lettersnail

= Lettersnail
Clemens Fries <github-lettersnail@xenoworld.de>
:source-highlighter: pygments
:toc: left
:lettersnail-ini: lettersnail.ini
:lettersnail-base: lettersnail
:version: 0.0.1

lettersnail v{version} — a simple email notification helper.

IMPORTANT: This program is in development and might have some rough edges. The
documentation on `master` should still accurately reflect the current state of
the program.

== What is `lettersnail`?

`lettersnail` is a “note to my future self” email notification tool. You write a
simple text file, with some metadata, and it will, upon invocation, send a
message when the time has come.

.Example message
----
to: me@example.com
subject: Watch Halley's Comet
date: 2061-07-28

Greetings!

Go outside at night, if the curfew of the – highly welcomed — alien overlords
permits, and watch Halley's Comet.
----

=== Motivation

I needed a fairly simple tool to send some one-off reminders to myself, and
possibly to others. Plus, I wanted the messages to live in my home directory,
so I would not forget them if I move to another server. You could realize
most of this with `atd`, but it is a bit clumsy if want to quickly write a
message, plus I'd totally forget to copy `/var/spool/at`.

`lettersnail` is not meant to be a daemon. It should be executed regularly by a
cron job or other method. For the `date` parameter it also supports having a
specific time, which acts as a “not before” constraint. If you run your cron
job often enough (for example: every five minutes) the message will, of course,
be sent very close to the given time.


== Quick Start

=== Building

In order to check out and build the project in its own directory in `/tmp`,
write the following:

[source,shell]
----
cd $(mktemp -d)
git clone http://github.com/githubert/lettersnail
go build
----

=== Running

Create `.config/{lettersnail-ini}`:
[source,ini]
----
[default]
server = smtp.example.com
user = me
password = aengeequ6xeiseoY
from = me@example.com
----

Create a new message:
----
lettersnail create --to me@example.com
----

Add a cron job:
----
0 6 * * * /path/to/lettersnail run
----

List messages due in the next days:
----
lettersnail next
----

Run manually:
----
lettersnail run
----

== Quick Start Walkthrough

Create a file `.config/{lettersnail-ini}` and provide a server, credentials and a
from address:

[source,ini]
----
[default]
server = smtp.example.com
user = me
password = aengeequ6xeiseoY
from = me@example.com
----

NOTE: `port` defaults to `587`. If it doesn't work, try setting `port` to
`25`.

Now ready some message to yourself:

----
lettersnail create --to me@example.com
----

This will open a new file using the editor set in the `VISUAL` environment
variable, or if no editor is set, it will default to `vi`.

Fill in `date` in the format `YYYY-mm-dd` (for example `date: 2016-01-01`) and
add a meaningful `subject`. Add a blank line between the configuration in the
header and your message's body.

Save and exit the editor. `lettersnail` will ask you what to do. Press `ENTER` to
save the message to the `{lettersnail-base}/todo` folder.

If you set `date` to today's date you can test if everything works. First check
if everything is okay by running `lettersnail check`, if it reports no errors,
you can see with `lettersnail next` if the message is scheduled for being sent
out in the next seven days.

Finally, if you type `lettersnail run`, it will deliver all messages that were
due.

As `lettersnail` is not a daemon, you should run it daily by adding it as a cron
job.

Type `crontab -e` and add a entry to run the command every day at 6 in the
morning:

----
0 6 * * * /path/to/lettersnail run
----

== Folder structure

The default working directory is `lettersnail`, located in the user's home
directory. There are several folders created beneath it, when the program
is invoked.

----
lettersnail/
  todo/
  done/
  errors/
  drafts/
----

`todo/` is the message queue. All `.msg` files in that folder are considered
when running `lettersnail run`.

`done/` contains all messages that were successfully delivered. For every
message there is also a corresponding `.log` file.

`errors/` contains all messages that could not be delivered. For every message
there is also a corresponding `.log` file.

`drafts/` contains messages that can be used with `lettersnail create --draft
FILENAME`. Additionally, messages in this folder will also be checked with
`lettersnail check`.

== Global Settings File `.config/{lettersnail-ini}`

Global settings can be put into the optional file `.config/{lettersnail-ini}`.

All _global_ settings can also be overridden on the command line.

`.config/{lettersnail-ini}` is a simple ini-style settings file with a `default`
section, plus optional sections for every command, in order to overrule the
settings in the `default` section.

.Example file
[source,ini]
----
[default]
workdir = ~/lettersnail
server = smtp.example.com
port = 587
from = me@example.com

[run]
bcc = me@example.com
----

=== Settings

NOTE: Empty values are valid and mean that a setting has been un-set.

==== Global and Command Line

workdir:: The working directory, defaults to `~/lettersnail`.
server:: Address of the SMTP server. Defaults to `localhost`.
port:: Port of the SMTP server. Defaults to the SMTP submission port `587`.
not-before:: Do not sent messages before the specified time. (`00:00` until `not-before`)
not-after:: Do not sent messages after the specified time. (`not-after` until `23:59`)

TODO: not-after / not-before warrant some better explanation

Priority of these is as follows `command line > global`.

==== Global, Command Line and as Configuration

These parameters are valid everywhere and may also be included in the
configuration part of a message.

NOTE: `date` is not allowed anywhere except in the message configuration.

from:: `from` as in <<Configuration>>
to:: `to` as in <<Configuration>>
cc:: `cc` as in <<Configuration>>
bcc:: `bcc` as in <<Configuration>>
subject:: `subject` as in <<Configuration>>
reply-to:: `reply-to` as in <<Configuration>>

Priority of these is as follows `configuration > command line > global`.

== Message format

Messages consist of two parts *separated by a single empty line*. The first part
is the configuration and the second part is the actual message.

.Example message
----
to: cryogenics-department@example.com
from: me-bot@example.com
cc: me@example.com
subject: Unfreeze Clemens
date: 2134-01-01

Dear Cryogenics Department,

please unfreeze Clemens, as he wanted to watch this year's close pass of
Halley's Comet. This one is going to have an apparent magnitude of -2.0 — it's
gonna be fun, so feel free to join him!
----


[[Configuration]]
=== Configuration

The following parameters are permitted, everything else is going to be ignored.

==== Required parameters

NOTE: Except for `date`, other required parameters may be specified outside the
message configuration, either on the command line or in the ini-file.

date:: The "not before" date. This may either be a simple date in the format
`YYYY-mm-dd`, which will be interpreted as `YYYY-mm-dd 00:00`, or a date with a
time in the form of `YYYY-mm-dd HH:MM`.

to:: A single address to where the message will be sent. It may either be a
simple email address such as `foo@example.net` or an address including a
name such as `Foo bar <foo@example.net>`.

subject:: A short subject.

from:: Same format as `to`.

==== Optional parameters

cc:: Same format as `to`, but multiple comma-separated entries are allowed,
works like `Cc` in email.

bcc:: Same format as `to`, but multiple comma-separated entries are allowed,
works like `Bcc` in email.

reply-to:: Same format as `to`, works like `Reply-To` in email.

=== Message Body

Simple, plain text. It is assumed to be in UTF-8, though.

== Writing a New Message

Either edit a file, directly in `{lettersnail-base}/todo`, or use the command line tool
to initialize an empty message and start your favourite editor. The file name
must end in `.msg`, otherwise it will be ignored.

.Using the command line tool
----
$ lettersnail create --to "foo@example.com"
----

== Command Line Options

Use `--help` after any command to get the full help message shown.

----
include::lettersnail.go[tag=main]
----

=== `next` command

----
include::cmd/next.go[tag=next]
----

This will show which messages are going to be sent within the next 7 days. Use
the `--days` parameter to change how many days in advance are processed. If you
use the `--all` parameter, all pending messages will be listed.
The format is simply `date  subject (filename)`.

----
$ lettersnail next --all
Showing all messages.

2061-07-28 00:00  Watch Halley's Comet (halley.msg)
2134-01-01 00:00  Unfreeze Clemens (unfreeze.msg)
----


=== `run` command

----
include::cmd/run.go[tag=run]
----

This will send out all pending messages. There will be no output, unless there
were errors. Any message that could not be sent will be moved to the `errors`
folder, and a corresponding `.log`-file will be created with all available
information; additionally, the program will start to complain at every
invocation that there were messages with errors. Messages that were delivered
successfully are moved to the `done` folder and a corresponding `.log`-file is
created there, too.


=== `create` command

----
include::cmd/create.go[tag=create]
----

The `create` command will assist you in creating a new message. It will open a
new file for you, filled in with any parameters you provided on the command
line. If you provide a file name through the `--draft` parameter, it will
create a new file based on the given file name in the `drafts` folder.

----
lettersnail create --to foo@example.com --subject "Something"
----

It will use the editor configured in `$VISUAL` or `$EDITOR` or `vi`, if the
former are empty.

`date` will be set to tomorrow's date.

----
1 to: foo@example.com
2 subject: Something
3 date: 2016-01-01
4
5 Add message to the world of tomorrow here.
~
~
~
~
 INSERT >> [No Name][+]               <<<
-- INSERT --
----

After editing it will ask you if you want to add the message to the `todo`
folder.

----
Save message? ([(y)es], (r)enamed, (d)raft, (n)o):
----

Answering `n` or `no` will discard the message, answering `d` or `draft` will
add it to the `drafts` folder. If you type `y`, `yes`, or simply hit `ENTER` it
will be added to the `todo` folder. If you want to save the message under a
different name, but still into the `todo` folder, you may anwer with `r` or
`renamed` — the program will then prompt you for a new name, without the `.msg`
extension.

=== `check` command

----
include::cmd/check.go[tag=check]
----

The `check` command will check all messages in the `todo` and `drafts` folder
and report any messages that can't be processed. Optionally a file name can be
provided to check only the given file. It will exit with a code of `0` if no
errors were found, otherwise with a code of `1`.

NOTE: `--silent` will not suppress output of errors, such as problems loading a
file.

----
$ lettersnail check

in drafts:
 foo.msg:
    missing the 'to' parameter
    missing the 'subject' parameter

in todo:
 bar.msg:
    'date' parameter is invalid
----

=== `debug` command

----
include::cmd/debug.go[tag=debug]
----

The `debug` command will print out the effective configuration for a message,
plus the email message.  This shows all settings as they are seen at that
point. Note that this also shows settings — such as `workdir` and `config` —
that cannot be overridden by the message. Please note that for the email
message there are several places, such as the `Message-Id`, that vary from
invocation to invocation as they are randomly generated.

----
$ lettersnail debug lettersnail/todo/2061.msg
Configuration
-------------
config: /home/me/.config/config.ini
date: 2061-07-28
days: 7
from: me@example.com
not-after: 23:59
not-before: 00:00
port: 578
server: smtp.example.com
subject: Watch Halley's Comet
to: me@example.com
workdir: /home/me/lettersnail

Email message
-------------
Content-Type: multipart/mixed;
 boundary=8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2
To: <me@example.com>
Subject: Watch Halley's Comet
Message-Id: <1464969109987565122.18908.793296386389602001@smtp.example.com>
From: me@example.com
Date: Fri, 03 Jun 2016 17:51:49 +0200
Mime-Version: 1.0

--8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2
Content-Type: multipart/alternative;
 boundary=70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc

--70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Greetings!

Go outside at night, if the curfew of the – highly welcomed — alien overlords
permits, and watch Halley's Comet.
--70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc--

--8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2--
----