132 lines
4.5 KiB
Go
132 lines
4.5 KiB
Go
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package handlers
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import (
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"html/template"
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"io"
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"net/http"
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"os"
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"path/filepath"
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"strings"
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"sync"
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"thermograph/frontend/internal/render"
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)
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// headVerifyHTML is content.head_verify_html for the SPA shells: the
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// search-engine ownership-verification <meta> tags, from env (empty when
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// unset). The SSR pages carry the identical markup via the template FuncMap's
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// head_verify entry (internal/content owns that copy); the shells need it
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// here because their HTML never passes through the template engine.
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// template.HTMLEscapeString emits the same five entities markupsafe escaped
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// (& < > ' ").
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func headVerifyHTML(google, bing string) template.HTML {
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var metas []string
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if google != "" {
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metas = append(metas, `<meta name="google-site-verification" content="`+
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template.HTMLEscapeString(google)+`">`)
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}
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if bing != "" {
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metas = append(metas, `<meta name="msvalidate.01" content="`+
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template.HTMLEscapeString(bing)+`">`)
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}
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return template.HTML(strings.Join(metas, "\n "))
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}
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// shellMemoMax bounds the per-origin memo. The origin is client-controlled
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// (Host/X-Forwarded-Host), so an unbounded map is the same cheap
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// memory-exhaustion vector api_client.py's LRU cap closed — the Python's
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// _by_origin dict had no bound (one canonical origin in every real topology
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// made it moot); a flat cap keeps that property for legit traffic and just
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// resets the memo under abuse instead of growing forever.
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const shellMemoMax = 1024
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// shell is one SPA-shell route's state — the Go port of app.py's _page():
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// the file (and the verification <meta> tags, both constant for the process's
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// lifetime) is read and prepped once, not on every request; only the
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// __ORIGIN__ substitution actually varies per request, and even that repeats
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// across requests (one canonical origin in the common topology), so the
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// substituted HTML + its ETag are memoized per origin instead of
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// re-read-and-re-sha1'd every time.
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type shell struct {
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srv *Server
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file string
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mu sync.Mutex
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template string // "" = not loaded yet; a failed read retries next request
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byOrigin map[string]shellEntry
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}
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type shellEntry struct {
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html string
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etag string
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}
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// shellHandler builds the handler for one SPA-shell HTML page (the
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// interactive tool's calendar/day/score/compare/legend/alerts views). It
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// serves the file with its __ORIGIN__ placeholder (the link-preview/Open
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// Graph tags) filled in — preview crawlers need absolute URLs, and the host
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// differs between LAN and prod. originOf (not a simpler duplicate) matters
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// here: this route is reached both directly (Caddy) and through backend's
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// proxy fallback, and only that version prefers X-Forwarded-Host over Host —
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// required for the proxied case to resolve the real browser-facing host
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// instead of this internal hop's own address.
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func (s *Server) shellHandler(file string) http.HandlerFunc {
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sh := &shell{srv: s, file: file, byOrigin: make(map[string]shellEntry)}
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return sh.serve
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}
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// load reads and preps the shell file; the caller holds sh.mu. Search-engine
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// verification <meta> tags (same source as the SSR content pages) are folded
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// in here, so the interactive tool's own pages carry them too.
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func (sh *shell) load() (string, error) {
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if sh.template != "" {
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return sh.template, nil
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}
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raw, err := os.ReadFile(filepath.Join(sh.srv.staticDir, sh.file))
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if err != nil {
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return "", err
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}
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html := string(raw)
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if verify := string(sh.srv.headVerify); verify != "" {
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html = strings.Replace(html, "<head>", "<head>\n "+verify, 1)
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}
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sh.template = html
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return html, nil
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}
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func (sh *shell) serve(w http.ResponseWriter, r *http.Request) {
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originPrefix := originOf(r) + sh.srv.base
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sh.mu.Lock()
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ent, ok := sh.byOrigin[originPrefix]
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if !ok {
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tpl, err := sh.load()
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if err != nil {
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sh.mu.Unlock()
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sh.srv.serverError(w, r, err)
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return
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}
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html := strings.ReplaceAll(tpl, "__ORIGIN__", originPrefix)
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ent = shellEntry{html: html, etag: render.ETag([]byte(html))}
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if len(sh.byOrigin) >= shellMemoMax {
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clear(sh.byOrigin)
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}
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sh.byOrigin[originPrefix] = ent
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}
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sh.mu.Unlock()
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// app.py's _page compared If-None-Match to the ETag verbatim (no
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// comma-splitting) — NotModifiedExact keeps that precise behavior.
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if render.NotModifiedExact(r.Header.Get("If-None-Match"), ent.etag) {
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w.Header().Set("ETag", ent.etag)
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w.WriteHeader(http.StatusNotModified)
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return
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}
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w.Header().Set("ETag", ent.etag)
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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w.WriteHeader(http.StatusOK)
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if r.Method != http.MethodHead {
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_, _ = io.WriteString(w, ent.html)
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}
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}
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