113 lines
2.9 KiB
Go
113 lines
2.9 KiB
Go
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package pointerstructure
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import (
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"fmt"
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"reflect"
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)
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// Delete deletes the value specified by the pointer p in structure s.
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//
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// When deleting a slice index, all other elements will be shifted to
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// the left. This is specified in RFC6902 (JSON Patch) and not RFC6901 since
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// RFC6901 doesn't specify operations on pointers. If you don't want to
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// shift elements, you should use Set to set the slice index to the zero value.
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//
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// The structures s must have non-zero values set up to this pointer.
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// For example, if deleting "/bob/0/name", then "/bob/0" must be set already.
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//
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// The returned value is potentially a new value if this pointer represents
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// the root document. Otherwise, the returned value will always be s.
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func (p *Pointer) Delete(s interface{}) (interface{}, error) {
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// if we represent the root doc, we've deleted everything
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if len(p.Parts) == 0 {
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return nil, nil
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}
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// Save the original since this is going to be our return value
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originalS := s
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// Get the parent value
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var err error
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s, err = p.Parent().Get(s)
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if err != nil {
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return nil, err
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}
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// Map for lookup of getter to call for type
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funcMap := map[reflect.Kind]deleteFunc{
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reflect.Array: p.deleteSlice,
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reflect.Map: p.deleteMap,
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reflect.Slice: p.deleteSlice,
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}
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val := reflect.ValueOf(s)
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for val.Kind() == reflect.Interface {
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val = val.Elem()
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}
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for val.Kind() == reflect.Ptr {
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val = reflect.Indirect(val)
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}
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f, ok := funcMap[val.Kind()]
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if !ok {
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return nil, fmt.Errorf("delete %s: invalid value kind: %s", p, val.Kind())
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}
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result, err := f(originalS, val)
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if err != nil {
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return nil, fmt.Errorf("delete %s: %s", p, err)
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}
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return result, nil
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}
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type deleteFunc func(interface{}, reflect.Value) (interface{}, error)
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func (p *Pointer) deleteMap(root interface{}, m reflect.Value) (interface{}, error) {
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part := p.Parts[len(p.Parts)-1]
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key, err := coerce(reflect.ValueOf(part), m.Type().Key())
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if err != nil {
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return root, err
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}
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// Delete the key
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var elem reflect.Value
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m.SetMapIndex(key, elem)
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return root, nil
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}
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func (p *Pointer) deleteSlice(root interface{}, s reflect.Value) (interface{}, error) {
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// Coerce the key to an int
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part := p.Parts[len(p.Parts)-1]
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idxVal, err := coerce(reflect.ValueOf(part), reflect.TypeOf(42))
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if err != nil {
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return root, err
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}
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idx := int(idxVal.Int())
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// Verify we're within bounds
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if idx < 0 || idx >= s.Len() {
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return root, fmt.Errorf(
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"index %d is out of range (length = %d)", idx, s.Len())
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}
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// Mimicing the following with reflection to do this:
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//
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// copy(a[i:], a[i+1:])
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// a[len(a)-1] = nil // or the zero value of T
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// a = a[:len(a)-1]
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// copy(a[i:], a[i+1:])
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reflect.Copy(s.Slice(idx, s.Len()), s.Slice(idx+1, s.Len()))
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// a[len(a)-1] = nil // or the zero value of T
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s.Index(s.Len() - 1).Set(reflect.Zero(s.Type().Elem()))
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// a = a[:len(a)-1]
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s = s.Slice(0, s.Len()-1)
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// set the slice back on the parent
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return p.Parent().Set(root, s.Interface())
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}
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