package sharding

import (
	"context"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/go-nunu/nunu-layout-advanced/pkg/log"
	"gorm.io/gorm"
)

// TableModel 支持分表的模型接口
type TableModel interface {
	GetBaseTableName() string
	GetCreatedAt() time.Time
}

// ThresholdConfig 阈值配置
type ThresholdConfig struct {
	Enabled       bool
	MaxRows       int64
	CheckInterval time.Duration
}

// ShardingManager 分表管理器
type ShardingManager struct {
	strategy        ShardingStrategy
	logger          *log.Logger
	thresholdConfig *ThresholdConfig
}

func NewShardingManager(strategy ShardingStrategy, logger *log.Logger) *ShardingManager {
	return &ShardingManager{
		strategy: strategy,
		logger:   logger,
	}
}

func NewShardingManagerWithThreshold(strategy ShardingStrategy, logger *log.Logger, thresholdConfig *ThresholdConfig) *ShardingManager {
	return &ShardingManager{
		strategy:        strategy,
		logger:          logger,
		thresholdConfig: thresholdConfig,
	}
}

// GetWriteTableName 获取写入表名(基于记录的创建时间)
func (sm *ShardingManager) GetWriteTableName(model TableModel) string {
	baseTableName := model.GetBaseTableName()
	createdAt := model.GetCreatedAt()
	
	if createdAt.IsZero() {
		createdAt = time.Now()
	}
	
	return sm.strategy.GetTableName(baseTableName, createdAt)
}

// GetCurrentTableName 获取当前表名(用于写入新记录)
func (sm *ShardingManager) GetCurrentTableName(baseTableName string) string {
	return sm.strategy.GetCurrentTableName(baseTableName)
}

// GetQueryTableNames 获取查询需要的所有表名
func (sm *ShardingManager) GetQueryTableNames(baseTableName string, start, end *time.Time) []string {
	if start == nil || end == nil {
		// 如果没有指定时间范围，默认查询最近3个月的表
		now := time.Now()
		defaultStart := now.AddDate(0, -2, 0) // 前2个月
		defaultEnd := now
		return sm.strategy.GetTableNamesByRange(baseTableName, defaultStart, defaultEnd)
	}
	return sm.strategy.GetTableNamesByRange(baseTableName, *start, *end)
}

// EnsureTableExists 确保表存在，不存在则创建
func (sm *ShardingManager) EnsureTableExists(ctx context.Context, db *gorm.DB, tableName string, model interface{}) error {
	// 检查表是否存在
	if db.Migrator().HasTable(tableName) {
		return nil
	}

	sm.logger.Info(fmt.Sprintf("创建分表: %s", tableName))
	
	// 使用指定的表名创建表
	return db.Table(tableName).AutoMigrate(model)
}

// BuildUnionQuery 构建联合查询(用于跨表查询)
func (sm *ShardingManager) BuildUnionQuery(ctx context.Context, db *gorm.DB, tableNames []string, baseQuery func(*gorm.DB) *gorm.DB) *gorm.DB {
	if len(tableNames) == 0 {
		return db
	}

	// 过滤存在的表
	var existingTables []string
	for _, tableName := range tableNames {
		if db.Migrator().HasTable(tableName) {
			existingTables = append(existingTables, tableName)
		}
	}

	if len(existingTables) == 0 {
		return db
	}

	// 如果只有一个表，直接查询该表
	if len(existingTables) == 1 {
		return baseQuery(db.Table(existingTables[0]))
	}

	// 多表联合查询
	var subQueries []string
	for _, tableName := range existingTables {
		subQueries = append(subQueries, fmt.Sprintf("SELECT * FROM %s", tableName))
	}

	unionSQL := strings.Join(subQueries, " UNION ALL ")
	return baseQuery(db.Table(fmt.Sprintf("(%s) as sharded_table", unionSQL)))
}

// GetTableNamesWithExistenceCheck 获取存在的表名列表(只返回分表，不包含原表)
func (sm *ShardingManager) GetTableNamesWithExistenceCheck(db *gorm.DB, baseTableName string, start, end *time.Time) []string {
	allTableNames := sm.GetQueryTableNames(baseTableName, start, end)
	var existingTables []string
	
	for _, tableName := range allTableNames {
		if db.Migrator().HasTable(tableName) {
			existingTables = append(existingTables, tableName)
		}
	}
	
	// 还要检查动态分表(带序号的表)
	dynamicTables := sm.findDynamicTables(db, allTableNames)
	existingTables = append(existingTables, dynamicTables...)
	
	return existingTables
}

// findDynamicTables 查找动态分表(带序号的表)
func (sm *ShardingManager) findDynamicTables(db *gorm.DB, baseTableNames []string) []string {
	var dynamicTables []string
	
	for _, baseTableName := range baseTableNames {
		// 查找类似 log_202408_01, log_202408_02 这样的表
		pattern := fmt.Sprintf("%s_\\d+", baseTableName)
		if tables := sm.findTablesByPattern(db, pattern); len(tables) > 0 {
			dynamicTables = append(dynamicTables, tables...)
		}
	}
	
	return dynamicTables
}

// findTablesByPattern 根据模式查找表
func (sm *ShardingManager) findTablesByPattern(db *gorm.DB, pattern string) []string {
	var tables []string
	
	// 获取所有表名
	rows, err := db.Raw("SHOW TABLES").Rows()
	if err != nil {
		sm.logger.Error("获取表列表失败: " + err.Error())
		return tables
	}
	defer rows.Close()
	
	regex, err := regexp.Compile(pattern)
	if err != nil {
		sm.logger.Error("编译正则表达式失败: " + err.Error())
		return tables
	}
	
	for rows.Next() {
		var tableName string
		if err := rows.Scan(&tableName); err != nil {
			continue
		}
		if regex.MatchString(tableName) {
			tables = append(tables, tableName)
		}
	}
	
	return tables
}

// GetOptimalWriteTable 获取最优的写入表(考虑数据量阈值)
func (sm *ShardingManager) GetOptimalWriteTable(ctx context.Context, db *gorm.DB, model TableModel, maxRows int64) (string, error) {
	baseTableName := model.GetBaseTableName()
	createdAt := model.GetCreatedAt()
	
	if createdAt.IsZero() {
		createdAt = time.Now()
	}
	
	// 先获取基础表名
	baseShardTableName := sm.strategy.GetTableName(baseTableName, createdAt)
	
	// 如果没有启用阈值检查，直接返回基础表名
	if sm.thresholdConfig == nil || !sm.thresholdConfig.Enabled {
		return baseShardTableName, nil
	}
	
	// 使用配置的maxRows，如果没有则使用默认值
	if maxRows <= 0 {
		maxRows = sm.thresholdConfig.MaxRows
	}
	
	// 检查当前表是否已达到阈值
	currentTable := baseShardTableName
	for {
		if !db.Migrator().HasTable(currentTable) {
			// 表不存在，可以使用
			return currentTable, nil
		}
		
		// 检查表的数据量
		var count int64
		err := db.Table(currentTable).Count(&count).Error
		if err != nil {
			sm.logger.Error(fmt.Sprintf("检查表 %s 数据量失败: %v", currentTable, err))
			return currentTable, nil // 出错时返回当前表
		}
		
		if count < maxRows {
			// 当前表还有空间
			return currentTable, nil
		}
		
		// 当前表已满，尝试下一个序号的表
		currentTable = sm.getNextSequenceTable(currentTable)
		sm.logger.Info(fmt.Sprintf("表 %s 已达到阈值 %d，尝试使用 %s", baseShardTableName, maxRows, currentTable))
	}
}

// getNextSequenceTable 获取下一个序号的表名
func (sm *ShardingManager) getNextSequenceTable(currentTableName string) string {
	// 检查是否已经有序号
	re := regexp.MustCompile(`^(.+)_(\d+)$`)
	matches := re.FindStringSubmatch(currentTableName)
	
	if len(matches) == 3 {
		// 已有序号，递增
		baseName := matches[1]
		seq, _ := strconv.Atoi(matches[2])
		return fmt.Sprintf("%s_%02d", baseName, seq+1)
	} else {
		// 没有序号，添加序号01
		return fmt.Sprintf("%s_01", currentTableName)
	}
}

// CheckAndCreateNewTable 检查是否需要创建新表(基于时间周期)
func (sm *ShardingManager) CheckAndCreateNewTable(ctx context.Context, db *gorm.DB, baseTableName string, modelExample interface{}) error {
	currentTime := time.Now()
	expectedTableName := sm.strategy.GetTableName(baseTableName, currentTime)
	
	// 检查当前期间的表是否存在
	if !db.Migrator().HasTable(expectedTableName) {
		sm.logger.Info(fmt.Sprintf("创建新周期分表: %s", expectedTableName))
		return sm.EnsureTableExists(ctx, db, expectedTableName, modelExample)
	}
	
	return nil
}