greypot

An experimental library for generating PDF reports from HTML templates or "designs".

You can use it in three ways

• As a Go Library
• As an API which can be interacted with from any library
• Use the Greypot Studio for designing and testing the templates in browser

Quick API Example

You can use the following command to generate a PDF using the Greypot Studio API running on Fly.io

$ curl --request POST --url https://greypot-studio.fly.dev/_studio/generate/pdf/test \
  --header 'Content-Type: application/json' \
  --data '{ "Name": "test.html", "Template": "<h1>Hello {{data.name}}</h1>", "Data": { "name": "John Smith" } }' | jq -r '.data' | base64 --decode > test.pdf

Use as a Go Library

Say you want to produce reports or other such type of documents in your applications. greypot allows you to design your reports with HTML as template files that use a Django-like templating engine. We also support the standard Go html/template.

These HTML reports can then be generated as HTML, PNG or PDF via endpoints that greypot adds to your application when you use the framework support (for Fiber or Gin).

Once you add the middleware to your application, it adds the following routes:

GET /reports/list

GET /reports/preview/:reportTemplateName

GET /reports/render/:reportTemplateName

POST /reports/export/html/:reportTemplateName

POST /reports/export/png/:reportTemplateName

POST /reports/export/pdf/:reportTemplateName

POST /reports/export/bulk/html/:reportTemplateName

POST /reports/export/bulk/png/:reportTemplateName

POST /reports/export/bulk/pdf/:reportTemplateName

You can then call these from within your applications to generate/export the reports e.g. from a frontend UI.

Using Greypot with Gin

package main

import (
	"embed"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/nndi-oss/greypot"
	greypotGin "github.com/nndi-oss/greypot/http/gin"
)

//go:embed "templates"
var templatesFS embed.FS

func main() {
	app := gin.New()

	module := greypot.NewModule(
		greypot.WithRenderTimeout(10*time.Second),
		greypot.WithViewport(2048, 1920),
		greypot.WithDjangoTemplateEngine(),
		greypot.WithTemplatesFromFilesystem("./templates/"),
		greypot.WithPlaywrightRenderer(),
	)

	greypotGin.Use(app, module)

	embedModule := greypot.NewModule(
		greypot.WithRenderTimeout(10*time.Second),
		greypot.WithViewport(2048, 1920),
		greypot.WithTemplatesFromFS(templatesFS),
		greypot.WithGolangTemplateEngine(),
		greypot.WithPlaywrightRenderer(),
	)

	greypotGin.Use(app.Group("/embedded/"), embedModule)

	app.Run(":3000")
}

Using Greypot with Fiber

package main

import (
	"embed"
	"time"

	"github.com/gofiber/fiber/v2"
	"github.com/nndi-oss/greypot"
	greypotFiber "github.com/nndi-oss/greypot/http/fiber"
)

//go:embed "templates"
var templatesFS embed.FS

func main() {
	app := fiber.New()

	module := greypot.NewModule(
		greypot.WithRenderTimeout(10*time.Second),
		greypot.WithViewport(2048, 1920),
		greypot.WithDjangoTemplateEngine(),
		greypot.WithTemplatesFromFilesystem("./templates/"),
		greypot.WithPlaywrightRenderer(),
	)

	greypotFiber.Use(app, module)

	embedModule := greypot.NewModule(
		greypot.WithRenderTimeout(10*time.Second),
		greypot.WithViewport(2048, 1920),
		greypot.WithTemplatesFromFS(templatesFS),
		greypot.WithGolangTemplateEngine(),
		greypot.WithPlaywrightRenderer(),
	)

	greypotFiber.Use(app.Group("/embedded/"), embedModule)

	app.Listen(":3000")
}

Build Docker Image and run the Container

$ docker build -t greypot-server .

$ docker run -p "7665:7665" -v "$(pwd)/examples/fiber_example/templates:/templates" greypot-server

Playwright Rendering Engine

Currently, we are focusing on making the playwright based renderer work really good! The base project used Chrome Developer Protocol to connect with a Chromium instance. We decided to remove support for that.

In order to use the Playwright rendering functionality, you will need to have the playwright dependencies installed.

Read here for more info. But in short, you can use the following command to do so:

$ npx playwright install-deps chromium

Prior art

• Greypot is based on go-report-builder