From 93c1b7a8b0fc502a5ea9172493b40c351c508527 Mon Sep 17 00:00:00 2001
From: Sebastian Tobie <sebastian@sebastian-tobie.de>
Date: Sun, 6 Nov 2022 10:53:38 +0100
Subject: [PATCH] added an wellknown middleware

---
 middleware/wellknown/doc.go       |   2 +
 middleware/wellknown/site.go      |  15 ++++
 middleware/wellknown/wellknown.go | 130 ++++++++++++++++++++++++++++++
 3 files changed, 147 insertions(+)
 create mode 100644 middleware/wellknown/doc.go
 create mode 100644 middleware/wellknown/site.go
 create mode 100644 middleware/wellknown/wellknown.go

diff --git a/middleware/wellknown/doc.go b/middleware/wellknown/doc.go
new file mode 100644
index 0000000..deaee9a
--- /dev/null
+++ b/middleware/wellknown/doc.go
@@ -0,0 +1,2 @@
+// Package wellknown provides an middleware that lets sites to register themselfs to wellknown uris
+package wellknown
diff --git a/middleware/wellknown/site.go b/middleware/wellknown/site.go
new file mode 100644
index 0000000..e09a1cb
--- /dev/null
+++ b/middleware/wellknown/site.go
@@ -0,0 +1,15 @@
+package wellknown
+
+import "go.sebtobie.de/httpserver"
+
+// Finger is an Simple Type for site to transport the information about the webfinger to the middleware
+type Finger struct {
+	Webfinger Webfinger
+	Protocol  string
+}
+
+// FingerSite is an type of site that provide content and want to publish it with webfinger
+type FingerSite interface {
+	httpserver.Site
+	RegisterFingers() []*Finger
+}
diff --git a/middleware/wellknown/wellknown.go b/middleware/wellknown/wellknown.go
new file mode 100644
index 0000000..dc728cd
--- /dev/null
+++ b/middleware/wellknown/wellknown.go
@@ -0,0 +1,130 @@
+package wellknown
+
+import (
+	"encoding/json"
+	"net/url"
+
+	"github.com/gin-gonic/gin"
+	"github.com/rs/zerolog/log"
+	"go.sebtobie.de/httpserver"
+	"go.sebtobie.de/httpserver/middleware"
+)
+
+var _ middleware.Middleware = &Middleware{}
+var _ httpserver.Site = &Middleware{}
+
+type (
+
+	// Link is the reference where the application can find the object
+	Link struct {
+		Rel  string
+		Type string
+		Href *url.URL
+	}
+
+	// Middleware is an middleware for sites to register themselfs to provide wellknown urls
+	Middleware struct {
+		// webfinger is an map consisting of protocol as key and an array of WebfingerAccount as value
+		webfinger map[string][]Webfinger
+	}
+
+	// Webfinger is an function that accepts the account part(after ?resource=<protocol>:) and returns the aliases and the links.
+	// The bool value if for faster detection if the account was found.
+	Webfinger func(resource string) ([]string, []*Link, bool)
+)
+
+// New creates a new initialized Middleware
+func New() *Middleware {
+	return &Middleware{
+		webfinger: map[string][]Webfinger{},
+	}
+}
+
+// Defaults returns the default config values for the middleware
+func (*Middleware) Defaults() middleware.Config {
+	return nil
+}
+
+// Gin does nothing.
+func (*Middleware) Gin(c *gin.Context) {
+	c.Next()
+}
+
+// Setup does nothing
+func (*Middleware) Setup(middleware.Config) {}
+
+// Teardown does nothing
+func (*Middleware) Teardown() {}
+
+// Sites goes through all sites and collects all registrations for wellknown uris
+func (m *Middleware) Sites(s []any) error {
+	for _, site := range s {
+		if wfs, ok := site.(FingerSite); ok {
+			for _, finger := range wfs.RegisterFingers() {
+				if _, ok := m.webfinger[finger.Protocol]; !ok {
+					m.webfinger[finger.Protocol] = []Webfinger{}
+				}
+				m.webfinger[finger.Protocol] = append(m.webfinger[finger.Protocol], finger.Webfinger)
+			}
+		}
+	}
+	return nil
+}
+
+// Init initializes the routergroup. It must always run on /
+func (m *Middleware) Init(rg *gin.RouterGroup) {
+	if len(m.webfinger) > 0 {
+		rg.GET(".well-known/webfinger", m.webfingerhf)
+	}
+}
+
+func (m *Middleware) webfingerhf(c *gin.Context) {
+	resource := c.Query("resource")
+	if resource == "" {
+		c.AbortWithStatus(404)
+		return
+	}
+	uri, err := url.Parse(resource)
+	if err != nil {
+		log.Error().Err(err).Str("uri", resource).Msg("Failed to parse uri")
+		c.AbortWithStatus(404)
+		return
+	}
+	var wf []Webfinger
+	var found bool
+	if wf, found = m.webfinger[uri.Scheme]; !found {
+		c.AbortWithStatus(404)
+		return
+	}
+	var output = struct {
+		Subject string   `json:"subject,omitempty"`
+		Aliases []string `json:"aliases,omitempty"`
+		Links   []*Link  `json:"links,omitempty"`
+	}{Subject: resource, Aliases: []string{}, Links: []*Link{}}
+	var aliases = []string{}
+	var links = []*Link{}
+	var input = uri.Opaque
+	if uri.Opaque == "" {
+		input = resource
+	}
+	outputok := false
+	for _, finger := range wf {
+		aliases, links, found = finger(input)
+		if !found {
+			continue
+		}
+		output.Aliases = append(output.Aliases, aliases...)
+		output.Links = append(output.Links, links...)
+		outputok = true
+	}
+	if outputok {
+		c.Header("Access-Control-Allow-Origin", "*")
+		json, err := json.Marshal(output)
+		if err != nil {
+			c.AbortWithStatus(500)
+			return
+		}
+		c.Data(200, "application/jrd+json", json)
+	}
+	c.AbortWithStatus(404)
+}