#!/bin/bash

# flags
# -a  append to data file (default off = truncate)
# -p  pad sizes within data file to next block size (default off)

# parameters
# 1 - input filename of text file containing list of effects (probably FX.CONF or DFX.CONF)
# 2 - output filename for index file
# 3 - output filename for data file
# 4 - input directory of files to merge into data file

pad=false
append=false
standardsize=0
while getopts ":ap" opt; do
    case $opt in
        a) append=true
           ;;
        p) pad=true
           ;;
    esac
done
shift $((OPTIND-1))

if [ -f "$4"/STANDARD ]; then
    cp "$4"/STANDARD "$3"
    standardsize=$(wc -c < "$3")
elif [ "$append" = false ]; then
    rm -f "$3"
fi
touch "$3"

# make temp file with list of lines that contain keys
records=$(mktemp)
awk '!/^$|^#|^\[/ { print }' < "$1" > "$records"

# make temp assembly source file that represents the binary OKVS data structure
source=$(mktemp)
(echo "*=0"                            # dummy program counter for assembler
 echo "!le16 $(wc -l <"$records"), 0"  # OKVS header
 while IFS="=" read -r key value; do
     echo "!byte ${#key}+7"            # OKVS record length
     echo "!byte ${#key}"              # OKVS key length
     echo "!text \"$key\""             # OKVS key
     if [ -f "$4/$key" ]; then         # if file exists, determine offset and size
         offset=$(wc -c < "$3")
         echo "!be24 $offset"          # offset into merged data file
         echo -n "!le16 "
         size=$(wc -c < "$4/$key")
         if [ "$pad" = true ]; then
             # If offset+size does not cross a block boundary, use file's true size.
             # Otherwise, round up size to the next block boundary.
             # This padding does not get added to the file; it is just an
             # optimization to avoid a partial copy on the last block read.
             if [ $(($offset / 512)) -eq $((($offset + $size) / 512)) ]; then
                 echo "$size"
             else
                 echo "$(((($offset + $size + 511) & -512) - $offset))"
             fi
         else
             # Caller said never pad, so always use file's true size.
             echo "$size"
         fi
         cat "$4/$key" >> "$3"         # append this file to the end of the merged data file
     else                              # if file does not exist, reuse placeholder at offset 0
         echo "!be24 0"
         echo "!le16 $standardsize"
     fi
 done < "$records") > "$source"

# assemble temp source file to create binary OKVS data structure
acme -o "$2" "$source"

# clean up
rm "$source"
rm "$records"