unroll.sh

#!/bin/bash
#
# vim: ft=bash :
#
# A simple shell based macro expander.
# THIS IS NOT SAFE TO UNTRUSTED INPUT!
#
# First character of the line defines what to do:
#
# #	comment, ignored
# :name	define macro
# !name	set input for macro
# @name	run macro
#
# The macro is defined as a shell function.
# The macro lines (:) are appended to each other for this.
#
# Macros with ':' in their name use input from everything before this ':',
# so you can parse input multiply with different macro commands.
#
# Input is gathered until the macro is invoked.  Input which comes later
# is appended for later macro calls.
#
# Usage: unroll.sh input input input > output

STDOUT() { printf '%q' "$1"; printf ' %q' "${@:2}"; printf '\n'; }
STDERR() { STDOUT "$@" >&2; }
OOPS() { STDERR OOPS: "$@"; exit 23; }
o() { "$@" || OOPS fail $?: "$@"; }
D() { STDERR DEBUG: "$@"; }
D() { :; }

declare -A MACROS
macro_set()
{
  D macro_set "$@"
  read -r name cmd <<<"$1" || OOPS cannot parse macro name: "$1"
  IFS='$' read -ra args <<<"$cmd" || OOPS cannot parse macro args: "$1" "$cmd"
  printf -v esc %q "$args"
  out=("$esc")
  p=
  for a in "${args[@]:1}"
  do
    p="$p$a"
    case "$p" in
    ([1-9]*)	n="${p%%[^0-9]*}"; p="${p#"$n"}"; out+=("\"\${$n}\"");;		# $NNN => ${NNN}

    (\[*\]*)	n="${p%%\]*}"							# $[calc]
                n="${n#\[}"
                p="${p#"[$n]"}"
                case "$n" in
                (*[^0-9$+\*/\(\)\ -]*)	OOPS wrong character in expansion: "\$[$n]";;	# we only support simple calculations
                esac
                out+=("\"\$[$n]\"")
                ;;
    (\[*)	p="$p\$"; continue;;						# $[xxx$ without ]

    (*)		out+=("'$'");;							# else
    esac
    printf -v esc %q "$p"
    out+=("$esc")
    p=
  done
  [ -z "$p" ] || OOPS unterminated '$[' sequence
  MACROS["$name"]="${MACROS["$name"]}"$' &&\n printf %s '"${out[*]}"$' &&\n echo'
}

declare -A INPUTS
input_add()
{
  D input_add "$@"
  read -r name cmd <<<"$1" || OOPS cannot parse input: "$1"
  INPUTS["$name"]="${INPUTS["$name"]}"$'\n'"$cmd"
}

macro_run()
{
  D macro_run "$@"
  read -r name <<<"$1" || OOPS invalid macro name: "$1"

  IN="${INPUTS["${name%%:*}"]}"
  [ -n "$IN" ] || OOPS missing input 'for' "$name"

  macro="${MACROS["$name"]}"
  [ -n "$macro" ] || OOPS missing macro "$name"

  vars="${VARS[@]}"
  macro() { . <(echo "$vars"); . <(echo ":$macro"); } || OOPS macro definition fail: "$name";

#  echo "$macro" >&2
  while read -ru6 line
  do
        [ -n "$line" ] || continue
        read -ra args <<<"$line"
        macro "${args[@]}" || { printf 'Args: %q\n' "${args[@]}"; echo "Macro:"; cat -n <<<":$macro"; macro "${args[@]}"; OOPS macro fail: "$name"; } >&2
  done 6<<<"$IN"
}

declare -A VARS
vars_set()
{
  D vars_set "$@"
  read -r var def <<<"$1" || OOPS invalid variable definition: "$1"
  o printf -v quote %q "$def"
  VARS["$var"]="$var=$quote"
}

STDOUT // DO NOT EDIT. Automatically generated by "$0" "$@"
STDOUT // src $(sha256sum -- "$@")
while IFS= read -ru6 line
do
        case "$line" in
        ('#'*)		continue;;
        (':'*)		macro_set "${line#':'}";;
        ('!'*)		input_add "${line#'!'}";;
        ('@'*)		macro_run "${line#'@'}";;
        ('='*)		vars_set  "${line#'='}";;
        ('')		;;
        (*)		echo "$line";;
        esac <&6-
done 6< <(cat -- "$@")