mktoc

#!/bin/sh
# $0 [-d Depth] [FilePath]
DEFAULT_DEPTH=2
MAX_DEPTH=5

# Analyze option & params
if [ "$1" = "-d" ]; then
  depth=$2
  file_path=${3-}
else
  depth=$DEFAULT_DEPTH
  file_path=${1-}
fi

if [ $depth -le 1 -o $depth -gt $MAX_DEPTH ]; then
  echo "Err: ingore -d Depth (${MAX_DEPTH} >= Depth >= 2)" 1>&2
  exit 1
fi

# Make table of contents from markdown
pick_header(){
  grep '^\(#\{2,'"$1"'\}[^#]\|```\)'  \
  | sed '/^```/','/^```/d'            \
  | sed 's/^\(#\{1,\}\) *\(.*\) *$/\1\2/'
}
make_link_path(){
  tr -d '!"#$%&()~=^|{}[]`*@:+;?\<>,./\' \
  | tr -d '！”＃＄％＆（）〜＝＾｜｛｝「」｀＊＠：＋；？￥＜＞、。・' \
  | tr -d "'’"                           \
  | tr '[A-Z ]' '[a-z-]'                \
  | sed 's/^\(.*\)$/#\1/'
}
make_link_title(){
  sed 's/^#\{1,\}\(.*\)$/\1/'
}
make_indent(){
  sed 's/^#\{2\}\(.*\)$/\1/'            \
  | sed 's/^\( *\)#\(#*\).*$/    \1\2/' \
  | sed 's/^\( *\)#\(#*\).*$/    \1\2/' \
  | sed 's/^\( *\)#\(#*\).*$/    \1\2/' \
  | sed 's/^\( *\).*$/\1/'
}
make_toc(){
  while read header; do
    path=$(echo "$header" | make_link_path)
    title=$(echo "$header" | make_link_title)
    indent=$(echo "$header" | make_indent)
    echo "${indent}- [$title]($path)"
  done
}

if [ -n "$file_path" ]; then
  # input by file
  pick_header $depth < "$file_path" | make_toc
else
  # input by stdin
  pick_header $depth | make_toc
fi