configure

#!/usr/bin/env sh

DEFAULT_FILE=./src/defaults.h
CONFIG_FILE=./src/config.h

if [ ! -e "$DEFAULT_FILE" ]; then
   printf 'No default configuration header found\n'
   exit
fi

if [ ! -e "$CONFIG_FILE" ]; then
   printf 'No configuration header found\n'
   exit
fi

CONFIG_KEYS=$(sed -E -n 's/^#define ([^_][^(]+) .+/\1/p' "$DEFAULT_FILE")

len=$(mktemp)
_firstlen='reset-config'
printf '%d\n' "${#_firstlen}" > "$len"
printf '%s\n' "$CONFIG_KEYS" | while IFS= read -r key; do
    IFS= read -r printlen <"$len"
    if [ "$((${#key}))" -gt "$printlen" ]; then
        printf '%d\n' "${#key}" > "$len"
    fi
done
IFS= read -r printlen <"$len"

show_config () {
    printf '%s\n' "$CONFIG_KEYS" | while IFS= read -r key; do
        DEFAULT=$(sed -E -n "s/^#define $key (.+)/\1/p" "$DEFAULT_FILE")
        CONFIGD=$(sed -E -n "s/^#define $key (.+)/\1/p" "$CONFIG_FILE")

        printf '%s = ' "$key"
        if [ -n "$CONFIGD" ]; then
            printf '%s (%s)' "$CONFIGD" "$DEFAULT"
        else
            printf '%s' "$DEFAULT"
        fi; printf '\n'
    done
}

optusage () {
    printf '  --%-*s\t%s\n' "$printlen" "$1" "$2"
}

usage () {
    printf 'Usage: %s [options]\n\nOptions:\n' "$0"
    printf '%s\n' "$CONFIG_KEYS" | while IFS= read -r key; do
        OPT=$(printf '%s' "$key" | tr '[:upper:]_' '[:lower:]-')
        HELP=$(sed -E -n "s|^#ifndef $key // (.+)|\1|p" "$DEFAULT_FILE")

        optusage "$OPT" "$HELP"
    done

    optusage 'reset-config' 'reset configuration to the defaults'
    optusage 'help' 'print this help and exit'
}

update () {
    sed -i "$CONFIG_FILE" -re "s|^(//)?#define $1 \"(.*)\"$|#define $1 \"$2\"|"
}

restore_default_config () {
    sed -re 's|^#define [^_][^()]+ .+|//&|' -i "$CONFIG_FILE"
}

for setting in "$@"; do
    OPT=$(printf '%s' "$setting" | cut -d' ' -f1 | sed -E -n 's/--//p')
    KEY=$(printf '%s' "$OPT" | sed -E -n 's/([^=]+)=.*/\1/p' | tr '[:lower:]-' '[:upper:]_')
    VAL=$(printf '%s' "$OPT" | sed -E -n 's/.*=([^[:space:]]+)/\1/p')

    case "$OPT" in
        *'='*)
            case "$CONFIG_KEYS" in
                *"$KEY"*) update "$KEY" "$VAL";;
                *)
                    printf 'unrecognized option: --%s\n' "$OPT"
                    exit
                    ;;
            esac;;
        help)
            usage
            exit
            ;;
        reset-config)
            restore_default_config
            show_config
            exit
            ;;
        *)
            printf 'unrecognized option: --%s\n' "$OPT"
            exit
            ;;
    esac
done

show_config