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parse.go
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parse.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 (
"bufio"
"io"
"regexp"
"strings"
"github.com/pkg/errors"
)
var commandRegexp = regexp.MustCompile(`\A\s*//\s*@`)
// Parse parses a template.
func Parse(r io.Reader) (*Template, error) {
var stack []*Template
top := &Template{typ: blockStatement}
s := bufio.NewScanner(r)
for lineNumber := 1; s.Scan(); lineNumber++ {
line := s.Text()
loc := commandRegexp.FindStringIndex(line)
if loc == nil {
top.children = append(top.children, &Template{typ: echoStatement, arg: line})
continue
}
fields := strings.Fields(line[loc[1]:])
if len(fields) != 2 {
return nil, errorLocation("invalid directive", lineNumber)
}
directive, label := fields[0], fields[1]
var begin bool
var typ statementType
switch directive {
case "done":
begin = false
typ = forStatement
case "fi":
begin = false
typ = ifStatement
case "for":
begin = true
typ = forStatement
case "if":
begin = true
typ = ifStatement
default:
return nil, errorLocation("unrecognized directive", lineNumber)
}
if begin {
stack = append(stack, top)
top = &Template{typ: typ, arg: label}
continue
}
if len(stack) == 0 {
return nil, errorLocation("unexpected end directive", lineNumber)
}
if typ != top.typ {
return nil, errorLocation("end directive does not match beginning", lineNumber)
}
if label != top.arg {
return nil, errorLocation("end label does not match beginning", lineNumber)
}
var parent *Template
n := len(stack) - 1
stack, parent = stack[:n], stack[n]
parent.children = append(parent.children, top)
top = parent
}
if s.Err() != nil {
return nil, s.Err()
}
if len(stack) > 0 {
return nil, errors.New("unexpected end of input")
}
return top, nil
}
func errorLocation(message string, lineNumber int) error {
return errors.Wrapf(errors.New(message), "line %d", lineNumber)
}