#!/bin/bash
# Verify that stack_png can handle reading from the same file multiple times.

set -euo pipefail

if [[ $# -ne 1 ]]; then
   echo "$0 <stack_png.exe>"
   exit 1
fi

STACK_PNG=$1

# Build input.
INPUT_PIXELS=$(mktemp -p .)
cat <<EOT > "$INPUT_PIXELS"
P2
4 3
255
255 255 255 255
255 255 255 255
255 255 255 255
EOT

INPUT_ALPHA=$(mktemp -p .)
cat <<EOT > "$INPUT_ALPHA"
P2
4 3
255
128 128 128  64
128 128  64 128
128  64 128 128
EOT

INPUT_PNG=$(mktemp -p .)
pnmtopng -alpha="$INPUT_ALPHA" "$INPUT_PIXELS" > "$INPUT_PNG"

# Run tool.
ACTUAL=$(mktemp -p .)
"./$STACK_PNG" "$INPUT_PNG" "$INPUT_PNG" > "$ACTUAL"

# Actual pixels should be the same as input pixels,
# the only difference would be in the alpha channel.
DIFF=$(mktemp -p .)
pngtopam "$ACTUAL" \
   | ppmtopgm \
   | pamarith -difference "$INPUT_PIXELS" - > "$DIFF"
if ! ( perl -e '
   $bytes = join "", <>;
   die "Unexpected difference\n" unless( $bytes =~ /^P\d+\s\d+\s\d+\s\d+\s[\x00]*$/s );' "$DIFF" ); then
   rm -f "$INPUT_PIXELS" "$INPUT_ALPHA" "$INPUT_PNG" "$ACTUAL" "$DIFF"
   exit 1
fi

# Compare alpha channel.
cat <<EOT > "$INPUT_ALPHA"
P2
4 3
255
191 191 191 111
191 191 111 191
191 111 191 191
EOT
pngtopam -alpha "$ACTUAL" \
   | ppmtopgm \
   | pamarith -difference "$INPUT_ALPHA" - > "$DIFF"
if ! ( perl -e '
   $bytes = join "", <>;
   die "Unexpected difference\n" unless( $bytes =~ /^P\d+\s\d+\s\d+\s\d+\s[\x00]*$/s );' "$DIFF" ); then
   rm -f "$INPUT_PIXELS" "$INPUT_ALPHA" "$INPUT_PNG" "$ACTUAL" "$DIFF"
   exit 1
fi

# Do the same test again, but this time with input fed from stdin.
# Output should be byte-for-byte identical with what we got when
# reading from file.
if ! ( cat "$INPUT_PNG" | "./$STACK_PNG" - - | diff -q "$ACTUAL" - ); then
   echo "$LINENO: Output mismatched when reading from stdin"
   rm -f "$INPUT_PIXELS" "$INPUT_ALPHA" "$INPUT_PNG" "$ACTUAL" "$DIFF"
   exit 1
fi

rm -f "$INPUT_PIXELS" "$INPUT_ALPHA" "$INPUT_PNG" "$ACTUAL" "$DIFF"
exit 0