Refactor formatter.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

command/formatter/network.go

@@ -1,7 +1,6 @@
 package formatter
 
 import (
-	"bytes"
 	"fmt"
 	"strings"
 
@@ -17,60 +16,45 @@ const (
 	internalHeader  = "INTERNAL"
 )
 
-// NetworkContext contains network specific information required by the formatter,
-// encapsulate a Context struct.
-type NetworkContext struct {
-	Context
-	// Networks
-	Networks []types.NetworkResource
+// NewNetworkFormat returns a Format for rendering using a network Context
+func NewNetworkFormat(source string, quiet bool) Format {
+	switch source {
+	case TableFormatKey:
+		if quiet {
+			return defaultQuietFormat
+		}
+		return defaultNetworkTableFormat
+	case RawFormatKey:
+		if quiet {
+			return `network_id: {{.ID}}`
+		}
+		return `network_id: {{.ID}}\nname: {{.Name}}\ndriver: {{.Driver}}\nscope: {{.Scope}}\n`
+	}
+	return Format(source)
 }
 
-func (ctx NetworkContext) Write() {
-	switch ctx.Format {
-	case tableFormatKey:
-		if ctx.Quiet {
-			ctx.Format = defaultQuietFormat
-		} else {
-			ctx.Format = defaultNetworkTableFormat
-		}
-	case rawFormatKey:
-		if ctx.Quiet {
-			ctx.Format = `network_id: {{.ID}}`
-		} else {
-			ctx.Format = `network_id: {{.ID}}\nname: {{.Name}}\ndriver: {{.Driver}}\nscope: {{.Scope}}\n`
+// NetworkWrite writes the context
+func NetworkWrite(ctx Context, networks []types.NetworkResource) error {
+	render := func(format func(subContext subContext) error) error {
+		for _, network := range networks {
+			networkCtx := &networkContext{trunc: ctx.Trunc, n: network}
+			if err := format(networkCtx); err != nil {
+				return err
+			}
 		}
+		return nil
 	}
-
-	ctx.buffer = bytes.NewBufferString("")
-	ctx.preformat()
-
-	tmpl, err := ctx.parseFormat()
-	if err != nil {
-		return
-	}
-
-	for _, network := range ctx.Networks {
-		networkCtx := &networkContext{
-			trunc: ctx.Trunc,
-			n:     network,
-		}
-		err = ctx.contextFormat(tmpl, networkCtx)
-		if err != nil {
-			return
-		}
-	}
-
-	ctx.postformat(tmpl, &networkContext{})
+	return ctx.Write(&networkContext{}, render)
 }
 
 type networkContext struct {
-	baseSubContext
+	HeaderContext
 	trunc bool
 	n     types.NetworkResource
 }
 
 func (c *networkContext) ID() string {
-	c.addHeader(networkIDHeader)
+	c.AddHeader(networkIDHeader)
 	if c.trunc {
 		return stringid.TruncateID(c.n.ID)
 	}
@@ -78,32 +62,32 @@ func (c *networkContext) ID() string {
 }
 
 func (c *networkContext) Name() string {
-	c.addHeader(nameHeader)
+	c.AddHeader(nameHeader)
 	return c.n.Name
 }
 
 func (c *networkContext) Driver() string {
-	c.addHeader(driverHeader)
+	c.AddHeader(driverHeader)
 	return c.n.Driver
 }
 
 func (c *networkContext) Scope() string {
-	c.addHeader(scopeHeader)
+	c.AddHeader(scopeHeader)
 	return c.n.Scope
 }
 
 func (c *networkContext) IPv6() string {
-	c.addHeader(ipv6Header)
+	c.AddHeader(ipv6Header)
 	return fmt.Sprintf("%v", c.n.EnableIPv6)
 }
 
 func (c *networkContext) Internal() string {
-	c.addHeader(internalHeader)
+	c.AddHeader(internalHeader)
 	return fmt.Sprintf("%v", c.n.Internal)
 }
 
 func (c *networkContext) Labels() string {
-	c.addHeader(labelsHeader)
+	c.AddHeader(labelsHeader)
 	if c.n.Labels == nil {
 		return ""
 	}
@@ -120,7 +104,7 @@ func (c *networkContext) Label(name string) string {
 	r := strings.NewReplacer("-", " ", "_", " ")
 	h := r.Replace(n[len(n)-1])
 
-	c.addHeader(h)
+	c.AddHeader(h)
 
 	if c.n.Labels == nil {
 		return ""