import collectd
import btrfs

PLUGIN = 'btrfs'
TYPE_STATS = "stats"

mount_paths = []

def configure_callback(conf):
    """
    Populate mount_paths
    """
    global mount_paths
    mount_paths = [path for path in btrfs.utils.mounted_filesystem_paths()]
    collectd.info("btrfs: config done. mount_paths: {}".format(mount_paths))

def read_callback():
    """Read Btrfs device information and dispatch values to collectd."""
    metric = collectd.Values()
    metric.plugin = PLUGIN
    for path in mount_paths:
        try:
            with btrfs.FileSystem(path) as fs:
                for device in list(fs.devices()):
                    stats = fs.dev_stats(device.devid)
                    dev_info = fs.dev_info(device.devid)
                    metric.plugin_instance = dev_info.path
                    for counter, value in stats.counters.items():
                        metric.type_instance = counter
                        metric.dispatch(TYPE_STATS, [value])
        except Exception as e:
            collectd.error("btrfs: read_callback: {}".format(e))
    collectd.debug("btrfs: read done")

if __name__ != "__main__":
    # Register callbacks
    collectd.register_config(configure_callback)
    collectd.register_read(read_callback)