import time

import prometheus_client
from prometheus_client import start_http_server, Gauge, Counter
import sys
import argparse
import os
import stat
from http.server import HTTPServer

prometheus_client.REGISTRY.unregister(prometheus_client.GC_COLLECTOR)
prometheus_client.REGISTRY.unregister(prometheus_client.PLATFORM_COLLECTOR)
prometheus_client.REGISTRY.unregister(prometheus_client.PROCESS_COLLECTOR)

# Create a metric to track time spent and requests made.
FILE_TIME = Gauge("file_time_seconds", "File last modification time", labelnames=['path', 'type'])
FILE_SIZE = Gauge("file_size", "File size in bytes", labelnames=['path', 'type'])


class Handler(prometheus_client.MetricsHandler):
    def do_GET(self) -> None:
        for file in FILES.keys():
            type = FILES[file]
            try:
                FILE_TIME.labels(file, type).set(0)
                FILE_SIZE.labels(file, type).set(0)
                # follow symlinks
                stats = os.stat(path=file)
                if stat.S_ISREG(stats.st_mode):
                    FILE_TIME.labels(file, type).set(stats.st_mtime)
                    FILE_SIZE.labels(file, type).set(stats.st_size)
            except:
                pass

        return super().do_GET()


# map of filename to type 
FILES = {}

if __name__ == '__main__':
    DEFAULT_PORT = 8080
    parser = argparse.ArgumentParser(prog=sys.argv[0],
                                     description=f"""Statistics on a (backup) file,
                            
                            Usage: ${sys.argv[0]} [-p|--port <port>] <label1>:<filepath1> .... <labeln>:<filepathn>
                            
                            Listens on port {DEFAULT_PORT} by default. It exposes statistics
                            on the monitored files to prometheus. Current metrics are
                            
                              {FILE_TIME._name}{{path="/path/to/file"}}: file modification time in seconds since 1970
                              {FILE_SIZE._name}{{path="/path/to/file"}}: file size in bytes
                              
                            If a path does not exist or is not a regular file then the value 0 is returned.  
                            The exporter follow symlinks. 
                            
                            The synax of each file is fo theform <label>:<file> where <label> is the value of 
                            the type label in the prometheus export. 

                            """,
                                     epilog="Have a lot of fun!",
                                     formatter_class=argparse.RawTextHelpFormatter)
    parser.add_argument("files", nargs="*", help="Files to monitor")
    parser.add_argument("-p", "--port", type=int, default=DEFAULT_PORT, help="Port to listen on")
    args = parser.parse_args()

    filespecs = args.files
    for filespec in filespecs:
      ind = filespec.index(":")
      fname = filespec[ind+1:]
      label= filespec[:ind]
      FILES[fname] = label
      
    
    PORT = args.port

    print(f"Monitoring files {FILES}")
    # Start up the server to expose the metrics.
    print(f"Listening on port {PORT}")

    HTTPServer(('0.0.0.0', PORT), Handler).serve_forever()