#!/usr/bin/python3

import bottle
import datetime
import logging
from collections import defaultdict
from sys import stderr


def format_metrics(metric_data, entries, timestamps=False):
    """ metric_data = { 'metric_name' : ('gauge'|'counter', 'description') 
        entries = [ (datetime, 'metric_name', { 'attr': 'key' }, value) ]
    """
    
    collected = defaultdict(list)
    for entry in entries:
        collected[entry[1]].append(entry)

    for metric in collected:
        md = metric_data.get(metric)
        if md is not None:
            yield "# TYPE {} {}\n".format(metric, md[0])
            yield "# HELP {} {}\n".format(metric, md[1])

        for (time, metric, attrs, value) in collected[metric]:
            time_s = int(time.timestamp() * 1000)
            attr_s = ""
            if attrs:
                attr_s = "{" + ','.join('{}="{}"'.format(k, attrs[k]) for k in attrs ) + "}"
            if timestamps:
                yield f"{metric} {attr_s} {value} {time_s}\n"
            else:
                yield f"{metric} {attr_s} {value}\n"

def run(collect, metric_data, description='Mini Prometheus Exporter',
        host='localhost', port=9150, timestamps=False, debug=False):

    @bottle.route('/')
    def root():
        return description

    @bottle.route('/metrics')
    def metrics():
        return format_metrics(metric_data, collect(), timestamps)

    bottle.run(host=host, port=port, debug=debug)
    
if __name__ == "__main__":
    def collect_dummy():
        now = datetime.datetime.now()
        yield (now, 'pi', {'one': '1', 'two': '2' }, 3.14)
        yield (now, 'e', {'three': '3'}, 2.72)

    metric_data = { 'pi': ['gauge', 'Pi value'],
                    'e': ['counter', 'E counter'] }

    run(collect_dummy, metric_data, port=9159)