package utils

import (
	"crypto/rand"
	"errors"
	"math/big"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"golang.org/x/crypto/bcrypt"
)

func HashPassword(password string) (string, error) {
	bytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(bytes), err
}

// dbLocation is the timezone the database records wall-clock timestamps in: the
// connection DSN sets TimeZone=Asia/Kolkata, so CURRENT_TIMESTAMP column
// defaults write IST wall-clock into timestamp-without-timezone columns.
var dbLocation = func() *time.Location {
	if loc, err := time.LoadLocation("Asia/Kolkata"); err == nil {
		return loc
	}
	// A container without tzdata can't load the database; IST observes no DST,
	// so a fixed +05:30 offset is exact rather than an approximation.
	return time.FixedZone("IST", 5*3600+30*60)
}()

// DBNow returns the current moment expressed as the wall-clock the database
// stores, tagged UTC so the driver sends exactly those digits. Use it for any
// comparison against a stored timestamp: comparing the container's UTC clock
// against IST-stamped rows is what made date-range reports undercount.
//
// Deliberately independent of the container's own TZ, so it stays correct
// whether or not TZ=Asia/Kolkata is set.
func DBNow() time.Time {
	n := time.Now().In(dbLocation)
	return time.Date(n.Year(), n.Month(), n.Day(), n.Hour(), n.Minute(), n.Second(), n.Nanosecond(), time.UTC)
}

// DBToday returns midnight at the start of the current database-local day.
func DBToday() time.Time {
	n := DBNow()
	return time.Date(n.Year(), n.Month(), n.Day(), 0, 0, 0, 0, time.UTC)
}

// GenerateNumericOTP returns a random n-digit code, leading zeros preserved.
// crypto/rand rather than math/rand: this is the only thing standing between a
// parcel and someone claiming it was delivered, so a predictable sequence would
// defeat the point.
func GenerateNumericOTP(n int) string {
	const digits = "0123456789"
	out := make([]byte, n)
	for i := range out {
		idx, err := rand.Int(rand.Reader, big.NewInt(int64(len(digits))))
		if err != nil {
			// A failing system RNG must not silently downgrade to a guessable
			// code; the caller treats an empty OTP as "not issued".
			return ""
		}
		out[i] = digits[idx.Int64()]
	}
	return string(out)
}

func CheckPasswordHash(password, hash string) bool {
	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
	return err == nil
}

type Claims struct {
	UserID   int    `json:"userid"`
	Email    string `json:"email"`
	RoleID   int    `json:"roleid"`
	TenantID int    `json:"tenantid"`
	ConfigID int    `json:"configid,omitempty"`
	HubID    int    `json:"hubid,omitempty"`
	jwt.RegisteredClaims
}

func GenerateToken(userID int, email string, roleID int, tenantID int, configID int, secret string) (string, error) {
	expirationTime := time.Now().Add(24 * time.Hour)
	claims := &Claims{
		UserID:   userID,
		Email:    email,
		RoleID:   roleID,
		TenantID: tenantID,
		ConfigID: configID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expirationTime),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(secret))
}

// GenerateHubStaffToken issues a JWT for hub console staff (role 6), carrying
// HubID instead of TenantID/ConfigID so hub handlers can scope queries via
// c.Locals("hubid") without colliding with the Miler role (5).
func GenerateHubStaffToken(userID int, email string, hubID int, secret string) (string, error) {
	expirationTime := time.Now().Add(24 * time.Hour)
	claims := &Claims{
		UserID: userID,
		Email:  email,
		RoleID: 6,
		HubID:  hubID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expirationTime),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(secret))
}

func ParseToken(tokenString string, secret string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		return []byte(secret), nil
	})

	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*Claims); ok && token.Valid {
		return claims, nil
	}

	return nil, errors.New("invalid token")
}

func IntPtr(v int) *int {
	return &v
}