package stream

import (
	"encoding/json"
	"errors"
	"io"
	"reflect"
	"strings"
	"testing"
)

const evJSON = `{"event_id":"evt_1","timestamp":1,"type":"node_command","node_id":"n1","payload":{"action":"drain"}}`

var evWant = Event{
	ID:        "evt_1",
	Timestamp: 1,
	Type:      EventNodeCommand,
	NodeID:    "n1",
	Payload:   json.RawMessage(`{"action":"drain"}`),
}

func decodeAll(t *testing.T, input string) ([]Event, error) {
	t.Helper()
	dec := NewDecoder(strings.NewReader(input))
	var out []Event
	for {
		ev, err := dec.Next()
		if err != nil {
			return out, err
		}
		out = append(out, ev)
	}
}

func TestDecoder(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  []Event
	}{
		{"einzelnes Event", "id: evt_1\nevent: node_command\ndata: " + evJSON + "\n\n", []Event{evWant}},
		{"Keepalives werden übersprungen", ":\n\n:\n\ndata: " + evJSON + "\n\n:\n\n", []Event{evWant}},
		{"CRLF-Zeilenenden", "id: evt_1\r\ndata: " + evJSON + "\r\n\r\n", []Event{evWant}},
		{"data ohne Leerzeichen", "data:" + evJSON + "\n\n", []Event{evWant}},
		{
			"mehrere data-Zeilen",
			"data: {\"event_id\":\"evt_1\",\"timestamp\":1,\ndata: \"type\":\"node_command\",\"node_id\":\"n1\",\ndata: \"payload\":{\"action\":\"drain\"}}\n\n",
			[]Event{evWant},
		},
		{"unbekannte Felder ignoriert", "retry: 1000\nfoo: bar\ndata: " + evJSON + "\n\n", []Event{evWant}},
		{"Leerzeilen ohne Daten", "\n\n\nevent: x\n\n", nil},
		{"zwei Events", "data: " + evJSON + "\n\ndata: " + evJSON + "\n\n", []Event{evWant, evWant}},
		{"leerer Stream", "", nil},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := decodeAll(t, tt.input)
			if !errors.Is(err, io.EOF) {
				t.Fatalf("erwartet io.EOF am Ende, bekommen %v", err)
			}
			if !reflect.DeepEqual(got, tt.want) {
				t.Errorf("Events weichen ab\n got: %+v\nwant: %+v", got, tt.want)
			}
		})
	}
}

func TestDecoder_Errors(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  error
	}{
		{"ungültiges JSON", "data: {kaputt\n\n", ErrInvalidEvent},
		{"Event ohne Typ", "data: {\"event_id\":\"evt_1\"}\n\n", ErrInvalidEvent},
		{"abgeschnittenes Event", "data: " + evJSON + "\n", io.ErrUnexpectedEOF},
		{"Zeile zu lang", "data: " + strings.Repeat("x", MaxEventSize+1) + "\n\n", ErrEventTooLarge},
		{"Summe der data-Zeilen zu lang", strings.Repeat("data: "+strings.Repeat("x", MaxEventSize/4)+"\n", 5) + "\n", ErrEventTooLarge},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			_, err := decodeAll(t, tt.input)
			if !errors.Is(err, tt.want) {
				t.Errorf("erwartet %v, bekommen %v", tt.want, err)
			}
		})
	}
}

func TestEncodeDecodeRoundTrip(t *testing.T) {
	ev, err := NewEvent(EventServiceState, map[string]any{"labels": map[string]string{"traefik.enable": "true"}})
	if err != nil {
		t.Fatal(err)
	}
	ev.NodeID = "n1"
	frame, err := encode(ev)
	if err != nil {
		t.Fatal(err)
	}
	if !strings.HasPrefix(string(frame), "id: "+ev.ID+"\nevent: service_state\ndata: ") || !strings.HasSuffix(string(frame), "\n\n") {
		t.Errorf("unerwarteter SSE-Rahmen: %q", frame)
	}
	got, err := NewDecoder(strings.NewReader(string(frame))).Next()
	if err != nil {
		t.Fatal(err)
	}
	if !reflect.DeepEqual(got, ev) {
		t.Errorf("Round-Trip weicht ab\n got: %+v\nwant: %+v", got, ev)
	}
}