package stacks

import (
	"reflect"
	"testing"
)

// R-591 follow-up: deepCopyStack's contract is "a snapshot the caller may mutate", and the I18n hole
// was not the only one — DataPaths, AfterLoad (and every other reference added to Metadata after the
// copy was written) stayed shared. Instead of one assertion per field, this fills EVERY pointer, slice
// and map reachable from Stack.Meta with a non-empty value and then walks the copy beside the original:
// any reference the two share is a field a caller's write would leak through. A field added to
// Metadata tomorrow is covered the day it is added.
func TestDeepCopyStackMetaSharesNoReference(t *testing.T) {
	orig := &Stack{Name: "demo"}
	fillAll(reflect.ValueOf(&orig.Meta).Elem(), 0)
	cp := deepCopyStack(orig)
	var shared []string
	findAliases(reflect.ValueOf(orig.Meta), reflect.ValueOf(cp.Meta), "Meta", &shared)
	for _, p := range shared {
		t.Errorf("R-591: deepCopyStack leaves %s shared with the original — a write through the copy changes the stack", p)
	}
}

// fillAll gives every pointer, slice (one element) and map (one entry) under v a non-nil value.
func fillAll(v reflect.Value, depth int) {
	if depth > 6 || !v.CanSet() && v.Kind() != reflect.Struct {
		return
	}
	switch v.Kind() {
	case reflect.Ptr:
		if v.IsNil() {
			v.Set(reflect.New(v.Type().Elem()))
		}
		fillAll(v.Elem(), depth+1)
	case reflect.Slice:
		if v.Len() == 0 {
			v.Set(reflect.MakeSlice(v.Type(), 1, 1))
		}
		fillAll(v.Index(0), depth+1)
	case reflect.Map:
		if v.Len() == 0 {
			m := reflect.MakeMap(v.Type())
			k := reflect.New(v.Type().Key()).Elem()
			if k.Kind() == reflect.String {
				k.SetString("k")
			}
			e := reflect.New(v.Type().Elem()).Elem()
			fillAll(e, depth+1)
			m.SetMapIndex(k, e)
			v.Set(m)
		}
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			if v.Type().Field(i).IsExported() {
				fillAll(v.Field(i), depth+1)
			}
		}
	case reflect.String:
		if v.String() == "" {
			v.SetString("x")
		}
	}
}

// findAliases records every pointer/slice/map under a and b that points at the same memory.
func findAliases(a, b reflect.Value, path string, out *[]string) {
	switch a.Kind() {
	case reflect.Ptr:
		if a.IsNil() || b.IsNil() {
			return
		}
		if a.Pointer() == b.Pointer() {
			*out = append(*out, path)
			return
		}
		findAliases(a.Elem(), b.Elem(), path, out)
	case reflect.Slice:
		if a.Len() == 0 || b.Len() == 0 {
			return
		}
		if a.Pointer() == b.Pointer() {
			*out = append(*out, path)
			return
		}
		for i := 0; i < a.Len() && i < b.Len(); i++ {
			findAliases(a.Index(i), b.Index(i), path+"[]", out)
		}
	case reflect.Map:
		if a.Len() == 0 || b.Len() == 0 {
			return
		}
		if a.Pointer() == b.Pointer() {
			*out = append(*out, path)
			return
		}
		for _, k := range a.MapKeys() {
			if bv := b.MapIndex(k); bv.IsValid() {
				findAliases(a.MapIndex(k), bv, path+"[k]", out)
			}
		}
	case reflect.Struct:
		for i := 0; i < a.NumField(); i++ {
			if a.Type().Field(i).IsExported() {
				findAliases(a.Field(i), b.Field(i), path+"."+a.Type().Field(i).Name, out)
			}
		}
	}
}