#!/bin/bash - not strictly necessary, but helps nano with syntax highlighting.

__find_ssh_agent_sock() {
  # Returns: 0 = Found an alternative socket.
  #          1 = Did not find a viable socket.
  local ERR I

  # Search the SSH_AUTH_SOCKS array for a viable socket.
  for ((I = 0; I < ${#SSH_AUTH_SOCKS[@]}; I++)); do
    SSH_AUTH_SOCK="${SSH_AUTH_SOCKS[$I]}" ssh-add -l >/dev/null 2>&1
    (( $? < 2 )) && { export SSH_AUTH_SOCK="${SSH_AUTH_SOCKS[$I]}"; break; }
    unset SSH_AUTH_SOCK
  done

  [[ -z "$SSH_AUTH_SOCK" ]] && return 1
  return 0
}

__read_ssh_agents() {
  # Returns: 0 = Processed and read the agents file without issue.
  #          1 = Error processing/read the agents file.
  local ERR FD I SOCK

  [[ ! -e ~/.ssh/agents ]] && touch ~/.ssh/agents

  # Lock the ~/.ssh/agents file.
  if [[ "$(uname -s)" == "Linux" ]]; then
    # Linux has 'flock', thankfully.
    { exec {FD}<~/.ssh/agents && flock -E 10 -e -w 0.5 "$FD"; } || {
      ERR=$?
      if (( ERR == 10 )); then
        printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2
      else
        printf "\\033[1;31;40m%s\\033[0;39m\\n" "Flock usage error." >&2
      fi
      return 1
    }

    # Make note of the mtime for use in write_ssh_agents.
    SSH_AGENTS_MTIME="$(stat --format=%.9Y ~/.ssh/agents)"
  elif [[ "$(uname -s)" == "Darwin" ]]; then
    # Do locking the sucky way on macOS.
    for ((I = 0; I < 6; I++)); do
      if shlock -p "$$" -f ~/.ssh/agents.lock; then
        exec {FD}<~/.ssh/agents
        # Make note of the mtime for use in write_ssh_agents.
        SSH_AGENTS_MTIME="$(stat -f %Fm ~/.ssh/agents)"
        ERR=0
        break
      else
        ERR=1
        sleep 0.1
      fi
    done
    (( ERR != 0 )) && { printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2; return 1; }
  else
    printf "\\033[1;31;40m%s\\033[0;39m\\n" "File locking unsupported on this platform." >&2
    return 1
  fi

  # Read the socket list (bash v3+ compliant)
  while read -u "$FD" -r SOCK; do
    [[ -n "$SOCK" ]] && SSH_AUTH_SOCKS+=("$SOCK")
  done
  ERR=$?

  # Close the file descriptor (which on Linux releases the lock too).
  exec {FD}<&-

  # On Darwin, release the lock on the file.
  rm -f  ~/.ssh/agents.lock

  # Remove the . in the mtime.
  SSH_AGENTS_MTIME="${SSH_AGENTS_MTIME/\.}"

  # Error out if the data couldn't be read.
  (( ERR != 0 )) && { printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to read ssh-agent socket list." >&2; unset SSH_AUTH_SOCKS; return 1; }
  return 0
}

__write_ssh_agents() {
  # Returns: 0 = Processed and wrote the agents file without issue.
  #          1 = Error processing/writing the agents file.
  #          2 = The SSH_AUTH_SOCKS array may be out of date as the agents file'a mtime has changed.
  local FD ERR I J MTIME SOCKS

  # Add the current agent socket to the sockets array.
  SSH_AUTH_SOCKS=("$SSH_AUTH_SOCK" "${SSH_AUTH_SOCKS[@]}")

  # Remove any duplicates from SSH_AUTH_SOCKS.
  for ((I = 0; I < ${#SSH_AUTH_SOCKS[@]}; I++)); do
    for ((J = 0; J < ${#SOCKS[@]}; J++)); do
      [[ "${SSH_AUTH_SOCKS[$I]}" == "${SOCKS[$J]}" ]] && continue 2
    done
    # Only add the socket if it's still viable.
    [[ -n "${SSH_AUTH_SOCKS[$I]}" ]] && {
      SSH_AUTH_SOCK="${SSH_AUTH_SOCKS[$I]}" ssh-add -l >/dev/null 2>&1
      (( $? < 2 )) && SOCKS+=("${SSH_AUTH_SOCKS[$I]}")
    }
  done

  # Lock the ~/.ssh/agents file.
  if [[ "$(uname -s)" == "Linux" ]]; then
    # Make sure SSH_AUTH_SOCKS has the most up to date data.
    MTIME="$(stat --format=%.9Y ~/.ssh/agents)"
    (( ${MTIME/\.} > SSH_AGENTS_MTIME )) && return 2

    # Lock the agents file.
    { exec {FD}>~/.ssh/agents && flock -E 10 -e -w 0.5 "$FD"; } || {
      if (( $? == 10 )); then
        printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2
      else
        printf "\\033[1;31;40m%s\\033[0;39m\\n" "Flock usage error" >&2
      fi
      return 1
    }
  elif [[ "$(uname -s)" == "Darwin" ]]; then
    # Make sure SSH_AUTH_SOCKS has the most up to date data.
    MTIME="$(stat --format=%.9Y ~/.ssh/agents)"
    (( ${MTIME/\.} > SSH_AGENTS_MTIME )) && return 2

    # Do locking the sucky way on OSX.
    for ((I = 0; I < 6; I++)); do
      if shlock -p "$$" -f ~/.ssh/agents.lock; then
        exec {FD}>~/.ssh/agents
        ERR=0
        break
      else
        ERR=1
        sleep 0.1
      fi
    done
    (( ERR != 0 )) && { printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2; return 1; }
  else
    printf "\\033[1;31;40m%s\\033[0;39m\\n" "File locking unsupported on this platform." >&2
    return 1
  fi

  # Write the cleaned array to disk.
  printf "%s\\n" "${SOCKS[@]}" >~/.ssh/agents 2>/dev/null
  ERR=$?

  # Release locks.
  exec {FD}>&-
  rm -f  ~/.ssh/agents.lock

  # Error out if the data couldn't be written.
  (( ERR != 0 )) && { printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to write ssh-agent socket list." >&2; return 1; }
  return 0
}

__ssh_agent_prompt_command() {
  # Returns: 0 = All is good.
  #          1 = And error occured.
  local ERR SSH_AUTH_SOCKS=()

  if [[ -z "$SSH_AUTH_SOCK" ]]; then
    ERR=2
  else
    SSH_AUTH_SOCK="$SSH_AUTH_SOCK" ssh-add -l >/dev/null 2>&1
    ERR=$?
  fi
  (( ERR == 2 )) && {
    # Read previous sockets from ~/.ssh/agents.
    __read_ssh_agents || {
      unset SSH_AUTH_SOCK
      return 1
    }

    # Find a new socket to use.
    if __find_ssh_agent_sock; then
      printf "\\033[1;33;40m%s\\033[0;39m\\n" "Connected to existing ssh-agent socket."
    else
      # Start a new agent.
      eval "$(ssh-agent -s 2>/dev/null | grep -v 'echo'; printf "%s" "ERR=${PIPESTATUS[0]}")"
      (( ERR > 0 )) && { printf "\\033[1;31;40m%s\\033[0;39m\\n" "Failed to start ssh-agent - continuing with no agent." >&2; return 1; }
      printf "\\033[1;32;40m%s\\033[0;39m\\n" "Started new ssh-agent."
    fi

    # Update the agents file.
    while :; do
      __write_ssh_agents
      ERR=$?
      (( ERR == 2 )) &&  { __read_ssh_agents || return 1; } && continue
      (( ERR == 1 )) && return 1
      break
    done
  }
  return 0
}

imagebin() {
  [[ -z "$1" ]] && { printf "%s: %s\\n" "Usage" "${FUNCNAME[0]} <filename>" >&2; return 1; }
  curl -F file="@${1:-}" https://imagebin.ca/upload.php | grep ^url: | cut -d: -f2-
}

# 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%%.*}"
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
  # 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.
  # 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.
export PS4="+(\[\e[1;33;40m\]\$?\[$(tput sgr0)\]) \[$(tput bold)$(tput setaf 4)\]\${BASH_SOURCE##*/}\[$(tput sgr0)\]\${FUNCNAME[0]:+(\[$(tput bold)$(tput setaf 2)\]\${FUNCNAME[0]}\[$(tput sgr0)\])}:\[$(tput bold)$(tput setaf 1)\]\$LINENO\[$(tput sgr0)\]: "

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

# Common aliases.
hash bc >/dev/null 2>&1 && alias bc='bc -lq'
hash diff >/dev/null 2>&1 && alias diff='diff --color=auto -u'
hash grep >/dev/null 2>&1 && alias egrep='grep -E --color=auto'
hash grep >/dev/null 2>&1 && alias fgrep='grep -F --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'
hash scp ssh ssh-add >/dev/null 2>&1 && alias scp='_EXEC=scp ssh'
hash sftp ssh ssh-add >/dev/null 2>&1 && alias sftp='_EXEC=sftp ssh'
hash ssh ssh-add >/dev/null 2>&1 && ssh() {
  local ERR

  if [[ -z "$SSH_AUTH_SOCK" ]]; then
    ERR=2
  else
    SSH_AUTH_SOCK="$SSH_AUTH_SOCK" ssh-add -l >/dev/null 2>&1
    ERR=$?
  fi
  (( ERR == 2 )) && __ssh_agent_prompt_command && ssh-add
  (( ERR == 1 )) && ssh-add
  command "${_EXEC:-${FUNCNAME[0]}}" "$@"
  unset _EXEC
}

# Determine the platform being logged into.
PLATFORM="$(uname -s)"

# Platform specific set up.
if [[ "$PLATFORM" = "Linux" ]]; then
  # Linux specific functions.
  psgrep() {
    [[ -z "$1" ]] && { printf "%s: %s\\n" "Usage" "${FUNCNAME[0]} <something>" >&2; return 1; }
    ps -auwwx | command grep -E --color=always -- "(.*RSS.*|$1)" | grep -F -v "(.*RSS.*|"
  }

  # 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 iotop >/dev/null 2>&1 && alias iotop='TERM=linux iotop'
  hash ip >/dev/null 2>&1 && alias ip='ip -color=auto'
  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 mkpasswd='mkpasswd -m sha512crypt'
  hash mkpasswd >/dev/null 2>&1 && alias pwgen='mkpasswd -m sha512crypt'
  hash pinfo >/dev/null 2>&1 && alias info='pinfo'
  hash ping >/dev/null 2>&1 && alias ping='ping -b'
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