This file has notes useful for mox developers.

# Code style, guidelines, notes

- Keep the same style as existing code.
- For Windows: use package "path/filepath" when dealing with files/directories.
  Test code can pass forward-slashed paths directly to standard library functions,
  but use proper filepath functions when parameters are passed and in non-test
  code.  Mailbox names always use forward slash, so use package "path" for mailbox
  name/path manipulation. Do not remove/rename files that are still open.
- Not all code uses adns, the DNSSEC-aware resolver. Such as code that makes
  http requests, like mtasts and autotls/autocert.
- We don't have an internal/ directory, really just to prevent long paths in
  the repo, and to keep all Go code matching *.go */*.go (without matching
  vendor/). Part of the packages are reusable by other software. Those reusable
  packages must not cause mox implementation details (such as bstore) to get out,
  which would cause unexpected dependencies. Those packages also only expose the
  standard slog package for logging, not our mlog package. Packages not intended
  for reuse do use mlog as it is more convenient. Internally, we always use
  mlog.Log to do the logging, wrapping an slog.Logger.

# Reusable packages

Most non-server Go packages are meant to be reusable. This means internal
details are not exposed in the API, and we don't make unneeded changes. We can
still make breaking changes when it improves mox: We don't want to be stuck
with bad API. Third party users aren't affected too seriously due to Go's
minimal version selection. The reusable packages are in apidiff/packages.txt.
We generate the incompatible changes with each release.

# TLS certificates

https://github.com/cloudflare/cfssl is useful for testing with TLS
certificates. Create a CA and configure it in mox.conf TLS.CA.CertFiles, and
sign host certificates and configure them in the listeners TLS.KeyCerts.

Setup a local CA with cfssl, run once:

```sh
go install github.com/cloudflare/cfssl/cmd/cfssl@latest
go install github.com/cloudflare/cfssl/cmd/cfssljson@latest

mkdir -p local/cfssl
cd local/cfssl

cfssl print-defaults config > ca-config.json # defaults are fine

# Based on: cfssl print-defaults csr > ca-csr.json
cat <<EOF >ca-csr.json
{
    "CN": "mox ca",
    "key": {
        "algo": "ecdsa",
        "size": 256
    },
    "names": [
        {
            "C": "NL"
        }
    ]
}
EOF

cfssl gencert -initca ca-csr.json | cfssljson -bare ca - # Generate ca key and cert.

# Generate wildcard certificates for one or more domains, add localhost for use with pebble, see below.
domains="moxtest.example localhost"
for domain in $domains; do
	cat <<EOF >wildcard.$domain.csr.json
{
  "key": {
    "algo": "ecdsa",
    "size": 256
  },
  "names": [
  {
    "O": "mox"
  }
  ],
  "hosts": [
    "$domain",
    "*.$domain"
  ]
}
EOF
	cfssl gencert -ca ca.pem -ca-key ca-key.pem -profile=www wildcard.$domain.csr.json | cfssljson -bare wildcard.$domain
done
```

Now configure mox.conf to add the cfssl CA root certificate:

```
TLS:
	CA:
		AdditionalToSystem: true
		CertFiles:
			# Assuming local/<env>/config/mox.conf and local/cfssl/.
			- ../../cfssl/ca.pem

[...]

Listeners:
	public:
                TLS:
			KeyCerts:
				# Assuming local/<env>/config/mox.conf and local/cfssl/.
				CertFile: ../../cfssl/wildcard.$domain.pem
				KeyFile: ../../cfssl/wildcard.$domain-key.pem
```

# ACME

https://github.com/letsencrypt/pebble is useful for testing with ACME. Start a
pebble instance that uses the localhost TLS cert/key created by cfssl for its
TLS serving. Pebble generates a new CA certificate for its own use each time it
is started. Fetch it from https://localhost:15000/roots/0, write it to a file, and
add it to mox.conf TLS.CA.CertFiles. See below.

Setup pebble, run once:

```sh
go install github.com/letsencrypt/pebble/cmd/pebble@latest

mkdir -p local/pebble
cat <<EOF >local/pebble/config.json
{
  "pebble": {
    "listenAddress": "localhost:14000",
    "managementListenAddress": "localhost:15000",
    "certificate": "local/cfssl/localhost.pem",
    "privateKey": "local/cfssl/localhost-key.pem",
    "httpPort": 80,
    "tlsPort": 443,
    "ocspResponderURL": "",
    "externalAccountBindingRequired": false
  }
}
EOF
```

Start pebble, this generates a new temporary pebble CA certificate:

```sh
pebble -config local/pebble/config.json
```

Write new CA bundle that includes pebble's temporary CA cert:

```sh
export CURL_CA_BUNDLE=local/ca-bundle.pem # for curl
export SSL_CERT_FILE=local/ca-bundle.pem # for go apps
cat /etc/ssl/certs/ca-certificates.crt local/cfssl/ca.pem >local/ca-bundle.pem
curl https://localhost:15000/roots/0 >local/pebble/ca.pem # fetch temp pebble ca, DO THIS EVERY TIME PEBBLE IS RESTARTED!
cat /etc/ssl/certs/ca-certificates.crt local/cfssl/ca.pem local/pebble/ca.pem >local/ca-bundle.pem # create new list that includes cfssl ca and temp pebble ca.
rm -r local/*/data/acme/keycerts/pebble # remove existing pebble-signed certs in acme cert/key cache, they are invalid due to newly generated temp pebble ca.
```

Edit mox.conf, adding pebble ACME and its ca.pem:

```
ACME:
	pebble:
		DirectoryURL: https://localhost:14000/dir
		ContactEmail: root@mox.example
TLS:
	CA:
		AdditionalToSystem: true
		CertFiles:
			# Assuming local/<env>/config/mox.conf and local/pebble/ca.pem and local/cfssl/ca.pem.
			- ../../pebble/ca.pem
			- ../../cfssl/ca.pem

[...]

Listeners:
	public:
                TLS:
                        ACME: pebble
```

For mail clients and browsers to accept pebble-signed certificates, you must add
the temporary pebble CA cert to their trusted root CA store each time pebble is
started (e.g. to your thunderbird/firefox testing profile). Pebble has no option
to not regenerate its CA certificate, presumably for fear of people using it for
non-testing purposes. Unfortunately, this also makes it inconvenient to use for
testing purposes.


# Messages for testing

For compatibility and preformance testing, it helps to have many messages,
created a long time ago and recently, by different mail user agents. A helpful
source is the Linux kernel mailing list. Archives are available as multiple git
repositories (split due to size) at
https://lore.kernel.org/lkml/_/text/mirror/.  The git repo's can be converted
to compressed mbox files (about 800MB each) with:

```
# 0 is the first epoch (with over half a million messages), 12 is last
# already-complete epoch at the time of writing (with a quarter million
# messages). The archives are large, converting will take some time.
for i in 0 12; do
        git clone --mirror http://lore.kernel.org/lkml/$i lkml-$i.git
        (cd lkml-$i.git && time ./tombox.sh | gzip >../lkml-$i.mbox.gz)
done
```

With the following "tobmox.sh" script:

```
#!/bin/sh
pre=''
for rev in $(git rev-list master | reverse); do
        printf "$pre"
        echo "From sender@host  $(date '+%a %b %e %H:%M:%S %Y' -d @$(git show -s --format=%ct $rev))"
        git show ${rev}:m | sed 's/^>*From />&/'
        pre='\n'
done
```


# Release proces

- Gather feedback on recent changes.
- Check if dependencies need updates.
- Check code if there are deprecated features that can be removed.
- Generate apidiff and check if breaking changes can be prevented.
- Update features & roadmap in README.md
- Write release notes.
- Build and run tests with previous major Go release.
- Run tests, including with race detector.
- Run integration and upgrade tests.
- Run fuzzing tests for a while.
- Deploy to test environment. Test the update instructions.
- Send and receive email through the major webmail providers, check headers.
- Send and receive email with imap4/smtp clients.
- Check DNS check admin page.
- Check with https://internet.nl
- Create git tag, push code.
- Publish new docker image.
- Publish signed release notes for updates.xmox.nl and update DNS record.
- Publish new cross-referenced code/rfc to www.xmox.nl/xr/.
- Create new release on the github page, so watchers get a notification.