#!/usr/bin/env bash
#
# JbTecWiz Support Centre -- generated fix script
#
# Fault : Apache will not start -- port in use, ServerName, or a bad module
# Fix   : Find what already holds the port
# Source: https://jbtecwiz.com/support/lnx-web-apache-start
#
# Run as     : Root shell
# Expect     : 15 minutes
# Risk       : medium
# Reversible : yes
#
# WHEN THIS IS THE RIGHT FIX
#   Address already in use.
#
# HOW TO UNDO IT
#   Re-enable whichever service was disabled.
#
# Walks the fix one step at a time and asks before each. Steps with no
# command are yours to do -- it prints those and waits. DRYRUN=1 prints
# without executing; UNATTENDED=1 does not ask.
#
# --------------------------------------------------------------------
# NO WARRANTY - USE AT YOUR OWN RISK
#
# This script is provided by JbTecWiz as-is and with no warranty of any
# kind, express or implied. You run it entirely at your own risk.
#
# JbTecWiz accepts no liability for any loss or damage arising from its
# use, including but not limited to data loss, downtime, or configuration
# changes that turn out to be wrong for your system.
#
# You are responsible for reading this script before running it, for
# satisfying yourself that it suits the machine in front of you, and for
# having a working backup first. Some steps cannot be undone.
# --------------------------------------------------------------------

set -uo pipefail
DRYRUN="${DRYRUN:-0}"
UNATTENDED="${UNATTENDED:-0}"
failed=0

if [ "$(id -u)" -ne 0 ]; then
  echo "  This fix is documented as needing root. Re-run with sudo." >&2
  exit 3
fi

rule() { printf "\n%s\n" "$(printf '-%.0s' $(seq 1 70))"; if [ $# -gt 0 ]; then echo "$1"; fi; }
prose() { echo "$1" | fold -s -w 74 | sed "s/^/  /"; }

# Returns 0 when the caller should run the command, 1 when it should not.
# A manual step always returns 1 -- there is nothing for the caller to run.
step() {  # step <n> <do> <why> <manual|cmd> [command lines...]
  local n="$1" dotext="$2" why="$3" mode="$4"; shift 4
  rule "  Step $n of 4"
  prose "$dotext"
  if [ -n "$why" ]; then echo; prose "$why"; fi
  if [ "$mode" = "manual" ]; then
    echo; echo "  -> Do this yourself, then press Enter to carry on."
    if [ "$UNATTENDED" = "0" ] && [ "$DRYRUN" = "0" ]; then read -r _; fi
    return 1
  fi
  echo; printf "    %s\n" "$@"; echo
  if [ "$DRYRUN" = "1" ]; then echo "  (dry run -- not executed)"; return 1; fi
  if [ "$UNATTENDED" = "0" ]; then
    read -r -p "  Run this step? [Y]es / [S]kip / [Q]uit " a
    case "$a" in
      [Qq]*) echo "  Stopped at your request."; exit 0 ;;
      [Ss]*) echo "  Skipped."; return 1 ;;
    esac
  fi
  return 0
}

rule
echo "  Apache will not start -- port in use, ServerName, or a bad module"
echo "  Find what already holds the port"
echo
echo "  Risk: medium   Reversible   15 minutes"
echo
prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.'
rule
echo
if [ "$UNATTENDED" = "0" ] && [ "$DRYRUN" = "0" ]; then
  read -r -p "  Ready? [y/N] " go
  case "$go" in [Yy]*) ;; *) echo "  Nothing was changed."; exit 0;; esac
fi

if step 1 'Find the process.' '' cmd 'sudo ss -tlnp | grep -E '\'':80 |:443 '\''' 'sudo fuser -v 80/tcp 443/tcp'; then
  sudo ss -tlnp | grep -E ':80 |:443 '
  sudo fuser -v 80/tcp 443/tcp
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 1 failed. The rest of the fix may depend on it." >&2
  fi
fi

if step 2 'It is usually nginx installed alongside Apache, or an old Apache process that did not exit.' 'Both web servers installed and both enabled is extremely common after following two different guides. Whichever starts first wins the port and the other fails at every boot.' cmd 'systemctl is-active nginx apache2 httpd 2>/dev/null' 'ps aux | grep -E '\''apache|httpd|nginx'\'' | grep -v grep'; then
  systemctl is-active nginx apache2 httpd 2>/dev/null
  ps aux | grep -E 'apache|httpd|nginx' | grep -v grep
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 2 failed. The rest of the fix may depend on it." >&2
  fi
fi

if step 3 'Decide which one should own the port and disable the other.' '' cmd 'sudo systemctl disable --now nginx' 'sudo systemctl enable --now apache2'; then
  sudo systemctl disable --now nginx
  sudo systemctl enable --now apache2
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 3 failed. The rest of the fix may depend on it." >&2
  fi
fi

if step 4 'If both are wanted, put one behind the other on a different port rather than fighting over 80.' '' cmd 'sudo sed -i '\''s/^Listen 80$/Listen 8080/'\'' /etc/apache2/ports.conf' 'sudo systemctl restart apache2'; then
  sudo sed -i 's/^Listen 80$/Listen 8080/' /etc/apache2/ports.conf
  sudo systemctl restart apache2
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 4 failed. The rest of the fix may depend on it." >&2
  fi
fi

rule "  Confirm it worked"
prose 'The intended server is listening and answering.'
if [ "$DRYRUN" = "0" ]; then
  sudo ss -tlnp | grep -E ':80 |:8080 '
  curl -sI http://localhost/ | head -3
fi

rule
if [ "$failed" -gt 0 ]; then
  echo "  Finished with $failed failed step(s)."
  echo "  Read the full write-up at https://jbtecwiz.com/support/lnx-web-apache-start"
else
  echo "  Finished."
fi
echo
prose 'To undo: Re-enable whichever service was disabled.'
rule