cleanphotos() {
    local basename
    local photo
    local sub

    while IFS= read -r photo; do
        basename=$(basename "$photo")

        if [[ -f "$INCOMING_DIR/$basename" ]] \
            && is_supported_image_file "$basename"; then
            continue
        fi

        log_info "Cleaning up $(_display_path "$photo")"
        for sub in thumbs blurs photos; do
            if [ -f "$DIST_DIR/$sub/$basename" ]; then
                rm -f "$DIST_DIR/$sub/$basename"
                log_info "removed '$(_display_path "$DIST_DIR/$sub/$basename")'"
            fi
        done
    done < <(find "$DIST_DIR/photos" -maxdepth 1 -type f)
}

is_supported_image_file() {
    local -r file="$1"; shift
    local extension

    if [[ "$file" != *.* ]]; then
        return 1
    fi

    extension="${file##*.}"
    extension="${extension,,}"

    case "$extension" in
        gif|jpeg|jpg|png|webp)
            return 0
            ;;
        *)
            return 1
            ;;
    esac
}

incoming_image_files() {
    local file

    while IFS= read -r file; do
        if is_supported_image_file "$file"; then
            printf '%s\n' "$file"
        fi
    done < <(find "$INCOMING_DIR" -maxdepth 1 -type f -printf '%f\n') \
        | sort
}

# File counters for the source tree and the generated dist. Moved here from
# album-metadata.source.sh (task 6r0): counting incoming/generated files is part
# of this module's file-enumeration concern -- count_incoming_images is a direct
# wrapper of incoming_image_files above, and count_files/count_tree_files are the
# generic siblings the generation-metadata and dry-run modules use to tally the
# produced photos, thumbs and HTML pages. Behaviour and signatures are unchanged.
count_files() {
    local -r dir="$1"; shift
    local -r name="${1:-}"; shift || true

    if [ ! -d "$dir" ]; then
        printf '0\n'
        return
    fi

    if [ -n "$name" ]; then
        find "$dir" -maxdepth 1 -type f -name "$name" | wc -l
    else
        find "$dir" -maxdepth 1 -type f | wc -l
    fi
}

count_incoming_images() {
    incoming_image_files | wc -l
}

count_tree_files() {
    local -r dir="$1"; shift
    local -r name="$1"; shift

    if [ ! -d "$dir" ]; then
        printf '0\n'
        return
    fi

    find "$dir" -type f -name "$name" | wc -l
}

warn_unsupported_incoming_files() {
    local file

    while IFS= read -r file; do
        if ! is_supported_image_file "$file"; then
            log_warning "Ignoring unsupported incoming file: $file"
        fi
    done < <(find "$INCOMING_DIR" -maxdepth 1 -type f -printf '%f\n' | sort)
}

scalephotos() {
    local photo

    # Throttled background job pool (max IMAGE_JOBS concurrent), addressed by the
    # single handle "image_jobs". job_pool_wait returns 1 if any job failed.
    job_pool_init image_jobs

    while IFS= read -r photo; do
        job_pool_submit image_jobs "image job for photo $photo" \
            scale_photo "$photo"
    done < <(incoming_image_files)

    job_pool_wait image_jobs
}

scale_photo() {
    local -r photo="$1"; shift
    local destphoto
    local dirname

    destphoto="$DIST_DIR/photos/$photo"
    dirname=$(dirname "$destphoto")
    mkdir -p "$dirname"

    if [ -f "$destphoto" ]; then
        log_verbose "Skipped existing photo $(_display_path "$destphoto")"
        return
    fi

    log_info "Processing $photo to $(_display_path "$destphoto")"
    if [ -n "$HEIGHT" ]; then
        # Scale down size.
        imagemagick \
            "$INCOMING_DIR/$photo" \
            -auto-orient \
            -geometry "x${HEIGHT}>" \
            "$destphoto"
    else
        # Keep original size.
        imagemagick \
            "$INCOMING_DIR/$photo" \
            -auto-orient \
            "$destphoto"
    fi
}