package mockid

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"math/big"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"sync"
	"time"

	"git.rootprojects.org/root/keypairs"
	//jwt "github.com/dgrijalva/jwt-go"
)

type PublicJWK struct {
	Crv   string `json:"crv"`
	KeyID string `json:"kid,omitempty"`
	Kty   string `json:"kty,omitempty"`
	X     string `json:"x"`
	Y     string `json:"y"`
}

type InspectableToken struct {
	Public    keypairs.PublicKey     `json:"jwk"`
	Protected map[string]interface{} `json:"protected"`
	Payload   map[string]interface{} `json:"payload"`
	Signature string                 `json:"signature"`
	Verified  bool                   `json:"verified"`
	Errors    []string               `json:"errors"`
}

func (t *InspectableToken) MarshalJSON() ([]byte, error) {
	pub := keypairs.MarshalJWKPublicKey(t.Public)
	header, _ := json.Marshal(t.Protected)
	payload, _ := json.Marshal(t.Payload)
	errs, _ := json.Marshal(t.Errors)
	return []byte(fmt.Sprintf(
		`{"jwk":%s,"protected":%s,"payload":%s,"signature":%q,"verified":%t,"errors":%s}`,
		pub, header, payload, t.Signature, t.Verified, errs,
	)), nil
}

var defaultFrom string
var defaultReplyTo string

//var nonces map[string]int64
//var nonCh chan string
var nonces sync.Map
var salt []byte

func Init() {
	var err error
	salt64 := os.Getenv("SALT")
	salt, err = base64.RawURLEncoding.DecodeString(salt64)
	if len(salt64) < 22 || nil != err {
		panic("SALT must be set as 22+ character base64")
	}
	defaultFrom = os.Getenv("MAILER_FROM")
	defaultReplyTo = os.Getenv("MAILER_REPLY_TO")
	//nonces = make(map[string]int64)
	//nonCh = make(chan string)

	/*
		  go func() {
		    for {
		      nonce := <- nonCh
			    nonces[nonce] = time.Now().Unix()
		    }
		  }()
	*/
}

func GenToken(host string, privkey keypairs.PrivateKey, query url.Values) (string, string, string) {
	thumbprint := keypairs.ThumbprintPublicKey(keypairs.NewPublicKey(privkey.Public()))
	// TODO keypairs.Alg(key)
	alg := "ES256"
	switch privkey.(type) {
	case *rsa.PrivateKey:
		alg = "RS256"
	}
	protected := fmt.Sprintf(`{"typ":"JWT","alg":%q,"kid":"%s"}`, alg, thumbprint)
	protected64 := base64.RawURLEncoding.EncodeToString([]byte(protected))

	exp, err := parseExp(query.Get("exp"))
	if nil != err {
		// cryptic error code
		// TODO propagate error
		exp = 422
	}

	payload := fmt.Sprintf(
		`{"iss":"%s/","sub":"dummy","exp":%s}`,
		host, strconv.FormatInt(time.Now().Add(time.Duration(exp)*time.Second).Unix(), 10),
	)
	payload64 := base64.RawURLEncoding.EncodeToString([]byte(payload))

	hash := sha256.Sum256([]byte(fmt.Sprintf(`%s.%s`, protected64, payload64)))
	sig := JOSESign(privkey, hash[:])
	sig64 := base64.RawURLEncoding.EncodeToString(sig)
	token := fmt.Sprintf("%s.%s.%s\n", protected64, payload64, sig64)
	return protected, payload, token
}

// TODO: move to keypairs

func JOSEVerify(pubkey keypairs.PublicKey, hash []byte, sig []byte) bool {
	var verified bool

	switch pub := pubkey.Key().(type) {
	case *rsa.PublicKey:
		// TODO keypairs.Size(key) to detect key size ?
		//alg := "SHA256"
		// TODO: this hasn't been tested yet
		if err := rsa.VerifyPKCS1v15(pub, crypto.SHA256, hash, sig); nil != err {
			verified = true
		}
	case *ecdsa.PublicKey:
		r := &big.Int{}
		r.SetBytes(sig[0:32])
		s := &big.Int{}
		s.SetBytes(sig[32:])
		fmt.Println("debug: sig len:", len(sig))
		fmt.Println("debug: r, s:", r, s)
		verified = ecdsa.Verify(pub, hash, r, s)
	default:
		panic("impossible condition: non-rsa/non-ecdsa key")
	}

	return verified
}

func JOSESign(privkey keypairs.PrivateKey, hash []byte) []byte {
	var sig []byte

	switch k := privkey.(type) {
	case *rsa.PrivateKey:
		panic("TODO: implement rsa sign")
	case *ecdsa.PrivateKey:
		r, s, _ := ecdsa.Sign(rand.Reader, k, hash[:])
		rb := r.Bytes()
		fmt.Println("debug:")
		fmt.Println(r, s)
		for len(rb) < 32 {
			rb = append([]byte{0}, rb...)
		}
		sb := s.Bytes()
		for len(rb) < 32 {
			sb = append([]byte{0}, sb...)
		}
		sig = append(rb, sb...)
	}
	return sig
}

func issueNonce(w http.ResponseWriter, r *http.Request) {
	b := make([]byte, 16)
	_, _ = rand.Read(b)
	nonce := base64.RawURLEncoding.EncodeToString(b)
	//nonCh <- nonce
	nonces.Store(nonce, time.Now())

	w.Header().Set("Replay-Nonce", nonce)
}

func requireNonce(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		nonce := r.Header.Get("Replay-Nonce")
		// TODO expire nonces every so often
		//t := nonces[nonce]
		var t time.Time
		tmp, ok := nonces.Load(nonce)
		if ok {
			t = tmp.(time.Time)
		}
		if !ok || time.Now().Sub(t) > 15*time.Minute {
			http.Error(
				w,
				`{ "error": "invalid or expired nonce", "error_code": "ENONCE" }`,
				http.StatusBadRequest,
			)
			return
		}

		//delete(nonces, nonce)
		nonces.Delete(nonce)
		issueNonce(w, r)

		next(w, r)
	}
}