package app

import (
	"bytes"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"time"

	"git.optclblast.xyz/draincloud/draincloud-core/internal/domain"
	"git.optclblast.xyz/draincloud/draincloud-core/internal/logger"
	"git.optclblast.xyz/draincloud/draincloud-core/internal/storage/models"
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"golang.org/x/crypto/bcrypt"
)

var (
	ErrorAccessDenied   = errors.New("access denied")
	ErrorSessionExpired = errors.New("session expired")
)

func (d *DrainCloud) Login(ctx *gin.Context) {
	logger.Debug(ctx, "[Login] new request")

	req := new(domain.LoginRequest)
	err := ctx.BindJSON(req)
	if err != nil {
		logger.Error(ctx, "[Login] failed to bind request", logger.Err(err))
		ctx.JSON(http.StatusBadRequest, map[string]string{
			"error": "bad request",
		})
		return
	}

	resp, err := d.login(ctx, req)
	if err != nil {
		logger.Error(ctx, "[Login] failed to login user", logger.Err(err))
		ctx.JSON(http.StatusInternalServerError, map[string]string{
			"error": err.Error(),
		})
		return
	}

	ctx.JSON(http.StatusOK, resp)
}

func (d *DrainCloud) login(ctx *gin.Context, req *domain.LoginRequest) (*domain.LoginResponse, error) {
	session, err := d.getSession(ctx)
	if err != nil && !errors.Is(err, http.ErrNoCookie) {
		return nil, err
	}

	if session != nil {
		if err := validateSession(ctx, session); err != nil {
			// TODO add audit log entry
			return nil, err
		}

		logger.Debug(ctx, "[login] user is already logged in", slog.String("session_id", session.ID.String()))
		return &domain.LoginResponse{
			Ok: true,
		}, nil
	}
	logger.Debug(ctx, "[login] session not found. trying to authorize")

	passwordHash, err := bcrypt.GenerateFromPassword([]byte(req.Password), 10)
	if err != nil {
		logger.Error(ctx, "[login] failed to generate password hash", logger.Err(err))
		return nil, fmt.Errorf("failed to generate password hash: %w", err)
	}

	user, err := d.database.GetUserByLogin(ctx, req.Login)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch user by login: %w", err)
	}

	if bytes.Equal(passwordHash, user.PasswordHash) {
		logger.Warn(ctx, "[login] failed to login user. passwords hashes not equal")
		return nil, ErrorAccessDenied
	}

	sessionCreatedAt := time.Now()
	sessionExpiredAt := sessionCreatedAt.Add(time.Hour * 24 * 7)

	sessionToken, err := generateSessionToken(100)
	if err != nil {
		return nil, fmt.Errorf("failed to generate a session token: %w", err)
	}
	ctx.SetCookie(sessionTokenCookie, sessionToken, int(sessionExpiredAt.Sub(sessionCreatedAt).Seconds()), "_path", "_domain", true, true)

	csrfToken, err := generateSessionToken(100)
	if err != nil {
		return nil, fmt.Errorf("failed to generate a csrf token: %w", err)
	}
	ctx.SetCookie(csrfTokenCookie, csrfToken, int(sessionExpiredAt.Sub(sessionCreatedAt).Seconds()), "_path", "_domain", true, false)

	sessionID, err := uuid.NewV7()
	if err != nil {
		return nil, fmt.Errorf("failed to generate session id: %w", err)
	}

	if _, err = d.database.AddSession(ctx, &models.Session{
		ID:           sessionID,
		SessionToken: sessionToken,
		CsrfToken:    csrfToken,
		UserID:       user.ID,
		CreatedAt:    sessionCreatedAt,
		ExpiredAt:    sessionExpiredAt,
	}); err != nil {
		return nil, fmt.Errorf("failed to save session: %w", err)
	}

	// TODO add audit log entry

	return &domain.LoginResponse{
		Ok: true,
	}, nil
}

func (d *DrainCloud) getSession(ctx *gin.Context) (*models.Session, error) {
	token, err := ctx.Cookie(sessionTokenCookie)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch session cookie from request: %w", err)
	}
	csrfToken, err := ctx.Cookie(csrfTokenCookie)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch csrf cookie from request: %w", err)
	}

	if len(csrfToken) == 0 || len(token) == 0 {
		return nil, fmt.Errorf("session token or csrf token is empty")
	}

	session, err := d.database.GetSession(ctx, token)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch session from repo: %w", err)
	}

	return session, nil
}

func validateSession(ctx *gin.Context, session *models.Session) error {
	if session == nil {
		return ErrorAccessDenied
	}

	csrfToken, err := ctx.Cookie(csrfTokenCookie)
	if err != nil {
		return fmt.Errorf("failed to fetch csrf cookie from request: %w", err)
	}

	if session.CsrfToken != csrfToken {
		return ErrorAccessDenied
	}

	if session.ExpiredAt.Before(time.Now()) {
		return ErrorSessionExpired
	}

	return nil
}