#!/bin/bash
# Postfix IP-warmup scheduler.
#
# Gradually expands the outbound sending-IP rotation pool over a warmup window,
# so we don't blast 20 brand-new IPs at consumer ISPs on day one (which looks
# like snowshoe spam and torches reputation).
#
# IP layout:
#   .90 / mta01  -> dedicated Yahoo/AOL recovery IP (transport: yahooslow)
#   .91-.109 / mta02-mta20 -> rotation pool (transports: out02..out20)
#
# transport_maps = hash:/etc/postfix/transport, randmap:{<active pool>}
#   - hash routes yahoo/aol -> yahooslow (the dedicated .90 trickle)
#   - randmap round-robins the source IP across the *active* rotation pool
#
# This script (run daily by cron) recomputes the active pool from the warmup
# start date and reloads Postfix only when the pool changes. It never shrinks.
#
# Run once with `--start` to stamp the start date.
set -euo pipefail

STATE=/etc/postfix/pw-warmup-start
MAINCF=/etc/postfix/main.cf
POSTCONF=/usr/sbin/postconf
POSTFIX=/usr/sbin/postfix

# Rotation transports. .90 is Yahoo-dedicated, not in rotation. out02/03/04
# (.91/.92/.93) were reputation-torched by the May 30-31 over-volume blast and
# are retired. Warmup starts at fresh out05 (.94).
ALL=(out05 out06 out07 out08 out09 out10 out11 \
     out12 out13 out14 out15 out16 out17 out18 out19 out20)

if [ "${1:-}" = "--start" ]; then
  date +%s | sudo tee "$STATE" >/dev/null
  echo "warmup start stamped: $(date)"
fi
[ -f "$STATE" ] || date +%s | sudo tee "$STATE" >/dev/null

START=$(cat "$STATE"); NOW=$(date +%s); DAYS=$(( (NOW - START) / 86400 ))

# Warmup schedule: day-since-start -> active rotation IPs
if   [ "$DAYS" -le 3 ];  then N=3
elif [ "$DAYS" -le 7 ];  then N=5
elif [ "$DAYS" -le 11 ]; then N=8
elif [ "$DAYS" -le 17 ]; then N=12
elif [ "$DAYS" -le 24 ]; then N=16
else N=16; fi

# Safety: never request more transports than exist in ALL.
if [ "$N" -gt "${#ALL[@]}" ]; then N=${#ALL[@]}; fi

POOL=""
for ((i=0; i<N; i++)); do POOL="${POOL}${ALL[$i]}:,"; done
POOL="${POOL%,}"
NEWVAL="hash:/etc/postfix/transport, randmap:{${POOL}}"

CUR=$($POSTCONF -h transport_maps 2>/dev/null || echo "")
if [ "$CUR" != "$NEWVAL" ]; then
  sudo $POSTCONF -e "transport_maps=${NEWVAL}"
  sudo $POSTFIX reload >/dev/null 2>&1 || true
  logger -t pw-warmup "day $DAYS -> $N rotation IPs active"
  echo "$(date '+%F %T') warmup: day=$DAYS active_rotation_ips=$N"
else
  echo "$(date '+%F %T') warmup: day=$DAYS active_rotation_ips=$N (no change)"
fi