__author__ = 'Manuela Kuhn <marnuel.kuhn@desy.de>'


import time
import logging
import os
from stat import S_ISREG, ST_MTIME, ST_MODE
import helperScript


class RingBuffer:
    targetDir                = None
    ringBuffer               = []
    maxRingBufferSize        = None

    log                      = None

    def __init__(self, maxRingBufferSize, targetDir = None):
        self.targetDir          = targetDir
        self.maxRingBufferSize  = maxRingBufferSize

        self.log = self.getLogger()
        self.log.debug("Init")

        # initialize ring buffer
        # get all entries in the directory
        if targetDir:
            # TODO empty target dir -> ringBuffer = []
            self.ringBuffer = (os.path.join(self.targetDir, fn) for fn in os.listdir(self.targetDir))
            # get the corresponding stats
            self.ringBuffer = ((os.stat(path), path) for path in self.ringBuffer)
            # leave only regular files, insert modification date
            self.ringBuffer = [[stat[ST_MTIME], path]
                    for stat, path in self.ringBuffer if S_ISREG(stat[ST_MODE])]

            # sort the ring buffer in descending order (new to old files)
            self.ringBuffer = sorted(self.ringBuffer, reverse=True)
            self.log.debug("Init ring buffer with files in specified directory")


    def getLogger(self):
        logger = logging.getLogger("RingBuffer")
        return logger


    def __str__(self):
        returnString = ""

        if self.ringBuffer:
            for i in self.ringBuffer[:-1]:
                returnString += str(i) + "\n"
            returnString += str(self.ringBuffer[-1])

        return returnString


    def getNewestFile(self):
        # send first element in ring buffer to live viewer (the path of this file is the second entry)
        if self.ringBuffer:
            self.log.debug("Newest Event: " + str(self.ringBuffer[0][1]) )
            return self.ringBuffer[0][1]
        else:
            self.log.debug("Newest Event: None")
            return "None"


    def add(self, filename, fileModTime):
        # prepend file to ring buffer and restore order
        self.ringBuffer[:0] = [[fileModTime, filename]]
        self.ringBuffer = sorted(self.ringBuffer, reverse=True)

        # if the maximal size is exceeded: remove the oldest files
        if len(self.ringBuffer) > self.maxRingBufferSize:
            for mod_time, path in self.ringBuffer[self.maxRingBufferSize:]:
                self.log.debug("Remove file from ring buffer: " + str(path) )
                os.remove(path)
                self.ringBuffer.remove([mod_time, path])


if __name__ == "__main__":
    logfile = "/space/projects/live-viewer/logs/RingBuffer.log"
    targetDir = "/space/projects/live-viewer/data/zmq_target/"

    #enable logging
    helperScript.initLogging(logfile, True)

    ringbuffer = RingBuffer(2, targetDir)

    print "init"
    print ringbuffer

    # add a file
    newFileName1 = targetDir + "file1.tif"
    newFile = open(newFileName1, "w")
    newFile.write("test")
    newFile.close()

    newFileModTime = os.stat(newFileName1).st_mtime

    ringbuffer.add(newFileName1, newFileModTime)

    print "\nadded"
    print ringbuffer

    time.sleep(1)
    # add another file
    newFileName2 = targetDir + "file2.tif"
    newFile = open(newFileName2, "w")
    newFile.write("test")
    newFile.close()

    newFileModTime = os.stat(newFileName2).st_mtime

    ringbuffer.add(newFileName2, newFileModTime)

    print "\nadded"
    print ringbuffer

    os.remove(newFileName1)
    os.remove(newFileName2)