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// Copyright 2023 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build !genassets
// +build !genassets
//go:generate go run -tags genassets gen_assets.go
package web
import (
"bytes"
_ "embed"
"net/http"
"strings"
"text/template"
)
// Config represents the configuration of the web listener.
type LandingConfig struct {
RoutePrefix string // The route prefix for the exporter.
HeaderColor string // Used for the landing page header.
CSS string // CSS style tag for the landing page.
Name string // The name of the exporter, generally suffixed by _exporter.
Description string // A short description about the exporter.
Form LandingForm // A POST form.
Links []LandingLinks // Links displayed on the landing page.
ExtraHTML string // Additional HTML to be embedded.
ExtraCSS string // Additional CSS to be embedded.
Version string // The version displayed.
}
// LandingForm provides a configuration struct for creating a POST form on the landing page.
type LandingForm struct {
Action string
Inputs []LandingFormInput
Width float64
}
// LandingFormInput represents a single form input field.
type LandingFormInput struct {
Label string
Type string
Name string
Placeholder string
Value string
}
type LandingLinks struct {
Address string // The URL the link points to.
Text string // The text of the link.
Description string // A descriptive textfor the link.
}
type LandingPageHandler struct {
landingPage []byte
routePrefix string
}
var (
//go:embed landing_page.html
landingPagehtmlContent string
//go:embed landing_page.css
landingPagecssContent string
)
func NewLandingPage(c LandingConfig) (*LandingPageHandler, error) {
var buf bytes.Buffer
length := 0
for _, input := range c.Form.Inputs {
inputLength := len(input.Label)
if inputLength > length {
length = inputLength
}
}
c.Form.Width = (float64(length) + 1) / 2
if c.CSS == "" {
if c.HeaderColor == "" {
// Default to Prometheus orange.
c.HeaderColor = "#e6522c"
}
cssTemplate := template.Must(template.New("landing css").Parse(landingPagecssContent))
if err := cssTemplate.Execute(&buf, c); err != nil {
return nil, err
}
c.CSS = buf.String()
}
if c.RoutePrefix == "" {
c.RoutePrefix = "/"
} else if !strings.HasSuffix(c.RoutePrefix, "/") {
c.RoutePrefix += "/"
}
// Strip leading '/' from Links if present
for i, link := range c.Links {
c.Links[i].Address = strings.TrimPrefix(link.Address, "/")
}
t := template.Must(template.New("landing page").Parse(landingPagehtmlContent))
buf.Reset()
if err := t.Execute(&buf, c); err != nil {
return nil, err
}
return &LandingPageHandler{
landingPage: buf.Bytes(),
routePrefix: c.RoutePrefix,
}, nil
}
func (h *LandingPageHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != h.routePrefix {
http.NotFound(w, r)
return
}
w.Header().Add("Content-Type", "text/html; charset=UTF-8")
w.Write(h.landingPage)
}
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