package service

import (
	"strings"

	"gorm.io/gorm"

	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
	"github.com/mhsanaei/3x-ui/v3/internal/xray"
)

// sqliteMaxVars is a safe ceiling for the number of bind parameters in a
// single SQL statement. SQLite's SQLITE_MAX_VARIABLE_NUMBER is 999 on builds
// before 3.32 and 32766 after; staying under 999 keeps queries portable
// across forks/old binaries and also bounds per-query memory on truly large
// installs (>32k clients) where even modern SQLite would refuse a single IN.
const sqliteMaxVars = 900

// normalizeSubSortIndex maps omitted/zero to 1; explicit negatives are kept
// so a primary inbound can sort ahead of the default.
func normalizeSubSortIndex(v int) int {
	if v == 0 {
		return 1
	}
	return v
}

// uniqueNonEmptyStrings returns a deduplicated copy of in with empty strings
// removed, preserving the order of first occurrence.
func uniqueNonEmptyStrings(in []string) []string {
	if len(in) == 0 {
		return nil
	}
	seen := make(map[string]struct{}, len(in))
	out := make([]string, 0, len(in))
	for _, v := range in {
		if v == "" {
			continue
		}
		if _, ok := seen[v]; ok {
			continue
		}
		seen[v] = struct{}{}
		out = append(out, v)
	}
	return out
}

// trimmedUniqueEmails trims each address before deduplicating, so the bulk
// client operations treat " a@x " and "a@x" as the same row.
func trimmedUniqueEmails(in []string) []string {
	trimmed := make([]string, 0, len(in))
	for _, e := range in {
		trimmed = append(trimmed, strings.TrimSpace(e))
	}
	return uniqueNonEmptyStrings(trimmed)
}

// uniqueInts returns a deduplicated copy of in, preserving order of first occurrence.
func uniqueInts(in []int) []int {
	if len(in) == 0 {
		return nil
	}
	seen := make(map[int]struct{}, len(in))
	out := make([]int, 0, len(in))
	for _, v := range in {
		if _, ok := seen[v]; ok {
			continue
		}
		seen[v] = struct{}{}
		out = append(out, v)
	}
	return out
}

// chunkStrings splits s into consecutive sub-slices of at most size elements.
// Returns nil for an empty input or non-positive size.
func chunkStrings(s []string, size int) [][]string {
	if size <= 0 || len(s) == 0 {
		return nil
	}
	out := make([][]string, 0, chunkCount(len(s), size))
	for i := 0; i < len(s); i += size {
		end := min(i+size, len(s))
		out = append(out, s[i:end])
	}
	return out
}

// chunkInts splits s into consecutive sub-slices of at most size elements.
// Returns nil for an empty input or non-positive size.
func chunkInts(s []int, size int) [][]int {
	if size <= 0 || len(s) == 0 {
		return nil
	}
	out := make([][]int, 0, chunkCount(len(s), size))
	for i := 0; i < len(s); i += size {
		end := min(i+size, len(s))
		out = append(out, s[i:end])
	}
	return out
}

// chunkCount is ceil(n/size) without the n+size-1 sum, which overflows for a size near MaxInt.
func chunkCount(n, size int) int {
	count := n / size
	if n%size != 0 {
		count++
	}
	return count
}

// attachClientStats fills each inbound's ClientStats in chunks: GORM's Preload binds one
// variable per inbound, and nodes alone can report more inbounds than SQLite binds.
func attachClientStats(db *gorm.DB, inbounds []*model.Inbound) error {
	byID := make(map[int]*model.Inbound, len(inbounds))
	ids := make([]int, 0, len(inbounds))
	for _, ib := range inbounds {
		byID[ib.Id] = ib
		ids = append(ids, ib.Id)
	}
	for _, batch := range chunkInts(ids, sqliteMaxVars) {
		var stats []xray.ClientTraffic
		if err := db.Where("inbound_id IN ?", batch).Order("id ASC").Find(&stats).Error; err != nil {
			return err
		}
		for _, st := range stats {
			if ib := byID[st.InboundId]; ib != nil {
				ib.ClientStats = append(ib.ClientStats, st)
			}
		}
	}
	return nil
}

// saveInChunks saves rows a slice at a time: one slice Save binds every column of every
// row in a single statement, past SQLite's variable limit once there are enough rows.
func saveInChunks[T any](tx *gorm.DB, rows []T) error {
	const rowsPerStatement = 100
	for start := 0; start < len(rows); start += rowsPerStatement {
		if err := tx.Save(rows[start:min(start+rowsPerStatement, len(rows))]).Error; err != nil {
			return err
		}
	}
	return nil
}