#!/bin/sh
#
# Check that watching a process's file descriptors works as expected.

# Dummy assignments for "shellcheck".
testSubject="${testSubject:-false}"; workFile1="${workFile1:-.tmp1}"; workFile2="${workFile2:-.tmp2}"; workFile3="${workFile3:-.tmp3}"

# Skip the test if "-d" is not available.
if ! "${testSubject}" -h | grep -Fq ' -d'; then
	echo "no \`--watchfd' / \`-d' option on this platform"
	exit 77
fi

seq 1 100 > "${workFile1}"
seq 1 300 > "${workFile2}"

# Run a background process to perform a few reads from a file, opening a
# second file after a moment.
# NB we just export line to make shellcheck think it's used.
(
export line
sleep 1
read -r line
exec 9<"${workFile2}"
sleep 1
read -r line
sleep 1
) <"${workFile1}" &
pid=$!

sleep 0.1
"${testSubject}" -d "${pid}" -f -i 0.5 >/dev/null 2>"${workFile3}"

# Skip the test if "-d" does not work.
if grep -Fq ' -d: not available' "${workFile3}"; then
	echo "no \`--watchfd' / \`-d' option on this platform"
	exit 77
fi

# Process the output to make it easier to handle.
# NB "ESC [ A" is "cursor up", we turn that into "-" and a newline.
tr '\r' '\n' < "${workFile3}" | sed 's/.\[A/-!/g' | tr '!' '\n' > "${workFile1}"

# We should see at least 2 file positions for fd 0.
positionsReported="$(awk '/^ *0:/ {print $2}' < "${workFile1}" | sort -n | uniq)"
differentNumbers="$(printf "%s\n" "${positionsReported}" | grep -Ec .)"
if ! test "${differentNumbers}" -gt 1; then
	printf "%s\n" "Expected at least 2 different numbers to be output for fd 0"
	printf "%s:\n%s\n" "Positions reported" "${positionsReported}"
	printf "%s: %s\n" "Number of different values seen" "${differentNumbers}"
	printf "%s\n" "Raw output:"
	cat "${workFile1}"
	exit 1
fi

# We should see file descriptor 9 appear.
if ! grep -Eq '^ *9:' < "${workFile1}"; then
	printf "%s\n" "Expected to see information for fd 9"
	printf "%s\n" "Raw output:"
	cat "${workFile1}"
	exit 1
fi

# We should see the last 6 characters of fd 9's filename appear.
lastChars="$(printf "%s\n" "${workFile2}" | rev | cut -b1-6 | rev)"
if ! grep -Fq "${lastChars}:" < "${workFile1}"; then
	printf "%s\n" "Expected to see a filename for fd 9"
	printf "%s\n" "Raw output:"
	cat "${workFile1}"
	exit 1
fi

exit 0