Initial

README.mkd

@@ -0,0 +1,16 @@
+# Golang Link Header Parser
+
+Library for parsing HTTP Link headers.
+
+## Example
+
+```go
+header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
+links := linkheader.Parse(header)
+
+for _, link := range links {
+	fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
+}
+```
+
+

examples_test.go

@@ -0,0 +1,49 @@
+package linkheader_test
+
+import (
+	"fmt"
+
+	"github.com/tomnomnom/linkheader"
+)
+
+func ExampleParse() {
+	header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
+	links := linkheader.Parse(header)
+
+	for _, link := range links {
+		fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
+	}
+
+	// Output:
+	// URL: https://api.github.com/user/58276/repos?page=2; Rel: next
+	// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
+}
+
+func ExampleParseMultiple() {
+	headers := []string{
+		"<https://api.github.com/user/58276/repos?page=2>; rel=\"next\"",
+		"<https://api.github.com/user/58276/repos?page=2>; rel=\"last\"",
+	}
+	links := linkheader.ParseMultiple(headers)
+
+	for _, link := range links {
+		fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
+	}
+
+	// Output:
+	// URL: https://api.github.com/user/58276/repos?page=2; Rel: next
+	// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
+}
+
+func ExampleFilterByRel() {
+	header := "<https://api.github.com/user/58276/repos?page=2>; rel=\"next\", <https://api.github.com/user/58276/repos?page=2>; rel=\"last\""
+	links := linkheader.Parse(header)
+
+	for _, link := range links.FilterByRel("last") {
+		fmt.Printf("URL: %s; Rel: %s\n", link.URL, link.Rel)
+	}
+
+	// Output:
+	// URL: https://api.github.com/user/58276/repos?page=2; Rel: last
+
+}

main.go

@@ -0,0 +1,119 @@
+package linkheader
+
+import (
+	"fmt"
+	"strings"
+)
+
+// A Link is a single URL and related parameters
+type Link struct {
+	URL    string
+	Rel    string
+	Params map[string]string
+}
+
+// HasParam returns if a Link has a particular parameter or not
+func (l Link) HasParam(key string) bool {
+	for p, _ := range l.Params {
+		if p == key {
+			return true
+		}
+	}
+	return false
+}
+
+// Param returns the value of a parameter, or an error on failure
+func (l Link) Param(key string) (string, error) {
+	for k, v := range l.Params {
+		if key == k {
+			return v, nil
+		}
+	}
+	return "", fmt.Errorf("Could not find param '%s'", key)
+}
+
+// Type Links is a slice of Link structs
+type Links []Link
+
+// FilterByRel filters a group of Links by the provided Rel attribute
+func (l Links) FilterByRel(r string) Links {
+	links := make(Links, 0)
+	for _, link := range l {
+		if link.Rel == r {
+			links = append(links, link)
+		}
+	}
+	return links
+}
+
+// Parse parses a raw Link header in the form:
+//   <url>; rel="foo", <url>; rel="bar"; wat="dis"
+// returning a slice of Link structs
+func Parse(raw string) Links {
+	links := make(Links, 0)
+
+	// One chunk: <url>; rel="foo"
+	for _, chunk := range strings.Split(raw, ",") {
+
+		link := Link{URL: "", Rel: "", Params: make(map[string]string)}
+
+		// Figure out what each piece of the chunk is
+		for _, piece := range strings.Split(chunk, ";") {
+
+			piece = strings.Trim(piece, " ")
+			if piece == "" {
+				continue
+			}
+
+			// URL
+			if piece[0] == '<' && piece[len(piece)-1] == '>' {
+				link.URL = strings.Trim(piece, "<>")
+				continue
+			}
+
+			// Params
+			key, val := parseParam(piece)
+			if key == "" {
+				continue
+			}
+
+			// Special case for rel
+			if strings.ToLower(key) == "rel" {
+				link.Rel = val
+			}
+
+			link.Params[key] = val
+
+		}
+
+		links = append(links, link)
+	}
+
+	return links
+}
+
+// ParseMultiple is like Parse, but accepts a slice of headers
+// rather than just one header string
+func ParseMultiple(headers []string) Links {
+	links := make(Links, 0)
+	for _, header := range headers {
+		links = append(links, Parse(header)...)
+	}
+	return links
+}
+
+// parseParam takes a raw param in the form key="val" and
+// returns the key and value as seperate strings
+func parseParam(raw string) (key, val string) {
+
+	parts := strings.SplitN(raw, "=", 2)
+	if len(parts) != 2 {
+		return "", ""
+	}
+
+	key = parts[0]
+	val = strings.Trim(parts[1], "\"")
+
+	return key, val
+
+}

main_test.go

@@ -0,0 +1,105 @@
+package linkheader
+
+import (
+	"testing"
+)
+
+func TestSimple(t *testing.T) {
+	// Test case stolen from https://github.com/thlorenz/parse-link-header :)
+	header := "<https://api.github.com/user/9287/repos?page=3&per_page=100>; rel=\"next\", " +
+		"<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"prev\"; pet=\"cat\", " +
+		"<https://api.github.com/user/9287/repos?page=5&per_page=100>; rel=\"last\""
+
+	links := Parse(header)
+
+	if len(links) != 3 {
+		t.Errorf("Should have been 3 links returned, got %d", len(links))
+	}
+
+	if links[0].URL != "https://api.github.com/user/9287/repos?page=3&per_page=100" {
+		t.Errorf("First link should have URL 'https://api.github.com/user/9287/repos?page=3&per_page=100'")
+	}
+
+	if links[0].Rel != "next" {
+		t.Errorf("First link should have rel=\"next\"")
+	}
+
+	if len(links[0].Params) != 1 {
+		t.Errorf("First link should have exactly 1 params, but has %d", len(links[0].Params))
+	}
+
+	if len(links[1].Params) != 2 {
+		t.Errorf("Second link should have exactly 2 params, but has %d", len(links[1].Params))
+	}
+
+	if links[1].Params["pet"] != "cat" {
+		t.Errorf("Second link's 'pet' param should be 'cat', but was %s", links[1].Params["pet"])
+	}
+
+}
+
+func TestLinkMethods(t *testing.T) {
+	header := "<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"prev\"; pet=\"cat\""
+	links := Parse(header)
+	link := links[0]
+
+	if !link.HasParam("rel") {
+		t.Errorf("Link should have param 'rel'")
+	}
+
+	if link.HasParam("foo") {
+		t.Errorf("Link should not have param 'foo'")
+	}
+
+	val, err := link.Param("pet")
+	if err != nil {
+		t.Errorf("Error value should be nil")
+	}
+	if val != "cat" {
+		t.Errorf("Link should have param pet=\"cat\"")
+	}
+
+	val, err = link.Param("foo")
+	if err == nil {
+		t.Errorf("Error value should not be nil")
+	}
+
+}
+
+func testLinksMethods(t *testing.T) {
+	header := "<https://api.github.com/user/9287/repos?page=3&per_page=100>; rel=\"next\", " +
+		"<https://api.github.com/user/9287/repos?page=1&per_page=100>; rel=\"stylesheet\"; pet=\"cat\", " +
+		"<https://api.github.com/user/9287/repos?page=5&per_page=100>; rel=\"stylesheet\""
+
+	links := Parse(header)
+
+	filtered := links.FilterByRel("next")
+
+	if filtered[0].URL != "https://api.github.com/user/9287/repos?page=3&per_page=100" {
+		t.Errorf("URL did not match expected")
+	}
+
+	filtered = links.FilterByRel("stylesheet")
+	if len(filtered) != 2 {
+		t.Errorf("Filter for stylesheet should yield 2 results but got %d", len(filtered))
+	}
+
+	filtered = links.FilterByRel("notarel")
+	if len(filtered) != 0 {
+		t.Errorf("Filter by non-existant rel should yeild no results")
+	}
+
+}
+
+func testParseMultiple(t *testing.T) {
+	headers := []string{
+		"<https://api.github.com/user/58276/repos?page=2>; rel=\"next\"",
+		"<https://api.github.com/user/58276/repos?page=2>; rel=\"last\"",
+	}
+
+	links := ParseMultiple(headers)
+
+	if len(links) != 2 {
+		t.Errorf("Should have returned 2 links")
+	}
+}