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Tom Hudson
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16
README.mkd
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16
README.mkd
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# Golang Link Header Parser
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Library for parsing HTTP Link headers.
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## Example
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```go
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header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
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links := linkheader.Parse(header)
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for _, link := range links {
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fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
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}
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```
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49
examples_test.go
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examples_test.go
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package linkheader_test
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import (
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"fmt"
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"github.com/tomnomnom/linkheader"
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)
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func ExampleParse() {
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header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
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links := linkheader.Parse(header)
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for _, link := range links {
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fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
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}
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// Output:
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// URL: https://api.github.com/user/58276/repos?page=2; Rel: next
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// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
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}
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func ExampleParseMultiple() {
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headers := []string{
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"<https://api.github.com/user/58276/repos?page=2>; rel=\"next\"",
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"<https://api.github.com/user/58276/repos?page=2>; rel=\"last\"",
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}
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links := linkheader.ParseMultiple(headers)
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for _, link := range links {
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fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
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}
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// Output:
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// URL: https://api.github.com/user/58276/repos?page=2; Rel: next
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// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
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}
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func ExampleFilterByRel() {
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header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
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links := linkheader.Parse(header)
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for _, link := range links.FilterByRel("last") {
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fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
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}
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// Output:
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// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
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}
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119
main.go
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119
main.go
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package linkheader
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import (
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"fmt"
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"strings"
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)
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// A Link is a single URL and related parameters
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type Link struct {
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URL string
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Rel string
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Params map[string]string
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}
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// HasParam returns if a Link has a particular parameter or not
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func (l Link) HasParam(key string) bool {
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for p, _ := range l.Params {
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if p == key {
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return true
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}
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}
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return false
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}
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// Param returns the value of a parameter, or an error on failure
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func (l Link) Param(key string) (string, error) {
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for k, v := range l.Params {
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if key == k {
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return v, nil
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}
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}
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return "", fmt.Errorf("Could not find param '%s'", key)
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}
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// Type Links is a slice of Link structs
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type Links []Link
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// FilterByRel filters a group of Links by the provided Rel attribute
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func (l Links) FilterByRel(r string) Links {
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links := make(Links, 0)
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for _, link := range l {
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if link.Rel == r {
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links = append(links, link)
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}
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}
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return links
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}
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// Parse parses a raw Link header in the form:
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// <url>; rel="foo", <url>; rel="bar"; wat="dis"
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// returning a slice of Link structs
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func Parse(raw string) Links {
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links := make(Links, 0)
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// One chunk: <url>; rel="foo"
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for _, chunk := range strings.Split(raw, ",") {
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link := Link{URL: "", Rel: "", Params: make(map[string]string)}
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// Figure out what each piece of the chunk is
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for _, piece := range strings.Split(chunk, ";") {
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piece = strings.Trim(piece, " ")
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if piece == "" {
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continue
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}
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// URL
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if piece[0] == '<' && piece[len(piece)-1] == '>' {
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link.URL = strings.Trim(piece, "<>")
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continue
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}
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// Params
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key, val := parseParam(piece)
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if key == "" {
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continue
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}
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// Special case for rel
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if strings.ToLower(key) == "rel" {
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link.Rel = val
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}
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link.Params[key] = val
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}
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links = append(links, link)
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}
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return links
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}
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// ParseMultiple is like Parse, but accepts a slice of headers
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// rather than just one header string
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func ParseMultiple(headers []string) Links {
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links := make(Links, 0)
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for _, header := range headers {
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links = append(links, Parse(header)...)
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}
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return links
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}
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// parseParam takes a raw param in the form key="val" and
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// returns the key and value as seperate strings
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func parseParam(raw string) (key, val string) {
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parts := strings.SplitN(raw, "=", 2)
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if len(parts) != 2 {
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return "", ""
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}
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key = parts[0]
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val = strings.Trim(parts[1], "\"")
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return key, val
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}
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105
main_test.go
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105
main_test.go
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package linkheader
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import (
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"testing"
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)
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func TestSimple(t *testing.T) {
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// Test case stolen from https://github.com/thlorenz/parse-link-header :)
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header := "<https://api.github.com/user/9287/repos?page=3&per_page=100>; rel=\"next\", " +
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"<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"prev\"; pet=\"cat\", " +
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"<https://api.github.com/user/9287/repos?page=5&per_page=100>; rel=\"last\""
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links := Parse(header)
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if len(links) != 3 {
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t.Errorf("Should have been 3 links returned, got %d", len(links))
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}
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if links[0].URL != "https://api.github.com/user/9287/repos?page=3&per_page=100" {
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t.Errorf("First link should have URL 'https://api.github.com/user/9287/repos?page=3&per_page=100'")
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}
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if links[0].Rel != "next" {
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t.Errorf("First link should have rel=\"next\"")
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}
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if len(links[0].Params) != 1 {
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t.Errorf("First link should have exactly 1 params, but has %d", len(links[0].Params))
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}
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if len(links[1].Params) != 2 {
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t.Errorf("Second link should have exactly 2 params, but has %d", len(links[1].Params))
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}
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if links[1].Params["pet"] != "cat" {
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t.Errorf("Second link's 'pet' param should be 'cat', but was %s", links[1].Params["pet"])
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}
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}
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func TestLinkMethods(t *testing.T) {
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header := "<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"prev\"; pet=\"cat\""
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links := Parse(header)
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link := links[0]
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if !link.HasParam("rel") {
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t.Errorf("Link should have param 'rel'")
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}
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if link.HasParam("foo") {
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t.Errorf("Link should not have param 'foo'")
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}
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val, err := link.Param("pet")
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if err != nil {
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t.Errorf("Error value should be nil")
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}
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if val != "cat" {
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t.Errorf("Link should have param pet=\"cat\"")
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}
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val, err = link.Param("foo")
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if err == nil {
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t.Errorf("Error value should not be nil")
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}
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}
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func testLinksMethods(t *testing.T) {
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header := "<https://api.github.com/user/9287/repos?page=3&per_page=100>; rel=\"next\", " +
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"<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"stylesheet\"; pet=\"cat\", " +
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"<https://api.github.com/user/9287/repos?page=5&per_page=100>; rel=\"stylesheet\""
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links := Parse(header)
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filtered := links.FilterByRel("next")
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if filtered[0].URL != "https://api.github.com/user/9287/repos?page=3&per_page=100" {
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t.Errorf("URL did not match expected")
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}
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filtered = links.FilterByRel("stylesheet")
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if len(filtered) != 2 {
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t.Errorf("Filter for stylesheet should yield 2 results but got %d", len(filtered))
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}
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filtered = links.FilterByRel("notarel")
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if len(filtered) != 0 {
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t.Errorf("Filter by non-existant rel should yeild no results")
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}
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}
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func testParseMultiple(t *testing.T) {
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headers := []string{
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"<https://api.github.com/user/58276/repos?page=2>; rel=\"next\"",
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"<https://api.github.com/user/58276/repos?page=2>; rel=\"last\"",
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}
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links := ParseMultiple(headers)
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if len(links) != 2 {
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t.Errorf("Should have returned 2 links")
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}
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}
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