package auth

import (
	"encoding/json"
	"net/http"
	"time"

	"github.com/labstack/echo/v4"

	"dynatron.me/x/blasphem/pkg/auth/provider"
)

type SessionStore struct {
	s        map[TokenID]*Token
	lastCull time.Time
}

type TokenID string

func (t *TokenID) IsValid() bool {
	// TODO: more validation than this
	return *t != ""
}

type Token struct { // TODO: jwt bro
	ID      TokenID
	Ctime   time.Time
	Expires time.Time
	Addr    string

	user provider.ProviderUser `json:"-"`
}

func (ss *SessionStore) init() {
	ss.s = make(map[TokenID]*Token)
}

const cullInterval = 5 * time.Minute

func (ss *SessionStore) cull() {
	if now := time.Now(); now.Sub(ss.lastCull) > cullInterval {
		for k, v := range ss.s {
			if now.After(v.Expires) {
				delete(ss.s, k)
			}
		}
	}
}

func (ss *SessionStore) register(t *Token) {
	ss.cull()
	ss.s[t.ID] = t
}

func (ss *SessionStore) verify(tr *TokenRequest, r *http.Request) (provider.ProviderUser, bool) {
	if t, hasToken := ss.s[tr.Code]; hasToken {
		// TODO: JWT
		if t.Expires.After(time.Now()) {
			return t.user, true
		} else {
			delete(ss.s, t.ID)
		}
	}

	return nil, false
}

type Credential struct {
	ID               CredID          `json:"id"`
	UserID           UserID          `json:"user_id"`
	AuthProviderType string          `json:"auth_provider_type"`
	AuthProviderID   *string         `json:"auth_provider_id"`
	DataRaw          json.RawMessage `json:"data,omitempty"`
	user             provider.ProviderUser
}

func (cred *Credential) MarshalJSON() ([]byte, error) {
	rm := map[string]interface{}{
		"id":                 cred.ID,
		"user_id":            cred.UserID,
		"auth_provider_type": cred.user.ProviderType(),
		"auth_provider_id":   cred.user.ProviderID(),
	}

	providerData := cred.user.ProviderUserData()
	if providerData != nil {
		rm["data"] = providerData
	}

	return json.Marshal(rm)
}

func (ss *SessionStore) verifyAndGetCredential(tr *TokenRequest, r *http.Request) *Credential {
	user, success := ss.verify(tr, r)
	if !success {
		return nil
	}

	return &Credential{user: user}
}

const defaultExpiration = 2 * time.Hour

func (a *Authenticator) NewToken(r *http.Request, user provider.ProviderUser, f *Flow) TokenID {
	id := TokenID(genUUID())
	now := time.Now()

	t := &Token{
		ID:      id,
		Ctime:   now,
		Expires: now.Add(defaultExpiration),
		Addr:    r.RemoteAddr,

		user: user,
	}

	a.sessions.register(t)

	return id
}

type GrantType string

const (
	GTAuthorizationCode GrantType = "authorization_code"
	GTRefreshToken      GrantType = "refresh_token"
)

type ClientID string

func (c *ClientID) IsValid() bool {
	// TODO: || !indieauth.VerifyClientID(rq.ClientID)?
	return *c != ""
}

type TokenRequest struct {
	ClientID  ClientID  `form:"client_id"`
	Code      TokenID   `form:"code"`
	GrantType GrantType `form:"grant_type"`
}

func (a *Authenticator) TokenHandler(c echo.Context) error {
	rq := new(TokenRequest)
	err := c.Bind(rq)
	if err != nil {
		return err
	}

	switch rq.GrantType {
	case GTAuthorizationCode:
		if !rq.ClientID.IsValid() {
			return c.JSON(http.StatusBadRequest, AuthError{Error: "invalid_request", Description: "invalid client ID"})
		}

		if !rq.Code.IsValid() {
			return c.JSON(http.StatusBadRequest, AuthError{Error: "invalid_request", Description: "invalid code"})
		}

		if cred := a.sessions.verifyAndGetCredential(rq, c.Request()); cred != nil {
			// TODO: success
			user, err := a.getOrCreateUser(cred)
			if err != nil {
				return c.JSON(http.StatusUnauthorized, AuthError{Error: "access_denied", Description: err.Error()})
			}

			if err := user.allowedToAuth(); err != nil {
				return c.JSON(http.StatusUnauthorized, AuthError{Error: "access_denied", Description: err.Error()})
			}
			return c.String(http.StatusOK, "token good I guess")
		}
	case GTRefreshToken:
		return c.String(http.StatusNotImplemented, "not implemented")
	}

	return c.String(http.StatusUnauthorized, "token bad I guess")
}