#!/usr/bin/env zsh

sram() {
    die() {
        echo -E "$@">&2
        exit 1
    }

    crop() {
        tail -n +$((($1)/16+1))
    }

    revend() {
        objcopy -I binary -O binary --reverse-bytes=4 "$@"
    }

    dump() {
        xxd -ps -c 16 "$@"
    }

    zeros() {
        # one row (16) of zeros
        yes "00000000000000000000000000000000" | head -n $1
    }

    game="$1"
    in="$2"
    out="$3"

    if [[ "$game" == "mm" ]]; then
        headsize=$((0x20800))
    elif [[ "$game" == "oot" ]]; then
        headsize=$((0x40800))
    else
        echo "Unknown game." >&2
        return 1
    fi

    [ -e "$2" ] || die "input save does not exist"

    if [[ "${in##*.}" == "SaveRAM" ]] then
        dump "$in" | crop $headsize | dump -r > "$out"
    else
        cat <(zeros $(($headsize/16))) <(dump "$in") | dump -r > "$out"
    fi

    revend "$out"
}

sram "$@"