// Copyright 2016 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package xorm

import (
	"database/sql"
	"errors"
	"fmt"
	"math/big"
	"reflect"
	"time"

	"xorm.io/xorm/v2/internal/convert"
	"xorm.io/xorm/v2/internal/core"
	"xorm.io/xorm/v2/internal/utils"
	"xorm.io/xorm/v2/schemas"
)

// ErrObjectIsNil return error of object is nil
var ErrObjectIsNil = errors.New("object should not be nil")

// Get retrieve one record from database, bean's non-empty fields
// will be as conditions
func (session *Session) Get(beans ...interface{}) (bool, error) {
	if session.isAutoClose {
		defer session.Close()
	}
	return session.get(beans...)
}

func isPtrOfTime(v interface{}) bool {
	if _, ok := v.(*time.Time); ok {
		return true
	}

	el := reflect.ValueOf(v).Elem()
	if el.Kind() != reflect.Struct {
		return false
	}

	return el.Type().ConvertibleTo(schemas.TimeType)
}

func (session *Session) get(beans ...interface{}) (bool, error) {
	defer session.resetStatement()

	if session.statement.LastError != nil {
		return false, session.statement.LastError
	}
	if len(beans) == 0 {
		return false, errors.New("needs at least one parameter for get")
	}

	beanValue := reflect.ValueOf(beans[0])
	if beanValue.Kind() != reflect.Ptr {
		return false, errors.New("needs a pointer to a value")
	} else if beanValue.Elem().Kind() == reflect.Ptr {
		return false, errors.New("a pointer to a pointer is not allowed")
	} else if beanValue.IsNil() {
		return false, ErrObjectIsNil
	}

	isStruct := beanValue.Elem().Kind() == reflect.Struct && !isPtrOfTime(beans[0])
	if isStruct {
		if err := session.statement.SetRefBean(beans[0]); err != nil {
			return false, err
		}
	}

	var sqlStr string
	var args []interface{}
	var err error

	if session.statement.RawSQL == "" {
		if len(session.statement.TableName()) == 0 {
			return false, ErrTableNotFound
		}
		session.statement.Limit(1)
		sqlStr, args, err = session.statement.GenGetSQL(beans[0])
		if err != nil {
			return false, err
		}
	} else {
		sqlStr = session.statement.GenRawSQL()
		args = session.statement.RawParams
	}

	table := session.statement.RefTable
	context := session.statement.Context
	if context != nil && isStruct {
		res := context.Get(fmt.Sprintf("%v-%v", sqlStr, args))
		if res != nil {
			session.engine.logger.Debugf("hit context cache: %s", sqlStr)

			structValue := reflect.Indirect(reflect.ValueOf(beans[0]))
			structValue.Set(reflect.Indirect(reflect.ValueOf(res)))
			session.lastSQL = ""
			session.lastSQLArgs = nil
			return true, nil
		}
	}

	has, err := session.nocacheGet(beanValue.Elem().Kind(), table, beans, sqlStr, args...)
	if err != nil || !has {
		return has, err
	}

	if context != nil && isStruct {
		context.Put(fmt.Sprintf("%v-%v", sqlStr, args), beans[0])
	}

	return true, nil
}

func isScannableStruct(bean interface{}, typeLen int) bool {
	switch bean.(type) {
	case *time.Time:
		return false
	case sql.Scanner:
		return false
	case convert.Conversion:
		return typeLen > 1
	case *big.Float:
		return false
	}
	return true
}

func (session *Session) nocacheGet(beanKind reflect.Kind, table *schemas.Table, beans []interface{}, sqlStr string, args ...interface{}) (bool, error) {
	rows, err := session.queryRows(sqlStr, args...)
	if err != nil {
		return false, err
	}
	defer rows.Close()

	if !rows.Next() {
		return false, rows.Err()
	}

	// WARN: Alougth rows return true, but we may also return error.
	types, err := rows.ColumnTypes()
	if err != nil {
		return true, err
	}
	fields, err := rows.Columns()
	if err != nil {
		return true, err
	}

	columnsSchema := ParseColumnsSchema(fields, types, table)

	if err := session.scan(rows, table, beanKind, beans, columnsSchema, types, fields); err != nil {
		return true, err
	}
	rows.Close()

	return true, session.executeProcessors()
}

func (session *Session) scan(rows *core.Rows, table *schemas.Table, firstBeanKind reflect.Kind, beans []interface{}, columnsSchema *ColumnsSchema, types []*sql.ColumnType, fields []string) error {
	if len(beans) == 1 {
		bean := beans[0]
		switch firstBeanKind {
		case reflect.Struct:
			if !isScannableStruct(bean, len(types)) {
				break
			}
			scanResults, err := session.row2Slice(rows, fields, types, bean)
			if err != nil {
				return err
			}

			dataStruct := utils.ReflectValue(bean)
			_, err = session.slice2Bean(scanResults, columnsSchema, fields, bean, &dataStruct, table)
			return err
		case reflect.Slice:
			return session.getSlice(rows, types, fields, bean)
		case reflect.Map:
			return session.getMap(rows, types, fields, bean)
		}
	}

	if len(beans) != len(types) {
		return fmt.Errorf("expected columns %d, but only %d variables", len(types), len(beans))
	}

	return session.engine.scan(rows, fields, types, beans...)
}

func (session *Session) getSlice(rows *core.Rows, types []*sql.ColumnType, fields []string, bean interface{}) error {
	switch t := bean.(type) {
	case *[]string:
		res, err := session.engine.scanStringInterface(rows, fields, types)
		if err != nil {
			return err
		}

		needAppend := len(*t) == 0 // both support slice is empty or has been initlized
		for i, r := range res {
			if needAppend {
				*t = append(*t, r.(*sql.NullString).String)
			} else {
				(*t)[i] = r.(*sql.NullString).String
			}
		}
		return nil
	case *[]interface{}:
		scanResults, err := session.engine.scanInterfaces(rows, fields, types)
		if err != nil {
			return err
		}
		needAppend := len(*t) == 0
		for ii := range fields {
			s, err := convert.Interface2Interface(session.engine.DatabaseTZ, scanResults[ii])
			if err != nil {
				return err
			}
			if needAppend {
				*t = append(*t, s)
			} else {
				(*t)[ii] = s
			}
		}
		return nil
	default:
		return fmt.Errorf("unspoorted slice type: %t", t)
	}
}

func (session *Session) getMap(rows *core.Rows, types []*sql.ColumnType, fields []string, bean interface{}) error {
	switch t := bean.(type) {
	case *map[string]string:
		scanResults, err := session.engine.scanStringInterface(rows, fields, types)
		if err != nil {
			return err
		}
		for ii, key := range fields {
			(*t)[key] = scanResults[ii].(*sql.NullString).String
		}
		return nil
	case *map[string]interface{}:
		scanResults, err := session.engine.scanInterfaces(rows, fields, types)
		if err != nil {
			return err
		}
		for ii, key := range fields {
			s, err := convert.Interface2Interface(session.engine.DatabaseTZ, scanResults[ii])
			if err != nil {
				return err
			}
			(*t)[key] = s
		}
		return nil
	default:
		return fmt.Errorf("unspoorted map type: %t", t)
	}
}

// Exist returns true if the record exist otherwise return false
func (session *Session) Exist(bean ...interface{}) (bool, error) {
	if session.isAutoClose {
		defer session.Close()
	}

	if session.statement.LastError != nil {
		return false, session.statement.LastError
	}

	sqlStr, args, err := session.statement.GenExistSQL(bean...)
	if err != nil {
		return false, err
	}

	rows, err := session.queryRows(sqlStr, args...)
	if err != nil {
		return false, err
	}
	defer rows.Close()

	if rows.Next() {
		return true, nil
	}
	return false, rows.Err()
}