package waagent

import (
	"encoding/json"
	"encoding/xml"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"path"
)

type waagent struct {
	root     string
	readFile func(filename string) ([]byte, error)
}

func NewDatasource(root string) *waagent {
	return &waagent{root, ioutil.ReadFile}
}

func (a *waagent) IsAvailable() bool {
	_, err := os.Stat(path.Join(a.root, "provisioned"))
	return !os.IsNotExist(err)
}

func (a *waagent) AvailabilityChanges() bool {
	return true
}

func (a *waagent) ConfigRoot() string {
	return a.root
}

func (a *waagent) FetchMetadata() ([]byte, error) {
	metadataBytes, err := a.tryReadFile(path.Join(a.root, "SharedConfig.xml"))
	if err != nil {
		return nil, err
	}
	if len(metadataBytes) == 0 {
		return metadataBytes, nil
	}

	type Instance struct {
		Id             string `xml:"id,attr"`
		Address        string `xml:"address,attr"`
		InputEndpoints struct {
			Endpoints []struct {
				LoadBalancedPublicAddress string `xml:"loadBalancedPublicAddress,attr"`
			} `xml:"Endpoint"`
		}
	}

	type SharedConfig struct {
		Incarnation struct {
			Instance string `xml:"instance,attr"`
		}
		Instances struct {
			Instances []Instance `xml:"Instance"`
		}
	}

	var metadata SharedConfig
	if err := xml.Unmarshal(metadataBytes, &metadata); err != nil {
		return nil, err
	}

	var instance Instance
	for _, i := range metadata.Instances.Instances {
		if i.Id == metadata.Incarnation.Instance {
			instance = i
			break
		}
	}

	attrs := map[string]string{
		"local-ipv4": instance.Address,
	}
	for _, e := range instance.InputEndpoints.Endpoints {
		host, _, err := net.SplitHostPort(e.LoadBalancedPublicAddress)
		if err == nil {
			attrs["public-ipv4"] = host
			break
		}
	}
	return json.Marshal(attrs)
}

func (a *waagent) FetchUserdata() ([]byte, error) {
	return a.tryReadFile(path.Join(a.root, "CustomData"))
}

func (a *waagent) FetchNetworkConfig(filename string) ([]byte, error) {
	return nil, nil
}

func (a *waagent) Type() string {
	return "waagent"
}

func (a *waagent) tryReadFile(filename string) ([]byte, error) {
	fmt.Printf("Attempting to read from %q\n", filename)
	data, err := a.readFile(filename)
	if os.IsNotExist(err) {
		err = nil
	}
	return data, err
}