package client

import (
	"bytes"
	"crypto/rsa"
	"crypto/sha256"
	"encoding/json"
	"errors"
	"net/http"
	"time"

	"github.com/dgrijalva/jwt-go"

	peering "forge.cadoles.com/wpetit/go-http-peering"
	"forge.cadoles.com/wpetit/go-http-peering/crypto"
	"forge.cadoles.com/wpetit/go-http-peering/server"
)

const (
	DefaultBody = "{}"
)

var (
	ErrInvalidPrivateKey  = errors.New("invalid private key")
	ErrUnexpectedResponse = errors.New("unexpected response")
	ErrUnauthorized       = errors.New("unauthorized")
	ErrRejected           = errors.New("rejected")
	ErrInvalidServerToken = errors.New("invalid server token")
)

type Client struct {
	options *Options
}

func (c *Client) Advertise(attrs peering.PeerAttributes) error {
	url := c.options.BaseURL + peering.AdvertisePath

	publicKey, err := crypto.EncodePublicKeyToPEM(c.options.PrivateKey.Public())
	if err != nil {
		return err
	}

	data := &peering.AdvertisingRequest{
		Attributes: attrs,
		PublicKey:  publicKey,
	}

	res, err := c.Post(url, data)
	if err != nil {
		return err
	}

	switch res.StatusCode {
	case http.StatusCreated:
		return nil
	case http.StatusConflict:
		return peering.ErrPeerExists
	default:
		return ErrUnexpectedResponse
	}
}

func (c *Client) UpdateAttributes(attrs peering.PeerAttributes) error {
	url := c.options.BaseURL + peering.UpdatePath

	data := &peering.UpdateRequest{
		Attributes: attrs,
	}

	res, err := c.Post(url, data)
	if err != nil {
		return err
	}

	switch res.StatusCode {
	case http.StatusNoContent:
		return nil
	case http.StatusUnauthorized:
		return ErrUnauthorized
	case http.StatusForbidden:
		return ErrRejected
	default:
		return ErrUnexpectedResponse
	}
}

func (c *Client) Ping() error {
	url := c.options.BaseURL + peering.PingPath

	res, err := c.Post(url, nil)
	if err != nil {
		return err
	}

	switch res.StatusCode {
	case http.StatusNoContent:
		return nil
	case http.StatusUnauthorized:
		return ErrUnauthorized
	case http.StatusForbidden:
		return ErrRejected
	default:
		return ErrUnexpectedResponse
	}
}

func (c *Client) Get(url string) (*http.Response, error) {
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}
	if err := c.addClientToken(req, nil); err != nil {
		return nil, err
	}
	return c.options.HTTPClient.Do(req)
}

func (c *Client) Post(url string, data interface{}) (*http.Response, error) {
	req, body, err := c.createPostRequest(url, data)
	if err != nil {
		return nil, err
	}
	if err := c.addClientToken(req, body); err != nil {
		return nil, err
	}
	return c.options.HTTPClient.Do(req)
}

func (c *Client) createPostRequest(url string, data interface{}) (*http.Request, []byte, error) {
	body, err := json.Marshal(data)
	if err != nil {
		return nil, nil, err
	}

	req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return nil, nil, err
	}

	req.Header.Set("Content-Type", "application/json")

	return req, body, nil
}

func (c *Client) addServerToken(r *http.Request) {
	r.Header.Set(
		server.ServerTokenHeader,
		c.options.ServerToken,
	)
}

func (c *Client) addClientToken(r *http.Request, body []byte) error {
	bodySum, err := c.createBodySum(body)
	if err != nil {
		return err
	}

	token := jwt.NewWithClaims(jwt.SigningMethodRS256, peering.ClientTokenClaims{
		StandardClaims: jwt.StandardClaims{
			NotBefore: time.Now().Unix(),
			ExpiresAt: time.Now().Add(time.Minute * 10).Unix(),
		},
		BodySum: bodySum,
	})

	tokenStr, err := token.SignedString(c.options.PrivateKey)
	if err != nil {
		return err
	}

	r.Header.Set(server.ClientTokenHeader, tokenStr)

	c.addServerToken(r)

	return nil
}

func (c *Client) createBodySum(body []byte) ([]byte, error) {
	if body == nil || len(body) == 0 {
		body = []byte(DefaultBody)
	}
	sha := sha256.New()
	_, err := sha.Write(body)
	if err != nil {
		return nil, err
	}
	return sha.Sum(nil), nil
}

func (c *Client) PeerID(serverPublicKey *rsa.PublicKey) (peering.PeerID, error) {
	token, err := jwt.ParseWithClaims(
		c.options.ServerToken,
		&peering.ServerTokenClaims{},
		func(token *jwt.Token) (interface{}, error) {
			return serverPublicKey, nil
		},
	)
	if err != nil {
		return "", err
	}
	if !token.Valid {
		return "", ErrInvalidServerToken
	}
	serverClaims, ok := token.Claims.(*peering.ServerTokenClaims)
	if !ok {
		return "", ErrInvalidServerToken
	}
	return serverClaims.PeerID, nil
}

func New(funcs ...OptionFunc) *Client {
	options := createOptions(funcs...)
	return &Client{options}
}