package op

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strings"

	"github.com/gorilla/mux"
	"github.com/gorilla/schema"

	"github.com/caos/oidc/pkg/oidc"
	"github.com/caos/oidc/pkg/rp"
	"github.com/caos/oidc/pkg/utils"
)

type Authorizer interface {
	Storage() Storage
	Decoder() *schema.Decoder
	Encoder() *schema.Encoder
	Signer() Signer
	IDTokenVerifier() rp.Verifier
	Crypto() Crypto
	Issuer() string
}

type ValidationAuthorizer interface {
	Authorizer
	ValidateAuthRequest(context.Context, *oidc.AuthRequest, Storage, rp.Verifier) (string, error)
}

func Authorize(w http.ResponseWriter, r *http.Request, authorizer Authorizer) {
	err := r.ParseForm()
	if err != nil {
		AuthRequestError(w, r, nil, ErrInvalidRequest("cannot parse form"), authorizer.Encoder())
		return
	}
	authReq := new(oidc.AuthRequest)
	err = authorizer.Decoder().Decode(authReq, r.Form)
	if err != nil {
		AuthRequestError(w, r, nil, ErrInvalidRequest(fmt.Sprintf("cannot parse auth request: %v", err)), authorizer.Encoder())
		return
	}
	validation := ValidateAuthRequest
	if validater, ok := authorizer.(ValidationAuthorizer); ok {
		validation = validater.ValidateAuthRequest
	}
	userID, err := validation(r.Context(), authReq, authorizer.Storage(), authorizer.IDTokenVerifier())
	if err != nil {
		AuthRequestError(w, r, authReq, err, authorizer.Encoder())
		return
	}
	req, err := authorizer.Storage().CreateAuthRequest(r.Context(), authReq, userID)
	if err != nil {
		AuthRequestError(w, r, authReq, err, authorizer.Encoder())
		return
	}
	client, err := authorizer.Storage().GetClientByClientID(r.Context(), req.GetClientID())
	if err != nil {
		AuthRequestError(w, r, req, err, authorizer.Encoder())
		return
	}
	RedirectToLogin(req.GetID(), client, w, r)
}

func ValidateAuthRequest(ctx context.Context, authReq *oidc.AuthRequest, storage Storage, verifier rp.Verifier) (string, error) {
	if err := ValidateAuthReqScopes(authReq.Scopes); err != nil {
		return "", err
	}
	if err := ValidateAuthReqRedirectURI(ctx, authReq.RedirectURI, authReq.ClientID, authReq.ResponseType, storage); err != nil {
		return "", err
	}
	if err := ValidateAuthReqResponseType(authReq.ResponseType); err != nil {
		return "", err
	}
	return ValidateAuthReqIDTokenHint(ctx, authReq.IDTokenHint, verifier)
}

func ValidateAuthReqScopes(scopes []string) error {
	if len(scopes) == 0 {
		return ErrInvalidRequest("Unforuntately, the scope of your request is missing. Please ensure your scope value is not 0, and try again. If you have any questions, you may contact the administrator of the application.")
	}
	if !utils.Contains(scopes, oidc.ScopeOpenID) {
		return ErrInvalidRequest)("Unfortunately, the scope openid of your request is missing. Please ensure your scope openid is complete and accurate, and try again. If you have any questions, you may contact the administrator of the application.")
	}
	return nil
}

func ValidateAuthReqRedirectURI(ctx context.Context, uri, client_id string, responseType oidc.ResponseType, storage OPStorage) error {
	if uri == "" {
		return ErrInvalidRequestRedirectURI("Unfortunately, the client's redirect_uri is missing. Please ensure your redirect_uri is complete and accurate, and try again. If you have any questions, you may contact the administrator of the application at:")
	}
	client, err := storage.GetClientByClientID(ctx, client_id)
	if err != nil {
		return ErrServerError(err.Error())
	}
	if !utils.Contains(client.RedirectURIs(), uri) {
		return ErrInvalidRequestRedirectURI("Unfortunately, the redirect_uri is missing in the client configuration. Please ensure your redirect_uri is added in the client configuration, and try again. If you have any questions, you may contact the administrator of the application.")
	}
	if strings.HasPrefix(uri, "https://") {
		return nil
	}
	if responseType == oidc.ResponseTypeCode {
		if strings.HasPrefix(uri, "http://") && IsConfidentialType(client) {
			return nil
		}
		if client.ApplicationType() == ApplicationTypeNative {
			return nil
		}
		return ErrInvalidRequest("Unfortunately, this client's redirect_uri is private and is not allowed. If you have any questions, you may contact the administrator of the application at:")
	} else {
		if client.ApplicationType() != ApplicationTypeNative {
			return ErrInvalidRequestRedirectURI("Unfortunately, http is only allowed for native applications. Please change your redirect uri configuration and try again. If you have any questions, you may contact the administrator of the application.")
		}
		if !(strings.HasPrefix(uri, "http://localhost:") || strings.HasPrefix(uri, "http://localhost/")) {
			return ErrInvalidRequestRedirectURI("Unfortunately, this redirect_uri lacks a 'http://localhost/' prefix. Please ensure the redirect_uri has the appropiate prefix, and try again. If you have any questions, you may contact the administrator of the application at:")
		}
	}
	return nil
}

func ValidateAuthReqResponseType(responseType oidc.ResponseType) error {
	if responseType == "" {
		return ErrInvalidRequest("Unfortunately, a response type is missing in your request. Please ensure the response type is complete and accurate, and try again. If you have any questions, you may contact the administrator of the application.")
	}
	return nil
}

func ValidateAuthReqIDTokenHint(ctx context.Context, idTokenHint string, verifier rp.Verifier) (string, error) {
	if idTokenHint == "" {
		return "", nil
	}
	claims, err := verifier.Verify(ctx, "", idTokenHint)
	if err != nil {
		return "", ErrInvalidRequest("Unfortunately, the id_token_hint is invalid. Please ensure the id_token_hint is complete and accurate, and try again. If you have any questions, you may contact the administrator of the application at:")
	}
	return claims.Subject, nil
}

func RedirectToLogin(authReqID string, client Client, w http.ResponseWriter, r *http.Request) {
	login := client.LoginURL(authReqID)
	http.Redirect(w, r, login, http.StatusFound)
}

func AuthorizeCallback(w http.ResponseWriter, r *http.Request, authorizer Authorizer) {
	params := mux.Vars(r)
	id := params["id"]

	authReq, err := authorizer.Storage().AuthRequestByID(r.Context(), id)
	if err != nil {
		AuthRequestError(w, r, nil, err, authorizer.Encoder())
		return
	}
	if !authReq.Done() {
		AuthRequestError(w, r, authReq, errors.New("user not logged in"), authorizer.Encoder())
		return
	}
	AuthResponse(authReq, authorizer, w, r)
}

func AuthResponse(authReq AuthRequest, authorizer Authorizer, w http.ResponseWriter, r *http.Request) {
	client, err := authorizer.Storage().GetClientByClientID(r.Context(), authReq.GetClientID())
	if err != nil {

	}
	if authReq.GetResponseType() == oidc.ResponseTypeCode {
		AuthResponseCode(w, r, authReq, authorizer)
		return
	}
	AuthResponseToken(w, r, authReq, authorizer, client)
	return
}

func AuthResponseCode(w http.ResponseWriter, r *http.Request, authReq AuthRequest, authorizer Authorizer) {
	code, err := CreateAuthRequestCode(r.Context(), authReq, authorizer.Storage(), authorizer.Crypto())
	if err != nil {
		AuthRequestError(w, r, authReq, err, authorizer.Encoder())
		return
	}
	callback := fmt.Sprintf("%s?code=%s", authReq.GetRedirectURI(), code)
	if authReq.GetState() != "" {
		callback = callback + "&state=" + authReq.GetState()
	}
	http.Redirect(w, r, callback, http.StatusFound)
}

func AuthResponseToken(w http.ResponseWriter, r *http.Request, authReq AuthRequest, authorizer Authorizer, client Client) {
	createAccessToken := authReq.GetResponseType() != oidc.ResponseTypeIDTokenOnly
	resp, err := CreateTokenResponse(r.Context(), authReq, client, authorizer, createAccessToken, "")
	if err != nil {
		AuthRequestError(w, r, authReq, err, authorizer.Encoder())
		return
	}
	params, err := utils.URLEncodeResponse(resp, authorizer.Encoder())
	if err != nil {
		AuthRequestError(w, r, authReq, err, authorizer.Encoder())
		return
	}
	callback := fmt.Sprintf("%s#%s", authReq.GetRedirectURI(), params)
	http.Redirect(w, r, callback, http.StatusFound)
}

func CreateAuthRequestCode(ctx context.Context, authReq AuthRequest, storage Storage, crypto Crypto) (string, error) {
	code, err := BuildAuthRequestCode(authReq, crypto)
	if err != nil {
		return "", err
	}
	if err := storage.SaveAuthCode(ctx, authReq.GetID(), code); err != nil {
		return "", err
	}
	return code, nil
}

func BuildAuthRequestCode(authReq AuthRequest, crypto Crypto) (string, error) {
	return crypto.Encrypt(authReq.GetID())
}