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// Copyright 2022 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package foreachref
import (
"bufio"
"bytes"
"fmt"
"io"
"strings"
)
// Parser parses 'git for-each-ref' output according to a given output Format.
type Parser struct {
// tokenizes 'git for-each-ref' output into "reference paragraphs".
scanner *bufio.Scanner
// format represents the '--format' string that describes the expected
// 'git for-each-ref' output structure.
format Format
// err holds the last encountered error during parsing.
err error
}
// NewParser creates a 'git for-each-ref' output parser that will parse all
// references in the provided Reader. The references in the output are assumed
// to follow the specified Format.
func NewParser(r io.Reader, format Format) *Parser {
scanner := bufio.NewScanner(r)
// in addition to the reference delimiter we specified in the --format,
// `git for-each-ref` will always add a newline after every reference.
refDelim := make([]byte, 0, len(format.refDelim)+1)
refDelim = append(refDelim, format.refDelim...)
refDelim = append(refDelim, '\n')
// Split input into delimiter-separated "reference blocks".
scanner.Split(
func(data []byte, atEOF bool) (advance int, token []byte, err error) {
// Scan until delimiter, marking end of reference.
delimIdx := bytes.Index(data, refDelim)
if delimIdx >= 0 {
token := data[:delimIdx]
advance := delimIdx + len(refDelim)
return advance, token, nil
}
// If we're at EOF, we have a final, non-terminated reference. Return it.
if atEOF {
return len(data), data, nil
}
// Not yet a full field. Request more data.
return 0, nil, nil
})
return &Parser{
scanner: scanner,
format: format,
err: nil,
}
}
// Next returns the next reference as a collection of key-value pairs. nil
// denotes EOF but is also returned on errors. The Err method should always be
// consulted after Next returning nil.
//
// It could, for example return something like:
//
// { "objecttype": "tag", "refname:short": "v1.16.4", "object": "f460b7543ed500e49c133c2cd85c8c55ee9dbe27" }
//
func (p *Parser) Next() map[string]string {
if !p.scanner.Scan() {
return nil
}
fields, err := p.parseRef(p.scanner.Text())
if err != nil {
p.err = err
return nil
}
return fields
}
// Err returns the latest encountered parsing error.
func (p *Parser) Err() error {
return p.err
}
// parseRef parses out all key-value pairs from a single reference block, such as
//
// "objecttype tag\0refname:short v1.16.4\0object f460b7543ed500e49c133c2cd85c8c55ee9dbe27"
//
func (p *Parser) parseRef(refBlock string) (map[string]string, error) {
if refBlock == "" {
// must be at EOF
return nil, nil
}
fieldValues := make(map[string]string)
fields := strings.Split(refBlock, p.format.fieldDelimStr)
if len(fields) != len(p.format.fieldNames) {
return nil, fmt.Errorf("unexpected number of reference fields: wanted %d, was %d",
len(fields), len(p.format.fieldNames))
}
for i, field := range fields {
field = strings.TrimSpace(field)
var fieldKey string
var fieldVal string
firstSpace := strings.Index(field, " ")
if firstSpace > 0 {
fieldKey = field[:firstSpace]
fieldVal = field[firstSpace+1:]
} else {
// could be the case if the requested field had no value
fieldKey = field
}
// enforce the format order of fields
if p.format.fieldNames[i] != fieldKey {
return nil, fmt.Errorf("unexpected field name at position %d: wanted: '%s', was: '%s'",
i, p.format.fieldNames[i], fieldKey)
}
fieldValues[fieldKey] = fieldVal
}
return fieldValues, nil
}
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