package remnawave

// Local account storage: after the first successful provisioning the client
// "remembers" the panel user in configs/account.json (never committed) and
// from then on only renews that same user — it never creates a second one.

import (
	"bytes"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"time"
)

// Account is the locally remembered panel user.
type Account struct {
	Username          string `json:"username"`
	UUID              string `json:"uuid"`
	ShortUUID         string `json:"short_uuid,omitempty"`
	SubscriptionURL   string `json:"subscription_url,omitempty"`
	TrafficLimitBytes int64  `json:"traffic_limit_bytes,omitempty"`
	ExpireAt          int64  `json:"expire_at,omitempty"`        // unix seconds; 0 = unknown
	CreatedAt         int64  `json:"created_at,omitempty"`       // unix seconds
	LastRenewedAt     int64  `json:"last_renewed_at,omitempty"`  // unix seconds; anti-loop guard
	LastRenewCheckAt  int64  `json:"last_renew_check,omitempty"` // unix seconds of last auto check
}

// AccountPath returns configs/account.json next to the main config.json.
func AccountPath(cfgPath string) string {
	return filepath.Join(filepath.Dir(cfgPath), "account.json")
}

// LoadAccount reads the remembered account; returns (nil, nil) when absent.
func LoadAccount(path string) (*Account, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	var a Account
	if err := json.Unmarshal(bytes.TrimPrefix(data, []byte{0xEF, 0xBB, 0xBF}), &a); err != nil {
		return nil, fmt.Errorf("account.json: некорректный JSON: %w", err)
	}
	if a.Username == "" && a.UUID == "" {
		return nil, nil
	}
	return &a, nil
}

// SaveAccount persists the account with restrictive permissions.
func SaveAccount(path string, a *Account) error {
	if a == nil {
		return fmt.Errorf("пустой аккаунт")
	}
	data, err := json.MarshalIndent(a, "", "  ")
	if err != nil {
		return err
	}
	data = append(data, '\n')
	if dir := filepath.Dir(path); dir != "." && dir != "" {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return err
		}
	}
	return os.WriteFile(path, data, 0o600)
}

// NeedsRenewal reports whether the plan should be renewed now:
// expiry within 72h / past, or traffic exhausted (usedBytes vs limit).
func (a *Account) NeedsRenewal(usedBytes int64, now time.Time) bool {
	if a == nil {
		return false
	}
	if a.ExpireAt > 0 && time.Unix(a.ExpireAt, 0).Before(now.Add(72*time.Hour)) {
		return true
	}
	if a.TrafficLimitBytes > 0 && usedBytes >= a.TrafficLimitBytes {
		return true
	}
	return false
}