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Golang package that generates clean, responsive HTML e-mails for sending transactional mail
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README.md

Hermes

Go Version Go Version Build Status

Hermes is the Go port of the great mailgen engine for Node.js. Check their work, it's awesome! It's a package that generates clean, responsive HTML e-mails for sending transactional e-mails (welcome e-mails, reset password e-mails, receipt e-mails and so on), and associated plain text fallback.

Note about this fork

This fork modifies Hermes in such way that it is possible to customize the Intros, Outros with HTML by replacing the string type to template.HTML. It also adds a way of adding non-http links in Button by replacing the string type of the Link field to template.URL.

Use this fork at your own risks.

Demo

Usage

First install the package:

go get -u github.com/matcornic/hermes

Then, start using the package by importing and configuring it:

// Configure hermes by setting a theme and your product info
h := hermes.Hermes{
    // Optional Theme
    // Theme: new(Default) 
    Product: hermes.Product{
        // Appears in header & footer of e-mails
        Name: "Hermes",
        Link: "https://example-hermes.com/",
        // Optional product logo
        Logo: "http://www.duchess-france.org/wp-content/uploads/2016/01/gopher.png",
    },
}

Next, generate an e-mail using the following code:

email := hermes.Email{
    Body: hermes.Body{
        Name: "Jon Snow",
        Intros: []string{
            "Welcome to Hermes! We're very excited to have you on board.",
        },
        Actions: []hermes.Action{
            {
                Instructions: "To get started with Hermes, please click here:",
                Button: hermes.Button{
                    Color: "#22BC66", // Optional action button color
                    Text:  "Confirm your account",
                    Link:  "https://hermes-example.com/confirm?token=d9729feb74992cc3482b350163a1a010",
                },
            },
        },
        Outros: []string{
            "Need help, or have questions? Just reply to this email, we'd love to help.",
        },
    },
}

// Generate an HTML email with the provided contents (for modern clients)
emailBody, err := h.GenerateHTML(email)
if err != nil {
    panic(err) // Tip: Handle error with something else than a panic ;)
}

// Generate the plaintext version of the e-mail (for clients that do not support xHTML)
emailText, err := h.GeneratePlainText(email)
if err != nil {
    panic(err) // Tip: Handle error with something else than a panic ;)
}

// Optionally, preview the generated HTML e-mail by writing it to a local file
err = ioutil.WriteFile("preview.html", []byte(emailBody), 0644)
if err != nil {
    panic(err) // Tip: Handle error with something else than a panic ;)
}

This code would output the following HTML template:

And the following plain text:

------------
Hi Jon Snow,
------------

Welcome to Hermes! We're very excited to have you on board.

To get started with Hermes, please click here: https://hermes-example.com/confirm?token=d9729feb74992cc3482b350163a1a010

Need help, or have questions? Just reply to this email, we'd love to help.

Yours truly,
Hermes - https://example-hermes.com/

Copyright © 2017 Hermes. All rights reserved.

Theme templates will be embedded in your application binary. If you want to use external templates (for configuration), use your own theme by implementing hermes.Theme interface with code searching for your files.

More Examples

To run the examples, go to examples folder, then run go run *.go. HTML and Plaintext example should be created in given theme folders.

Plaintext E-mails

To generate a plaintext version of the e-mail, simply call GeneratePlainText function:

// Generate plaintext email using hermes
emailText, err := h.GeneratePlainText(email)
if err != nil {
    panic(err) // Tip: Handle error with something else than a panic ;)
}

Supported Themes

The following open-source themes are bundled with this package:

RTL Support

To change the default text direction (left-to-right), simply override it as follows:

// Configure hermes by setting a theme and your product info
h := hermes.Hermes {
    // Custom text direction
    TextDirection: hermes.TDRightToLeft,
}

Language Customizations

To customize the e-mail's greeting ("Hi") or signature ("Yours truly"), supply custom strings within the e-mail's Body:

email := hermes.Email{
    Body: hermes.Body{
        Greeting: "Dear",
        Signature: "Sincerely",
    },
}

To use a custom title string rather than a greeting/name introduction, provide it instead of Name:

email := hermes.Email{
    Body: hermes.Body{
        // Title will override `Name`
        Title: "Welcome to Hermes",
    },
}

To customize the Copyright, override it when initializing Hermes within your Product as follows:

// Configure hermes by setting a theme and your product info
h := hermes.Hermes{
    // Optional Theme
    // Theme: new(Default)
    Product: hermes.Product{
        // Appears in header & footer of e-mails
        Name: "Hermes",
        Link: "https://example-hermes.com/",
        // Custom copyright notice
        Copyright: "Copyright © 2017 Dharma Initiative. All rights reserved."
    },
}

To use a custom fallback text at the end of the email, change the TroubleText field of the hermes.Product struct. The default value is If you’re having trouble with the button '{ACTION}', copy and paste the URL below into your web browser.. The {ACTION} placeholder will be replaced with the corresponding text of the supplied action button:

// Configure hermes by setting a theme and your product info
h := hermes.Hermes{
    // Optional Theme
    // Theme: new(Default)
    Product: hermes.Product{
        // Custom trouble text
        TroubleText: "If the {ACTION}-button is not working for you, just copy and paste the URL below into your web browser."
    },
}

Elements

Hermes supports injecting custom elements such as dictionaries, tables and action buttons into e-mails.

Action

To inject an action button in to the e-mail, supply the Actions object as follows:

email := hermes.Email{
    Body: hermes.Body{
        Actions: []hermes.Action{
            {
                Instructions: "To get started with Hermes, please click here:",
                Button: hermes.Button{
                    Color: "#22BC66", // Optional action button color
                    Text:  "Confirm your account",
                    Link:  "https://hermes-example.com/confirm?token=d9729feb74992cc3482b350163a1a010",
                },
            },
        },
    },
}

To inject multiple action buttons in to the e-mail, supply another struct in Actions slice Action.

Table

To inject a table into the e-mail, supply the Table object as follows:

email := hermes.Email{
    Body: hermes.Body{
        Table: hermes.Table{
            Data: [][]hermes.Entry{
                // List of rows
                {   
                    // Key is the column name, Value is the cell value
                    // First object defines what columns will be displayed
                    {Key: "Item", Value: "Golang"},
                    {Key: "Description", Value: "Open source programming language that makes it easy to build simple, reliable, and efficient software"},
                    {Key: "Price", Value: "$10.99"},
                },
                {
                    {Key: "Item", Value: "Hermes"},
                    {Key: "Description", Value: "Programmatically create beautiful e-mails using Golang."},
                    {Key: "Price", Value: "$1.99"},
                },
            },
            Columns: hermes.Columns{
                // Custom style for each rows
                CustomWidth: map[string]string{
                    "Item":  "20%",
                    "Price": "15%",
                },
                CustomAlignment: map[string]string{
                    "Price": "right",
                },
            },
        },
    },
}

Dictionary

To inject key-value pairs of data into the e-mail, supply the Dictionary object as follows:

email := hermes.Email{
    Body: hermes.Body{
        Dictionary: []hermes.Entry{
            {Key: "Date", Value: "20 November 1887"},
            {Key: "Address", Value: "221B Baker Street, London"},
        },
    },
}

Free Markdown

If you need more flexibility in the content of your generated e-mail, while keeping the same format than any other e-mail, use Markdown content. Supply the FreeMarkdown object as follows:

email := hermes.Email{
		Body: hermes.Body{
			FreeMarkdown: `
> _Hermes_ service will shutdown the **1st August 2017** for maintenance operations. 

Services will be unavailable based on the following schedule:

| Services | Downtime |
| :------:| :-----------: |
| Service A | 2AM to 3AM |
| Service B | 4AM to 5AM |
| Service C | 5AM to 6AM |

---

Feel free to contact us for any question regarding this matter at [support@hermes-example.com](mailto:support@hermes-example.com) or in our [Gitter](https://gitter.im/)

`,
		},
	}
}

This code would output the following HTML template:

And the following plaintext:

------------
Hi Jon Snow,
------------

> 
> 
> 
> Hermes service will shutdown the *1st August 2017* for maintenance
> operations.
> 
> 

Services will be unavailable based on the following schedule:

+-----------+------------+
| SERVICES  |  DOWNTIME  |
+-----------+------------+
| Service A | 2AM to 3AM |
| Service B | 4AM to 5AM |
| Service C | 5AM to 6AM |
+-----------+------------+

Feel free to contact us for any question regarding this matter at support@hermes-example.com ( support@hermes-example.com ) or in our Gitter ( https://gitter.im/ )

Yours truly,
Hermes - https://example-hermes.com/

Copyright © 2017 Hermes. All rights reserved.

Be aware that this content will replace existing tables, dictionary and actions. Only intros, outros, header and footer will be kept.

This is helpful when your application needs sending e-mails, wrote on-the-fly by adminstrators.

Markdown is rendered with Blackfriday, so every thing Blackfriday can do, Hermes can do it as well.

Troubleshooting

  1. After sending multiple e-mails to the same Gmail / Inbox address, they become grouped and truncated since they contain similar text, breaking the responsive e-mail layout.

Simply sending the X-Entity-Ref-ID header with your e-mails will prevent grouping / truncation.

Contributing

See CONTRIBUTING.md

License

Apache 2.0

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