package gorm

import (
	"database/sql"
	"database/sql/driver"
	"reflect"
	"strings"
	"time"

	"gorm.io/gorm/schema"
)

func prepareValues(values []interface{}, db *DB, columnTypes []*sql.ColumnType, columns []string) {
	if db.Statement.Schema != nil {
		for idx, name := range columns {
			if field := db.Statement.Schema.LookUpField(name); field != nil {
				values[idx] = reflect.New(reflect.PtrTo(field.FieldType)).Interface()
				continue
			}
			values[idx] = new(interface{})
		}
	} else if len(columnTypes) > 0 {
		for idx, columnType := range columnTypes {
			if columnType.ScanType() != nil {
				values[idx] = reflect.New(reflect.PtrTo(columnType.ScanType())).Interface()
			} else {
				values[idx] = new(interface{})
			}
		}
	} else {
		for idx := range columns {
			values[idx] = new(interface{})
		}
	}
}

func scanIntoMap(mapValue map[string]interface{}, values []interface{}, columns []string) {
	for idx, column := range columns {
		if reflectValue := reflect.Indirect(reflect.Indirect(reflect.ValueOf(values[idx]))); reflectValue.IsValid() {
			mapValue[column] = reflectValue.Interface()
			if valuer, ok := mapValue[column].(driver.Valuer); ok {
				mapValue[column], _ = valuer.Value()
			} else if b, ok := mapValue[column].(sql.RawBytes); ok {
				mapValue[column] = string(b)
			}
		} else {
			mapValue[column] = nil
		}
	}
}

func Scan(rows *sql.Rows, db *DB, initialized bool) {
	columns, _ := rows.Columns()
	values := make([]interface{}, len(columns))
	db.RowsAffected = 0

	switch dest := db.Statement.Dest.(type) {
	case map[string]interface{}, *map[string]interface{}:
		if initialized || rows.Next() {
			columnTypes, _ := rows.ColumnTypes()
			prepareValues(values, db, columnTypes, columns)

			db.RowsAffected++
			db.AddError(rows.Scan(values...))

			mapValue, ok := dest.(map[string]interface{})
			if !ok {
				if v, ok := dest.(*map[string]interface{}); ok {
					mapValue = *v
				}
			}
			scanIntoMap(mapValue, values, columns)
		}
	case *[]map[string]interface{}:
		columnTypes, _ := rows.ColumnTypes()
		for initialized || rows.Next() {
			prepareValues(values, db, columnTypes, columns)

			initialized = false
			db.RowsAffected++
			db.AddError(rows.Scan(values...))

			mapValue := map[string]interface{}{}
			scanIntoMap(mapValue, values, columns)
			*dest = append(*dest, mapValue)
		}
	case *int, *int8, *int16, *int32, *int64,
		*uint, *uint8, *uint16, *uint32, *uint64, *uintptr,
		*float32, *float64,
		*bool, *string, *time.Time,
		*sql.NullInt32, *sql.NullInt64, *sql.NullFloat64,
		*sql.NullBool, *sql.NullString, *sql.NullTime:
		for initialized || rows.Next() {
			initialized = false
			db.RowsAffected++
			db.AddError(rows.Scan(dest))
		}
	default:
		Schema := db.Statement.Schema

		switch db.Statement.ReflectValue.Kind() {
		case reflect.Slice, reflect.Array:
			var (
				reflectValueType = db.Statement.ReflectValue.Type().Elem()
				isPtr            = reflectValueType.Kind() == reflect.Ptr
				fields           = make([]*schema.Field, len(columns))
				joinFields       [][2]*schema.Field
			)

			if isPtr {
				reflectValueType = reflectValueType.Elem()
			}

			db.Statement.ReflectValue.Set(reflect.MakeSlice(db.Statement.ReflectValue.Type(), 0, 20))

			if Schema != nil {
				if reflectValueType != Schema.ModelType && reflectValueType.Kind() == reflect.Struct {
					Schema, _ = schema.Parse(db.Statement.Dest, db.cacheStore, db.NamingStrategy)
				}

				for idx, column := range columns {
					if field := Schema.LookUpField(column); field != nil && field.Readable {
						fields[idx] = field
					} else if names := strings.Split(column, "__"); len(names) > 1 {
						if rel, ok := Schema.Relationships.Relations[names[0]]; ok {
							if field := rel.FieldSchema.LookUpField(strings.Join(names[1:], "__")); field != nil && field.Readable {
								fields[idx] = field

								if len(joinFields) == 0 {
									joinFields = make([][2]*schema.Field, len(columns))
								}
								joinFields[idx] = [2]*schema.Field{rel.Field, field}
								continue
							}
						}
						values[idx] = &sql.RawBytes{}
					} else {
						values[idx] = &sql.RawBytes{}
					}
				}
			}

			// pluck values into slice of data
			isPluck := false
			if len(fields) == 1 {
				if _, ok := reflect.New(reflectValueType).Interface().(sql.Scanner); ok || // is scanner
					reflectValueType.Kind() != reflect.Struct || // is not struct
					Schema.ModelType.ConvertibleTo(schema.TimeReflectType) { // is time
					isPluck = true
				}
			}

			for initialized || rows.Next() {
				initialized = false
				db.RowsAffected++

				elem := reflect.New(reflectValueType)
				if isPluck {
					db.AddError(rows.Scan(elem.Interface()))
				} else {
					for idx, field := range fields {
						if field != nil {
							values[idx] = reflect.New(reflect.PtrTo(field.IndirectFieldType)).Interface()
						}
					}

					db.AddError(rows.Scan(values...))

					for idx, field := range fields {
						if len(joinFields) != 0 && joinFields[idx][0] != nil {
							value := reflect.ValueOf(values[idx]).Elem()
							relValue := joinFields[idx][0].ReflectValueOf(elem)

							if relValue.Kind() == reflect.Ptr && relValue.IsNil() {
								if value.IsNil() {
									continue
								}
								relValue.Set(reflect.New(relValue.Type().Elem()))
							}

							field.Set(relValue, values[idx])
						} else if field != nil {
							field.Set(elem, values[idx])
						}
					}
				}

				if isPtr {
					db.Statement.ReflectValue.Set(reflect.Append(db.Statement.ReflectValue, elem))
				} else {
					db.Statement.ReflectValue.Set(reflect.Append(db.Statement.ReflectValue, elem.Elem()))
				}
			}
		case reflect.Struct:
			if db.Statement.ReflectValue.Type() != Schema.ModelType {
				Schema, _ = schema.Parse(db.Statement.Dest, db.cacheStore, db.NamingStrategy)
			}

			if initialized || rows.Next() {
				for idx, column := range columns {
					if field := Schema.LookUpField(column); field != nil && field.Readable {
						values[idx] = reflect.New(reflect.PtrTo(field.IndirectFieldType)).Interface()
					} else if names := strings.Split(column, "__"); len(names) > 1 {
						if rel, ok := Schema.Relationships.Relations[names[0]]; ok {
							if field := rel.FieldSchema.LookUpField(strings.Join(names[1:], "__")); field != nil && field.Readable {
								values[idx] = reflect.New(reflect.PtrTo(field.IndirectFieldType)).Interface()
								continue
							}
						}
						values[idx] = &sql.RawBytes{}
					} else {
						values[idx] = &sql.RawBytes{}
					}
				}

				db.RowsAffected++
				db.AddError(rows.Scan(values...))

				for idx, column := range columns {
					if field := Schema.LookUpField(column); field != nil && field.Readable {
						field.Set(db.Statement.ReflectValue, values[idx])
					} else if names := strings.Split(column, "__"); len(names) > 1 {
						if rel, ok := Schema.Relationships.Relations[names[0]]; ok {
							if field := rel.FieldSchema.LookUpField(strings.Join(names[1:], "__")); field != nil && field.Readable {
								relValue := rel.Field.ReflectValueOf(db.Statement.ReflectValue)
								value := reflect.ValueOf(values[idx]).Elem()

								if relValue.Kind() == reflect.Ptr && relValue.IsNil() {
									if value.IsNil() {
										continue
									}
									relValue.Set(reflect.New(relValue.Type().Elem()))
								}

								field.Set(relValue, values[idx])
							}
						}
					}
				}
			}
		}
	}

	if db.RowsAffected == 0 && db.Statement.RaiseErrorOnNotFound {
		db.AddError(ErrRecordNotFound)
	}
}