One Daily Email for Your Whole Homelab (Python + msmtp)

#!/usr/bin/env bash
# daily-digest installer — one morning email for the whole lab.
# Run as root on the ONE machine that already has a working mail path
# (set that up first with the msmtp + Gmail playbook on this site).

set -euo pipefail

# 1) A home for the feed files — every *.json in here becomes a card.
mkdir -p /var/lib/digest-feeds

# 2) Install the digest script itself.
cat > /usr/local/bin/daily-digest.py <<'PYEOF'
#!/usr/bin/env python3
"""daily-digest.py — one homelab, one morning email.

Reads small JSON "feed" files that your other scripts write, optionally asks
Prometheus for firing alerts, renders email-safe HTML that survives Gmail AND
Outlook, and sends ONE email via msmtp to everyone in RECIPIENTS.

  daily-digest.py            gather, render, send
  daily-digest.py --dry-run  gather, render to /tmp/digest-preview.html, no send

Python standard library only. Pairs with the msmtp + Gmail playbook, which
gives this machine its outbound mail path in the first place.
"""
import glob
import html
import json
import os
import subprocess
import sys
import urllib.parse
import urllib.request
from datetime import date
from email.message import EmailMessage

# ==== MAKE THESE VALUES YOUR OWN =============================================
RECIPIENTS = ["you@example.com", "family@example.com"]  # who gets the digest
FROM_ADDR  = "you@example.com"    # must match the account in ~/.msmtprc
APPROVE_TO = "you@example.com"    # where mailto: "Approve" replies land
# Every *.json in FEED_DIR becomes a card. The env override means you can
# test as a normal user:  DIGEST_FEEDS=~/feeds ./daily-digest.py --dry-run
FEED_DIR   = os.environ.get("DIGEST_FEEDS", "/var/lib/digest-feeds")
PROM_URL   = ""                   # e.g. "http://10.0.0.5:9090" — blank = skip
SITE_NAME  = "My Homelab"
PREVIEW    = "/tmp/digest-preview.html"
# =============================================================================

# Email clients ignore CSS variables, so every color is a hardcoded hex,
# repeated inline on every element. Ugly on purpose — it renders everywhere.
FONT = "-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif"
TONES = {  # border, background, text
    "ok":     ("#16a34a", "#e9f9ef", "#15803d"),
    "info":   ("#2563eb", "#eaf1ff", "#1d4ed8"),
    "warn":   ("#f97316", "#fff4ea", "#ea580c"),
    "urgent": ("#e74c3c", "#fdecec", "#c0392b"),
}
DRY = "--dry-run" in sys.argv


def esc(s):
    return html.escape(str(s), quote=True)


def mailto(subject, body):
    """One-tap approve link. RFC 6068 wants percent-encoding (%20 for spaces,
    %0D%0A for line breaks) — urlencode's default form-style '+' is NOT part
    of the mailto spec, so pass quote_via=quote."""
    enc = urllib.parse.urlencode(
        {"subject": subject, "body": body.replace("\n", "\r\n")},
        quote_via=urllib.parse.quote)
    return f"mailto:{APPROVE_TO}?{enc}"


# ---------------------------------------------------------------- gathering --

def read_feeds():
    """The whole trick. Each producer script writes ONE tiny JSON file:

      {"title": "Backups", "status": "ok|info|warn|urgent",
       "summary": "one sentence", "lines": ["detail", ...],
       "action": {"label": "Approve — ...", "subject": "APPROVE: ...",
                  "body": "Approved — go ahead and ..."}}

    Only "title" is required. Files render in name order, so a 10-/20-/30-
    prefix is your layout engine. A feed that fails to parse becomes a warn
    card instead of killing the digest."""
    feeds = []
    for path in sorted(glob.glob(FEED_DIR + "/*.json")):
        name = path.rsplit("/", 1)[-1]
        try:
            d = json.loads(open(path, encoding="utf-8").read())
            d.setdefault("title", name)
            feeds.append(d)
        except Exception as ex:
            feeds.append({"title": name, "status": "warn",
                          "summary": f"This feed file could not be read ({ex}). "
                                     "Its producer may be broken."})
    return feeds


def prometheus_alerts():
    """Firing alerts from Prometheus's HTTP API (GET /api/v1/alerts).
    Returns a list of alerts, or None when Prometheus itself is unreachable —
    which is worth a card of its own, not a silent shrug."""
    if not PROM_URL:
        return []
    try:
        with urllib.request.urlopen(PROM_URL + "/api/v1/alerts", timeout=6) as r:
            alerts = json.load(r).get("data", {}).get("alerts", [])
        return [a for a in alerts if a.get("state") == "firing"]
    except Exception:
        return None


# ---------------------------------------------------------------- rendering --
# Layout rules that keep Gmail AND Outlook happy: real <table> elements with
# role="presentation", widths as attributes, styles inline, no float, no
# flexbox, no grid, no CSS variables, no background images.

def pill(text, tone):
    border, bg, fg = TONES[tone]
    return (f'<span style="display:inline-block;padding:3px 11px;border-radius:999px;'
            f'font-family:{FONT};font-size:12px;font-weight:600;'
            f'color:{fg};background:{bg};border:1px solid {border};">{esc(text)}</span>')


def button(action, tone):
    border, _bg, _fg = TONES[tone]
    href = mailto(action.get("subject", "APPROVE"), action.get("body", "Approved."))
    return (f'<p style="margin:12px 0 0;"><a href="{esc(href)}" '
            f'style="font-family:{FONT};font-size:13px;font-weight:700;'
            f'color:#ffffff;background:{border};padding:9px 16px;border-radius:8px;'
            f'text-decoration:none;">{esc(action.get("label", "Approve"))}</a>'
            f'<span style="font-family:{FONT};font-size:12px;color:#6b7280;"> '
            f'&nbsp;replies by email &mdash; nothing exposed to the internet</span></p>')


def card(title, tone, summary="", lines=None, action=None):
    border, _bg, _fg = TONES[tone]
    body = ""
    if summary:
        body += (f'<p style="margin:8px 0 0;font-family:{FONT};font-size:14px;'
                 f'line-height:1.5;color:#374151;">{esc(summary)}</p>')
    for line in (lines or []):
        body += (f'<p style="margin:4px 0 0;font-family:{FONT};font-size:13px;'
                 f'line-height:1.5;color:#6b7280;">&bull; {esc(line)}</p>')
    if action:
        body += button(action, tone)
    return (f'<table role="presentation" width="100%" cellpadding="0" cellspacing="0" '
            f'style="border:1.5px solid {border};border-radius:12px;background:#ffffff;'
            f'margin:0 0 12px;"><tr><td style="padding:14px 16px;">'
            f'<table role="presentation" width="100%" cellpadding="0" cellspacing="0"><tr>'
            f'<td style="font-family:{FONT};font-size:15px;font-weight:700;'
            f'color:#111827;">{esc(title)}</td>'
            f'<td align="right" style="vertical-align:top;">{pill(tone.upper(), tone)}</td>'
            f'</tr></table>{body}</td></tr></table>')


def feed_card(feed):
    tone = feed.get("status", "info")
    if tone not in TONES:
        tone = "info"
    return card(feed.get("title", "Untitled feed"), tone,
                feed.get("summary", ""), feed.get("lines"), feed.get("action"))


def alert_card(a):
    labels = a.get("labels", {})
    ann = a.get("annotations", {})
    name = labels.get("alertname", "unnamed alert")
    tone = "urgent" if labels.get("severity") == "critical" else "warn"
    what = ann.get("description") or ann.get("summary") or \
        "A monitored condition crossed its alert threshold."
    return card(f"Alert firing: {name}", tone, what,
                [f"instance: {labels['instance']}"] if labels.get("instance") else None)


def render(cards_html, verdict, any_urgent):
    today = date.today().strftime("%A %d %B")
    banner = ""
    if any_urgent:
        banner = ('<table role="presentation" width="100%" cellpadding="0" cellspacing="0" '
                  'style="background:#fdecec;border:1.5px solid #e74c3c;border-radius:10px;'
                  'margin:0 0 14px;"><tr><td style="padding:10px 16px;font-family:' + FONT +
                  ';font-size:13px;font-weight:700;color:#c0392b;">'
                  'Something below needs you today &mdash; it&rsquo;s marked in red.</td></tr></table>')
    return (f'<!doctype html><html><head><meta charset="utf-8"></head>'
            f'<body style="margin:0;padding:0;background:#f3f4f6;">'
            f'<table role="presentation" width="100%" cellpadding="0" cellspacing="0" '
            f'style="background:#f3f4f6;"><tr><td align="center" style="padding:26px 10px;">'
            f'<table role="presentation" width="640" cellpadding="0" cellspacing="0" '
            f'style="width:640px;max-width:100%;">'
            f'<tr><td style="padding:0 2px 4px;font-family:{FONT};font-size:20px;'
            f'font-weight:800;color:#111827;">{esc(SITE_NAME)} &middot; {today}</td></tr>'
            f'<tr><td style="padding:0 2px 16px;font-family:{FONT};font-size:14px;'
            f'line-height:1.5;color:#374151;">{verdict}</td></tr>'
            f'<tr><td>{banner}{cards_html}</td></tr>'
            f'<tr><td style="padding:8px 2px 0;font-family:{FONT};font-size:12px;'
            f'color:#9ca3af;">This is the one email this lab sends per day. '
            f'Add a signal by dropping a JSON file in the feeds folder &mdash; '
            f'the digest does the rest.</td></tr>'
            f'</table></td></tr></table></body></html>')


def text_version(items, verdict_plain):
    lines = [f"{SITE_NAME} — {date.today().strftime('%A %d %B')}", verdict_plain, ""]
    for title, tone, summary in items:
        lines.append(f"* [{tone.upper()}] {title}" + (f" — {summary}" if summary else ""))
    lines.append("")
    lines.append("(The HTML version has the approve buttons.)")
    return "\n".join(lines)


# ------------------------------------------------------------------ sending --

def send(subject, text_body, html_body):
    msg = EmailMessage()
    msg["From"] = FROM_ADDR
    msg["To"] = ", ".join(RECIPIENTS)
    msg["Subject"] = subject
    msg.set_content(text_body)                    # plain-text part first,
    msg.add_alternative(html_body, subtype="html")  # HTML as the alternative
    try:
        p = subprocess.run(["msmtp", "-t"], input=msg.as_bytes(),
                           capture_output=True)
    except FileNotFoundError:
        sys.exit("msmtp not found — set up the msmtp + Gmail playbook first.")
    if p.returncode != 0:
        sys.exit("msmtp failed: " + p.stderr.decode(errors="replace").strip())


def main():
    feeds = read_feeds()
    alerts = prometheus_alerts()

    cards_html = ""
    items = []
    if alerts is None:
        cards_html += card("Prometheus didn't answer", "warn",
                           f"The digest couldn't reach {PROM_URL} — the monitoring "
                           "stack itself may be down.")
        items.append(("Prometheus didn't answer", "warn", "monitoring unreachable"))
    for a in (alerts or []):
        cards_html += alert_card(a)
        items.append((f"Alert firing: {a.get('labels', {}).get('alertname', '?')}",
                      "urgent" if a.get("labels", {}).get("severity") == "critical"
                      else "warn", ""))
    for f in feeds:
        cards_html += feed_card(f)
        tone = f.get("status", "info")
        items.append((f.get("title", "?"), tone if tone in TONES else "info",
                      f.get("summary", "")))
    if not items:
        cards_html = card("Nothing reported", "info",
                          f"No feeds in {FEED_DIR} and no alert source configured. "
                          "The digest works — it just has nothing to say yet.")
        items = [("Nothing reported", "info", "")]

    n_attn = sum(1 for _, tone, _ in items if tone in ("warn", "urgent"))
    any_urgent = any(tone == "urgent" for _, tone, _ in items)
    if any_urgent:
        verdict = ('<span style="color:#c0392b;font-weight:700;">Something needs '
                   'you today.</span> The red cards are the reason this email exists.')
        verdict_plain = "Something needs you today — see the red items."
    elif n_attn:
        s = "s" if n_attn != 1 else ""
        verdict = (f'Everything&rsquo;s running normally. {n_attn} thing{s} would '
                   'like your attention when you have a minute &mdash; none are urgent.')
        verdict_plain = (f"Everything's running normally. {n_attn} thing{s} would "
                         "like your attention — none urgent.")
    else:
        verdict = "All quiet. Nothing needs you today."
        verdict_plain = "All quiet. Nothing needs you today."

    subject = "%s %s%s" % (SITE_NAME, date.today().strftime("%a %d %b"),
                           " — NEEDS YOU" if any_urgent else "")
    doc = render(cards_html, verdict, any_urgent)
    text = text_version(items, verdict_plain)

    if DRY:
        open(PREVIEW, "w", encoding="utf-8").write(doc)
        print(f"dry run: wrote {PREVIEW}")
        print(f"subject: {subject}")
        print(f"cards: {len(items)}  attention: {n_attn}  urgent: {any_urgent}")
        return
    send(subject, text, doc)


if __name__ == "__main__":
    main()
PYEOF
chmod 0755 /usr/local/bin/daily-digest.py

# 3) Open it and make the values yours: RECIPIENTS, FROM_ADDR, APPROVE_TO,
#    PROM_URL (leave blank to skip Prometheus), SITE_NAME.
${EDITOR:-nano} /usr/local/bin/daily-digest.py

# 4) Two sample feeds so the first render isn't empty. Delete them once
#    your real producers exist.
cat > /var/lib/digest-feeds/10-backups.json <<'EOF'
{"title": "Backups", "status": "ok",
 "summary": "Last night's backups all finished.",
 "lines": ["3 of 3 guests backed up to the backup server",
           "Newest snapshot finished at 01:12 this morning"]}
EOF
cat > /var/lib/digest-feeds/90-disk.json <<'EOF'
{"title": "Disk getting full", "status": "warn",
 "summary": "Storage local-lvm is at 84% - time to plan a cleanup.",
 "action": {"label": "Approve - clean it up",
            "subject": "APPROVE: storage cleanup",
            "body": "Approved - prune old ISOs and stale snapshots on local-lvm."}}
EOF

# 5) Preview without sending — writes /tmp/digest-preview.html. Open that
#    in a browser and admire your one email.
/usr/local/bin/daily-digest.py --dry-run

# 6) Send yourself one for real, right now.
/usr/local/bin/daily-digest.py

# 7) Then make it a habit: one email, 08:30, every morning.
cat > /etc/cron.d/daily-digest <<'EOF'
30 8 * * * root /usr/local/bin/daily-digest.py >> /var/log/daily-digest.log 2>&1
EOF