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// Copyright (c) 2020, Maxime Soulé
// All rights reserved.
//
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree.
package anchors
import (
"errors"
"fmt"
"math"
"reflect"
"time"
"github.com/maxatome/go-testdeep/internal/types"
)
type anchorableType struct {
typ reflect.Type
builder reflect.Value
}
// AnchorableTypes contains all non-native types that can be
// anchorable. See [AddAnchorableStructType] to add a new type to it.
var AnchorableTypes []anchorableType
func init() {
AddAnchorableStructType(func(nextAnchor int) time.Time { //nolint: errcheck
return time.Unix(math.MaxInt64-1000424443-int64(nextAnchor), 42)
})
}
// AddAnchorableStructType declares a struct type as anchorable. fn
// is a function allowing to return a unique and identifiable instance
// of the struct type.
//
// fn has to have the following signature:
//
// func (nextAnchor int) TYPE
//
// TYPE is the struct type to make anchorable and nextAnchor is an
// index to allow to differentiate several instances of the same type.
//
// For example, the [time.Time] type which is anchorable by default,
// is declared as:
//
// AddAnchorableStructType(func (nextAnchor int) time.Time {
// return time.Unix(math.MaxInt64-1000424443-int64(nextAnchor), 42)
// })
//
// Just as a note, the 1000424443 constant allows to avoid to flirt
// with the [math.MaxInt64] extreme limit and so avoid possible
// collision with real world values.
//
// It returns an error if the provided fn is not a function or if it
// has not the expected signature (see above).
func AddAnchorableStructType(fn any) error {
vfn := reflect.ValueOf(fn)
if vfn.Kind() == reflect.Func {
fnType := vfn.Type()
if !fnType.IsVariadic() &&
fnType.NumIn() == 1 && fnType.NumOut() == 1 &&
fnType.In(0) == types.Int &&
fnType.Out(0).Kind() == reflect.Struct {
typ := fnType.Out(0)
if !typ.Comparable() {
return fmt.Errorf(
"type %s is not comparable, it cannot be anchorable", typ)
}
for i, at := range AnchorableTypes {
if at.typ == typ {
AnchorableTypes[i].builder = vfn
return nil
}
}
AnchorableTypes = append(AnchorableTypes, anchorableType{
typ: typ,
builder: vfn,
})
return nil
}
}
return errors.New("usage: AddAnchorableStructType(func (nextAnchor int) STRUCT_TYPE)")
}
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