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package pub
import (
"context"
"encoding/json"
"errors"
"fmt"
"net/http"
"github.com/superseriousbusiness/activity/streams"
)
var ErrNotFound = errors.New("go-fed/activity: ActivityStreams data not found")
// HandlerFunc determines whether an incoming HTTP request is an ActivityStreams
// GET request, and if so attempts to serve ActivityStreams data.
//
// If an error is returned, then the calling function is responsible for writing
// to the ResponseWriter as part of error handling.
//
// If 'isASRequest' is false and there is no error, then the calling function
// may continue processing the request, and the HandlerFunc will not have
// written anything to the ResponseWriter. For example, a webpage may be served
// instead.
//
// If 'isASRequest' is true and there is no error, then the HandlerFunc
// successfully served the request and wrote to the ResponseWriter.
//
// Callers are responsible for authorized access to this resource.
type HandlerFunc func(c context.Context, w http.ResponseWriter, r *http.Request) (isASRequest bool, err error)
// NewActivityStreamsHandler creates a HandlerFunc to serve ActivityStreams
// requests which are coming from other clients or servers that wish to obtain
// an ActivityStreams representation of data.
//
// Strips retrieved ActivityStreams values of sensitive fields ('bto' and 'bcc')
// before responding with them. Sets the appropriate HTTP status code for
// Tombstone Activities as well.
//
// Defaults to supporting content to be retrieved by HTTPS only.
func NewActivityStreamsHandler(db Database, clock Clock) HandlerFunc {
return NewActivityStreamsHandlerScheme(db, clock, "https")
}
// NewActivityStreamsHandlerScheme creates a HandlerFunc to serve
// ActivityStreams requests which are coming from other clients or servers that
// wish to obtain an ActivityStreams representation of data provided by the
// specified protocol scheme.
//
// Strips retrieved ActivityStreams values of sensitive fields ('bto' and 'bcc')
// before responding with them. Sets the appropriate HTTP status code for
// Tombstone Activities as well.
//
// Specifying the "scheme" allows for retrieving ActivityStreams content with
// identifiers such as HTTP, HTTPS, or other protocol schemes.
//
// Returns ErrNotFound when the database does not retrieve any data and no
// errors occurred during retrieval.
func NewActivityStreamsHandlerScheme(db Database, clock Clock, scheme string) HandlerFunc {
return func(c context.Context, w http.ResponseWriter, r *http.Request) (isASRequest bool, err error) {
// Do nothing if it is not an ActivityPub GET request
if !isActivityPubGet(r) {
return
}
isASRequest = true
id := requestId(r, scheme)
// Lock and obtain a copy of the requested ActivityStreams value
err = db.Lock(c, id)
if err != nil {
return
}
// WARNING: Unlock not deferred
t, err := db.Get(c, id)
if err != nil {
db.Unlock(c, id)
return
}
db.Unlock(c, id)
// Unlock must have been called by this point and in every
// branch above
if t == nil {
err = ErrNotFound
return
}
// Remove sensitive fields.
clearSensitiveFields(t)
// Serialize the fetched value.
m, err := streams.Serialize(t)
if err != nil {
return
}
raw, err := json.Marshal(m)
if err != nil {
return
}
// Construct the response.
addResponseHeaders(w.Header(), clock, raw)
// Write the response.
if streams.IsOrExtendsActivityStreamsTombstone(t) {
w.WriteHeader(http.StatusGone)
} else {
w.WriteHeader(http.StatusOK)
}
n, err := w.Write(raw)
if err != nil {
return
} else if n != len(raw) {
err = fmt.Errorf("only wrote %d of %d bytes", n, len(raw))
return
}
return
}
}
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