SetExportedOnly(true)
-	p.Print(res)
+	p := &printer{w: os.Stdout}
+
+	for _, w := range res.Worlds {
+		describeWorld(p, w)
+	}
 
 	return nil
 }
+
+func describeWorld(p *printer, w *wit.World) {
+	name := w.Package.Name.String() + "/" + w.Name
+	if len(w.Imports) == 0 && len(w.Exports) == 0 {
+		p.Printf("world %s {}", name)
+		return
+	}
+	// TODO: print World.Docs
+	p.Printf("world %s {", name)
+	{
+		p := p.indent()
+		for name, item := range w.Imports {
+			describeWorldItem(p, "import ", name, item)
+		}
+		for name, item := range w.Exports {
+			describeWorldItem(p, "export ", name, item)
+		}
+	}
+	p.Println("}")
+	p.Println()
+}
+
+func describeWorldItem(p *printer, pfx, name string, item wit.WorldItem) {
+	switch v := item.(type) {
+	case *wit.Interface:
+		describeWorldInterface(p, pfx, name, v)
+	case *wit.TypeDef:
+		describeWorldTypeDef(p, pfx, name, v)
+	case *wit.Function:
+		describeWorldFunction(p, pfx, name, v)
+	}
+}
+
+func describeWorldInterface(p *printer, pfx, name string, i *wit.Interface) {
+	if i.Name != nil {
+		name = i.Package.Name.String() + "/" + *i.Name
+	}
+	// TODO: print Interface.Docs
+	if len(i.TypeDefs) == 0 && len(i.Functions) == 0 {
+		p.Printf("%s%s {}", pfx, name)
+		return
+	}
+	p.Printf("%s%s {", pfx, name)
+	{
+
+	}
+	p.Println("}")
+}
+
+func describeWorldTypeDef(p *printer, pfx, name string, t *wit.TypeDef) {
+	// TODO
+}
+
+func describeWorldFunction(p *printer, pfx, name string, t *wit.Function) {
+	// TODO
+}
+
+type printer struct {
+	w     io.Writer
+	depth int
+}
+
+func (p *printer) indent() *printer {
+	pi := *p
+	pi.depth++
+	return &pi
+}
+
+func (p *printer) println(s string) {
+	fmt.Fprintln(p.w, strings.Repeat("\t", p.depth), s)
+}
+
+func (p *printer) Println(a ...any) {
+	s := fmt.Sprint(a...)
+	for _, line := range strings.Split(s, "\n") {
+		p.println(line)
+	}
+}
+
+func (p *printer) Printf(format string, a ...any) {
+	s := fmt.Sprintf(format, a...)
+	for _, line := range strings.Split(s, "\n") {
+		p.println(line)
+	}
+}