package util

import (
	"database/sql"
	"errors"
	"fmt"
	"reflect"
	"strconv"
	"strings"
)

func ScanStruct(rows *sql.Rows, dest interface{}) error {
	rv := reflect.ValueOf(dest)
	if rv.Kind() != reflect.Ptr {
		return errors.New("must pass a pointer, not a value, to StructScan destination")
	}
	if rv.IsNil() {
		return errors.New("nil pointer passed to StructScan destination")
	}
	direct := rv.Elem()
	dtype := direct.Type()
	if dtype.Kind() != reflect.Slice {
		return fmt.Errorf("expected %s but got %s", reflect.Slice, dtype.Kind())
	}
	elemType := dtype.Elem()
	var (
		field     reflect.StructField
		fmap      = map[string]TagIndex{}
		dbtagVal  string
		tagSplits []string
		fimap     = map[TagIndex]int{}
	)
	cols, _ := rows.Columns()
	for i := 0; i < elemType.NumField(); i++ {
		field = elemType.Field(i)
		dbtagVal = field.Tag.Get("db")
		if dbtagVal == "null" {
			continue
		}
		tagIdx := TagIndex{}
		tagSplits = strings.Split(dbtagVal, ",")
		if len(tagSplits) > 1 {
			dbtagVal = tagSplits[0]
			if tagSplits[1] == "omitempty" {
				tagIdx.IsOmitEmpty = true
			}
		}
		if dbtagVal == "" {
			dbtagVal = field.Name
		}
		tagIdx.Idx = i
		fmap[dbtagVal] = tagIdx
	}
	var (
		tempStr sql.NullString
		valArr  []interface{}
	)
	for rows.Next() {
		nelemVal := reflect.New(elemType)
		valArr = make([]interface{}, len(cols))
		for i, col := range cols {
			if fieldIdx, ok := fmap[col]; !ok {
				valArr[i] = new(interface{})
			} else {
				field = elemType.Field(fieldIdx.Idx)
				if fieldIdx.IsOmitEmpty {
					valArr[i] = &sql.NullString{}
					fimap[fieldIdx] = i
				} else {
					valArr[i] = nelemVal.Elem().Field(fieldIdx.Idx).Addr().Interface()
				}
			}
		}
		rows.Scan(valArr...)
		for k, v := range fimap {
			fval := reflect.ValueOf(valArr[v])
			if fval.IsValid() {
				field := elemType.Field(k.Idx)
				dstFval := reflect.New(field.Type)
				tempStr = fval.Elem().Interface().(sql.NullString)
				if !tempStr.Valid {
					continue
				}
				switch field.Type.Kind() {
				case reflect.Float64:
					float, _ := strconv.ParseFloat(tempStr.String, 64)
					float = ToFix(float, 2)
					dstFval.Elem().Set(reflect.ValueOf(float))
				case reflect.String:
					dstFval.Elem().Set(reflect.ValueOf(tempStr.String))
				case reflect.Int:
					intVal, _ := strconv.ParseInt(tempStr.String, 10, 0)
					dstFval.Elem().Set(reflect.ValueOf(int(intVal)))
				}
				//fmt.Println(dstFval.Elem().Interface())
				nelemVal.Elem().Field(k.Idx).Set(dstFval.Elem())
			}
		}
		direct.Set(reflect.Append(direct, nelemVal.Elem()))
	}
	return nil
}