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package combinator
import (
"fmt"
"reflect"
)
// Generate returns a slice of all possible value combinations for any given
// struct and a set of its potential member values.
func Generate(v interface{}, ov interface{}) error {
// verify supplied types
vPtr := reflect.ValueOf(v)
if vPtr.Kind() != reflect.Ptr {
return fmt.Errorf("non-pointer type supplied")
}
value := vPtr.Elem()
if value.Kind() != reflect.Slice {
return fmt.Errorf("pointer to non-slice type supplied")
}
vType := reflect.TypeOf(v).Elem().Elem()
ovType := reflect.TypeOf(ov)
ovValue := reflect.ValueOf(ov)
if ovValue.Kind() != reflect.Struct {
return fmt.Errorf("non-slice type supplied")
}
// calculate combinations
combinations := 1
members := ovType.NumField()
for i := 0; i < members; i++ {
if ovValue.Field(i).Kind() != reflect.Slice {
continue
}
if ovValue.Field(i).Len() == 0 {
// ignore empty option values
continue
}
fname := ovType.Field(i).Name
if _, ok := vType.FieldByName(fname); !ok {
return fmt.Errorf("can't access struct field %s", fname)
}
combinations *= ovValue.Field(i).Len()
}
// fill struct with all combinations
for i := 0; i < combinations; i++ {
vi := reflect.Indirect(reflect.New(vType))
offset := 1
for j := 0; j < members; j++ {
ovf := ovValue.Field(j)
var fvalue reflect.Value
if ovf.Kind() == reflect.Slice {
if ovf.Len() == 0 {
// ignore empty option values
continue
}
fvalue = ovf.Index((i / offset) % ovf.Len())
offset *= ovf.Len()
} else {
fvalue = ovf
}
fname := ovType.Field(j).Name
if vi.FieldByName(fname).CanSet() {
vi.FieldByName(fname).Set(fvalue)
}
// fmt.Println(fname, fvalue, offset)
}
// append item to original slice
value.Set(reflect.Append(value, vi))
}
return nil
}
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