fix: document exported API, fix naming, and harden Downloadv1.3.3

The remaining golangci-lint findings. These land together because the
Url -> URL rename spans util.go, parsers.go and wrapper.go, and splitting
it would leave an intermediate commit that does not compile.

Download() carried the most serious bug here: try() only prints an error,
it does not return, so a failed request fell through to
resp.Body.Close() on a nil resp and panicked. Every failure path now
returns the zero Downloaded, and callers check Status. ReturnHTTPError
guards against the resulting status 0, which would otherwise panic
WriteHeader. Requests carry a context with a timeout (noctx), and a
download-proxy now routes through ProxiedTransport so it keeps the DA
throttle and timeouts.

Also:
- doc comments on all 48 exported symbols (revive's exported rule, with
  checkPrivateReceivers, since most of app is exported methods on the
  unexported skunkyart type), plus package docs in new doc.go files so
  both the embed and non-embed builds are covered.
- ST1003 naming: UrlBuilder -> URLBuilder, id_search -> idSearch,
  cache_config -> cacheConfig, TXT_RAW -> TxtRaw, mediaUrl -> mediaURL.
- explicit json tags on structs that are unmarshaled (musttag); the
  hyphenated keys already had tags, the rest relied on case-insensitive
  fallback. Behaviour is unchanged.
- modernization: range-over-int, WaitGroup.Go, stale +build lines,
  interface{} -> any, strings.Builder over string concatenation in a loop.

1 files changed, 20 insertions, 12 deletions

diff --git a/app/wrapper.go b/app/wrapper.go
index 9668ce0..7b4fe89 100755
--- a/app/wrapper.go
+++ b/app/wrapper.go
@@ -10,6 +10,8 @@ import (
 	"golang.org/x/net/html"
 )
 
+// GRUser renders a group or user page: the about tab, the gallery, or favourites,
+// selected by the request's type argument.
 func (s skunkyart) GRUser() {
 	if len(s.Query) < 1 {
 		s.ReturnHTTPError(400)
@@ -70,7 +72,7 @@ func (s skunkyart) GRUser() {
 
 			case "cover_deviation":
 				group.About.BGMeta = x.ModuleData.CoverDeviation.Deviation
-				group.About.BGMeta.Url = ConvertDeviantArtUrlToSkunkyArt(group.About.BGMeta.Url)
+				group.About.BGMeta.Url = ConvertDeviantArtURLToSkunkyArt(group.About.BGMeta.Url)
 				group.About.BG = ParseMedia(group.About.BGMeta.Media)
 			case "group_admins":
 				var htm strings.Builder
@@ -120,9 +122,9 @@ func (s skunkyart) GRUser() {
 						if x.FolderId != -1 && x.Size != 0 {
 							folders.WriteString(`<div class="block folder-item">`)
 
-							if !(x.Thumb.NSFW && !CFG.Nsfw) {
+							if !x.Thumb.NSFW || CFG.Nsfw {
 								folders.WriteString(`<a href="`)
-								folders.WriteString(ConvertDeviantArtUrlToSkunkyArt(x.Thumb.Url))
+								folders.WriteString(ConvertDeviantArtURLToSkunkyArt(x.Thumb.Url))
 								folders.WriteString(`"><img loading="lazy" src="`)
 								folders.WriteString(ParseMedia(x.Thumb.Media))
 								folders.WriteString(`" title="`)
@@ -138,7 +140,7 @@ func (s skunkyart) GRUser() {
 							folders.WriteString("&q=")
 							folders.WriteString(s.Query)
 							folders.WriteString("&type=")
-							folders.WriteString(string(s.Type))
+							folders.WriteRune(s.Type)
 							folders.WriteString(`">`)
 							folders.WriteString(x.Name)
 							folders.WriteString(`</a>`)
@@ -167,10 +169,11 @@ func (s skunkyart) GRUser() {
 	}
 }
 
-// posts
+// Deviation renders a single artwork page, with its description, tags, comments
+// and related work. It responds 403 for NSFW posts on instances that disallow them.
 func (s skunkyart) Deviation(author, postname string) {
-	id_search := regexp.MustCompile("[0-9]+").FindAllString(postname, -1)
-	if len(id_search) < 1 {
+	idSearch := regexp.MustCompile("[0-9]+").FindAllString(postname, -1)
+	if len(idSearch) < 1 {
 		s.ReturnHTTPError(400)
 		return
 	}
@@ -178,7 +181,7 @@ func (s skunkyart) Deviation(author, postname string) {
 	var err devianter.Error
 	post := &s.Templates.Deviation
 
-	id := id_search[len(id_search)-1]
+	id := idSearch[len(idSearch)-1]
 	post.Post, err = devianter.GetDeviation(id, author)
 	if err.RAW != nil {
 		s.Error(err)
@@ -188,7 +191,7 @@ func (s skunkyart) Deviation(author, postname string) {
 	if post.Post.Deviation.NSFW && !CFG.Nsfw {
 		s.Writer.WriteHeader(403)
 		wr(s.Writer, `<html><link rel="stylesheet" href="`+
-			UrlBuilder("stylesheet")+
+			URLBuilder("stylesheet")+
 			`" /><h1>NSFW content are disabled on this instance.</h1></html>`)
 		return
 	}
@@ -213,7 +216,7 @@ func (s skunkyart) Deviation(author, postname string) {
 	for _, x := range post.Post.Deviation.Extended.Tags {
 		var tag strings.Builder
 		tag.WriteString(` <a href="`)
-		tag.WriteString(UrlBuilder("search", "?q=", x.Name, "&type=tag"))
+		tag.WriteString(URLBuilder("search", "?q=", x.Name, "&type=tag"))
 		tag.WriteString(`">#`)
 		tag.WriteString(x.Name)
 		tag.WriteString("</a>")
@@ -228,6 +231,7 @@ func (s skunkyart) Deviation(author, postname string) {
 	s.ExecuteTemplate("deviantion.htm", "html", &s)
 }
 
+// DD renders the Daily Deviations page, including each themed strip.
 func (s skunkyart) DD() {
 	dd, err := devianter.GetDailyDeviations(s.Page)
 	if err.RAW != nil {
@@ -256,6 +260,8 @@ func (s skunkyart) DD() {
 	}
 }
 
+// Search renders search results for the request's query. Group search is scraped
+// rather than fetched from the API, which DeviantArt does not expose to guests.
 func (s skunkyart) Search() {
 	if s.Query == "" {
 		s.ReturnHTTPError(400)
@@ -305,7 +311,7 @@ func (s skunkyart) Search() {
 
 		if l := len(usernames); l != 0 {
 			ss.List += `<div class="content plates">`
-			for x := 0; x < len(usernames); x++ {
+			for x := range len(usernames) {
 				ss.List += BuildUserPlate(usernames[x])
 			}
 			ss.List += `</div>`
@@ -334,8 +340,10 @@ func (s skunkyart) Search() {
 	s.ExecuteTemplate("search.htm", "html", &s)
 }
 
+// Emojitar proxies a user's avatar or emoji image, selected by the request's
+// type argument.
 func (s skunkyart) Emojitar(name string) {
-	if name == "" || !(s.Type == 'a' || s.Type == 'e') {
+	if name == "" || (s.Type != 'a' && s.Type != 'e') {
 		s.ReturnHTTPError(400)
 		return
 	}