#!/bin/bash
###########################################################################
##  Copyright (C) Wizardry and Steamworks 2020 - License: GNU GPLv3      ##
##  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  ##
##  rights of fair usage, the disclaimer and warranty conditions.        ##
###########################################################################
## The following is a short script meant to read a retroarch playlist    ##
## and assign a default core for all ROMs previously scanned.            ##
###########################################################################
## The script works on the principle that certain roms within ROM sets   ##
## (ie: Goodset, No-Intro or MAME ROMs) work best with a specific core   ##
## or core version and it is mostly impossible for retroarch to guess    ##
## what core variant a certain ROM works with.                           ##
##                                                                       ##
## A playlist generated by retroarch may contain set the "core_path" and ##
## "core_name" to "DETECT", indicating that the ROM will be ran with the ##
## best-guess core that retroarch can find. Then, assuming, for example, ##
## multiple MAME ROM sets stored on the drive in separate folders such   ##
## as 2003+, 0.37b5 or FBA 0.2.97.42, this script can be used to set the ##
## "core_path" parameter to the core matching the folder names.          ##
###########################################################################
## Requirements:                                                         ##
##   * jq                                                                ##
##   * Bourne Shell (pure POSIX will not work, ie: dash)                 ##
## Example invocation:                                                   ##
##    $ cat MAME.lpl | ./coreMapper.sh >> MAME_mapped.lpl                ##
###########################################################################

###########################################################################
##                            CONFIGURATION                              ##
###########################################################################

# An array containing parts of paths in a retroarch playlist for which
# cores should be assigned. 
PATH_MATCH=(
    "2003+"
    "FBA 0.2.97.42"
    "0.37b5"
)

# A list of retroarch cores matching the path parts that must be set.
ASSIGNED_CORE=(
    "/tmp/cores/mame2003_plus_libretro.so"
    "/tmp/cores/fbneo_libretro.so"
    "/tmp/cores/mame2003_plus_libretro.so"
)

ASSIGNED_CORE_NAME=(
    "MAME 2003-Plus"
    "FinalBurn Neo"
    "MAME 2000 (0.37b5)"
)

# Set the jq binary that should be used (default: jq-win64.exe for Windows)
JQ="jq-win64.exe"

###########################################################################
##                              INTERNALS                                ##
###########################################################################

# Grab STDIN (pine input)
INPUT="$(< /dev/stdin)"

# Split indices using IFS (without other tools).
OIFS=$IFS
IFS=" "
INDICES=${!PATH_MATCH[*]}
IFS=$OIFS

# Perform all core substitutions based on the matching path part.
JSON=$INPUT
for i in $INDICES; do
    MATCH="${PATH_MATCH[$i]}"
    CORE="${ASSIGNED_CORE[$i]}"
    NAME="${ASSIGNED_CORE_NAME[$i]}"
    # Variable overloading without storing intermediary partial results.
    IFS="{}"
    read -d '' JSON <<< $(printf '%s' "$JSON" | \
        $JQ "
            walk(
                if type == \"object\" and (.path | type == \"string\" and contains (\""$MATCH"\"))
                then 
                    (.core_path |= \""$CORE\"" | .core_name |= \""$NAME\"")
                else 
                    . 
                end
            )")
    IFS=$OIFS
done

# Pretty print JSON result.
echo $JSON | $JQ .