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engine.go
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engine.go
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package template
import (
"bytes"
"context"
"fmt"
"github.com/tiny-systems/module/module"
"github.com/tiny-systems/module/registry"
"html/template"
"time"
)
const (
EngineComponent = "template-engine"
EngineRequestPort = "request"
EngineResponsePort = "response"
EngineErrorPort = "error"
)
type Context any
type RenderContext any
type Template struct {
Name string `json:"name,omitempty" required:"true" title:"File name" Description:"e.g. footer.tmpl" propertyOrder:"1"`
Content string `json:"content,omitempty" required:"true" title:"Template" format:"textarea" propertyOrder:"2"`
}
type Settings struct {
EnableErrorPort bool `json:"enableErrorPort,omitempty" required:"true" title:"Enable Error Port" description:"If error happen during mail send, error port will emit an error message" propertyOrder:"1" tab:"Settings"`
Templates []Template `json:"templates,omitempty" required:"true" title:"Templates" minItems:"1" uniqueItems:"true" propertyOrder:"1" tab:"Templates"`
Partials []Template `json:"partials,omitempty" required:"true" title:"Partials" description:"All partials being loaded with each template" minItems:"0" uniqueItems:"true" propertyOrder:"1" tab:"Partials"`
}
type Error struct {
Input Input `json:"input"`
Error string `json:"error"`
}
type Input struct {
Context Context `json:"context,omitempty" configurable:"true" title:"Context" description:"Arbitrary message to be send alongside with rendered content" propertyOrder:"1"`
RenderContext RenderContext `json:"renderContext,omitempty" configurable:"true" title:"Render context" description:"Data being used to render the template" propertyOrder:"2"`
Template string `json:"template,omitempty" required:"true" title:"Template" description:"Template to render" propertyOrder:"3"`
}
type Output struct {
Input Input `json:"input"`
Content string `json:"content"`
}
type Engine struct {
templateSet map[string]*template.Template
settings Settings
}
var defaultEngineSettings = Settings{
Templates: []Template{
{
Name: "home.html",
Content: `{{template "layout.html" .}}
{{define "title"}}Welcome.{{end}}
{{define "content"}}
Welcome
{{end}}`,
},
{
Name: "page1.html",
Content: `{{template "layout.html" .}}
{{define "title"}} Page one.{{end}}
{{define "content"}}
I'm page 1
{{end}}`,
},
{
Name: "page2.html",
Content: `{{template "layout.html" .}}
{{define "title"}} Page 2 title {{end}}
{{define "content"}}
I'm page 2
{{end}}`,
},
},
Partials: []Template{
{
Name: "layout.html",
Content: `<!DOCTYPE html>
<html lang="en">
<head>
<title>{{block "title" .}}{{end}}</title>
</head>
<body>
{{block "nav" . }}{{end}}
<div style="padding:20px">
{{block "content" .}}{{end}}
</div>
{{block "footer" .}}{{end}}
</body>
</html>`,
},
{
Name: "footer.html",
Content: `{{define "footer"}}
<hr/>
<div style="text-align:center">
<p>© {{now.UTC.Year}}</p>
<p>{{builtWith}}</p>
</div>
{{end}}`,
},
{
Name: "nav.html",
Content: `{{define "nav"}}
<div>
<a href="/">Home page</a>
<a href="/page1">Page1</a>
<a href="/page2">Page2</a>
</div>
{{end}}`,
},
},
}
func (h *Engine) GetInfo() module.ComponentInfo {
return module.ComponentInfo{
Name: EngineComponent,
Description: "Template engine",
Info: "Renders templates using html/template standard package",
Tags: []string{"html", "template", "engine"},
}
}
func (h *Engine) Handle(ctx context.Context, handler module.Handler, port string, msg interface{}) error {
switch port {
case module.SettingsPort:
// compile template
in, ok := msg.(Settings)
if !ok {
return fmt.Errorf("invalid settings")
}
h.settings = in
ts := map[string]*template.Template{}
funcMap := template.FuncMap{
"now": time.Now,
"builtWith": func() template.HTML {
return `<a href="https://tinysystems.io?from=builtwith" target="_blank">Built with Tiny Systems</a>`
},
}
for _, t := range in.Templates {
tmpl, err := template.New(t.Name).Funcs(funcMap).Parse(t.Content)
if err != nil {
return err
}
for _, p := range in.Partials {
_, err = tmpl.New(p.Name).Parse(p.Content)
if err != nil {
return err
}
}
ts[t.Name] = tmpl
}
h.templateSet = ts
case EngineRequestPort:
in, ok := msg.(Input)
if !ok {
return fmt.Errorf("invalid input")
}
if h.templateSet == nil {
return fmt.Errorf("template set not loaded")
}
buf := &bytes.Buffer{}
t, ok := h.templateSet[in.Template]
if !ok {
err := fmt.Errorf("template not found")
if !h.settings.EnableErrorPort {
return err
}
return handler(ctx, EngineErrorPort, Error{
Input: in,
Error: err.Error(),
})
}
err := t.ExecuteTemplate(buf, in.Template, in.RenderContext)
if err != nil {
if !h.settings.EnableErrorPort {
return err
}
return handler(ctx, EngineErrorPort, Error{
Input: in,
Error: err.Error(),
})
}
return handler(ctx, EngineResponsePort, Output{
Content: buf.String(),
Input: in,
})
default:
return fmt.Errorf("port %s is not supoprted", port)
}
return nil
}
func (h *Engine) Ports() []module.NodePort {
ports := []module.NodePort{
{
Name: EngineRequestPort,
Label: "Request",
Position: module.Left,
Source: true,
Configuration: Input{},
},
{
Name: EngineResponsePort,
Position: module.Right,
Label: "Response",
Configuration: Output{},
},
{
Name: module.SettingsPort,
Label: "Settings",
Source: true,
Configuration: h.settings,
},
}
if !h.settings.EnableErrorPort {
return ports
}
return append(ports, module.NodePort{
Position: module.Bottom,
Name: EngineErrorPort,
Label: "Error",
Source: false,
Configuration: Error{},
})
}
func (h *Engine) Instance() module.Component {
return &Engine{
settings: defaultEngineSettings,
}
}
var _ module.Component = (*Engine)(nil)
func init() {
registry.Register(&Engine{})
}