package queryreq

import (
	"fmt"
	"strings"
)

// FieldMapper 字段映射函数类型：前端字段名 -> 数据库列名
type FieldMapper func(string) string

// DefaultFieldMapper 默认字段映射（直接使用原字段名）
func DefaultFieldMapper(field string) string {
	return field
}

// BuildWhereClause 安全构建WHERE子句
// 返回: WHERE条件字符串, 参数值数组
func BuildWhereClause(filters []FilterParam, fieldMapper FieldMapper) (string, []interface{}) {
	if len(filters) == 0 {
		return "", nil
	}

	var conditions []string
	var args []interface{}

	for _, filter := range filters {
		if !filter.Operator.IsValid() {
			continue
		}

		// 获取安全的数据库列名
		dbField := fieldMapper(filter.Field)
		if dbField == "" {
			continue // 无效字段，跳过
		}

		// 根据运算符构建条件
		condition, filterArgs := buildCondition(dbField, filter.Operator, filter.Value)
		if condition != "" {
			conditions = append(conditions, condition)
			args = append(args, filterArgs...)
		}
	}

	if len(conditions) == 0 {
		return "", nil
	}

	return "WHERE " + strings.Join(conditions, " AND "), args
}

// BuildOrderByClause 安全构建ORDER BY子句
// 返回: ORDER BY子句字符串
func BuildOrderByClause(sorts []SortParam, fieldMapper FieldMapper) string {
	if len(sorts) == 0 {
		return ""
	}

	var orderClauses []string
	for _, sort := range sorts {
		// 获取安全的数据库列名
		dbField := fieldMapper(sort.Field)
		if dbField == "" {
			continue // 无效字段，跳过
		}

		// 验证排序方向
		order := strings.ToUpper(sort.Order)
		if order != "ASC" && order != "DESC" {
			order = "ASC" // 默认升序
		}

		orderClauses = append(orderClauses, fmt.Sprintf("%s %s", dbField, order))
	}

	if len(orderClauses) == 0 {
		return ""
	}

	return "ORDER BY " + strings.Join(orderClauses, ", ")
}

// buildCondition 构建单个筛选条件
func buildCondition(field string, operator Operator, value interface{}) (string, []interface{}) {
	switch operator {
	case OpEquals, OpNotEquals, OpGreaterThan, OpLessThan, OpGreaterOrEq, OpLessOrEq:
		return fmt.Sprintf("%s %s ?", field, operator.ToSQL()), []interface{}{value}

	case OpLike:
		// LIKE操作自动添加通配符
		if strVal, ok := value.(string); ok {
			return fmt.Sprintf("%s LIKE ?", field), []interface{}{"%" + strVal + "%"}
		}
		// 非字符串类型，直接使用值
		return fmt.Sprintf("%s LIKE ?", field), []interface{}{value}

	case OpIn:
		return buildInCondition(field, value)

	default:
		return "", nil
	}
}

// buildInCondition 构建IN条件
func buildInCondition(field string, value interface{}) (string, []interface{}) {
	// 处理IN操作符的值
	values, ok := processInValue(value)
	if !ok || len(values) == 0 {
		return "", nil
	}

	// 构建占位符 (?, ?, ?)
	placeholders := strings.Repeat("?, ", len(values))
	placeholders = placeholders[:len(placeholders)-2] // 移除最后的逗号和空格

	return fmt.Sprintf("%s IN (%s)", field, placeholders), values
}

// processInValue 处理IN操作符的值，转换为参数数组
// 支持逗号分隔的字符串、字符串数组、接口数组等
func processInValue(value interface{}) ([]interface{}, bool) {
	switch v := value.(type) {
	case string:
		// 逗号分隔的字符串
		if strings.Contains(v, ",") {
			parts := strings.Split(v, ",")
			var result []interface{}
			for _, part := range parts {
				trimmed := strings.TrimSpace(part)
				if trimmed != "" {
					// 尝试解析为数值
					if num, err := parseNumber(trimmed); err == nil {
						result = append(result, num)
					} else {
						result = append(result, trimmed)
					}
				}
			}
			return result, len(result) > 0
		}
		// 单个字符串值
		return []interface{}{v}, true

	case []string:
		// 字符串数组
		var result []interface{}
		for _, item := range v {
			if trimmed := strings.TrimSpace(item); trimmed != "" {
				if num, err := parseNumber(trimmed); err == nil {
					result = append(result, num)
				} else {
					result = append(result, trimmed)
				}
			}
		}
		return result, len(result) > 0

	case []interface{}:
		// 接口数组
		var result []interface{}
		for _, item := range v {
			if item != nil {
				result = append(result, item)
			}
		}
		return result, len(result) > 0

	default:
		// 其他类型视为单个值
		return []interface{}{v}, true
	}
}

// parseNumber 尝试将字符串解析为数值
func parseNumber(s string) (interface{}, error) {
	// 尝试解析为整数
	if intVal, err := parseInt(s); err == nil {
		return intVal, nil
	}

	// 尝试解析为浮点数
	if floatVal, err := parseFloat(s); err == nil {
		return floatVal, nil
	}

	return nil, fmt.Errorf("not a number")
}

// parseInt 解析整数
func parseInt(s string) (int64, error) {
	var val int64
	_, err := fmt.Sscanf(s, "%d", &val)
	return val, err
}

// parseFloat 解析浮点数
func parseFloat(s string) (float64, error) {
	var val float64
	_, err := fmt.Sscanf(s, "%f", &val)
	return val, err
}