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

__prompt_git_status() {
  # Generate a git branch/status prompt.
  # Based on git-prompt.sh by Shawn O. Pearce <spearce@spearce.org>.
  # Arguments:
  #   $1					The printf format string for the prompt.  Must include %s.
  # Environment variables:
  #   GIT_PROMPT_SHOW_TYPE=1			Show type of repository (Bare, Shallow).
  #   GIT_PROMPT_SHOW_UPSTREAM=1		Show status of this repository compaired to upstream:
  #							?? - No upstream set.
  #							== - Working tree is equal to upstream.
  #							<> - Divergent from upstream.
  #							>> or >x - Working tree is ahead of upstream (x = commits ahead when used with next option).
  #							<< or <x - Working tree is behind upstream (x = commits behind when used with next option).
  #   GIT_PROMPT_SHOW_UPSTREAM_EXTENDED=1	In addition to upstream status, show the number of commits difference (inplies above).
  #   GIT_PROMPT_SHOW_IGNORED=1			Show a ! if the current directory is ignored, or _ if the git operation was timed out.
  #   GIT_PROMPT_SHOW_UNSTAGED=1		Show a * if there are unstaged changes (superceeded by above).
  #   GIT_PROMPT_SHOW_UNCOMMITTED=1		Show a & if there are staged but uncommitted changes (superceeded by above).
  #   GIT_PROMPT_SHOW_UNTRACKED=1		Show a + if there are untracked files in the working directory (superceeded by above).
  #   GIT_PROMPT_SHOW_STASH=1			Show a $ if there is a stash in this repository (superceeded by above).
  # Displays:					The printf formatted git prompt based upon $1 and the environment vaiables above, for example:
  #							S:branch_name >5 *
  # Returns:					0 = Produced a prompt successfully.
  #						1 = An error occured.
  local BRANCH COUNT GIT_PROMPT GIT_PROMPT_MARKER_SET GIT_REPO_INFO IFS=$'\n'

  # Bail out if there's no format argument given, or it doesn't contain %s
  (( $# !=  1 )) || [[ "$1" != *%s* ]] && return 1

  # Get some repository information.
  # shellcheck disable=SC2207
  GIT_REPO_INFO=( $( git rev-parse --is-bare-repository --is-shallow-repository --is-inside-git-dir --is-inside-work-tree 2>/dev/null) ) || return 1

  # Generate the prompt.
  if [[ "${GIT_REPO_INFO[2]}" == "true" ]]; then
    # In the git directory, use a special branch marker.
    GIT_PROMPT+="!GIT_DIR!"
  elif [[ "${GIT_REPO_INFO[3]}" == "true" ]]; then
    # In the working directory, generate the prompt.
    # Add type markers.
    [[ -n "$GIT_PROMPT_SHOW_TYPE" ]] && {
      if [[ "${GIT_REPO_INFO[0]}" == "true" ]]; then
        GIT_PROMPT+="B:"
      elif [[ "${GIT_REPO_INFO[1]}" == "true" ]]; then
        GIT_PROMPT+="S:"
      fi
    }

    # Add the branch or a no commits marker.
    BRANCH="$(git rev-parse --abbrev-ref HEAD 2>/dev/null)"
    if [[ "$BRANCH" == "HEAD" ]]; then
      GIT_PROMPT+="?NO COMMITS?"

      # Output the prompt and escape early.
      # shellcheck disable=SC2059
      printf -- "$1" "$GIT_PROMPT"
      return 0
    else
      GIT_PROMPT+="$BRANCH"
    fi

    # Add upstream status.
    [[ -n "$GIT_PROMPT_SHOW_UPSTREAM" ]] || [[ -n "$GIT_PROMPT_SHOW_UPSTREAM_EXTENDED" ]] && {
      COUNT="$(git rev-list --count --left-right "${BRANCH:+refs/prefetch/remotes/origin/}${BRANCH:-@{upstream\}}...HEAD" 2>/dev/null | tr '[:blank:]' ' ')"
      case "$COUNT" in
        "")
          # No upstream.
          GIT_PROMPT+=" ??"
        ;;
        "0 0")
          # Equal to upstream.
          GIT_PROMPT+=" =="
        ;;
        "0 "*)
          # Ahead of upstream.
          GIT_PROMPT+=" >"
          if [[ -n "$GIT_PROMPT_SHOW_UPSTREAM_EXTENDED" ]]; then
            # Show the number of the difference.
            GIT_PROMPT+="${COUNT#0 }"
          else
            GIT_PROMPT+=">"
          fi
        ;;
        *" 0")
          # Behind upstream.
          GIT_PROMPT+=" <"
          if [[ -n "$GIT_PROMPT_SHOW_UPSTREAM_EXTENDED" ]]; then
            # Show the number of the difference.
            GIT_PROMPT+="${COUNT% 0}"
          else
            GIT_PROMPT+="<"
          fi
        ;;
        *)
          # Divergent from upstream.
          GIT_PROMPT+=" <>"
        ;;
      esac
    }

    # Add a marker if directory is ignored, there's unstaged files, uncommitted changes, untracked files or a stash.
    [[ -n "$GIT_PROMPT_SHOW_IGNORED" ]] && git check-ignore . >/dev/null 2>&1 && {
      GIT_PROMPT+=" !"
      GIT_PROMPT_MARKER_SET=1
    }
    [[ -z "$GIT_PROMPT_MARKER_SET" ]] && [[ -n "$GIT_PROMPT_SHOW_UNSTAGED" ]] && {
      timeout --signal=KILL 2s git ls-files --modified --exclude-standard --directory --error-unmatch -- ':/*' >/dev/null 2>&1
      ERR=$?
      if (( ERR == 124 )) || (( ERR == 137 )); then
        GIT_PROMPT+=" _"
        GIT_PROMPT_MARKER_SET=1
      elif (( ERR == 0 )); then
        GIT_PROMPT+=" *"
        GIT_PROMPT_MARKER_SET=1
      fi
    }
    [[ -z "$GIT_PROMPT_MARKER_SET" ]] && [[ -n "$GIT_PROMPT_SHOW_UNCOMMITTED" ]] && ! git diff --name-only --cached --exit-code >/dev/null 2>&1 && {
      GIT_PROMPT+=" &"
      GIT_PROMPT_MARKER_SET=1
    }
    [[ -z "$GIT_PROMPT_MARKER_SET" ]] && [[ -n "$GIT_PROMPT_SHOW_UNTRACKED" ]] && {
      timeout --signal=KILL 2s git ls-files git ls-files --others --exclude-standard --directory --error-unmatch -- ':/*' >/dev/null 2>&1
      ERR=$?
      if (( ERR == 124 )) || (( ERR == 137 )); then
        GIT_PROMPT+=" _"
        GIT_PROMPT_MARKER_SET=1
      elif (( ERR == 0 )); then
        GIT_PROMPT+=" +"
        GIT_PROMPT_MARKER_SET=1
      fi
    }
    [[ -z "$GIT_PROMPT_MARKER_SET" ]] && [[ -n "$GIT_PROMPT_SHOW_STASH" ]] && git rev-parse --verify --quiet refs/stash >/dev/null && {
      GIT_PROMPT+=" $"
      GIT_PROMPT_MARKER_SET=1
    }
  fi

  # Output the prompt.
  # shellcheck disable=SC2059
  printf -- "$1" "$GIT_PROMPT"

  return 0
}

__prompt_user_colour() {
  # Determine the colour of the username in the prompt.

  if [[ "$LOGNAME" == "root" ]]; then
    printf "%s" "1;31m"		# Bright Red.
  elif [[ "$LOGNAME" == "tadgy" ]]; then
    printf "%s" "1;32m"		# Bright Green.
  else
    printf "%s" "1;36m"		# Bright Cyan.
  fi

  return 0
}

__git_prompt_command() {
  # Perform git actions.
  # Environment variables:
  #   GIT_DISABLE_PROMPT_PREFETCH=1	Disable automatic 'prefetch' of upstream refs.
  #					This can also be disabled on a per repository basis using:
  #						git config ---local -replace-all --type bool script.DisablePromptPrefetch true
  # Returns:				0 = Tasks completed successfully.
  #					1 = An error occured.
  local GIT_REPO_INFO LC_ALL="C" NOW REPO_TIMESTAMP TIMESTAMP_VAR

  # shellcheck disable=SC2207
  GIT_REPO_INFO=( $( git rev-parse --is-inside-work-tree --show-toplevel 2>/dev/null) ) || return 1

  # Only process if in a work directory.
  [[ "${GIT_REPO_INFO[0]}" == "true" ]] && {
    # Run prefetch tasks if not disabled.
    [[ -z "$GIT_DISABLE_PROMPT_PREFETCH" ]] && [[ "$(git config --local --get --type bool script.DisablePromptPrefetch 2>/dev/null)" != "true" ]] && {
      git maintenance run --task=prefetch 2>/dev/null || {
        printf "\\033[1;31m%s\\033[0m\\n" "Git maintenance 'prefetch' task failed." >&2
        return 1
      }
    }

    # The time now.
    if [[ "$PLATFORM" == "Linux" ]]; then
      NOW="$(date +'%s%3N')"
    elif [[ "$PLATFORM" == "Darwin" ]]; then
      NOW="$(perl -e 'use Time::HiRes; printf "%.3f", Time::HiRes::time();')"
      NOW="${NOW/.}"
    fi

    # Determine the timestamp variable name depending on bash version.
    if (( BASH_VERSINFO[0] >= 4 )); then
      TIMESTAMP_VAR="GIT_REPO_TIMESTAMP[${GIT_REPO_INFO[1]//[^[:alnum:]]/_}]"
    else
      # This is going to pollute the environment, but Darwin is a PITA.
      TIMESTAMP_VAR="GIT_REPO_TIMESTAMP_${GIT_REPO_INFO[1]//[^[:alnum:]]/_}"
    fi

    if [[ -n "${!TIMESTAMP_VAR}" ]]; then
      # Monitor the git repo.
      REPO_TIMESTAMP="$(git config --local --get --type int script.AutoMergeLast)"
      (( ${!TIMESTAMP_VAR:-0} < REPO_TIMESTAMP )) && {
        # Display message depending on status.
        if [[ "$(git config --local --get --type bool script.AutoMergeSuccess)" == "true" ]]; then
          printf "\\033[1;32m%s" "Git auto-merge succeeded for this repo."
          if [[ "${GIT_REPO_INFO[1]}" == "$HOME" ]]; then
            printf "  %s\\033[0m\\n" "Re-source .bash* files."
          else
            printf "\\033[0m\\n"
          fi
          # Update the timestamp in the environment.
          declare -g "$TIMESTAMP_VAR"="$NOW"
        else
          printf "\\033[1;31m%s\\033[0m\\n" "Git auto-merge failed for this repo - correct manually." >&2
        fi
      }
    else
      # Just set the timestamp in the environment.
      declare -g "$TIMESTAMP_VAR"="$NOW"
    fi
  }

  return 0
}

__nanorc_prompt_command() {
  # Dynamically handle .nanorc file versions.

  hash nano >/dev/null 2>&1 && {
    # shellcheck disable=SC2155
    local NANO_VER="$(command nano --version | awk '/version/ { print $4 }' | cut -d. -f1)"

    # Darwin specifc .nanorc version.
    [[ "$PLATFORM" == "Darwin" ]] && NANO_VER="darwin"

    if [[ -f "$HOME/.nanorc-$NANO_VER" ]]; then
      if (( NANO_VER <= 4 )); then
        ( cd "$HOME" && ln -sf ".nanorc-$NANO_VER" ".nanorc" )
      else
        # shellcheck disable=SC2139
        alias nano="nano -f \"$HOME/.nanorc-$NANO_VER\""
      fi
    else
      if (( NANO_VER <= 4 )); then
        [[ -L "$HOME/.nanorc" ]] && rm -f "$HOME/.nanorc"
      else
        unalias nano 2>/dev/null
      fi
      printf "\\033[1;31m%s\\033[0m\\n" "No .nanorc for version '$NANO_VER'." >&2
    fi
  }

  return 0
}

__ssh_agent_prompt_command() {
  # If necessary, find and activate a new ssh agent socket before each prompt is displayed.
  # Returns:	0 = All is good.
  #		1 = An error occured.
  local ERR

  if [[ -z "$SSH_AUTH_SOCK" ]]; then
    ERR=2
  else
    ssh-add -l >/dev/null 2>&1
    ERR=$?
  fi
  (( ERR == 2 )) && {
    # Read alternative 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;33m%s\\033[0m\\n" "Connected to existing ssh-agent socket."
      sleep 0.5
    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;31m%s\\033[0m\\n" "Failed to start new ssh-agent - continuing with no agent."
        sleep 0.5
        return 1
      }
      printf "\\033[1;32m%s\\033[0m\\n" "Started new ssh-agent."
      __write_ssh_agents
      sleep 0.5
    fi
  }

  return 0
}

__find_ssh_agent_sock() {
  # Find an *active* ssh agent socket.
  # Returns:	0 = Found an active socket.
  #		1 = Did not find a viable socket.
  local I

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

  return 1
}

__read_ssh_agents() {
  # Read all the known ssh agent sockets into an array.
  # Returns:	0 = Processed and read the agents file without issue.
  #		1 = Error processing/reading the agents file.
  local ERR I SOCK

  [[ ! -e "$HOME/.ssh/agents" ]] && touch "$HOME/.ssh/agents"

  # Lock the ~/.ssh/agents file.
  if [[ "$PLATFORM" == "Linux" ]]; then
    # Linux has 'flock', thankfully.
    exec 9<"$HOME/.ssh/agents" && flock -E 10 -e -w 0.5 9
    ERR=$?
    if (( ERR == 10 )); then
      printf "\\033[1;31m%s\\033[0m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2
      return 1
    elif (( ERR > 0 )); then
      printf "\\033[1;31m%s\\033[0m\\n" "Flock usage error." >&2
      return 1
    fi

    # Make note of the mtime for use in write_ssh_agents.
    SSH_AGENTS_MTIME="$(stat --format=%.9Y "$HOME/.ssh/agents")"
  elif [[ "$PLATFORM" == "Darwin" ]]; then
    # Do locking the sucky way on macOS.
    for ((I = 0; I <= 5; I++)); do
      if shlock -p "$$" -f "$HOME/.ssh/agents.lock"; then
        exec 9<"$HOME/.ssh/agents"
        # Make note of the mtime for use in write_ssh_agents.
        SSH_AGENTS_MTIME="$(stat -f %Fm "$HOME/.ssh/agents")"
        ERR=0
        break
      else
        ERR=1
        sleep 0.1
      fi
    done
    (( ERR != 0 )) && {
      printf "\\033[1;31m%s\\033[0m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2
      return 1
    }
  else
    printf "\\033[1;31m%s\\033[0m\\n" "File locking unsupported on '$PLATFORM'." >&2
    return 1
  fi

  # Read the socket list (bash v2+ compliant)
  while read -u 9 -r SOCK; do
    [[ -n "$SOCK" ]] && SSH_AUTH_SOCKS+=("$SOCK")
  done
  ERR=$?

  # Close the file descriptor (which on Linux releases the flock too).
  exec 9<&-

  # On Darwin, release the lock on the file.
  rm -f  "$HOME/.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;31m%s\\033[0m\\n" "Failed to read ssh-agent socket list." >&2
    unset SSH_AUTH_SOCKS SSH_AGENTS_MTIME
    return 1
  }

  return 0
}

__write_ssh_agents() {
  # Write all unique ssh agent sockets into the ~/.ssh/agents file.
  # 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 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 < ${#SSH_AUTH_SOCKS[@]}; I++)); do
    [[ -z "${SSH_AUTH_SOCKS[$I]}" ]] && continue
    for ((J = 0; J < ${#SOCKS[@]}; J++)); do
      [[ "${SSH_AUTH_SOCKS[$I]}" == "${SOCKS[$J]}" ]] && continue 2
    done
    # Only add the socket if it's still viable.
    SSH_AUTH_SOCK="${SSH_AUTH_SOCKS[$I]}" ssh-add -l >/dev/null 2>&1
    (( $? <= 1 )) && SOCKS+=("${SSH_AUTH_SOCKS[$I]}")
  done

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

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

    # Do locking the sucky way on OSX.
    for ((I = 0; I <= 5; I++)); do
      if shlock -p "$$" -f "$HOME/.ssh/agents.lock"; then
        exec 9<"$HOME/.ssh/agents"
        ERR=0
        break
      else
        ERR=1
        sleep 0.1
      fi
    done
    (( ERR != 0 )) && {
      printf "\\033[1;31m%s\\033[0m\\n" "Failed to obtain lock on ~/.ssh/agents." >&2
      return 1
    }
  else
    printf "\\033[1;31m%s\\033[0m\\n" "File locking unsupported on '$PLATFORM'." >&2
    return 1
  fi

  # Write the cleaned array to disk.
  ERR=-1
  [[ -n "${SOCKS[*]}" ]] && { printf "%s\\n" "${SOCKS[@]}" >"$HOME/.ssh/agents" 2>/dev/null; ERR=$?; }

  # Release locks.
  exec 9<&-
  rm -f  "$HOME/.ssh/agents.lock"

  # Error out if the data couldn't be written.
  if (( ERR == -1 )); then
    rm -f "$HOME/.ssh/agents" 2>/dev/null
  elif (( ERR >= 1 )); then
    rm -f "$HOME/.ssh/agents" 2>/dev/null
    printf "\\033[1;31m%s\\033[0m\\n" "Failed to write ssh-agent socket list." >&2
    return 1
  fi

  return 0
}

imagebin() {
  # Throw an image file into an imagebin.

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

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

# 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=1000000
HISTIGNORE="bg:bg *:fg:fg *:jobs:exit:clear:history"
HISTSIZE=1000000
HISTTIMEFORMAT="%d/%m/%y %H:%M:%S  "
history -a
history -r

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

# Git prompt options.
GIT_PROMPT_SHOW_TYPE=1
GIT_PROMPT_SHOW_UPSTREAM=1
GIT_PROMPT_SHOW_UPSTREAM_EXTENDED=1
GIT_PROMPT_SHOW_IGNORED=1
GIT_PROMPT_SHOW_UNSTAGED=1
GIT_PROMPT_SHOW_UNCOMMITTED=1
GIT_PROMPT_SHOW_UNTRACKED=1
GIT_PROMPT_SHOW_STASH=1

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

  # Trim the path in the prompt.
  PROMPT_DIRTRIM=2
  # Coloured username + host + directory:
  PS1='[\[\033[$(__prompt_user_colour)\]\u\[\033[0m\]@\[\033[1;33m\]\h\[\033[0m\]] \[\033[1;34m\]\w\[\033[0m\]$(__prompt_git_status "\[\\033[1;35m\] (%s)\[\\033[0m\]") ->'
else
  # Set the prompts.
  # Coloured username + host + directory:
  # shellcheck disable=SC2154
  PS1='[\[\033[$(__prompt_user_colour)\]\u\[\033[0m\]@\[\033[1;33m\]\h\[\033[0m\]] \[\033[1;34m\]$(printf "%s" "${PWD/#$HOME/~}" | awk -F/ '\''{if (NF>3) {printf ".../" $(NF-1) "/" $NF} else {printf $0}}'\'')\[\033[0m\]$(__prompt_git_status "\[\\033[1;35m\] (%s)\[\\033[0m\]") ->'
fi

# Set the debugger prompt.
# shellcheck disable=SC2155
export PS4='+(\[\033[1;33m\]$?\[\033[0m\]) \[\033[1;34m\]${BASH_SOURCE##*/}\[\033[0m\]${FUNCNAME[0]:+(\[\033[1;32m\]${FUNCNAME[0]}\[\033[0m\])}:\[\033[1;31m\]$LINENO\[\033[0m\]: '

# Common aliases.
hash bc >/dev/null 2>&1 && alias bc='bc -lq'
hash grep >/dev/null 2>&1 && {
  alias egrep='grep -E --color=auto'
  alias fgrep='grep -F --color=auto'
  alias grep='grep --color=auto'
}

# Auto start the ssh agent and add keys for scp/sftp/ssh.
__ssh_agent_prompt_command
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 "$SSH_AUTH_SOCK" ]]; then
    ERR=2
  else
    ssh-add -l >/dev/null 2>&1
    ERR=$?
  fi
  if (( ERR == 1 )); then
    ssh-add
  elif (( ERR == 2 )); then
    __ssh_agent_prompt_command
    ssh-add
  fi
  command "${_EXEC:-${FUNCNAME[0]}}" "$@"
}

# Handle the ~/.gitconfig link.
if [[ -e "$HOME/.gitconfig-$USER@$HOSTNAME" ]]; then
  FILENAME=".gitconfig-$USER@$HOSTNAME"
elif [[ -e "$HOME/.gitconfig-$USER@*.${HOSTNAME#*.}" ]]; then
  FILENAME=".gitconfig-$USER@*.${HOSTNAME#*.}"
elif [[ -e "$HOME/.gitconfig-$USER@*" ]]; then
  FILENAME=".gitconfig-$USER@*"
elif [[ -e "$HOME/.gitconfig-*@$HOSTNAME" ]]; then
  FILENAME=".gitconfig-*@$HOSTNAME"
elif [[ -e "$HOME/.gitconfig-*.${HOSTNAME#*.}" ]]; then
  FILENAME=".gitconfig-*.${HOSTNAME#*.}"
elif [[ -e "$HOME/.gitconfig-default" ]]; then
  FILENAME=".gitconfig-default"
else
  (cd "$HOME" && [[ -L ".gitconfig" ]] && rm -f ".gitconfig")
  printf "%s: %s\\n" "${BASH_SOURCE##*/}" "failed to update .gitconfig symlink" >&2
fi
[[ -n "$FILENAME" ]] && (cd "$HOME" && ln -sf "$FILENAME" ".gitconfig")
unset FILENAME

# Platform specific set up.
if [[ "$PLATFORM" = "Linux" ]]; then
  # Linux specific functions.
  hash ps grep >/dev/null 2>&1 && psgrep() {
    if [[ -n "$1" ]]; then
      # shellcheck disable=SC2009
      ps -auwwx | grep -E --color=always -- "(.*RSS.*|$1)" | grep -F -v '(.*RSS.*|'
    else
      printf "%s: %s\\n" "Usage" "${FUNCNAME[0]} <something>" >&2
      return 1
    fi
  }

  # Linux specific aliases.
  hash diff >/dev/null 2>&1 && alias diff='diff --color=auto -u'
  hash ftpwho >/dev/null 2>&1 && alias ftpwho='ftpwho -v'
  hash gpg2 >/dev/null 2>&1 && alias gpg='command gpg2' && alias gpg2='gpg2 --pinentry-mode=loopback'
  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 nc >/dev/null 2>&1 && alias pastebin='nc termbin.com 9999'
  hash pinfo >/dev/null 2>&1 && alias info='pinfo'
  hash ping >/dev/null 2>&1 && alias ping='ping -b'
elif [[ "$PLATFORM" = "Darwin" ]]; then
  # Darwin specific aliases (some dependant on macports)
  [[ ! -e "/opt/local/libexec/gnubin/df" ]] && alias df='df -kP'
  # shellcheck disable=SC2015
  [[ ! -e "/opt/local/libexec/gnubin//diff" ]] && alias diff='diff -u' || alias diff='diff --color=auto -u'
  hash last less >/dev/null 2>&1 && alias laston='last | less'
  # shellcheck disable=SC2015
  [[ ! -e "/opt/local/libexec/gnubin/ls" ]] && alias ls='ls -bFGO' || alias ls='ls -bFv --color=auto'
  [[ -e "/opt/local/libexec/gnubin/nc" ]] && alias pastebin='nc termbin.com 9999'
  [[ -e "/opt/local/bin/pinfo" ]] && alias info='pinfo'
  hash top >/dev/null 2>&1 && alias top='top -o cpu -S'
else
  printf "%s: %s\\n" "${BASH_SOURCE##*/}" "unsupported platform: $PLATFORM" >&2
fi