#! /bin/bash

declare -a paths
declare -i n=0

read_command() {
    local char

    read -rsn 1 char
    case "$char" in
        q | Q) echo 'CMD_QUIT';;
        h | H) echo 'CMD_MOVE_BACK';;
        l | L) echo 'CMD_MOVE_FORWARD';;
        f | F) echo 'CMD_FAVORITE';;
            *) echo 'CMD_UKNOWN';;
    esac
}

paths_find() {
    local -r root_dir="$1"
    local path

    IFS=$'\n'
    for path in $(find "$root_dir" -type f)
    do
        if file "$path" | grep 'image data' > /dev/null
        then
            (( n++ ))
            # \r jumps to the beginning of the line:
            printf '\rFound %d images.' "$n" >&2
            paths["$n"]="$path"
        fi
    done
    unset IFS
    printf '\n' >&2
}

paths_preview() {
    local -i i
    local path

    for ((i=1; i<=n; i++))
    do
        path="${paths[$i]}"

        printf '%d of %d : %s\n' "$i" "$n" "$path"
        feh --bg-scale "$path"

        case "$(read_command)" in
            CMD_QUIT)
                exit 0;;
            CMD_MOVE_BACK)
                # TODO Cycle around.
                # One step further back than needed,
                # to correct for the upcoming i++.
                ((i = i - 2))
                if [[ i -lt 0 ]]; then
                    i=-1
                fi;;
            CMD_MOVE_FORWARD)
                ;;
            CMD_FAVORITE)
                wallpaper_fav
                ((i--));;
            CMD_UKNOWN)
                # Remain
                ((i--));;
        esac
    done
}

main() {
    local root_dir

    case "$1" in
        '') root_dir="$DIR_WALLPAPERS";;
        *) root_dir="$1";;
    esac

    paths_find "$root_dir"
    paths_preview
}

main "$@"