import kubernetes as k8s
import time
import random

schedulerName = "random-scheduler"

class NewScheduler:
    clientset = k8s.client

    def schedule_pods(self):
        watch, err = k8s.watch.Watch()
        if err is not None:
            print("error when watching pods", err)
            return err

        for event in range(watch.stream(self.clientset.list_namespace, _request_timeout=60)):
            if event['type'] != "ADDED":
                continue
            p, ok = event['object']
            if not ok:
                print("unexpected type")
                continue

            print("found a pod to schedule:", p.Namespace, "/", p.Name)

            node, err = self.find_fit()
            if err is not None:
                print("cannot find node that fits pod", err)
                continue

            err = self.bindPod(p, node)
            if err is not None:
                print("failed to bind pod", err)
                continue
            message = "Placed pod [%s/%s] on %s\n" %  p.Namespace, p.Name, node.Name

            err = self.emitEvent(p, message)
            if err is not None:
                print("failed to emit scheduled event", err)
                continue

            print(message)
        return None

    def find_fit(self):
        nodes, err = self.clientset.CoreV1().Nodes().List(k8s.client.api_client.ListOptions({}))
        if err is not None:
            return None, err
        return nodes.Items[random.randint(0,len(nodes.Items))], None

    def bindPod(self, p, node):
        return self.clientset.CoreV1().Pods(p['Namespace']).Bind(self.clientset.CoreV1().Binding({
            "ObjectMeta": {
                "Name": p['Name'],
                "Namespace": p['Namespace']
            },
            "Target": {
                "APIVersion": "v1",
                "Kind": "Node",
                "Name": node['Name']
            }
        }))

    def emitEvent(self, p, message):
        timestamp = time.time()
        _, err = self.clientset.CoreV1().Events(p['Namespace']).Create(self.clientset.CoreV1().Event({
            "Count":          1,
            "Message":        message,
            "Reason":         "Scheduled",
            "LastTimestamp":  timestamp,
            "FirstTimestamp": timestamp,
            "Type":           "Normal",
            "Source": self.clientset.CoreV1().EventSource({
                "Component": schedulerName,
            }),
            "InvolvedObject": self.clientset.CoreV1().ObjectReference({
                "Kind":      "Pod",
                "Name":      p['Name'],
                "Namespace": p['Namespace'],
                "UID":       p['UID'],
            }),
            "ObjectMeta": self.clientset.CoreV1().ObjectMeta({
                "GenerateName": p['Name'] + "-",
            }),
        }))
        if err is not None:
            return err
        return None



if __name__ == '__main__':
    print("I'm a scheduler!")

    random.seed(time.time())

    scheduler = NewScheduler()
    scheduler.schedule_pods()