[chore] Rationalize HTTP return codes for fedi endpoints, other tidying up (#4503)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request does some refactoring of the fedi API endpoints and processing functions, and the authenticate + pub key deref functions, to try to return fewer silly HTTP codes like 410 Gone (when a *remote* account is gone, not a local one), and 500 errors where something isn't really an error.

Also does some general tidying up and renaming for consistency.

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4503
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

1 files changed, 44 insertions, 13 deletions

diff --git a/internal/processing/fedi/emoji.go b/internal/processing/fedi/emoji.go
index 8db8b48ea..e7e3ec406 100644
--- a/internal/processing/fedi/emoji.go
+++ b/internal/processing/fedi/emoji.go
@@ -19,38 +19,69 @@ package fedi
 
 import (
 	"context"
-	"fmt"
+	"errors"
 
 	"code.superseriousbusiness.org/gotosocial/internal/ap"
+	"code.superseriousbusiness.org/gotosocial/internal/config"
+	"code.superseriousbusiness.org/gotosocial/internal/db"
 	"code.superseriousbusiness.org/gotosocial/internal/gtserror"
 )
 
-// EmojiGet handles the GET for a federated emoji originating from this instance.
-func (p *Processor) EmojiGet(ctx context.Context, requestedEmojiID string) (interface{}, gtserror.WithCode) {
-	if _, errWithCode := p.federator.AuthenticateFederatedRequest(ctx, ""); errWithCode != nil {
+// EmojiGet handles the GET for an emoji originating from this instance.
+func (p *Processor) EmojiGet(ctx context.Context, emojiID string) (any, gtserror.WithCode) {
+	// Authenticate incoming request.
+	//
+	// Pass hostname string to this function to indicate
+	// it's the instance account being requested, as
+	// emojis are always owned by the instance account.
+	auth, errWithCode := p.authenticate(ctx, config.GetHost())
+	if errWithCode != nil {
 		return nil, errWithCode
 	}
 
-	requestedEmoji, err := p.state.DB.GetEmojiByID(ctx, requestedEmojiID)
-	if err != nil {
-		return nil, gtserror.NewErrorNotFound(fmt.Errorf("database error getting emoji with id %s: %s", requestedEmojiID, err))
+	if auth.handshakingURI != nil {
+		// We're currently handshaking, which means
+		// we don't know this account yet. This should
+		// be a very rare race condition.
+		err := gtserror.Newf("network race handshaking %s", auth.handshakingURI)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	// Get the requested emoji.
+	emoji, err := p.state.DB.GetEmojiByID(ctx, emojiID)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		err := gtserror.Newf("db error getting emoji %s: %w", emojiID, err)
+		return nil, gtserror.NewErrorNotFound(err)
 	}
 
-	if !requestedEmoji.IsLocal() {
-		return nil, gtserror.NewErrorNotFound(fmt.Errorf("emoji with id %s doesn't belong to this instance (domain %s)", requestedEmojiID, requestedEmoji.Domain))
+	if emoji == nil {
+		err := gtserror.Newf("emoji %s not found in the db", emojiID)
+		return nil, gtserror.NewErrorNotFound(err)
 	}
 
-	if *requestedEmoji.Disabled {
-		return nil, gtserror.NewErrorNotFound(fmt.Errorf("emoji with id %s has been disabled", requestedEmojiID))
+	// Only serve *our*
+	// emojis on this path.
+	if !emoji.IsLocal() {
+		err := gtserror.Newf("emoji %s doesn't belong to this instance (domain is %s)", emojiID, emoji.Domain)
+		return nil, gtserror.NewErrorNotFound(err)
 	}
 
-	apEmoji, err := p.converter.EmojiToAS(ctx, requestedEmoji)
+	// Don't serve emojis that have
+	// been disabled by an admin.
+	if *emoji.Disabled {
+		err := gtserror.Newf("emoji with id %s has been disabled by an admin", emojiID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	apEmoji, err := p.converter.EmojiToAS(ctx, emoji)
 	if err != nil {
-		return nil, gtserror.NewErrorInternalError(fmt.Errorf("error converting gtsmodel emoji with id %s to ap emoji: %s", requestedEmojiID, err))
+		err := gtserror.Newf("error converting emoji %s to ap: %s", emojiID, err)
+		return nil, gtserror.NewErrorInternalError(err)
 	}
 
 	data, err := ap.Serialize(apEmoji)
 	if err != nil {
+		err := gtserror.Newf("error serializing emoji %s: %w", emojiID, err)
 		return nil, gtserror.NewErrorInternalError(err)
 	}