Automatically add a mutt alias for the sender of each email you open

auto_add_alias.sh

#!/bin/sh

# Automatically add a mutt alias for the sender of each email you open.
# To use it, add to your muttrc (assuming the script is in your $PATH):
#
#   set alias_file=~/.mutt/aliases
#   set display_filter = 'auto-add_alias.sh ~/.mutt/aliases'
#
# Originally from https://web.archive.org/web/20130307065724/http://wcm1.web.rice.edu/mutt-tips.html and
# refined at https://github.com/teddywing/mutt-alias-auto-add

MESSAGE="$(cat)"
echo "${MESSAGE}"

alias_file="$1"
if [ -z "$alias_file" ]; then
  if command -v mutt >/dev/null 2>&1; then
    alias_file="$(mutt -Q "alias_file")"
  elif [ -f "$HOME/.muttrc" ]; then
    alias_file=$(grep -E --only-matching --no-filename '^\s*set\s+alias_file\s*=.*$' "$HOME/.muttrc")
  fi
  alias_file=$(echo "${alias_file}" | grep -E --only-matching '[^=]+$' -)
fi
alias_file=$(eval echo "${alias_file}")
alias_file=$(printf "%s" "$alias_file" | sed "s|~|$HOME|")

if ! [ -f "$alias_file" ]; then
  echo "No alias file found. Exiting!"
  exit 1
fi

# - Unfold and decode the From header (RFC 5322, RFC 2047).
# - Extract email and display name (prefer <...> form; otherwise first email token).
# - Derive alias: from display name (first-last) or sanitized local-part.
# - Normalize display name for storage and quote it.
# - Print one mutt alias line or nothing if no email was found.

NEWALIAS="$(
  # Unfold a possibly multiline From header (continues on lines starting with whitespace).
  FROM_UNFOLDED=$(
    printf "%s" "$MESSAGE" | awk '
      BEGIN { found=0 }
      /^[Ff]rom:[[:space:]]*/ && !found {
        found=1
        sub(/^[Ff]rom:[[:space:]]*/, "", $0)
        printf "%s", $0
        next
      }
      found && /^[[:space:]]/ {
        sub(/^[[:space:]]+/, " ")
        printf "%s", $0
        next
      }
      found { exit }
    '
  )

  # Trim surrounding whitespace.
  FROM_UNFOLDED=$(printf "%s" "$FROM_UNFOLDED" | sed -E 's/^[[:space:]]+//; s/[[:space:]]+$//')

  # Decode RFC 2047 encoded-words if possible.
  if command -v python3 >/dev/null 2>&1; then
    FROM_DECODED=$(python3 - "$FROM_UNFOLDED" <<'PY'
import sys
from email.header import decode_header, make_header
s = sys.argv[1]
try:
    print(str(make_header(decode_header(s))), end='')
except Exception:
    print(s, end='')
PY
)
  elif perl -MEncode::MIME::Header -e 1 >/dev/null 2>&1; then
    FROM_DECODED=$(perl -CS -MEncode -e 'binmode STDOUT, ":encoding(UTF-8)"; $_=shift; print decode("MIME-Header", $_)' -- "$FROM_UNFOLDED" 2>/dev/null)
  else
    FROM_DECODED=$FROM_UNFOLDED
  fi

  # Extract email address.
  EMAIL=$(printf "%s" "$FROM_DECODED" | sed -nE 's/.*<([^>]*)>.*/\1/p')
  if [ -z "$EMAIL" ]; then
    EMAIL=$(printf "%s" "$FROM_DECODED" | grep -Eo '[[:alnum:]._%+-]+@([[:alnum:]-]+\.)+[[:alpha:]]{2,}' | head -n1)
  fi
  [ -n "$EMAIL" ] || exit 0

  # Extract raw display name and drop RFC 5322 quoted-string wrappers.
  NAME=$(
      printf "%s" "$FROM_DECODED" \
        | sed 's/<[^>]*>.*$//' \
        | sed -E '
          s/^[[:space:]]+//; s/[[:space:]]+$//;         # trim
          s/"([^"]*)"/\1/g;                             # unquote tokens
          s/[[:space:]]+/ /g;                           # collapse spaces
          s/^[[:space:]]+//; s/[[:space:]]+$//          # trim again
          '
      )

  # Reorder "Last, First Middle" -> "First Middle Last" for alias derivation.
  if printf "%s" "$NAME" | grep -Eq '^[^,]+,[[:space:]]*[^,]+$'; then
    NAME=$(printf "%s" "$NAME" | sed -E 's/^([^,]+),[[:space:]]*(.+)$/\2 \1/')
  fi

  # Derive alias from display name when present.
  ALIAS=
  if [ -n "$NAME" ]; then
    NORM="$NAME"
    if command -v iconv >/dev/null 2>&1; then
      NORM=$(printf "%s" "$NORM" | iconv -f UTF-8 -t ASCII//TRANSLIT 2>/dev/null || printf "%s" "$NORM")
    fi
    NORM=$(printf "%s" "$NORM" | tr '[:upper:]' '[:lower:]')
    TOKENS=$(printf "%s" "$NORM" | sed -E 's/[^[:alnum:]-]+/ /g; s/[[:space:]]+/ /g; s/^[[:space:]]+//; s/[[:space:]]+$//')
    if [ -n "$TOKENS" ]; then
      FIRST=$(printf "%s\n" "$TOKENS" | awk '{print $1}')
      LAST=$(printf "%s\n" "$TOKENS" | awk '{print $NF}')
      if [ "$FIRST" != "$LAST" ]; then
        ALIAS="${FIRST}-${LAST}"
      else
        ALIAS="$FIRST"
      fi
    fi
  fi

  # Fallback alias from local-part.
  if [ -z "$ALIAS" ]; then
    LOCALPART=$(printf "%s" "$EMAIL" | sed 's/@.*$//')
    ALIAS=$(printf "%s" "$LOCALPART" | tr '[:upper:]' '[:lower:]' | sed -E 's/[^[:alnum:]]+/-/g; s/^-+//; s/-+$//; s/-{2,}/-/g')
  fi

  # Normalize display name for storage (collapse whitespace) and escape remaining quotes.
  NAME_OUT=$(
      printf "%s" "$NAME" \
        | sed -E 's/[[:space:]]+/ /g; s/^[[:space:]]+//; s/[[:space:]]+$//' \
        | sed 's/"/\\"/g'
    )

  # Print one alias line.
  printf 'alias %s "%s" <%s>\n' "$ALIAS" "$NAME_OUT" "$EMAIL"
)"

[ -n "$NEWALIAS" ] && ! grep -Fxq "$NEWALIAS" "$alias_file" && printf '%s\n' "$NEWALIAS" >> "$alias_file"