package authenticator

import (
	"fmt"
	"strconv"
	"strings"

	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
)

// HOTPAuthenticator implements RFC 4226 counter-based HOTP.
type HOTPAuthenticator struct {
	Base
	Counter uint64
}

// NewHOTPAuthenticator returns a fresh HOTP authenticator with the project
// defaults (6 digits, SHA1).
func NewHOTPAuthenticator() *HOTPAuthenticator {
	return &HOTPAuthenticator{Base: NewBase()}
}

// Name returns the short logger tag for this type.
func (h *HOTPAuthenticator) Name() string { return "hotp" }

// Enroll loads the secret from a base32 string and optionally seeds the
// counter.
func (h *HOTPAuthenticator) Enroll(b32 string, counter uint64) error {
	const fn = "internal.authenticator.HOTPAuthenticator.Enroll"
	raw, err := Base32Decode(b32)
	if err != nil {
		return err
	}
	h.SecretKey = raw
	h.Counter = counter
	global.Log.WithField("func", fn).WithField("counter", counter).Debug("enrolled HOTP")
	return nil
}

// CurrentCode increments the internal counter and returns the resulting code.
func (h *HOTPAuthenticator) CurrentCode() (string, error) {
	if h.SecretKey == nil {
		return "", fmt.Errorf("authenticator: no secret loaded")
	}
	h.Counter++
	digits := h.CodeDigits
	if digits == 0 {
		digits = DefaultCodeDigits
	}
	return hotpCode(h.SecretKey, h.Counter, digits, h.HMACType), nil
}

// Sync is a no-op for HOTP — there is no server clock to align against.
func (h *HOTPAuthenticator) Sync() error { return nil }

// SecretData appends "|<counter>" to the base secret data string, matching
// the C# HOTPAuthenticator.SecretData getter.
func (h *HOTPAuthenticator) SecretData() string {
	return h.EncodeSecretData() + "|" + strconv.FormatUint(h.Counter, 10)
}

// SetSecretData parses the "<base>|<counter>" form.
func (h *HOTPAuthenticator) SetSecretData(value string) error {
	if err := h.DecodeSecretData(value); err != nil {
		return err
	}
	if idx := strings.Index(value, "|"); idx >= 0 {
		c, err := strconv.ParseUint(strings.TrimSpace(value[idx+1:]), 10, 64)
		if err == nil {
			h.Counter = c
		}
	}
	return nil
}