providers: a custom provider's icon can come from its website (#12) — From the website, beside Choose a picture, finds the site behind the base URL (its host, then the domains it sits under: api.deepseek.com, then deepseek.com) and keeps the icon its home page names (an SVG first, then the apple-touch-icon, data: URIs too) or its /favicon.ico, like a picture picked by hand; only public https hosts are reached. Icons are fetched as magpie, since deepseek.com turns Go's own User-Agent away

internal/gui/assets/app.js

@@ -2040,9 +2040,28 @@ function iconPicker(ed) {
     };
     const choose = el("button", "text", t("Choose a picture…"));
     choose.onclick = () => file.click();
+    // the site's own icon, looked for from the base URL typed above
+    const site = el("button", "text", t("From the website"));
+    site.title = t("Look for the icon of the site the base URL is on");
+    site.onclick = async () => {
+      const base = draft[apiField[draft.api]] || draft.chat || draft.responses || draft.anthropic || "";
+      site.disabled = true;
+      site.textContent = t("Looking…");
+      try {
+        const data = await api("icons/favicon", { url: base });
+        draft.icon = data.icon;
+        editorError("");
+        draw();
+        syncHead();
+      } catch (e) {
+        editorError(e.message);
+        site.disabled = false;
+        site.textContent = t("From the website");
+      }
+    };
     const builtin = el("button", "text", t("Built-in icons"));
     builtin.onclick = () => { open = !open; draw(); };
-    box.append(file, choose, builtin);
+    box.append(file, choose, site, builtin);
     if (draft.icon && draft.icon !== "generic") {
       const reset = el("button", "text", t("Default"));
       reset.onclick = () => { draft.icon = ""; draw(); syncHead(); };

internal/gui/assets/i18n.js

@@ -135,6 +135,9 @@ const I18N = {
     "Icon": "图标",
     "Choose a picture…": "选择图片…",
     "Built-in icons": "内置图标",
+    "From the website": "从网站获取",
+    "Look for the icon of the site the base URL is on": "按上面填的 Base URL 找到对应网站的图标",
+    "Looking…": "查找中…",
     "what {agent} ships with": "{agent} 自带的默认值",
     "current value": "当前值",
     "use as typed": "按输入使用",

internal/gui/providers.go

@@ -353,6 +353,20 @@ func providerRoutes(mux *http.ServeMux, w Windows) {
 		}
 		writeJSON(rw, map[string]string{"icon": icon})
 	})
+	// the site's own icon, found from the provider's base URL (#12)
+	mux.HandleFunc("POST /api/icons/favicon", func(rw http.ResponseWriter, r *http.Request) {
+		var in struct{ URL string }
+		if err := json.NewDecoder(io.LimitReader(r.Body, 64<<10)).Decode(&in); err != nil {
+			fail(rw, err)
+			return
+		}
+		icon, err := provider.FaviconFor(r.Context(), in.URL)
+		if err != nil {
+			fail(rw, err)
+			return
+		}
+		writeJSON(rw, map[string]string{"icon": icon})
+	})
 	mux.HandleFunc("GET /api/icons/{name}", func(rw http.ResponseWriter, r *http.Request) {
 		f := provider.IconFile(r.PathValue("name"))
 		if f == "" {

internal/provider/favicon.go

@@ -0,0 +1,184 @@
+package provider
+
+import (
+	"context"
+	"encoding/base64"
+	"errors"
+	"io"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+	"time"
+)
+
+// FaviconFor finds the site behind a provider's base URL and keeps its icon
+// like a picture picked by hand (#12). The API's own host is asked first,
+// then the domains it sits under (api.deepseek.com, then deepseek.com),
+// since an API host seldom has a page of its own. On each, the home page's
+// <link rel="icon"> pictures come before /favicon.ico. Only public https
+// hosts are reached, as for an import link's icon.
+func FaviconFor(ctx context.Context, base string) (string, error) {
+	sites, err := faviconSites(base)
+	if err != nil {
+		return "", err
+	}
+	return favicon(ctx, guardClient(), sites, iconURL)
+}
+
+// faviconSites are the https origins to look on for base's icon: its host
+// with its port, then each domain above it down to two labels.
+func faviconSites(base string) ([]string, error) {
+	u, err := url.Parse(strings.TrimSpace(base))
+	if err != nil || u.Hostname() == "" {
+		return nil, errors.New("type the provider's base URL first: its site's icon is looked for there")
+	}
+	host := u.Hostname()
+	if local(host) {
+		return nil, errors.New("the base URL is on this computer or the local network; its icon can't be fetched")
+	}
+	sites := []string{"https://" + u.Host}
+	if host != u.Host {
+		sites = append(sites, "https://"+host)
+	}
+	if strings.Trim(host, "0123456789.") != "" && !strings.Contains(host, ":") { // not an IP
+		labels := strings.Split(host, ".")
+		for i := 1; len(labels)-i >= 2; i++ {
+			sites = append(sites, "https://"+strings.Join(labels[i:], "."))
+		}
+	}
+	return sites, nil
+}
+
+// favicon tries each site in turn; check vets a picture's URL before it is
+// fetched (iconURL; tests pass one that lets a local server through).
+func favicon(ctx context.Context, c *http.Client, sites []string, check func(string) (string, error)) (string, error) {
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+	var last error
+	for _, site := range sites {
+		cands := append(pageIcons(ctx, c, site), site+"/favicon.ico")
+		for _, cand := range cands {
+			if data, ok := strings.CutPrefix(cand, "data:"); ok {
+				if b := dataURI(data); b != nil {
+					if icon, err := StoreIcon(b); err == nil {
+						return icon, nil
+					}
+				}
+				continue
+			}
+			u, err := check(cand)
+			if err != nil {
+				last = err
+				continue
+			}
+			icon, err := fetchIcon(ctx, c, u)
+			if err == nil {
+				return icon, nil
+			}
+			last = err
+		}
+		if ctx.Err() != nil {
+			break
+		}
+	}
+	if last == nil {
+		last = errors.New("no icon found")
+	}
+	return "", errorf("couldn't find the site's icon (%s): %v", strings.Join(sites, ", "), last)
+}
+
+// iconUA names magpie to the sites icons are fetched from: some (deepseek.com)
+// turn Go's own User-Agent away with a 429.
+const iconUA = "magpie"
+
+var (
+	linkTag  = regexp.MustCompile(`(?is)<link\b[^>]*>`)
+	tagAttr  = regexp.MustCompile(`(?is)\b(rel|href|sizes|type)\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s>]+))`)
+	headDone = regexp.MustCompile(`(?i)</head>|<body\b`)
+)
+
+// pageIcons are the pictures a site's home page names as its icon, the
+// likeliest to look good first: an SVG, then the larger apple-touch-icon,
+// then the rest in page order.
+func pageIcons(ctx context.Context, c *http.Client, site string) []string {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, site+"/", nil)
+	if err != nil {
+		return nil
+	}
+	req.Header.Set("Accept", "text/html")
+	req.Header.Set("User-Agent", iconUA)
+	res, err := c.Do(req)
+	if err != nil {
+		return nil
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return nil
+	}
+	b, _ := io.ReadAll(io.LimitReader(res.Body, 512<<10))
+	html := string(b)
+	if i := headDone.FindStringIndex(html); i != nil {
+		html = html[:i[0]]
+	}
+	var svg, touch, rest []string
+	for _, tag := range linkTag.FindAllString(html, -1) {
+		attrs := map[string]string{}
+		for _, m := range tagAttr.FindAllStringSubmatch(tag, -1) {
+			attrs[strings.ToLower(m[1])] = m[2] + m[3] + m[4]
+		}
+		rel := strings.Fields(strings.ToLower(attrs["rel"]))
+		href := strings.TrimSpace(attrs["href"])
+		if href == "" {
+			continue
+		}
+		isIcon, isTouch := false, false
+		for _, r := range rel {
+			switch r {
+			case "icon":
+				isIcon = true
+			case "apple-touch-icon", "apple-touch-icon-precomposed":
+				isTouch = true
+			}
+		}
+		if !isIcon && !isTouch {
+			continue
+		}
+		if !strings.HasPrefix(href, "data:") {
+			ref, err := url.Parse(href)
+			if err != nil {
+				continue
+			}
+			href = res.Request.URL.ResolveReference(ref).String()
+		}
+		switch {
+		case attrs["type"] == "image/svg+xml" || strings.HasSuffix(strings.ToLower(strings.SplitN(href, "?", 2)[0]), ".svg"):
+			svg = append(svg, href)
+		case isTouch:
+			touch = append(touch, href)
+		default:
+			rest = append(rest, href)
+		}
+	}
+	return append(append(svg, touch...), rest...)
+}
+
+// dataURI decodes what follows "data:" in a data URI, nil when it isn't one.
+func dataURI(s string) []byte {
+	meta, data, ok := strings.Cut(s, ",")
+	if !ok {
+		return nil
+	}
+	if strings.HasSuffix(strings.ToLower(meta), ";base64") {
+		b, err := base64.StdEncoding.DecodeString(data)
+		if err != nil {
+			return nil
+		}
+		return b
+	}
+	d, err := url.PathUnescape(data)
+	if err != nil {
+		return nil
+	}
+	return []byte(d)
+}

internal/provider/favicon_test.go

@@ -0,0 +1,119 @@
+package provider
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestFaviconSites(t *testing.T) {
+	for base, want := range map[string][]string{
+		"https://api.deepseek.com/v1":          {"https://api.deepseek.com", "https://deepseek.com"},
+		"https://open.bigmodel.cn/api/paas/v4": {"https://open.bigmodel.cn", "https://bigmodel.cn"},
+		"https://example.com:8443/v1":          {"https://example.com:8443", "https://example.com"},
+		"https://openrouter.ai/api/v1":         {"https://openrouter.ai"},
+	} {
+		if got, err := faviconSites(base); err != nil || !reflect.DeepEqual(got, want) {
+			t.Errorf("%s: %v %v, want %v", base, got, err, want)
+		}
+	}
+	for _, base := range []string{"", "http://127.0.0.1:11434/v1", "http://localhost:1234", "http://192.168.1.2/v1"} {
+		if _, err := faviconSites(base); err == nil {
+			t.Errorf("%q: looked for an icon", base)
+		}
+	}
+	// the guard itself refuses a loopback site
+	if _, err := FaviconFor(context.Background(), "http://localhost:3425/v1"); err == nil {
+		t.Error("a local base URL's icon was fetched")
+	}
+}
+
+func TestFavicon(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("XDG_CONFIG_HOME", filepath.Join(home, ".config"))
+
+	png := []byte("\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR")
+	svg := []byte(`<svg xmlns="http://www.w3.org/2000/svg"/>`)
+	pages := map[string]string{}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
+		if p, ok := pages[r.Host]; ok && r.URL.Path == "/" {
+			rw.Write([]byte(p))
+			return
+		}
+		switch r.URL.Path {
+		case "/static/touch.png", "/favicon.ico":
+			if strings.HasPrefix(r.Host, "bare.") || r.URL.Path == "/static/touch.png" {
+				rw.Write(png)
+				return
+			}
+		case "/logo.svg":
+			rw.Write(svg)
+			return
+		}
+		// a site that answers every path with its page, the icon's too
+		rw.Write([]byte("<html><body>not found</body></html>"))
+	})
+	srv := httptest.NewServer(mux)
+	defer srv.Close()
+	port := srv.URL[strings.LastIndex(srv.URL, ":"):]
+	// every site is the test server, told apart by the Host it is asked as
+	c := &http.Client{Transport: &http.Transport{DialContext: func(ctx context.Context, network, _ string) (net.Conn, error) {
+		var d net.Dialer
+		return d.DialContext(ctx, network, srv.Listener.Addr().String())
+	}}}
+	site := func(h string) string { return "http://" + h + port }
+	pass := func(s string) (string, error) { return s, nil }
+	stored := func(icon string, want []byte) {
+		t.Helper()
+		b, err := os.ReadFile(IconFile(strings.TrimPrefix(icon, iconPrefix)))
+		if err != nil || string(b) != string(want) {
+			t.Errorf("stored %q: %q %v, want %q", icon, b, err, want)
+		}
+	}
+
+	// an SVG link is taken before the touch icon, whatever the order
+	pages["svg.test"+port] = `<head><link rel="apple-touch-icon" href="/static/touch.png"><link rel="icon" type="image/svg+xml" href="/logo.svg"></head>`
+	icon, err := favicon(context.Background(), c, []string{site("svg.test")}, pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+	stored(icon, svg)
+
+	// a relative apple-touch-icon, in single quotes and odd case
+	pages["touch.test"+port] = `<HEAD><LINK REL='apple-touch-icon' HREF='static/touch.png'></HEAD>`
+	if icon, err = favicon(context.Background(), c, []string{site("touch.test")}, pass); err != nil {
+		t.Fatal(err)
+	}
+	stored(icon, png)
+
+	// a data: URI icon (#12)
+	pages["data.test"+port] = `<head><link rel="shortcut icon" href="data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%2F%3E"></head>`
+	if icon, err = favicon(context.Background(), c, []string{site("data.test")}, pass); err != nil {
+		t.Fatal(err)
+	}
+	stored(icon, svg)
+
+	// the API host has nothing; the domain above it has /favicon.ico
+	if icon, err = favicon(context.Background(), c, []string{site("api.none"), site("bare.test")}, pass); err != nil {
+		t.Fatal(err)
+	}
+	stored(icon, png)
+
+	// a page answered for the icon is not a picture: nothing is found
+	if _, err = favicon(context.Background(), c, []string{site("api.none")}, pass); err == nil {
+		t.Error("an HTML page was kept as the icon")
+	}
+	// a link in the body is not the page's icon
+	pages["body.test"+port] = `<head></head><body><link rel="icon" href="/logo.svg"></body>`
+	if _, err = favicon(context.Background(), c, []string{site("body.test")}, pass); err == nil {
+		t.Error("a link in the body was taken")
+	}
+}

internal/provider/icon.go

@@ -173,6 +173,7 @@ func fetchIcon(ctx context.Context, c *http.Client, u string) (string, error) {
 		return "", err
 	}
 	req.Header.Set("Accept", "image/*")
+	req.Header.Set("User-Agent", iconUA)
 	res, err := c.Do(req)
 	if err != nil {
 		return "", errorf("could not fetch the icon: %v", err)