printing: commit some refactors (probably broken)

internal/gen/gen.go

@@ -1,12 +1,10 @@
 package gen
 
 import (
-	"bytes"
-	"fmt"
 	"go/format"
-	"strings"
 
 	"github.com/mmcloughlin/avo/internal/inst"
+	"github.com/mmcloughlin/avo/printer"
 )
 
 type Interface interface {
@@ -19,23 +17,7 @@ func (f Func) Generate(is []inst.Instruction) ([]byte, error) {
 	return f(is)
 }
 
-type Config struct {
-	Name string
-	Argv []string
-}
-
-func (c Config) GeneratedBy() string {
-	if c.Argv == nil {
-		return c.Name
-	}
-	return fmt.Sprintf("command: %s", strings.Join(c.Argv, " "))
-}
-
-func (c Config) GeneratedWarning() string {
-	return fmt.Sprintf("Code generated by %s. DO NOT EDIT.", c.GeneratedBy())
-}
-
-type Builder func(Config) Interface
+type Builder func(printer.Config) Interface
 
 // GoFmt formats Go code produced from the given generator.
 func GoFmt(i Interface) Interface {
@@ -47,27 +29,3 @@ func GoFmt(i Interface) Interface {
 		return format.Source(b)
 	})
 }
-
-type generator struct {
-	buf bytes.Buffer
-	err error
-}
-
-func (g *generator) Printf(format string, args ...interface{}) {
-	if g.err != nil {
-		return
-	}
-	if _, err := fmt.Fprintf(&g.buf, format, args...); err != nil {
-		g.AddError(err)
-	}
-}
-
-func (g *generator) AddError(err error) {
-	if err != nil && g.err == nil {
-		g.err = err
-	}
-}
-
-func (g *generator) Result() ([]byte, error) {
-	return g.buf.Bytes(), g.err
-}