package main

import (
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"os/exec"

	"github.com/julienschmidt/httprouter"

	"git.nemunai.re/srs/adlin/libadlin"
)

func init() {
	router.GET("/api/collector_info", apiHandler(func(ps httprouter.Params, body []byte) (interface{}, error) {
		return "\"" + base64.StdEncoding.EncodeToString(adlin.GetCollectorPublic()) + "\"", nil
	}))
	router.GET("/api/wg.conf", func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
		w.Header().Set("Content-Type", "text/plain")

		err := GenWGConfig(w)

		if err != nil {
			w.Write([]byte(err.Error()))
		}
	})
	router.GET("/api/wg/", apiAuthHandler(showWgTunnel))
	router.GET("/api/wginfo", apiAuthHandler(func(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
		return getTunnelInfo(student.Id, 0), nil
	}))
	router.POST("/api/wg/", apiAuthHandler(genWgToken))
	router.GET("/api/wg/:token", getWgTunnelInfo)
	router.POST("/api/wg/:token", getWgTunnelInfo)
	router.PUT("/api/wg/:token", apiAuthHandler(updateWgTunnel))
	router.DELETE("/api/wg/:token", apiAuthHandler(deleteWgTunnel))
}

func showWgTunnel(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
	// Get tunnels assigned to the student
	return student.GetTunnelTokens()
}

func genWgToken(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
	// Generate a token to access related wg info
	return student.NewTunnelToken(0)
}

type TunnelInfo struct {
	Status    string `json:"status"`
	SrvPubKey []byte `json:"srv_pubkey"`
	SrvPort   uint16 `json:"srv_port"`
	CltIPv6   net.IP `json:"clt_ipv6"`
	CltRange  uint8  `json:"clt_range"`
	SrvGW6    string `json:"srv_gw6"`
}

func getTunnelInfo(student int64, idoverride int) TunnelInfo {
	srv_pubkey, _ := base64.StdEncoding.DecodeString("uSpqyYovvP4OG6wDxZ0Qkq45MfyK58PMUuPaLesY8FI=")
	return TunnelInfo{
		Status:    "OK",
		SrvPubKey: srv_pubkey,
		SrvPort:   42912,
		CltIPv6:   adlin.StudentIP(student, idoverride),
		CltRange:  adlin.StdNetmask,
		SrvGW6:    "2a01:e0a:518:833::1",
	}
}

type PubTunnel struct {
	PubKey []byte
}

func getWgTunnelInfo(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
	if addr := r.Header.Get("X-Forwarded-For"); addr != "" {
		r.RemoteAddr = addr
	}
	log.Printf("%s \"%s %s\" [%s]\n", r.RemoteAddr, r.Method, r.URL.Path, r.UserAgent())

	// Read the body
	if r.ContentLength < 0 || r.ContentLength > 6553600 {
		http.Error(w, "{errmsg:\"Request too large or request size unknown\"}", http.StatusRequestEntityTooLarge)
		return
	}

	// Access wg infos
	tokenhex := []byte(ps.ByName("token"))
	tokendec := make([]byte, hex.DecodedLen(len(tokenhex)))
	n, err := hex.Decode(tokendec, tokenhex)
	if err != nil {
		http.Error(w, fmt.Sprintf("{errmsg:%q}", err), http.StatusBadRequest)
		return
	}

	token, err := adlin.GetTunnelToken(tokendec[:n])
	if err != nil {
		http.Error(w, fmt.Sprintf("{errmsg:%q}", err), http.StatusBadRequest)
		return
	}

	var pt PubTunnel
	var version int
	if r.Method == "POST" {
		if err := json.NewDecoder(r.Body).Decode(&pt); err != nil {
			http.Error(w, fmt.Sprintf("{errmsg:%q}", err), http.StatusBadRequest)
			return
		}
		version = 2
	} else if pubkey := r.Header.Get("X-WG-PubKey"); pubkey != "" {
		pt.PubKey, _ = base64.StdEncoding.DecodeString(pubkey)
		version = 3
	} else {
		http.Error(w, fmt.Sprintf("{errmsg:\"No public key given\"}"), http.StatusBadRequest)
		return
	}

	token.PubKey = pt.PubKey
	token.Version = version
	_, err = token.Update()
	if err != nil {
		http.Error(w, fmt.Sprintf("{errmsg:%q}", err), http.StatusBadRequest)
		return
	}

	// 0 is considered default for suffix, apply default now
	if token.SuffixIP <= 0 {
		token.SuffixIP = 1
	}

	syncWgConf()

	tinfo := getTunnelInfo(token.IdStudent, token.OverrideID)

	var student *adlin.Student
	student, err = adlin.GetStudent(int(token.IdStudent))
	if err != nil {
		http.Error(w, fmt.Sprintf("{errmsg:%q}", err), http.StatusBadRequest)
		return
	}

	w.Header().Set("Content-Type", "text/plain")
	w.Write([]byte(fmt.Sprintf(`[Peer]
PublicKey = %s
Endpoint = %s:%d
AllowedIPs = ::/0
PersistentKeepalive = 5
# MyIPv6=%s%x/%d
# MyNetwork=%s/%d
# GWIPv6=%s
# MyLogin=%s
`, base64.StdEncoding.EncodeToString(tinfo.SrvPubKey), "82.64.151.41", tinfo.SrvPort, tinfo.CltIPv6, token.SuffixIP, 64, tinfo.CltIPv6, tinfo.CltRange, tinfo.SrvGW6, student.Login)))
	if version > 2 {
		w.Write([]byte(fmt.Sprintf(`# KeySign=%s`, base64.StdEncoding.EncodeToString(token.GenKeySign()))))
	}

}

func updateWgTunnel(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
	token, err := adlin.GetTunnelToken(adlin.TokenFromText(ps.ByName("token")))
	if err != nil {
		return nil, err
	}

	if token.IdStudent != student.Id {
		return nil, fmt.Errorf("Unauthorized")
	}

	var newToken adlin.TunnelToken
	if err := json.Unmarshal(body, &newToken); err != nil {
		return nil, err
	}

	token.TokenText = newToken.TokenText
	token.PubKey = newToken.PubKey
	token.SuffixIP = newToken.SuffixIP

	if _, err = token.Update(); err != nil {
		return nil, err
	}

	syncWgConf()

	return true, err
}

func deleteWgTunnel(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
	token, err := adlin.GetTunnelToken(adlin.TokenFromText(ps.ByName("token")))
	if err != nil {
		return nil, err
	}

	if token.IdStudent != student.Id {
		return nil, fmt.Errorf("Unauthorized")
	}

	if _, err = token.Delete(); err != nil {
		return nil, err
	}

	syncWgConf()

	return true, err
}

func GenWGConfig(w io.Writer) error {
	ts, err := adlin.GetStudentsTunnels()
	if err != nil {
		return err
	}

	for _, t := range ts {
		if t.PubKey == nil {
			continue
		}

		w.Write([]byte(fmt.Sprintf(`[Peer]
#IdStudent = %d
PublicKey = %s
AllowedIPs = %s/%d
`, t.IdStudent, base64.StdEncoding.EncodeToString(t.PubKey), adlin.StudentIP(t.IdStudent, t.OverrideID), 80)))
	}

	return nil
}

func syncWgConf() (err error) {
	_, err = exec.Command("sh", "/root/wg-sync.sh").Output()
	return
}