package frontend

import (
	"fmt"
	"github.com/Depado/ginprom"
	"github.com/gin-gonic/gin"
	"github.com/pboehm/ddns/shared"
	"github.com/prometheus/client_golang/prometheus"
	"html/template"
	"log"
	"net"
	"net/http"
	"regexp"
)

type Frontend struct {
	config   *shared.Config
	hosts    shared.HostBackend
	registry *prometheus.Registry
}

func NewFrontend(config *shared.Config, hosts shared.HostBackend, registry *prometheus.Registry) *Frontend {
	return &Frontend{
		config:   config,
		hosts:    hosts,
		registry: registry,
	}
}

func (f *Frontend) Run() error {
	prom := ginprom.New(ginprom.Namespace("ddns"),
		ginprom.Subsystem("frontend"), ginprom.Registry(f.registry))

	r := gin.New()
	r.Use(prom.Instrument())
	prom.Engine = r // we don't want to expose the metrics on the frontend, so we are not using `prom.Use(r)`

	r.Use(gin.Recovery())

	if f.config.Verbose {
		r.Use(gin.Logger())
	}

	r.SetHTMLTemplate(buildTemplate(f.config.CustomTemplatePath))

	r.GET("/", func(g *gin.Context) {
		g.HTML(200, "index.html", gin.H{"domain": f.config.Domain})
	})

	r.GET("/available/:hostname", func(c *gin.Context) {
		hostname, valid := isValidHostname(c.Params.ByName("hostname"))

		if valid {
			_, err := f.hosts.GetHost(hostname)
			valid = err != nil
		}

		c.JSON(200, gin.H{
			"available": valid,
		})
	})

	r.GET("/new/:hostname", func(c *gin.Context) {
		hostname, valid := isValidHostname(c.Params.ByName("hostname"))

		if !valid {
			c.JSON(404, gin.H{"error": "This hostname is not valid"})
			return
		}

		var err error

		if _, err := f.hosts.GetHost(hostname); err == nil {
			c.JSON(403, gin.H{"error": "This hostname has already been registered."})
			return
		}

		host := &shared.Host{Hostname: hostname, Ip: "127.0.0.1"}
		host.GenerateAndSetToken()

		if err = f.hosts.SetHost(host); err != nil {
			c.JSON(400, gin.H{"error": "Could not register host."})
			return
		}

		c.JSON(200, gin.H{
			"hostname":    host.Hostname,
			"token":       host.Token,
			"update_link": fmt.Sprintf("/update/%s/%s", host.Hostname, host.Token),
		})
	})

	r.GET("/update/:hostname/:token", func(c *gin.Context) {
		hostname, valid := isValidHostname(c.Params.ByName("hostname"))
		token := c.Params.ByName("token")

		if !valid {
			c.JSON(404, gin.H{"error": "This hostname is not valid"})
			return
		}

		host, err := f.hosts.GetHost(hostname)
		if err != nil {
			c.JSON(404, gin.H{
				"error": "This hostname has not been registered or is expired.",
			})
			return
		}

		if host.Token != token {
			c.JSON(403, gin.H{
				"error": "You have supplied the wrong token to manipulate this host",
			})
			return
		}

		ip, err := extractRemoteAddr(c.Request)
		if err != nil {
			c.JSON(400, gin.H{
				"error": "Your sender IP address is not in the right format",
			})
			return
		}

		host.Ip = ip
		if err = f.hosts.SetHost(host); err != nil {
			c.JSON(400, gin.H{
				"error": "Could not update registered IP address",
			})
		}

		c.JSON(200, gin.H{
			"current_ip": ip,
			"status":     "Successfuly updated",
		})
	})

	return r.Run(f.config.ListenFrontend)
}

// Get the Remote Address of the client. At First we try to get the
// X-Forwarded-For Header which holds the IP if we are behind a proxy,
// otherwise the RemoteAddr is used
func extractRemoteAddr(req *http.Request) (string, error) {
	header_data, ok := req.Header["X-Forwarded-For"]

	if ok {
		return header_data[0], nil
	} else {
		ip, _, err := net.SplitHostPort(req.RemoteAddr)
		return ip, err
	}
}

// Get index template from bindata
func buildTemplate(customTemplatePath string) *template.Template {
	var html *template.Template
	var err error

	if customTemplatePath != "" {
		html, err = template.ParseFiles(customTemplatePath)
	} else {
		html, err = template.New("index.html").Parse(indexTemplate)
	}

	if err != nil {
		log.Fatalf("Error parsing frontend template: %v", err)
	}

	return html
}

func isValidHostname(host string) (string, bool) {
	valid, _ := regexp.Match("^([a-zA-Z0-9]([a-zA-Z0-9\\-]{0,61}[a-zA-Z0-9])?)$", []byte(host))

	return host, valid
}