#!/usr/bin/env bash
set -euo pipefail
unset MAKEFLAGS MFLAGS GNUMAKEFLAGS
make_bin=$(command -v gmake || command -v make)
m() { "$make_bin" --no-print-directory -rR "$@"; }
work_dir=$(mktemp -d)
if [ "${KEEP_WORK:-0}" = 1 ]; then
  trap 'printf "Artifacts: %s\n" "$work_dir"' EXIT
else
  trap 'rm -rf -- "$work_dir"' EXIT
fi
cd "$work_dir"
export TMPDIR="$work_dir"
cat > main.tex <<'INPUT_80_1'
\documentclass{article}
\begin{document}
\input{sections/intro}
\end{document}
INPUT_80_1
mkdir -p sections
cat > sections/intro.tex <<'INPUT_80_2'
Original chapter text.
INPUT_80_2
cat > Makefile <<'MAKEFILE'
LATEXMK ?= latexmk
FLAGS := -norc -pdf -no-shell-escape
FLAGS += -interaction=nonstopmode -halt-on-error
.DELETE_ON_ERROR:
.DEFAULT_GOAL := all
CHAPTERS := $(wildcard sections/*.tex)
.PHONY: all
all: build/main.pdf
build/main.pdf: main.tex $(CHAPTERS) | build
	@printf "compile document and chapters\n"
	@$(LATEXMK) $(FLAGS) -outdir=build main.tex > build/latexmk.log 2>&1 || \
	  { cat build/latexmk.log >&2; exit 1; }
build:
	@mkdir -p $@
MAKEFILE
m -s all
m -q all
printf "Revised chapter text.\n" > sections/intro.tex
touch -t 202001010101 main.tex build/main.pdf
touch -t 202101010101 sections/intro.tex
m -s all
pdftotext build/main.pdf text.txt
grep -q 'Revised chapter text.' text.txt
if grep -q 'Original chapter text.' text.txt; then exit 1; fi
printf "edited chapter appears in the PDF\n"