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instantiate.go
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instantiate.go
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// Copyright 2017 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package template
import (
"fmt"
"io"
"regexp"
)
// Node is a type for hierarchical data.
type Node struct {
label string
replacements []replacement
children []*Node
}
type replacement struct {
expr *regexp.Regexp
repl string
}
// NewRoot returns a new root node.
func NewRoot() *Node {
return &Node{}
}
// AddReplacement adds a regexp replacement to the given node. The replacement
// value is formatted with a %s conversion.
func (node *Node) AddReplacement(expr string, repl interface{}) {
node.replacements = append(node.replacements, replacement{regexp.MustCompile(expr), fmt.Sprintf("%s", repl)})
}
// AddReplacementf adds a regexp replacement to the given node. The replacement
// format and arguments are formatted with fmt.Sprintf.
func (node *Node) AddReplacementf(expr string, replFormat string, a ...interface{}) {
node.AddReplacement(expr, fmt.Sprintf(replFormat, a...))
}
// NewChild adds a child with the given label to the given node.
func (node *Node) NewChild(label string) *Node {
child := &Node{label: label}
node.children = append(node.children, child)
return child
}
// Instantiate executes the given template on the given input.
func (tmpl *Template) Instantiate(w io.Writer, node *Node) error {
return tmpl.instantiate(w, node, append([]replacement(nil), node.replacements...))
}
func (tmpl *Template) instantiate(w io.Writer, node *Node, replacements []replacement) error {
switch tmpl.typ {
case blockStatement:
return tmpl.instantiateChildren(w, node, replacements)
case echoStatement:
text := tmpl.arg
for j := range replacements {
r := replacements[len(replacements)-1-j]
text = r.expr.ReplaceAllString(text, r.repl)
}
_, err := fmt.Fprintln(w, text)
return err
case forStatement:
for _, nodeChild := range node.children {
if nodeChild.label != tmpl.arg {
continue
}
if err := tmpl.instantiateChildren(w, nodeChild, append(replacements, nodeChild.replacements...)); err != nil {
return err
}
}
return nil
case ifStatement:
for _, nodeChild := range node.children {
if nodeChild.label != tmpl.arg {
continue
}
return tmpl.instantiateChildren(w, node, replacements)
}
return nil
default:
panic(fmt.Sprintf("case %d is not handled", tmpl.typ))
}
}
func (tmpl *Template) instantiateChildren(
w io.Writer, node *Node, replacements []replacement,
) error {
for _, child := range tmpl.children {
if err := child.instantiate(w, node, replacements); err != nil {
return err
}
}
return nil
}