package main

import (
	"bytes"
	"errors"
	"strconv"
	"strings"
	"text/template"
	"time"

	"github.com/BurntSushi/toml"
	"github.com/BurntSushi/ty/fun"
	log "github.com/Sirupsen/logrus"
	"github.com/cenkalti/backoff"
	"github.com/fsouza/go-dockerclient"
)

type DockerProvider struct {
	Watch    bool
	Endpoint string
	Filename string
	Domain   string
}

func NewDockerProvider() *DockerProvider {
	dockerProvider := new(DockerProvider)
	// default
	dockerProvider.Watch = true
	dockerProvider.Domain = "traefik"

	return dockerProvider
}

var DockerFuncMap = template.FuncMap{
	"getBackend": func(container docker.Container) string {
		for key, value := range container.Config.Labels {
			if key == "traefik.backend" {
				return value
			}
		}
		return getHost(container)
	},
	"getPort": func(container docker.Container) string {
		for key, value := range container.Config.Labels {
			if key == "traefik.port" {
				return value
			}
		}
		for key := range container.NetworkSettings.Ports {
			return key.Port()
		}
		return ""
	},
	"getWeight": func(container docker.Container) string {
		for key, value := range container.Config.Labels {
			if key == "traefik.weight" {
				return value
			}
		}
		return "0"
	},
	"replace": func(s1 string, s2 string, s3 string) string {
		return strings.Replace(s3, s1, s2, -1)
	},
	"getHost": getHost,
}

func (provider *DockerProvider) Provide(configurationChan chan<- configMessage) {
	if dockerClient, err := docker.NewClient(provider.Endpoint); err != nil {
		log.Fatalf("Failed to create a client for docker, error: %s", err)
	} else {
		err := dockerClient.Ping()
		if err != nil {
			log.Fatalf("Docker connection error %+v", err)
		}
		log.Debug("Docker connection established")
		if provider.Watch {
			dockerEvents := make(chan *docker.APIEvents)
			dockerClient.AddEventListener(dockerEvents)
			log.Debug("Docker listening")
			go func() {
				operation := func() error {
					for {
						event := <-dockerEvents
						if event == nil {
							return errors.New("Docker event nil")
							//							log.Fatalf("Docker connection error")
						}
						if event.Status == "start" || event.Status == "die" {
							log.Debugf("Docker event receveived %+v", event)
							configuration := provider.loadDockerConfig(dockerClient)
							if configuration != nil {
								configurationChan <- configMessage{"docker", configuration}
							}
						}
					}
				}
				notify := func(err error, time time.Duration) {
					log.Errorf("Docker connection error %+v, retrying in %s", err, time)
				}
				err := backoff.RetryNotify(operation, backoff.NewExponentialBackOff(), notify)
				if err != nil {
					log.Fatalf("Cannot connect to docker server %+v", err)
				}
			}()
		}

		configuration := provider.loadDockerConfig(dockerClient)
		configurationChan <- configMessage{"docker", configuration}
	}
}

func (provider *DockerProvider) loadDockerConfig(dockerClient *docker.Client) *Configuration {
	configuration := new(Configuration)
	containerList, _ := dockerClient.ListContainers(docker.ListContainersOptions{})
	containersInspected := []docker.Container{}
	hosts := map[string][]docker.Container{}

	// get inspect containers
	for _, container := range containerList {
		containerInspected, _ := dockerClient.InspectContainer(container.ID)
		containersInspected = append(containersInspected, *containerInspected)
	}

	// filter containers
	filteredContainers := fun.Filter(func(container docker.Container) bool {
		if len(container.NetworkSettings.Ports) == 0 {
			log.Debugf("Filtering container without port %s", container.Name)
			return false
		}
		_, err := strconv.Atoi(container.Config.Labels["traefik.port"])
		if len(container.NetworkSettings.Ports) > 1 && err != nil {
			log.Debugf("Filtering container with more than 1 port and no traefik.port label %s", container.Name)
			return false
		}
		if container.Config.Labels["traefik.enable"] == "false" {
			log.Debugf("Filtering disabled container %s", container.Name)
			return false
		}
		return true
	}, containersInspected).([]docker.Container)

	for _, container := range filteredContainers {
		hosts[getHost(container)] = append(hosts[getHost(container)], container)
	}

	templateObjects := struct {
		Containers []docker.Container
		Hosts      map[string][]docker.Container
		Domain     string
	}{
		filteredContainers,
		hosts,
		provider.Domain,
	}
	tmpl := template.New(provider.Filename).Funcs(DockerFuncMap)
	if len(provider.Filename) > 0 {
		_, err := tmpl.ParseFiles(provider.Filename)
		if err != nil {
			log.Error("Error reading file", err)
			return nil
		}
	} else {
		buf, err := Asset("providerTemplates/docker.tmpl")
		if err != nil {
			log.Error("Error reading file", err)
		}
		_, err = tmpl.Parse(string(buf))
		if err != nil {
			log.Error("Error reading file", err)
			return nil
		}
	}

	var buffer bytes.Buffer
	err := tmpl.Execute(&buffer, templateObjects)
	if err != nil {
		log.Error("Error with docker template", err)
		return nil
	}

	if _, err := toml.Decode(buffer.String(), configuration); err != nil {
		log.Error("Error creating docker configuration", err)
		return nil
	}
	return configuration
}

func getHost(container docker.Container) string {
	for key, value := range container.Config.Labels {
		if key == "traefik.host" {
			return value
		}
	}
	return strings.Replace(strings.Replace(container.Name, "/", "", -1), ".", "-", -1)
}