package service

import (
	"context"
	"crypto/rand"
	"crypto/subtle"
	"database/sql"
	"encoding/base64"
	"errors"
	"log/slog"
	"net/http"
	"net/mail"
	"net/url"
	"strings"
	"time"

	"me-fit/template"
	"me-fit/template/auth"
	tempMail "me-fit/template/mail"
	"me-fit/types"
	"me-fit/utils"

	"github.com/a-h/templ"
	"github.com/google/uuid"
	"golang.org/x/crypto/argon2"
)

func HandleSignInPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)

		if user == nil {
			userComp := UserInfoComp(nil)
			signIn := auth.SignInOrUpComp(true)
			err := template.Layout(signIn, userComp).Render(r.Context(), w)

			if err != nil {
				utils.LogError("Failed to render sign in page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}

		} else if !user.EmailVerified {
			utils.DoRedirect(w, r, "/auth/verify")
		} else {
			utils.DoRedirect(w, r, "/")
		}
	}
}

func HandleSignUpPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)

		if user == nil {
			userComp := UserInfoComp(nil)
			signUpComp := auth.SignInOrUpComp(false)
			err := template.Layout(signUpComp, userComp).Render(r.Context(), w)

			if err != nil {
				utils.LogError("Failed to render sign up page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}

		} else if !user.EmailVerified {
			utils.DoRedirect(w, r, "/auth/verify")
		} else {
			utils.DoRedirect(w, r, "/")
		}
	}
}

func HandleSignUpVerifyPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)
		if user == nil {
			utils.DoRedirect(w, r, "/auth/signin")
		} else if user.EmailVerified {
			utils.DoRedirect(w, r, "/")
		} else {
			userComp := UserInfoComp(user)
			signIn := auth.VerifyComp()
			err := template.Layout(signIn, userComp).Render(r.Context(), w)
			if err != nil {
				utils.LogError("Failed to render verify page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}
		}
	}
}

func HandleDeleteAccountPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// An unverified email should be able to delete their account
		user := utils.GetUserFromSession(db, r)
		if user == nil {
			utils.DoRedirect(w, r, "/auth/signin")
		} else {
			userComp := UserInfoComp(user)
			comp := auth.DeleteAccountComp()
			err := template.Layout(comp, userComp).Render(r.Context(), w)
			if err != nil {
				utils.LogError("Failed to render delete account page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}
		}
	}
}

func HandleSignUpVerifyResponsePage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		token := r.URL.Query().Get("token")

		if token == "" {
			utils.DoRedirect(w, r, "/auth/verify")
			return
		}

		result, err := db.Exec(`
			UPDATE user
			SET email_verified = true, email_verified_at = datetime()
			WHERE user_uuid = (
				SELECT user_uuid
				FROM user_token
				WHERE type = "email_verify"
				AND token = ?
			);
		`, token)

		if err != nil {
			utils.LogError("Could not update user on verify response", err)
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}

		i, err := result.RowsAffected()
		if err != nil {
			utils.LogError("Could not get rows affected on verify response", err)
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}

		if i == 0 {
			utils.DoRedirect(w, r, "/")
		} else {
			utils.DoRedirect(w, r, "/auth/signin")
		}
	}
}

func HandleChangePasswordPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		isPasswordReset := r.URL.Query().Has("token")

		user := utils.GetUserFromSession(db, r)
		if user == nil && !isPasswordReset {
			utils.DoRedirect(w, r, "/auth/signin")
		} else {
			userComp := UserInfoComp(user)
			comp := auth.ChangePasswordComp(isPasswordReset)
			err := template.Layout(comp, userComp).Render(r.Context(), w)
			if err != nil {
				utils.LogError("Failed to render change password page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}
		}
	}
}

func HandleResetPasswordPage(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		user := utils.GetUserFromSession(db, r)
		if user != nil {
			utils.DoRedirect(w, r, "/auth/signin")
		} else {
			userComp := UserInfoComp(nil)
			comp := auth.ResetPasswordComp()
			err := template.Layout(comp, userComp).Render(r.Context(), w)
			if err != nil {
				utils.LogError("Failed to render change password page", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}
		}
	}
}

func UserInfoComp(user *types.User) templ.Component {

	if user != nil {
		return auth.UserComp(user.Email)
	} else {
		return auth.UserComp("")
	}
}

func HandleSignUpComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var email = r.FormValue("email")
		var password = r.FormValue("password")

		_, err := mail.ParseAddress(email)
		if err != nil {
			http.Error(w, "Invalid email", http.StatusBadRequest)
			return
		}

		err = checkPassword(password)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		userId, err := uuid.NewRandom()
		if err != nil {
			utils.LogError("Could not generate UUID", err)
			auth.Error("Internal Server Error").Render(r.Context(), w)
			return
		}

		salt := make([]byte, 16)
		_, err = rand.Read(salt)
		if err != nil {
			utils.LogError("Could not generate salt", err)
			auth.Error("Internal Server Error").Render(r.Context(), w)
			return
		}

		hash := getHashPassword(password, salt)

		_, err = db.Exec("INSERT INTO user (user_uuid, email, email_verified, is_admin, password, salt, created_at) VALUES (?, ?, FALSE, FALSE, ?, ?, datetime())", userId, email, hash, salt)
		if err != nil {
			// This does leak information about the email being in use, though not specifically stated
			// It needs to be refacoteres to "If the email is not already in use, an email has been send to your address", or something
			// The happy path, currently a redirect, needs to send the same message!
			// Then it is also important to have the same compute time in both paths
			// Otherwise an attacker could guess emails when comparing the response time
			if strings.Contains(err.Error(), "email") {
				auth.Error("Bad Request").Render(r.Context(), w)
				return
			}

			utils.LogError("Could not insert user", err)
			auth.Error("Internal Server Error").Render(r.Context(), w)
			return
		}

		result := tryCreateSessionAndSetCookie(r, w, db, userId)
		if !result {
			return
		}

		// Send verification email as a goroutine
		go sendVerificationEmail(db, userId.String(), email)

		utils.DoRedirect(w, r, "/auth/verify")
	}
}

func HandleSignInComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var email = r.FormValue("email")
		var password = r.FormValue("password")

		var result bool = true
		start := time.Now()

		var (
			userId        uuid.UUID
			savedHash     []byte
			salt          []byte
			emailVerified bool
		)
		err := db.QueryRow("SELECT user_uuid, password, salt, email_verified FROM user WHERE email = ?", email).Scan(&userId, &savedHash, &salt, &emailVerified)
		if err != nil {
			result = false
		}

		if result {
			new_hash := getHashPassword(password, salt)

			if subtle.ConstantTimeCompare(new_hash, savedHash) == 0 {
				result = false
			}
		}

		if result {
			result := tryCreateSessionAndSetCookie(r, w, db, userId)
			if !result {
				return
			}
		}

		duration := time.Since(start)
		timeToWait := 100 - duration.Milliseconds()
		// It is important to sleep for a while to prevent timing attacks
		// If the email is correct, the server will calculate the hash, which will take some time
		// This way an attacker could guess emails when comparing the response time
		// Because of that, we cant use WriteHeader in the middle of the function. We have to wait until the end
		// Unfortunatly this makes the code harder to read
		time.Sleep(time.Duration(timeToWait) * time.Millisecond)

		if result {
			if !emailVerified {
				utils.DoRedirect(w, r, "/auth/verify")
			} else {
				utils.DoRedirect(w, r, "/")
			}
		} else {
			auth.Error("Invalid email or password").Render(r.Context(), w)
		}
	}
}

func HandleSignOutComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)

		if user != nil {
			_, err := db.Exec("DELETE FROM session WHERE session_id = ?", user.SessionId)
			if err != nil {
				utils.LogError("Could not delete session", err)
				utils.TriggerToast(w, r, "error", "Internal Server Error")
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
		}

		c := http.Cookie{
			Name:     "id",
			Value:    "",
			MaxAge:   -1,
			Secure:   true,
			HttpOnly: true,
			SameSite: http.SameSiteStrictMode,
			Path:     "/",
		}

		http.SetCookie(w, &c)
		utils.DoRedirect(w, r, "/")
	}
}

func HandleDeleteAccountComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)
		if user == nil {
			utils.DoRedirect(w, r, "/auth/signin")
			return
		}

		password := r.FormValue("password")
		if password == "" {
			utils.TriggerToast(w, r, "error", "Password is required")
			return
		}

		var (
			storedHash []byte
			salt       []byte
		)

		err := db.QueryRow("SELECT password, salt FROM user WHERE user_uuid = ?", user.Id).Scan(&storedHash, &salt)
		if err != nil {
			utils.LogError("Could not get password", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		currHash := getHashPassword(password, salt)
		if subtle.ConstantTimeCompare(currHash, storedHash) == 0 {
			utils.TriggerToast(w, r, "error", "Password is not correct")
			return
		}

		_, err = db.Exec("DELETE FROM workout WHERE user_id = ?", user.Id)
		if err != nil {
			utils.LogError("Could not delete workouts", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		_, err = db.Exec("DELETE FROM user_token WHERE user_uuid = ?", user.Id)
		if err != nil {
			utils.LogError("Could not delete user tokens", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		_, err = db.Exec("DELETE FROM session WHERE user_uuid = ?", user.Id)
		if err != nil {
			utils.LogError("Could not delete sessions", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		_, err = db.Exec("DELETE FROM user WHERE user_uuid = ?", user.Id)
		if err != nil {
			utils.LogError("Could not delete user", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		go utils.SendMail(user.Email, "Account deleted", "Your account has been deleted")

		utils.DoRedirect(w, r, "/")
	}
}

func HandleVerifyResendComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		user := utils.GetUserFromSession(db, r)
		if user == nil || user.EmailVerified {
			utils.DoRedirect(w, r, "/auth/signin")
			return
		}

		go sendVerificationEmail(db, user.Id.String(), user.Email)

		w.Write([]byte("<p class=\"mt-8\">Verification email sent</p>"))
	}
}

func HandleChangePasswordComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		user := utils.GetUserFromSession(db, r)
		if user == nil {
			utils.DoRedirect(w, r, "/auth/signin")
			return
		}

		currPass := r.FormValue("current-password")
		newPass := r.FormValue("new-password")

		err := checkPassword(newPass)
		if err != nil {
			utils.TriggerToast(w, r, "error", err.Error())
			return
		}

		if currPass == newPass {
			utils.TriggerToast(w, r, "error", "Please use a new password")
			return
		}

		var (
			storedHash []byte
			salt       []byte
		)

		err = db.QueryRow("SELECT password, salt FROM user WHERE user_uuid = ?", user.Id).Scan(&storedHash, &salt)
		if err != nil {
			utils.LogError("Could not get password", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		currHash := getHashPassword(currPass, salt)
		if subtle.ConstantTimeCompare(currHash, storedHash) == 0 {
			utils.TriggerToast(w, r, "error", "Current Password is not correct")
			return
		}

		newHash := getHashPassword(newPass, salt)

		_, err = db.Exec("UPDATE user SET password = ? WHERE user_uuid = ?", newHash, user.Id)
		if err != nil {
			utils.LogError("Could not update password", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		utils.TriggerToast(w, r, "success", "Password changed")
	}
}

func HandleActualResetPasswordComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		pageUrl, err := url.Parse(r.Header.Get("HX-Current-URL"))
		if err != nil {
			utils.LogError("Could not get current URL", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		token := pageUrl.Query().Get("token")
		if token == "" {
			utils.TriggerToast(w, r, "error", "No token")
			return
		}

		newPass := r.FormValue("new-password")

		err = checkPassword(newPass)
		if err != nil {
			utils.TriggerToast(w, r, "error", err.Error())
			return
		}

		var (
			userId uuid.UUID
			salt   []byte
		)

		err = db.QueryRow(`
			SELECT u.user_uuid, salt
			FROM user_token t
			INNER JOIN user u ON t.user_uuid = u.user_uuid
			WHERE t.token = ? 
			AND t.type = 'password_reset'
			AND t.expires_at > datetime()
			`, token).Scan(&userId, &salt)
		if err != nil {
			slog.Warn("Could not get user from token: " + err.Error())
			utils.TriggerToast(w, r, "error", "Invalid token")
			return
		}

		_, err = db.Exec("DELETE FROM user_token WHERE token = ? AND type = 'password_reset'", token)
		if err != nil {
			utils.LogError("Could not delete token", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		passHash := getHashPassword(newPass, salt)

		_, err = db.Exec("UPDATE user SET password = ? WHERE user_uuid = ?", passHash, userId)
		if err != nil {
			utils.LogError("Could not update password", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		utils.TriggerToast(w, r, "success", "Password changed")
	}
}
func HandleResetPasswordComp(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		email := r.FormValue("email")
		if email == "" {
			utils.TriggerToast(w, r, "error", "Please enter an email")
			return
		}

		var b []byte = make([]byte, 32)
		_, err := rand.Reader.Read(b)
		if err != nil {
			utils.LogError("Could not generate token", err)
			return
		}
		token := base64.StdEncoding.EncodeToString(b)

		res, err := db.Exec(`
			INSERT INTO user_token (user_uuid, type, token, created_at, expires_at)
			SELECT user_uuid, 'password_reset', ?, datetime(), datetime('now', '+15 minute')
			FROM user
			WHERE email = ?
			`, token, email)
		if err != nil {
			utils.LogError("Could not insert token", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		i, err := res.RowsAffected()
		if err != nil {
			utils.LogError("Could not get rows affected", err)
			utils.TriggerToast(w, r, "error", "Internal Server Error")
			return
		}

		if i != 0 {
			var mail strings.Builder
			err = tempMail.ResetPassword(token).Render(context.Background(), &mail)
			if err != nil {
				utils.LogError("Could not render reset password email", err)
				utils.TriggerToast(w, r, "error", "Internal Server Error")
				return
			}
			utils.SendMail(email, "Reset Password", mail.String())
		}

		utils.TriggerToast(w, r, "info", "If the email exists, an email has been sent")
	}
}
func sendVerificationEmail(db *sql.DB, userId string, email string) {

	var token string
	err := db.QueryRow("SELECT token FROM user_token WHERE user_uuid = ? AND type = 'email_verify'", userId).Scan(&token)
	if err != nil && err != sql.ErrNoRows {
		utils.LogError("Could not get token", err)
		return
	}

	if token == "" {
		var b []byte = make([]byte, 32)
		_, err = rand.Reader.Read(b)
		if err != nil {
			utils.LogError("Could not generate token", err)
			return
		}
		token = base64.StdEncoding.EncodeToString(b)

		_, err = db.Exec("INSERT INTO user_token (user_uuid, type, token, created_at) VALUES (?, 'email_verify', ?, datetime())", userId, token)
		if err != nil {
			utils.LogError("Could not insert token", err)
			return
		}
	}

	var w strings.Builder
	err = tempMail.Register(token).Render(context.Background(), &w)
	if err != nil {
		utils.LogError("Could not render welcome email", err)
		return
	}
	utils.SendMail(email, "Welcome to ME-FIT", w.String())
}

func tryCreateSessionAndSetCookie(r *http.Request, w http.ResponseWriter, db *sql.DB, user_uuid uuid.UUID) bool {
	var session_id_bytes []byte = make([]byte, 32)
	_, err := rand.Reader.Read(session_id_bytes)
	if err != nil {
		utils.LogError("Could not generate session ID", err)
		auth.Error("Internal Server Error").Render(r.Context(), w)
		return false
	}
	session_id := base64.StdEncoding.EncodeToString(session_id_bytes)

	// Delete old inactive sessions
	_, err = db.Exec("DELETE FROM session WHERE created_at < datetime('now','-8 hours') AND user_uuid = ?", user_uuid)
	if err != nil {
		utils.LogError("Could not delete old sessions", err)
	}

	_, err = db.Exec("INSERT INTO session (session_id, user_uuid, created_at) VALUES (?, ?, datetime())", session_id, user_uuid)
	if err != nil {
		utils.LogError("Could not insert session", err)
		auth.Error("Internal Server Error").Render(r.Context(), w)
		return false
	}

	cookie := http.Cookie{
		Name:     "id",
		Value:    session_id,
		MaxAge:   60 * 60 * 8, // 8 hours
		Secure:   true,
		HttpOnly: true,
		SameSite: http.SameSiteStrictMode,
		Path:     "/",
	}
	http.SetCookie(w, &cookie)

	return true
}

func getHashPassword(password string, salt []byte) []byte {
	return argon2.IDKey([]byte(password), salt, 1, 64*1024, 1, 16)
}

func checkPassword(password string) error {

	if len(password) < 8 ||
		!strings.ContainsAny(password, "0123456789") ||
		!strings.ContainsAny(password, "ABCDEFGHIJKLMNOPQRSTUVWXYZ") ||
		!strings.ContainsAny(password, "abcdefghijklmnopqrstuvwxyz") ||
		!strings.ContainsAny(password, "!@#$%^&*()_+-=[]{}\\|;:'\",.<>/?") {
		return errors.New("Password needs to be 8 characters long, contain at least one number, one special, one uppercase and one lowercase character")
	} else {
		return nil
	}
}