forked from jpillora/cloud-torrent
/
extractors.go
168 lines (152 loc) · 3.56 KB
/
extractors.go
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package scraper
import (
"bytes"
"encoding/json"
"fmt"
"regexp"
"strings"
"github.com/PuerkitoBio/goquery"
)
type Extractor struct {
val string
fn extractorFn
}
func NewExtractor(value string) (*Extractor, error) {
e := &Extractor{}
if err := e.Set(value); err != nil {
return nil, err
}
return e, nil
}
func MustExtractor(value string) *Extractor {
e := &Extractor{}
if err := e.Set(value); err != nil {
panic(err)
}
return e
}
//sets the current string Value as the Extractor function
func (e *Extractor) Set(value string) (err error) {
for re, generator := range generators {
m := re.FindStringSubmatch(value)
if len(m) > 0 {
if len(m) > 1 {
value = m[1]
}
e.val = value
e.fn, err = generator(value)
return
}
}
e.val = value
e.fn, err = defaultGenerator(value)
return
}
type extractorFn func(string, *goquery.Selection) (string, *goquery.Selection)
type extractorGenerator func(string) (extractorFn, error)
type Extractors []*Extractor
//execute all Extractors on the query
func (ex Extractors) execute(s *goquery.Selection) string {
v := ""
for _, e := range ex {
v, s = e.fn(v, s)
}
return v
}
func (ex *Extractors) UnmarshalJSON(data []byte) error {
//force array
if bytes.IndexRune(data, '[') != 0 {
data = append([]byte{'['}, append(data, ']')...)
}
//parse strings
strs := []string{}
if err := json.Unmarshal(data, &strs); err != nil {
return err
}
//reset Extractors
*ex = make(Extractors, len(strs))
//convert all strings
for i, s := range strs {
e := &Extractor{}
if err := e.Set(s); err != nil {
return err
}
(*ex)[i] = e
}
return nil
}
func (ex Extractors) MarshalJSON() ([]byte, error) {
strs := make([]string, len(ex))
for i, e := range ex {
strs[i] = e.val
}
return json.Marshal(strs)
}
//selector Extractor
var defaultGenerator = func(selstr string) (extractorFn, error) {
if err := checkSelector(selstr); err != nil {
return nil, fmt.Errorf("Invalid selector: %s", err)
}
return func(value string, sel *goquery.Selection) (string, *goquery.Selection) {
s := sel.Find(selstr)
if value == "" {
if l := s.Length(); l == 1 {
value = s.Text()
} else if l > 1 {
strs := make([]string, l)
s.Each(func(i int, s *goquery.Selection) {
strs[i] = s.Text()
})
value = strings.Join(strs, ",")
}
}
return value, s
}, nil
}
var generatorsPre = map[string]extractorGenerator{
//attr generator
`^@(.+)`: func(attr string) (extractorFn, error) {
//make attribute Extractor
return func(value string, sel *goquery.Selection) (string, *goquery.Selection) {
value, _ = sel.Attr(attr)
// h, _ := sel.Html()
// log.Printf("attr===\n%s\n\n", h)
return value, sel
}, nil
},
//regex generator
`^\/(.+)\/$`: func(reStr string) (extractorFn, error) {
re, err := regexp.Compile(reStr)
if err != nil {
return nil, fmt.Errorf("Invalid regex '%s': %s", reStr, err)
}
return func(value string, sel *goquery.Selection) (string, *goquery.Selection) {
ctx := value
if ctx == "" {
ctx, _ = sel.Html()
}
m := re.FindStringSubmatch(ctx)
if len(m) == 0 {
value = ""
} else if m[1] != "" {
value = m[1]
} else {
value = m[0]
}
return value, sel
}, nil
},
//first() generator
`^first\(\)$`: func(_ string) (extractorFn, error) {
return func(value string, sel *goquery.Selection) (string, *goquery.Selection) {
return value, sel.First()
}, nil
},
}
//run-time generators
var generators = map[*regexp.Regexp]extractorGenerator{}
func init() {
for str, gen := range generatorsPre {
generators[regexp.MustCompile(str)] = gen
}
}