package sharding

import (
	"fmt"
	"time"
)

// ShardingStrategy 分表策略接口
type ShardingStrategy interface {
	// GetTableName 根据时间获取表名
	GetTableName(baseTableName string, t time.Time) string
	// GetCurrentTableName 获取当前表名
	GetCurrentTableName(baseTableName string) string
	// GetTableNamesByRange 根据时间范围获取所有可能的表名
	GetTableNamesByRange(baseTableName string, start, end time.Time) []string
	// GetNextTableName 根据当前表名获取下一个表名(用于动态分表)
	GetNextTableName(currentTableName string) string
	// IsNewPeriod 检查是否应该开始新的分表周期
	IsNewPeriod(lastTableTime, currentTime time.Time) bool
}

// MonthlyShardingStrategy 按月分表策略 - 每月第一天分表
type MonthlyShardingStrategy struct{}

func NewMonthlyShardingStrategy() ShardingStrategy {
	return &MonthlyShardingStrategy{}
}

func (s *MonthlyShardingStrategy) GetTableName(baseTableName string, t time.Time) string {
	return fmt.Sprintf("%s_%d%02d", baseTableName, t.Year(), t.Month())
}

func (s *MonthlyShardingStrategy) GetCurrentTableName(baseTableName string) string {
	return s.GetTableName(baseTableName, time.Now())
}

func (s *MonthlyShardingStrategy) GetTableNamesByRange(baseTableName string, start, end time.Time) []string {
	var tableNames []string
	current := time.Date(start.Year(), start.Month(), 1, 0, 0, 0, 0, start.Location())
	endMonth := time.Date(end.Year(), end.Month(), 1, 0, 0, 0, 0, end.Location())

	for !current.After(endMonth) {
		tableNames = append(tableNames, s.GetTableName(baseTableName, current))
		current = current.AddDate(0, 1, 0)
	}

	return tableNames
}

func (s *MonthlyShardingStrategy) GetNextTableName(currentTableName string) string {
	// 解析当前表名，生成下一个序号的表名
	// 例如: log_202408 -> log_202408_01, log_202408_01 -> log_202408_02
	
	// 简单实现：在表名后添加序号
	return fmt.Sprintf("%s_01", currentTableName)
}

func (s *MonthlyShardingStrategy) IsNewPeriod(lastTableTime, currentTime time.Time) bool {
	// 检查是否到了新的月份
	lastMonth := time.Date(lastTableTime.Year(), lastTableTime.Month(), 1, 0, 0, 0, 0, lastTableTime.Location())
	currentMonth := time.Date(currentTime.Year(), currentTime.Month(), 1, 0, 0, 0, 0, currentTime.Location())
	
	return currentMonth.After(lastMonth)
}

// DailyShardingStrategy 按日分表策略 - 每天分表
type DailyShardingStrategy struct{}

func NewDailyShardingStrategy() ShardingStrategy {
	return &DailyShardingStrategy{}
}

func (s *DailyShardingStrategy) GetTableName(baseTableName string, t time.Time) string {
	return fmt.Sprintf("%s_%d%02d%02d", baseTableName, t.Year(), t.Month(), t.Day())
}

func (s *DailyShardingStrategy) GetCurrentTableName(baseTableName string) string {
	return s.GetTableName(baseTableName, time.Now())
}

func (s *DailyShardingStrategy) GetTableNamesByRange(baseTableName string, start, end time.Time) []string {
	var tableNames []string
	current := time.Date(start.Year(), start.Month(), start.Day(), 0, 0, 0, 0, start.Location())
	endDay := time.Date(end.Year(), end.Month(), end.Day(), 0, 0, 0, 0, end.Location())

	for !current.After(endDay) {
		tableNames = append(tableNames, s.GetTableName(baseTableName, current))
		current = current.AddDate(0, 0, 1) // 每次增加一天
	}

	return tableNames
}

func (s *DailyShardingStrategy) GetNextTableName(currentTableName string) string {
	// 日度分表的序号表名
	return fmt.Sprintf("%s_01", currentTableName)
}

func (s *DailyShardingStrategy) IsNewPeriod(lastTableTime, currentTime time.Time) bool {
	// 检查是否到了新的一天
	lastDay := time.Date(lastTableTime.Year(), lastTableTime.Month(), lastTableTime.Day(), 0, 0, 0, 0, lastTableTime.Location())
	currentDay := time.Date(currentTime.Year(), currentTime.Month(), currentTime.Day(), 0, 0, 0, 0, currentTime.Location())
	
	return currentDay.After(lastDay)
}