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colly.go
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// Package colly implements a HTTP scraping framework
package colly
import (
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
"sync"
"time"
"golang.org/x/net/html"
"golang.org/x/net/html/charset"
"github.com/PuerkitoBio/goquery"
)
// Collector provides the scraper instance for a scraping job
type Collector struct {
// UserAgent is the User-Agent string used by HTTP requests
UserAgent string
// MaxDepth limits the recursion depth of visited URLs.
// Set it to 0 for infinite recursion (default).
MaxDepth int
// AllowedDomains is a domain whitelist.
// Leave it blank to allow any domains to be visited
AllowedDomains []string
// DisallowedDomains is a domain blacklist.
DisallowedDomains []string
// AllowURLRevisit allows multiple downloads of the same URL
AllowURLRevisit bool
// MaxBodySize is the limit of the retrieved response body in bytes.
// `0` means unlimited.
// The default value for MaxBodySize is 10MB (10 * 1024 * 1024 bytes).
MaxBodySize int
// CacheDir specifies a location where GET requests are cached as files.
// When it's not defined, caching is disabled.
CacheDir string
visitedURLs []string
htmlCallbacks map[string]HTMLCallback
requestCallbacks []RequestCallback
responseCallbacks []ResponseCallback
errorCallbacks []ErrorCallback
backend *httpBackend
wg *sync.WaitGroup
lock *sync.Mutex
}
// Request is the representation of a HTTP request made by a Collector
type Request struct {
// URL is the parsed URL of the HTTP request
URL *url.URL
// Headers contains the Request's HTTP headers
Headers *http.Header
// Ctx is a context between a Request and a Response
Ctx *Context
// Depth is the number of the parents of this request
Depth int
collector *Collector
}
// Response is the representation of a HTTP response made by a Collector
type Response struct {
// StatusCode is the status code of the Response
StatusCode int
// Body is the content of the Response
Body []byte
// Ctx is a context between a Request and a Response
Ctx *Context
// Request is the Request object of the response
Request *Request
// Headers contains the Response's HTTP headers
Headers *http.Header
}
// HTMLElement is the representation of a HTML tag.
type HTMLElement struct {
// Name is the name of the tag
Name string
Text string
attributes []html.Attribute
// Request is the request object of the element's HTML document
Request *Request
// Response is the Response object of the element's HTML document
Response *Response
// DOM is the goquery parsed DOM object of the page. DOM is relative
// to the current HTMLElement
DOM *goquery.Selection
}
// Context provides a tiny layer for passing data between callbacks
type Context struct {
contextMap map[string]string
lock *sync.RWMutex
}
// RequestCallback is a type alias for OnRequest callback functions
type RequestCallback func(*Request)
// ResponseCallback is a type alias for OnResponse callback functions
type ResponseCallback func(*Response)
// HTMLCallback is a type alias for OnHTML callback functions
type HTMLCallback func(*HTMLElement)
// ErrorCallback is a type alias for OnError callback functions
type ErrorCallback func(*Response, error)
// NewCollector creates a new Collector instance with default configuration
func NewCollector() *Collector {
c := &Collector{}
c.Init()
return c
}
// NewContext initializes a new Context instance
func NewContext() *Context {
return &Context{
contextMap: make(map[string]string),
lock: &sync.RWMutex{},
}
}
// Init initializes the Collector's private variables and sets default
// configuration for the Collector
func (c *Collector) Init() {
c.UserAgent = "colly - https://github.com/asciimoo/colly"
c.MaxDepth = 0
c.visitedURLs = make([]string, 0, 8)
c.htmlCallbacks = make(map[string]HTMLCallback, 0)
c.requestCallbacks = make([]RequestCallback, 0, 8)
c.responseCallbacks = make([]ResponseCallback, 0, 8)
c.errorCallbacks = make([]ErrorCallback, 0, 8)
c.MaxBodySize = 10 * 1024 * 1024
c.backend = &httpBackend{}
c.backend.Init()
c.backend.Client.CheckRedirect = c.checkRedirectFunc()
c.wg = &sync.WaitGroup{}
c.lock = &sync.Mutex{}
}
// Visit starts Collector's collecting job by creating a
// request to the URL specified in parameter.
// Visit also calls the previously provided callbacks
func (c *Collector) Visit(URL string) error {
return c.scrape(URL, "GET", 1, nil, nil)
}
// Post starts a collector job by creating a POST request.
// Post also calls the previously provided callbacks
func (c *Collector) Post(URL string, requestData map[string]string) error {
return c.scrape(URL, "POST", 1, createFormReader(requestData), nil)
}
// PostRaw starts a collector job by creating a POST request with raw binary data.
// Post also calls the previously provided callbacks
func (c *Collector) PostRaw(URL string, requestData []byte) error {
return c.scrape(URL, "POST", 1, bytes.NewReader(requestData), nil)
}
func (c *Collector) scrape(u, method string, depth int, requestData io.Reader, ctx *Context) error {
c.wg.Add(1)
defer c.wg.Done()
if err := c.requestCheck(u, depth); err != nil {
return err
}
parsedURL, err := url.Parse(u)
if err != nil {
return err
}
if parsedURL.Scheme == "" {
parsedURL.Scheme = "http"
}
if !c.isDomainAllowed(parsedURL.Host) {
return errors.New("Forbidden domain")
}
req, err := http.NewRequest(method, parsedURL.String(), requestData)
if err != nil {
return err
}
req.Header.Set("User-Agent", c.UserAgent)
if ctx == nil {
ctx = NewContext()
}
request := &Request{
URL: parsedURL,
Headers: &req.Header,
Ctx: ctx,
Depth: depth,
collector: c,
}
c.handleOnRequest(request)
if method == "POST" && req.Header.Get("Content-Type") == "" {
req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
}
response, err := c.backend.Cache(req, c.MaxBodySize, c.CacheDir)
// TODO add OnError callback to handle these cases
if err != nil || response.StatusCode > 202 {
if err == nil {
err = errors.New(http.StatusText(response.StatusCode))
}
if response == nil {
response = &Response{
Request: request,
Ctx: ctx,
}
}
c.handleOnError(response, err)
return err
}
response.Ctx = ctx
response.Request = request
response.fixCharset()
c.handleOnResponse(response)
c.handleOnHTML(request, response)
return nil
}
func (c *Collector) requestCheck(u string, depth int) error {
if u == "" {
return errors.New("Missing URL")
}
if c.MaxDepth > 0 && c.MaxDepth < depth {
return errors.New("Max depth limit reached")
}
if !c.AllowURLRevisit {
for _, u2 := range c.visitedURLs {
if u2 == u {
return errors.New("URL already visited")
}
}
c.lock.Lock()
c.visitedURLs = append(c.visitedURLs, u)
c.lock.Unlock()
}
return nil
}
func (c *Collector) isDomainAllowed(domain string) bool {
for _, d2 := range c.DisallowedDomains {
if d2 == domain {
return false
}
}
if c.AllowedDomains == nil || len(c.AllowedDomains) == 0 {
return true
}
for _, d2 := range c.AllowedDomains {
if d2 == domain {
return true
}
}
return false
}
// Wait returns when the collector jobs are finished
func (c *Collector) Wait() {
c.wg.Wait()
}
// OnRequest registers a function. Function will be executed on every
// request made by the Collector
func (c *Collector) OnRequest(f RequestCallback) {
c.lock.Lock()
c.requestCallbacks = append(c.requestCallbacks, f)
c.lock.Unlock()
}
// OnResponse registers a function. Function will be executed on every response
func (c *Collector) OnResponse(f ResponseCallback) {
c.lock.Lock()
c.responseCallbacks = append(c.responseCallbacks, f)
c.lock.Unlock()
}
// OnHTML registers a function. Function will be executed on every HTML
// element matched by the `goquerySelector` parameter.
// `goquerySelector` is a selector used by https://github.com/PuerkitoBio/goquery
func (c *Collector) OnHTML(goquerySelector string, f HTMLCallback) {
c.lock.Lock()
c.htmlCallbacks[goquerySelector] = f
c.lock.Unlock()
}
// OnError registers a function. Function will be executed if an error
// occurs during the HTTP request.
func (c *Collector) OnError(f ErrorCallback) {
c.lock.Lock()
c.errorCallbacks = append(c.errorCallbacks, f)
c.lock.Unlock()
}
// WithTransport allows you to set a custom http.Transport for this collector.
func (c *Collector) WithTransport(transport *http.Transport) {
c.backend.Client.Transport = transport
}
// DisableCookies turns off cookie handling for this collector
func (c *Collector) DisableCookies() {
c.backend.Client.Jar = nil
}
// SetRequestTimeout overrides the default timeout (10 seconds) for this collector
func (c *Collector) SetRequestTimeout(timeout time.Duration) {
c.backend.Client.Timeout = timeout
}
func (c *Collector) handleOnRequest(r *Request) {
for _, f := range c.requestCallbacks {
f(r)
}
}
func (c *Collector) handleOnResponse(r *Response) {
for _, f := range c.responseCallbacks {
f(r)
}
}
func (c *Collector) handleOnHTML(req *Request, resp *Response) {
if strings.Index(strings.ToLower(resp.Headers.Get("Content-Type")), "html") == -1 {
return
}
doc, err := goquery.NewDocumentFromReader(bytes.NewBuffer(resp.Body))
if err != nil {
return
}
for expr, f := range c.htmlCallbacks {
doc.Find(expr).Each(func(i int, s *goquery.Selection) {
for _, n := range s.Nodes {
e := &HTMLElement{
Name: n.Data,
Request: req,
Response: resp,
Text: goquery.NewDocumentFromNode(n).Text(),
DOM: s,
attributes: n.Attr,
}
f(e)
}
})
}
}
func (c *Collector) handleOnError(r *Response, err error) {
for _, f := range c.errorCallbacks {
f(r, err)
}
}
// Limit adds a new `LimitRule` to the collector
func (c *Collector) Limit(rule *LimitRule) error {
return c.backend.Limit(rule)
}
// Limits adds new `LimitRule`s to the collector
func (c *Collector) Limits(rules []*LimitRule) error {
return c.backend.Limits(rules)
}
// SetCookies handles the receipt of the cookies in a reply for the given URL
func (c *Collector) SetCookies(URL string, cookies []*http.Cookie) error {
if c.backend.Client.Jar == nil {
return errors.New("Cookie jar is not available")
}
u, err := url.Parse(URL)
if err != nil {
return err
}
c.backend.Client.Jar.SetCookies(u, cookies)
return nil
}
// Cookies returns the cookies to send in a request for the given URL.
func (c *Collector) Cookies(URL string) []*http.Cookie {
if c.backend.Client.Jar == nil {
return nil
}
u, err := url.Parse(URL)
if err != nil {
return nil
}
return c.backend.Client.Jar.Cookies(u)
}
func (c *Collector) checkRedirectFunc() func(req *http.Request, via []*http.Request) error {
return func(req *http.Request, via []*http.Request) error {
if !c.isDomainAllowed(req.URL.Host) {
return fmt.Errorf("Not following redirect to %s because its not in AllowedDomains", req.URL.Host)
}
// Honor golangs default of maximum of 10 redirects
if len(via) >= 10 {
return http.ErrUseLastResponse
}
lastRequest := via[len(via)-1]
// Copy the headers from last request
req.Header = lastRequest.Header
// If domain has changed, remove the Authorization-header if it exists
if req.URL.Host != lastRequest.URL.Host {
req.Header.Del("Authorization")
}
return nil
}
}
// Attr returns the selected attribute of a HTMLElement or empty string
// if no attribute found
func (h *HTMLElement) Attr(k string) string {
for _, a := range h.attributes {
if a.Key == k {
return a.Val
}
}
return ""
}
// AbsoluteURL returns with the resolved absolute URL of an URL chunk.
// AbsoluteURL returns empty string if the URL chunk is a fragment or
// could not be parsed
func (r *Request) AbsoluteURL(u string) string {
if strings.HasPrefix(u, "#") {
return ""
}
absURL, err := r.URL.Parse(u)
if err != nil {
return ""
}
absURL.Fragment = ""
if absURL.Scheme == "//" {
absURL.Scheme = r.URL.Scheme
}
return absURL.String()
}
// Visit continues Collector's collecting job by creating a
// request and preserves the Context of the previous request.
// Visit also calls the previously provided callbacks
func (r *Request) Visit(URL string) error {
return r.collector.scrape(r.AbsoluteURL(URL), "GET", r.Depth+1, nil, r.Ctx)
}
// Post continues a collector job by creating a POST request and preserves the Context
// of the previous request.
// Post also calls the previously provided callbacks
func (r *Request) Post(URL string, requestData map[string]string) error {
return r.collector.scrape(r.AbsoluteURL(URL), "POST", r.Depth+1, createFormReader(requestData), r.Ctx)
}
// PostRaw starts a collector job by creating a POST request with raw binary data.
// PostRaw preserves the Context of the previous request
// and calls the previously provided callbacks
func (r *Request) PostRaw(URL string, requestData []byte) error {
return r.collector.scrape(r.AbsoluteURL(URL), "POST", r.Depth+1, bytes.NewReader(requestData), r.Ctx)
}
// UnmarshalBinary decodes Context value to nil
// This function is used by request caching
func (c *Context) UnmarshalBinary(_ []byte) error {
return nil
}
// MarshalBinary encodes Context value
// This function is used by request caching
func (c *Context) MarshalBinary() (_ []byte, _ error) {
return nil, nil
}
// Put stores a value in Context
func (c *Context) Put(key, value string) {
c.lock.Lock()
c.contextMap[key] = value
c.lock.Unlock()
}
// Get retrieves a value from Context. If no value found for `k`
// Get returns an empty string if key not found
func (c *Context) Get(key string) string {
c.lock.RLock()
if v, ok := c.contextMap[key]; ok {
c.lock.RUnlock()
return v
}
c.lock.RUnlock()
return ""
}
func createFormReader(data map[string]string) io.Reader {
form := url.Values{}
for k, v := range data {
form.Add(k, v)
}
return strings.NewReader(form.Encode())
}
func (r *Response) fixCharset() {
contentType := strings.ToLower(r.Headers.Get("Content-Type"))
if strings.Index(contentType, "charset") == -1 {
return
}
if strings.Index(contentType, "utf-8") != -1 || strings.Index(contentType, "utf8") != -1 {
return
}
encodedBodyReader, err := charset.NewReader(bytes.NewReader(r.Body), contentType)
if err != nil {
return
}
tmpBody, err := ioutil.ReadAll(encodedBodyReader)
if err != nil {
return
}
r.Body = tmpBody
}