# Functions.
_agent_prompt_command() {
  hash ssh-add >/dev/null 2>&1 && {
    local OUTPUT SOCK _PLATFORM="$(uname -s)"
    declare -g _SSH_PROMPT_ERROR_ISSUED
    # Check the ssh agent socket is still alive.
    # Need to work around an ssh-add bug here: ssh-add doesn't always return 2 on failure
    # to contact the agent, so also check if any errors were produced.
    OUTPUT="$(ssh-add -l 2>&1 >/dev/null)"
    if ((${PIPESTATUS[0]} >= 2)) || [[ ! -z "$OUTPUT" ]]; then
      # Auth socket has become unusable, search for a new one.
      SOCK="$(_find_agent_sock)"
      if ((${PIPESTATUS[0]} == 0)); then
        export SSH_AUTH_SOCK="$SOCK"
        _lock_agents_file && {
          if _push_agent_sock; then
            echo "Connected to alternate ssh-agent - you may need to re-add keys."
            _SSH_AGENT_REG_FAILED=0
          else
            echo "$(tput setaf 3)Connected to, but failed to register, alternate ssh-agent - you may need to re-add keys.$(tput op)"
            _SSH_AGENT_REG_FAILED=1
          fi
        }
        _unlock_agents_file
        _SSH_PROMPT_ERROR_ISSUED=0
      else
        # Failed to find a new socket.
        if [[ -z "$(egrep -v '^$' ~/.ssh/agents)" ]]; then
          ((${_SSH_PROMPT_ERROR_ISSUED:-0} == 0)) && {
            echo "$(tput setaf 1)Lost connection to ssh-agent - no alternate available!$(tput op)"
            unset SSH_AUTH_SOCK
            _SSH_PROMPT_ERROR_ISSUED=1
          }
        else
          ((${_SSH_PROMPT_ERROR_ISSUED:-0} == 0)) && {
            echo "$(tput setaf 1)Lost connection to ssh-agent - failed to connect to new agent!$(tput op)"
            unset SSH_AUTH_SOCK
            _SSH_PROMPT_ERROR_ISSUED=1
          }
        fi
      fi
    else
      _SSH_PROMPT_ERROR_ISSUED=0
    fi
  }
}

_clean_agent_socks() {
  local I OUTPUT SSH_AUTH_SOCK
  # Go through the array of sockets and validate each one.
  for ((I = 0; I < ${#SOCKS[@]}; I++)); do
    OUTPUT="$(SSH_AUTH_SOCK="${SOCKS[$I]}" ssh-add -l 2>&1 >/dev/null)"
    ((${PIPESTATUS[0]} >= 2)) || [[ ! -z "$OUTPUT" ]] && {
      unset SOCKS[$I]
    }
  done
}

_find_agent_sock() {
  local I IFS=$'\n' OUTPUT REPLY SOCKS=() SSH_AUTH_SOCK="$SSH_AUTH_SOCK"
  # Load the array of sockets, minus the one we know is unusable.
  if ((${BASH_VERSINFO[0]} >= 4)); then
    mapfile -t SOCKS < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
  else
    while read -r; do
      SOCKS+=("$REPLY")
    done < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
  fi
  # Search backwards through the list to find an active socket.
  for ((I = (${#SOCKS[@]} - 1); I >= 0; I--)); do
    OUTPUT="$(SSH_AUTH_SOCK="${SOCKS[$I]}" ssh-add -l 2>&1 >/dev/null)"
    { ((${PIPESTATUS[0]} <= 1)) && [[ -z "$OUTPUT" ]]; } && [[ ! -z "${SOCKS[$I]}" ]] && {
      printf "%s" "${SOCKS[$I]}"
      return 0
    }
  done
  return 1
}

_lock_agents_file() {
  local I
  # Lock the ~/.ssh/agents file.
  if [[ "$_PLATFORM" == "Linux" ]]; then
    # Linux has 'flock', thankfully.
    if exec 9>~/.ssh/agents.lock && flock -E 10 -w 0.5 9; then
      return 0
    else
      echo "$(tput setaf 1)Failed to obtain lockfile!$(tput op)"
    fi
  elif [[ "$_PLATFORM" == "Darwin" ]]; then
    # Do locking the sucky way on OSX.
    for ((I=0; I < 5; I++)); do
      if shlock -f "/tmp/agents.lock.$$" -p "$$"; then
        return 0
      else
        sleep 0.1
      fi
    done
    [[ "${_GOT_LOCK:-0}" == "0" ]] && echo "$(tput setaf 1)Failed to obtain lockfile!$(tput op)"
  else
    echo "$(tput setaf 1)File locking unsupported - skipping update of agents file!$(tput op)"
  fi
  return 1
}

_pop_agent_sock() {
  local I IFS=$'\n' REPLY SOCKS=()
  # Read the current list of auth sockets.
  if ((${BASH_VERSINFO[0]} >= 4)); then
    mapfile -t SOCKS <~/.ssh/agents
  else
    while read -r; do
      SOCKS+=("$REPLY")
    done <~/.ssh/agents
  fi
  # Remove the last instance of the socket in $SSH_AUTH_SOCK.
  for ((I = (${#SOCKS[@]} - 1); I >= 0; I--)); do
    [[ "${SOCKS[$I]}" == "$SSH_AUTH_SOCK" ]] && {
      unset SOCKS[$I]
      break
    }
  done
  # Clean up any dead sockets - this modifies the SOCKS array.
  _clean_agent_socks
  # Write the new list back to disk.
  printf "%s\n" "${SOCKS[@]}" >~/.ssh/agents
  return $?
}

_push_agent_sock() {
  local IFS=$'\n' REPLY SOCKS=()
  # Read the current list of auth sockets.
  if ((${BASH_VERSINFO[0]} >= 4)); then
    mapfile -t SOCKS <~/.ssh/agents
  else
    while read -r; do
      SOCKS+=("$REPLY")
    done <~/.ssh/agents
  fi
  # Clean up any dead sockets - this modifies the SOCKS array.
  _clean_agent_socks
  # Write the new list back to disk.
  printf "%s\n" "${SOCKS[@]}" "$SSH_AUTH_SOCK" >~/.ssh/agents
  return $?
}

_unlock_agents_file() {
  # Unlock the ~/.ssh/agents file.
  if [[ "$_PLATFORM" == "Linux" ]]; then
    exec 9>&-
  elif [[ "$_PLATFORM" == "Darwin" ]]; then
    rm -f "/tmp/agents.lock.$$"
  fi
}

screen_attach() {
  local TTY SCREENS
  # Only continue if it's not a remote connection, and not inside screen already.
  [[ -z "$SSH_TTY" ]] && [[ -z "$STY" ]] && {
    TTY="$(tty | cut -d/ -f3-)"
    SCREENS="$(screen -list | fgrep -v "Dead" | fgrep "$HOSTNAME" | fgrep "${TTY//\//-}")"
    case "$(echo "${SCREENS:--n}" | wc -l)" in
      0)
        # No screens found - start a new instance.
        screen
        ;;
      1)
        # Just one screen - reconnect.
        screen -dr "${TTY//\//-}.$HOSTNAME"
        ;;
      *)
        # Multiple screens - output a list
        echo "Multiple screens found for $TTY:"
        echo "$SCREENS" | sed -e 's/^/    /g'
        ;;
    esac
  }
}

# Make bash a little more pleasent - these are valid for all versions.
shopt -s cdspell checkhash checkwinsize cmdhist histappend no_empty_cmd_completion

# Exit the shell on a Ctl+D.
IGNOREEOF=0

# History control.
HISTCONTROL="ignoredups"
HISTFILE="$HOME/.bash_history-$(hostname --short)"
HISTFILESIZE=100000
HISTIGNORE="bg:bg *:fg:fg *:jobs:exit:clear:history"
HISTSIZE=-1
HISTTIMEFORMAT="%d/%m/%y %H:%M:%S  "
history -r

# Determine the colour of the username in the prompt.
if (( $(id -u) == 0 )); then
  _COLOUR=1	# Red
else
  _COLOUR=2	# Green
fi

# Version specific set up.
if (( ${BASH_VERSINFO[0]} >= 4 )); then
  # Add to the shopts.
  shopt -s checkjobs dirspell

  # Set the prompts.
  PROMPT_DIRTRIM=2
  # No colour:
  # PS1="[\u@\h] \w ->"
  # Coloured username:
  # PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\h] \w ->"
  # Coloured username + host:
  # PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\[$(tput bold)$(tput setaf 3)\]\h\[$(tput sgr0)\]] \w ->"
  # Coloured username + host + directory:
  PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\[$(tput bold)$(tput setaf 3)\]\h\[$(tput sgr0)\]] \[$(tput bold)$(tput setaf 4)\]\w\[$(tput sgr0)\] ->"
else
  # Set the prompts.
  # No colour:
  # PS1="[\u@\h] \$(echo \"\${PWD/#\$HOME/~}\" | awk -F/ '{if (NF>3) {printf \".../\" \$(NF-1) \"/\" \$NF} else {printf \$0}}') ->"
  # Coloured username:
  # PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\h] \$(echo \"\${PWD/#\$HOME/~}\" | awk -F/ '{if (NF>3) {printf \".../\" \$(NF-1) \"/\" \$NF} else {printf \$0}}') ->"
  # Coloured username + host:
  # PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\[$(tput bold)$(tput setaf 3)\]\h\[$(tput sgr0)\]] \$(echo \"\${PWD/#\$HOME/~}\" | awk -F/ '{if (NF>3) {printf \".../\" \$(NF-1) \"/\" \$NF} else {printf \$0}}') ->"
  # Coloured username + host + directory:
  PS1="[\[$(tput bold)$(tput setaf $_COLOUR)\]\u\[$(tput sgr0)\]@\[$(tput bold)$(tput setaf 3)\]\h\[$(tput sgr0)\]] \[$(tput bold)$(tput setaf 4)\]\$(echo \"\${PWD/#\$HOME/~}\" | awk -F/ '{if (NF>3) {printf \".../\" \$(NF-1) \"/\" \$NF} else {printf \$0}}')\[$(tput sgr0)\] ->"
fi
unset _COLOUR

# Set the debugger prompt.
# PS4="+(\\\$? = \$?) \${BASH_SOURCE##*/}\${FUNCNAME:+(\$FUNCNAME)}:\$LINENO: "
# PS4="+(\[\e[33m\]\\\$? = \$?\[$(tput sgr0)\]) \[$(tput bold)$(tput setaf 4)\]\${BASH_SOURCE##*/}\[$(tput sgr0)\]\${FUNCNAME:+(\[$(tput bold)$(tput setaf 2)\]\$FUNCNAME\[$(tput sgr0)\])}:\[$(tput bold)$(tput setaf 1)\]\$LINENO\[$(tput sgr0)\]: "
export PS4="+(\[\e[33m\]\$?\[$(tput sgr0)\]) \[$(tput bold)$(tput setaf 4)\]\${BASH_SOURCE##*/}\[$(tput sgr0)\]\${FUNCNAME:+(\[$(tput bold)$(tput setaf 2)\]\$FUNCNAME\[$(tput sgr0)\])}:\[$(tput bold)$(tput setaf 1)\]\$LINENO\[$(tput sgr0)\]: "

# The commands to execute before the prompt is displayed.
PROMPT_COMMAND="_agent_prompt_command"

# Platform specific set up.
_PLATFORM="$(uname -s)"
if [[ "$_PLATFORM" = "Linux" ]]; then
  # Linux specific aliases.
  hash ftpwho >/dev/null 2>&1 && alias ftpwho='ftpwho -v'
  hash iftop >/dev/null 2>&1 && alias iftop='TERM=vt100 iftop'
  hash last less >/dev/null 2>&1 && alias laston='last -a | less'
  hash ls >/dev/null 2>&1 && alias ls='ls -bFv --color=auto'
  hash minicom >/dev/null 2>&1 && alias minicom='minicom -m -c on'
  hash mkpasswd >/dev/null 2>&1 && alias pwgen='mkpasswd -m sha512crypt'
  hash pine >/dev/null 2>&1 && alias pine='pine -p "{mail.opensourcerers.net/Service=IMAP/User=darren@afterdark.org.uk/TLS/NoValidate-Cert/NoRsh}.pinerc"'
  hash pinfo >/dev/null 2>&1 && alias info='pinfo'
  hash ping >/dev/null 2>&1 && alias ping='ping -b'

  # Linux specific functions.
  psgrep() {
    ps -auwwx | egrep "(RSS|$1)" | fgrep -v "(RSS|"
  }
elif [[ "$_PLATFORM" = "Darwin" ]]; then
  # Darwin specific aliases.
  hash df >/dev/null 2>&1 && alias df='df -P'
  hash ls >/dev/null 2>&1 && alias ls='ls -bFG'
  hash top >/dev/null 2>&1 && alias top='top -o cpu -S'
else
  echo "${BASH_SOURCE##*/}: unsupported platform: $_PLATFORM" >&2
fi
unset _PLATFORM

# Common aliases.
hash bc >/dev/null 2>&1 && alias bc='bc -lq'
#hash curl >/dev/null 2>&1 && alias pastebin="curl -F 'sprunge=<-' http://sprunge.us"
hash curl >/dev/null 2>&1 && imagebin() { curl -F file="@${1:-}" https://imagebin.ca/upload.php | grep ^url: | cut -d: -f2-; }
hash diff >/dev/null 2>&1 && alias diff='diff -u'
hash egrep >/dev/null 2>&1 && alias egrep='egrep --color=auto'
hash fgrep >/dev/null 2>&1 && alias fgrep='fgrep --color=auto'
hash grep >/dev/null 2>&1 && alias grep='grep --color=auto'
hash nc >/dev/null 2>&1 && alias pastebin='nc termbin.com 9999'
hash screen >/dev/null 2>&1 && alias screen='screen -Ua'