package monstersirenfetch_test

import (
	"encoding/json"
	"reflect"
	"strconv"
	"testing"
	"unsafe"

	. "git.gensokyo.uk/yonah/monstersirenfetch"
)

func TestStringInt(t *testing.T) {
	testCases := []struct {
		name    string
		wantErr error
		data    string
		val     int
	}{
		{"valid", nil, `"3735928559"`, 0xdeadbeef},
		{"valid pad", nil, `"0009"`, 9},
		{"invalid json", newSyntaxError("unexpected end of JSON input", 11), `"3735928559`, -1},
		{"invalid number", &strconv.NumError{Func: "Atoi", Num: ":3735928559", Err: strconv.ErrSyntax}, `":3735928559"`, -1},
	}
	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			if tc.wantErr == nil {
				t.Run("marshal", func(t *testing.T) {
					v := StringInt(tc.val)
					if got, err := json.Marshal(&v); err != nil {
						t.Fatalf("Marshal: error = %v", err)
					} else if string(got) != tc.data {
						t.Errorf("Marshal: %s, want %s", string(got), tc.data)
					}
				})
			}

			t.Run("unmarshal", func(t *testing.T) {
				var got StringInt
				err := json.Unmarshal([]byte(tc.data), &got)

				if !reflect.DeepEqual(err, tc.wantErr) {
					t.Errorf("Unmarshal: error = %v, want %v", err, tc.wantErr)
				}

				if tc.wantErr == nil {
					if int(got) != tc.val {
						t.Errorf("Unmarshal: %d, want %d", got, tc.val)
					}
				}
			})
		})
	}
}

func newSyntaxError(msg string, offset int64) *json.SyntaxError {
	e := &json.SyntaxError{Offset: offset}
	msgV := reflect.ValueOf(e).Elem().FieldByName("msg")
	reflect.NewAt(msgV.Type(), unsafe.Pointer(msgV.UnsafeAddr())).Elem().SetString(msg)
	return e
}