#!/bin/bash

set -euo pipefail

if [[ $# -ne 2 ]]; then
   echo "$0 {head|tail} {tool}"
   exit 1
fi
FUNCTION=$1
TOOL=$2
TEST_DIR=$(mktemp -d)

# Delete temporary directory and exit with nonzero status.
function die
{
   echo "$1"

   rm -rf "$TEST_DIR"
   exit 1
}

# Run tool and check output.
function run_test
{
   "$TOOL" "$2" < "$TEST_DIR/input.txt" > "$TEST_DIR/actual.txt" \
      || die "$LINENO: $1 (run)"

   diff -q "$TEST_DIR/expected.txt" "$TEST_DIR/actual.txt" \
      || die "$LINENO: $1 (diff)"

   "$TOOL" "-$2" < "$TEST_DIR/input.txt" > "$TEST_DIR/actual.txt" \
      || die "$LINENO: $1 (run, negative input)"

   diff -q "$TEST_DIR/expected.txt" "$TEST_DIR/actual.txt" \
      || die "$LINENO: $1 (diff, negative input)"
}


# Check help message.
"$TOOL" > "$TEST_DIR/help.txt" && die "$LINENO: unexpected success"
grep -qF "line_count" "$TEST_DIR/help.txt" \
   || die "$LINENO: missing help message"

# Test empty input.
touch "$TEST_DIR/input.txt"
touch "$TEST_DIR/expected.txt"
run_test "$LINENO: empty input 0" 0
run_test "$LINENO: empty input 1" 1
run_test "$LINENO: empty input 2" 2

# Test empty output.
seq 10 > "$TEST_DIR/input.txt"
run_test "$LINENO: empty output" 0

# Select a subset of input lines.
"$FUNCTION" -1 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: select 1" 1
"$FUNCTION" -5 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: select 5" 5
"$FUNCTION" -10 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: select 10" 10

# Select more than available lines.
run_test "$LINENO: select 11" 11
run_test "$LINENO: select 999" 999

# Try consecutive blank lines.
perl -e 'print "\n" x 10' > "$TEST_DIR/input.txt"
"$FUNCTION" -1 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: consecutive 1" 1
"$FUNCTION" -5 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: consecutive 5" 5
cp -f "$TEST_DIR/input.txt" "$TEST_DIR/expected.txt"
run_test "$LINENO: consecutive 10" 10

# Try file with missing newline at the end.
echo -e -n "hoge\npiyo\nfuga" > "$TEST_DIR/input.txt"
"$FUNCTION" -1 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: truncated 1" 1
"$FUNCTION" -2 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: truncated 2" 2
"$FUNCTION" -3 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: truncated 3" 3

# Try a larger input file.
perl <<'EOT' > "$TEST_DIR/input.txt"
srand(1);
for($i = 0; $i < 20; $i++)
{
   for($j = int(rand(4096) + 256); $j > 0; $j--)
   {
      print chr(int(rand(95) + 32));
   }
   print "\n";
}
EOT
"$FUNCTION" -1 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: large 1" 1
"$FUNCTION" -10 "$TEST_DIR/input.txt" > "$TEST_DIR/expected.txt"
run_test "$LINENO: large 10" 10
cp -f "$TEST_DIR/input.txt" "$TEST_DIR/expected.txt"
run_test "$LINENO: large 100" 100

rm -rf "$TEST_DIR"
exit 0