[template] Add textAPI function

Signed-off-by: Knut Ahlers <knut@ahlers.me>

internal/template/api/api.go

@@ -4,6 +4,7 @@ import "github.com/Luzifer/twitch-bot/v3/plugins"
 
 func Register(args plugins.RegistrationArguments) error {
 	args.RegisterTemplateFunction("jsonAPI", plugins.GenericTemplateFunctionGetter(jsonAPI))
+	args.RegisterTemplateFunction("textAPI", plugins.GenericTemplateFunctionGetter(textAPI))
 
 	return nil
 }

internal/template/api/textAPI.go

@@ -0,0 +1,58 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"net/url"
+
+	"github.com/pkg/errors"
+)
+
+func textAPI(uri string, fallback ...string) (string, error) {
+	u, err := url.Parse(uri)
+	if err != nil {
+		return "", errors.Wrap(err, "parsing URL")
+	}
+
+	reqCtx, cancel := context.WithTimeout(context.Background(), remoteRequestTimeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(reqCtx, http.MethodGet, u.String(), nil)
+	if err != nil {
+		return "", errors.Wrap(err, "assembling request")
+	}
+	req.Header.Set("User-Agent", "Luzifer/twitch-bot template/api/jsonAPI (https://github.com/Luzifer/twitch-bot)")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", errors.Wrap(err, "executing request")
+	}
+	defer resp.Body.Close()
+
+	switch resp.StatusCode {
+	case http.StatusOK:
+		// That's what we wanna see
+
+	case http.StatusNoContent:
+		if len(fallback) > 0 {
+			return fallback[0], nil
+		}
+		return "", errors.Errorf("unexpected HTTP status %d without fallback", resp.StatusCode)
+
+	default:
+		return "", errors.Errorf("unexpected HTTP status %d", resp.StatusCode)
+	}
+
+	content, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", errors.Wrap(err, "reading response body")
+	}
+
+	if len(bytes.TrimSpace(content)) == 0 && len(fallback) > 0 {
+		return fallback[0], nil
+	}
+
+	return string(content), nil
+}

wiki/Templating.md

@@ -389,6 +389,21 @@ Example:
 < luziferus
 ```
 
+#### `textAPI`
+
+Fetches remote URL and returns the result as string. (Remote API needs to return status 200 within 5 seconds.)
+
+Syntax: `textAPI "https://example.com/" ["fallback"]`
+
+Example:
+
+```
+! !weather (.*)
+> !weather Hamburg
+# {{ textAPI (printf "https://api.scorpstuff.com/weather.php?units=metric&city=%s" (urlquery (group 1))) }}
+< Weather for Hamburg, DE: Few clouds with a temperature of 22 C (71.6 F). [...]
+```
+
 #### `variable`
 
 Returns the variable value or default in case it is empty