Initial implementation (#1)

.github/dependabot.yml

@@ -0,0 +1,18 @@
+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    commit-message:
+      prefix: "deps:"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "09:00"
+  - package-ecosystem: "github-actions"
+    commit-message:
+      prefix: "ci:"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "09:00"

.github/workflows/build.yml

@@ -0,0 +1,17 @@
+name: build
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  schedule:
+    - cron: '0 0 * * 0' # run "At 00:00 on Sunday"
+
+# See https://github.com/cristalhq/.github/.github/workflows
+jobs:
+  build:
+    uses: cristalhq/.github/.github/workflows/[email protected]
+
+  vuln:
+    uses: cristalhq/.github/.github/workflows/[email protected]

README.md

@@ -1,2 +1,41 @@
 # magneturi
-A Go package for magnet links
+
+[![build-img]][build-url]
+[![pkg-img]][pkg-url]
+[![version-img]][version-url]
+
+Go package for magnet links.
+
+## Features
+
+* Simple API.
+* Dependency-free.
+
+See [docs][pkg-url] for more details.
+
+## Install
+
+Go version 1.17+
+
+```
+go get github.com/cristalhq/magneturi
+```
+
+## Example
+
+```go
+TODO
+```
+
+See examples: [example_test.go](example_test.go).
+
+## License
+
+[MIT License](LICENSE).
+
+[build-img]: https://github.com/cristalhq/magneturi/workflows/build/badge.svg
+[build-url]: https://github.com/cristalhq/magneturi/actions
+[pkg-img]: https://pkg.go.dev/badge/cristalhq/magneturi
+[pkg-url]: https://pkg.go.dev/github.com/cristalhq/magneturi
+[version-img]: https://img.shields.io/github/v/release/cristalhq/magneturi
+[version-url]: https://github.com/cristalhq/magneturi/releases

example_test.go

@@ -0,0 +1 @@
+package magneturi_test

go.mod

@@ -0,0 +1,3 @@
+module github.com/cristalhq/magneturi
+
+go 1.17

magneturi.go

@@ -0,0 +1,226 @@
+package magneturi
+
+import (
+	"errors"
+	"net/url"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const magnetPrefix = "magnet:?"
+
+// Magnet represents a Magnet URI.
+type Magnet struct {
+	// ExactTopics is a "xt".
+	ExactTopics []string
+
+	// DisplayName is a "dn".
+	// A filename to display to the user, for convenience.
+	DisplayName string
+
+	// ExactLength is a "xl".
+	// The file size, in bytes
+	ExactLength int64
+
+	// Trackers is a "tr".
+	Trackers []string
+
+	// WebSeed is a "ws".
+	// The payload data served over HTTP(S)
+	// TODO(cristaloleg): clarify is this string or []string.
+
+	// AcceptableSources is "as".
+	// Refers to a direct download from a web server.
+	AcceptableSources []string
+
+	// ExactSource is a "xs".
+	ExactSource []string
+
+	// KeywordTopic is a "kt".
+	// Specifies a string of search keywords to search for in P2P networks, rather than a particular file.
+	KeywordTopic []string
+
+	// ManifestTopic is a "mt".
+	// Link to the metafile that contains a list of magneto.
+	ManifestTopic string
+
+	// Select Only
+	// Lists specific files torrent clients should download.
+	// TODO(cristaloleg): implement BEP53.
+
+	// Extra is a "x." and other unparsed params.
+	Extra map[string][]string
+}
+
+var errNoPrefix = errors.New("magnet URI prefix not found")
+
+// Parse magnet URI.
+func Parse(raw string) (*Magnet, error) {
+	if !strings.HasPrefix(raw, magnetPrefix) {
+		return nil, errNoPrefix
+	}
+
+	parts := strings.Split(raw, magnetPrefix)
+	if len(parts) <= 1 {
+		return nil, errNoPrefix
+	}
+
+	m := &Magnet{
+		Extra: make(map[string][]string),
+	}
+
+	exactTopics := make(map[string]struct{})
+	trackers := make(map[string]struct{})
+	acceptableSources := make(map[string]struct{})
+
+	params := strings.Split(parts[1], "&")
+
+	for _, param := range params {
+		params := strings.Split(param, "=")
+		if len(params) < 2 || params[1] == "" {
+			continue
+		}
+
+		switch key, value := params[0], params[1]; key {
+		case "dn":
+			decoded, err := url.QueryUnescape(value)
+			if err != nil {
+				return nil, err
+			}
+			m.DisplayName = decoded
+
+		case "xt":
+			exactTopics[value] = struct{}{}
+
+		case "kt":
+			m.KeywordTopic = append(m.KeywordTopic, strings.Split(value, "+")...)
+
+		case "mt":
+			m.ManifestTopic = value
+
+		case "tr":
+			v, err := url.QueryUnescape(value)
+			if err != nil {
+				return nil, err
+			}
+			trackers[v] = struct{}{}
+
+		case "as":
+			v, err := url.QueryUnescape(value)
+			if err != nil {
+				return nil, err
+			}
+			acceptableSources[v] = struct{}{}
+
+		case "xl":
+			size, err := strconv.ParseInt(value, 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			m.ExactLength = size
+
+		case "xs":
+			v, err := url.QueryUnescape(value)
+			if err != nil {
+				return nil, err
+			}
+			m.ExactSource = append(m.ExactSource, v)
+
+		default:
+			v, err := url.QueryUnescape(value)
+			if err != nil {
+				return nil, err
+			}
+			m.Extra[key] = append(m.Extra[key], v)
+		}
+	}
+
+	m.ExactTopics = make([]string, 0, len(exactTopics))
+	for topic := range exactTopics {
+		m.ExactTopics = append(m.ExactTopics, topic)
+	}
+
+	m.Trackers = make([]string, 0, len(trackers))
+	for tracker := range trackers {
+		m.Trackers = append(m.Trackers, tracker)
+	}
+
+	m.AcceptableSources = make([]string, 0, len(acceptableSources))
+	for as := range acceptableSources {
+		m.AcceptableSources = append(m.AcceptableSources, as)
+	}
+	return m, nil
+}
+
+// Normalize will sort all fields with multiple values.
+func (m *Magnet) Normalize() {
+	sort.Strings(m.ExactTopics)
+	sort.Strings(m.Trackers)
+	sort.Strings(m.AcceptableSources)
+	sort.Strings(m.ExactSource)
+	sort.Strings(m.KeywordTopic)
+	for _, v := range m.Extra {
+		sort.Strings(v)
+	}
+}
+
+// Encode magnet URI.
+func (m *Magnet) Encode() string {
+	var b strings.Builder
+	// TODO(cristaloleg): calculate this dynamically or estimate.
+	b.Grow(512)
+
+	b.WriteString(magnetPrefix)
+	b.WriteString("dn=")
+	b.WriteString(url.QueryEscape(m.DisplayName))
+
+	for _, xt := range m.ExactTopics {
+		b.WriteString("&xt=")
+		b.WriteString(xt)
+	}
+
+	if m.ExactLength > 0 {
+		b.WriteString("&xl=")
+		b.WriteString(strconv.FormatInt(m.ExactLength, 10))
+	}
+
+	for _, tr := range m.Trackers {
+		b.WriteString("&tr=")
+		b.WriteString(url.QueryEscape(tr))
+	}
+
+	// TODO(cristaloleg): add ws.
+
+	for _, as := range m.AcceptableSources {
+		b.WriteString("&as=")
+		b.WriteString(url.QueryEscape(as))
+	}
+
+	for _, xs := range m.ExactSource {
+		b.WriteString("&xs=")
+		b.WriteString(url.QueryEscape(xs))
+	}
+
+	if len(m.KeywordTopic) > 0 {
+		b.WriteString("&kt=")
+		b.WriteString(strings.Join(m.KeywordTopic, "+"))
+	}
+
+	if m.ManifestTopic != "" {
+		b.WriteString("&mt=")
+		b.WriteString(m.ManifestTopic)
+	}
+
+	// TODO(cristaloleg): add so.
+
+	for key, param := range m.Extra {
+		for _, paramValue := range param {
+			b.WriteByte('&')
+			b.WriteString(key)
+			b.WriteByte('=')
+			b.WriteString(paramValue)
+		}
+	}
+	return b.String()
+}