#!/bin/sh

set -ue

INPUT_DIR="$1"
OUTPUT_FILE="$2"

gx_usage() {
	echo "Usage: $0 <input_dir> <output_file>"
	echo ""
}

if [ -z "$INPUT_DIR" ]; then
	gx_usage
	exit 1
fi
if [ -z "$OUTPUT_FILE" ]; then
	gx_usage
	exit 1
fi

find -L "$INPUT_DIR" -regextype sed \( -regex '.*/[0-9][^/]*\.md' ! -regex '.*/_.*' \) -print0 \
	| sort -z \
	| xargs -0 -iFILE cat FILE \
	| sed -e 's/^\s*----\s*$//' -e 's,\[\](.*/images/,[](./images/,' \
	> "$OUTPUT_FILE"