package services

import (
	"encoding/json"
	"fmt"
	"net"
	"strconv"
	"strings"
	"time"

	"go.etcd.io/bbolt"
	"warpbox.dev/backend/libs/config"
)

var (
	settingsBucket = []byte("settings")
	usageBucket    = []byte("usage")
)

var settingsKey = []byte("upload_policy")

type UploadPolicySettings struct {
	AnonymousUploadsEnabled bool    `json:"anonymousUploadsEnabled"`
	AnonymousMaxUploadMB    float64 `json:"anonymousMaxUploadMb"`
	AnonymousDailyUploadMB  float64 `json:"anonymousDailyUploadMb"`
	UserDailyUploadMB       float64 `json:"userDailyUploadMb"`
	DefaultUserStorageMB    float64 `json:"defaultUserStorageMb"`
	UsageRetentionDays      int     `json:"usageRetentionDays"`
}

type UsageRecord struct {
	Key           string    `json:"key"`
	SubjectType   string    `json:"subjectType"`
	Subject       string    `json:"subject"`
	Date          string    `json:"date"`
	UploadedBytes int64     `json:"uploadedBytes"`
	UpdatedAt     time.Time `json:"updatedAt"`
}

type SettingsService struct {
	db       *bbolt.DB
	defaults UploadPolicySettings
}

func NewSettingsService(db *bbolt.DB, defaults config.SettingsDefaults) (*SettingsService, error) {
	service := &SettingsService{
		db: db,
		defaults: UploadPolicySettings{
			AnonymousUploadsEnabled: defaults.AnonymousUploadsEnabled,
			AnonymousMaxUploadMB:    defaults.AnonymousMaxUploadMB,
			AnonymousDailyUploadMB:  defaults.AnonymousDailyUploadMB,
			UserDailyUploadMB:       defaults.UserDailyUploadMB,
			DefaultUserStorageMB:    defaults.DefaultUserStorageMB,
			UsageRetentionDays:      defaults.UsageRetentionDays,
		},
	}
	if err := service.validate(service.defaults); err != nil {
		return nil, err
	}
	err := db.Update(func(tx *bbolt.Tx) error {
		for _, bucket := range [][]byte{settingsBucket, usageBucket} {
			if _, err := tx.CreateBucketIfNotExists(bucket); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return service, nil
}

func (s *SettingsService) UploadPolicy() (UploadPolicySettings, error) {
	settings := s.defaults
	err := s.db.View(func(tx *bbolt.Tx) error {
		data := tx.Bucket(settingsBucket).Get(settingsKey)
		if data == nil {
			return nil
		}
		return json.Unmarshal(data, &settings)
	})
	if err != nil {
		return UploadPolicySettings{}, err
	}
	if err := s.validate(settings); err != nil {
		return UploadPolicySettings{}, err
	}
	return settings, nil
}

func (s *SettingsService) UpdateUploadPolicy(settings UploadPolicySettings) error {
	if err := s.validate(settings); err != nil {
		return err
	}
	data, err := json.Marshal(settings)
	if err != nil {
		return err
	}
	return s.db.Update(func(tx *bbolt.Tx) error {
		return tx.Bucket(settingsBucket).Put(settingsKey, data)
	})
}

func (s *SettingsService) Usage(subjectType, subject string, now time.Time) (UsageRecord, error) {
	key := usageKey(subjectType, subject, now)
	var record UsageRecord
	err := s.db.View(func(tx *bbolt.Tx) error {
		data := tx.Bucket(usageBucket).Get([]byte(key))
		if data == nil {
			record = UsageRecord{Key: key, SubjectType: subjectType, Subject: subject, Date: usageDate(now)}
			return nil
		}
		return json.Unmarshal(data, &record)
	})
	return record, err
}

func (s *SettingsService) AddUsage(subjectType, subject string, bytes int64, now time.Time) error {
	if bytes <= 0 {
		return nil
	}
	key := usageKey(subjectType, subject, now)
	return s.db.Update(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(usageBucket)
		record := UsageRecord{Key: key, SubjectType: subjectType, Subject: subject, Date: usageDate(now)}
		data := bucket.Get([]byte(key))
		if data != nil {
			if err := json.Unmarshal(data, &record); err != nil {
				return err
			}
		}
		record.UploadedBytes += bytes
		record.UpdatedAt = now.UTC()
		next, err := json.Marshal(record)
		if err != nil {
			return err
		}
		return bucket.Put([]byte(key), next)
	})
}

func (s *SettingsService) CleanupUsage(now time.Time, retentionDays int) error {
	if retentionDays <= 0 {
		return fmt.Errorf("usage retention days must be positive")
	}
	cutoff := now.UTC().AddDate(0, 0, -retentionDays)
	return s.db.Update(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(usageBucket)
		return bucket.ForEach(func(key, value []byte) error {
			var record UsageRecord
			if err := json.Unmarshal(value, &record); err != nil {
				return err
			}
			date, err := time.Parse("2006-01-02", record.Date)
			if err != nil || date.Before(cutoff) {
				return bucket.Delete(key)
			}
			return nil
		})
	})
}

func (s *SettingsService) UsageForUser(userID string, now time.Time) (UsageRecord, error) {
	return s.Usage("user", userID, now)
}

func (s *SettingsService) UsageForIP(ip string, now time.Time) (UsageRecord, error) {
	return s.Usage("ip", ip, now)
}

func (s *SettingsService) validate(settings UploadPolicySettings) error {
	if settings.AnonymousMaxUploadMB <= 0 {
		return fmt.Errorf("anonymous max upload must be positive")
	}
	if settings.AnonymousDailyUploadMB <= 0 {
		return fmt.Errorf("anonymous daily upload must be positive")
	}
	if settings.UserDailyUploadMB <= 0 {
		return fmt.Errorf("user daily upload must be positive")
	}
	if settings.DefaultUserStorageMB <= 0 {
		return fmt.Errorf("default user storage must be positive")
	}
	if settings.UsageRetentionDays <= 0 {
		return fmt.Errorf("usage retention days must be positive")
	}
	return nil
}

func ParseMegabytesValue(value string) (float64, error) {
	value = strings.TrimSpace(value)
	if value == "" {
		return 0, fmt.Errorf("megabyte value is required")
	}
	value = strings.TrimSuffix(value, "MB")
	value = strings.TrimSuffix(value, "Mb")
	value = strings.TrimSuffix(value, "mb")
	value = strings.TrimSpace(value)
	parsed, err := strconv.ParseFloat(value, 64)
	if err != nil {
		return 0, err
	}
	if parsed <= 0 {
		return 0, fmt.Errorf("megabyte value must be positive")
	}
	return parsed, nil
}

func MegabytesToBytes(value float64) int64 {
	return int64(value * 1024 * 1024)
}

func FormatMegabytesFromBytes(value int64) string {
	mb := float64(value) / 1024 / 1024
	return FormatMegabytesLabel(mb)
}

func FormatMegabytesLabel(value float64) string {
	return strconv.FormatFloat(value, 'f', -1, 64) + " MB"
}

func usageKey(subjectType, subject string, now time.Time) string {
	return subjectType + ":" + subject + ":" + usageDate(now)
}

func usageDate(now time.Time) string {
	return now.UTC().Format("2006-01-02")
}

func ClientIP(remoteAddr, forwardedFor string) string {
	if forwardedFor != "" {
		parts := strings.Split(forwardedFor, ",")
		if ip := strings.TrimSpace(parts[0]); ip != "" {
			return ip
		}
	}
	host := remoteAddr
	if strings.Contains(remoteAddr, ":") {
		if splitHost, _, err := net.SplitHostPort(remoteAddr); err == nil {
			host = splitHost
		}
	}
	return host
}