package engine

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
	"time"
)

// sigQueue 是测试里每个引擎的入站信令 FIFO：单消费者保序处理，确保 offer/answer 先于
// 其后 trickle 的 ICE 候选被处理（pion 的 AddICECandidate 在 remote description 未设时报错）。
type sigQueue struct {
	ch  chan [2]string // [fromPeer, payloadJSON]
	eng *Engine
}

func newSigQueue() *sigQueue { return &sigQueue{ch: make(chan [2]string, 256)} }

func (q *sigQueue) run(t *testing.T, done <-chan struct{}) {
	go func() {
		for {
			select {
			case <-done:
				return
			case m := <-q.ch:
				if err := q.eng.HandleSignal(m[0], m[1]); err != nil {
					t.Logf("HandleSignal(%s) err: %v", m[0], err)
				}
			}
		}
	}()
}

// peerEvents 把一端的出站信令投到对端队列，并暴露 saved/failed 通道供断言。
type peerEvents struct {
	t        *testing.T
	selfName string
	out      *sigQueue // 对端队列
	saved    chan string
	failed   chan string
}

func (p *peerEvents) OnProgress(string, int64) {}
func (p *peerEvents) OnState(_ string, st string) {
	if st == "failed" {
		select {
		case p.failed <- st:
		default:
		}
	}
}
func (p *peerEvents) OnSignal(_ string, _ string, payloadJSON string) {
	// 对端看到的 fromPeer 即本端名字。
	p.out.ch <- [2]string{p.selfName, payloadJSON}
}
func (p *peerEvents) OnSaved(_ string, path string) {
	select {
	case p.saved <- path:
	default:
	}
}
func (p *peerEvents) OnIcePair(_ string, _ string, _ string) {}
func (p *peerEvents) OnLog(line string) { p.t.Log(line) }

// TestEngineTransfer 端到端：两个进程内 pion peer（A 发 / B 收）经 host 候选直连，传一个
// 3MB 已知内容的文件，断言落盘字节与源一致。覆盖线协议（meta/chunk/done/ack）、水位回压、
// 接收端落盘改名。
func TestEngineTransfer(t *testing.T) {
	dir := t.TempDir()
	srcPath := filepath.Join(dir, "payload.bin")
	dlDir := filepath.Join(dir, "downloads")
	if err := os.MkdirAll(dlDir, 0o755); err != nil {
		t.Fatal(err)
	}

	// 3MB 确定性内容：触发多片 + 至少一次回压窗口。
	const size = 3 * 1024 * 1024
	want := make([]byte, size)
	for i := range want {
		want[i] = byte(i*7 + 3)
	}
	if err := os.WriteFile(srcPath, want, 0o644); err != nil {
		t.Fatal(err)
	}

	qA, qB := newSigQueue(), newSigQueue()
	evA := &peerEvents{t: t, selfName: "A", out: qB, saved: make(chan string, 1), failed: make(chan string, 1)}
	evB := &peerEvents{t: t, selfName: "B", out: qA, saved: make(chan string, 1), failed: make(chan string, 1)}

	engA := New(Config{DownloadDir: dlDir}, evA) // 发送端（不落盘）
	engB := New(Config{DownloadDir: dlDir}, evB) // 接收端
	qA.eng, qB.eng = engA, engB

	done := make(chan struct{})
	defer close(done)
	qA.run(t, done)
	qB.run(t, done)

	const sid = "sess-1"
	if err := engB.StartIncoming(sid, "A", ""); err != nil { // 先武装接收端
		t.Fatalf("StartIncoming: %v", err)
	}
	if err := engA.StartOutgoing(sid, "B", srcPath, ""); err != nil {
		t.Fatalf("StartOutgoing: %v", err)
	}

	var savedPath string
	select {
	case savedPath = <-evB.saved:
	case <-evB.failed:
		t.Fatal("receiver reported failed")
	case <-evA.failed:
		t.Fatal("sender reported failed")
	case <-time.After(20 * time.Second):
		t.Fatal("timeout waiting for transfer to complete")
	}

	got, err := os.ReadFile(savedPath)
	if err != nil {
		t.Fatalf("read saved file: %v", err)
	}
	if len(got) != len(want) {
		t.Fatalf("size mismatch: got %d want %d", len(got), len(want))
	}
	if !bytes.Equal(got, want) {
		t.Fatal("content mismatch between source and received file")
	}

	// 给发送端 waitAck/收尾一点时间收束，避免泄漏 goroutine 噪声（非断言项）。
	time.Sleep(200 * time.Millisecond)
}

// TestParseICEServers 验证 urls 单串 / 数组两种形态都能解析（与 web getICEServers 输出兼容）。
func TestParseICEServers(t *testing.T) {
	out := parseICEServers(`[{"urls":"stun:a:1"},{"urls":["turns:b:2","turn:b:3"],"username":"u","credential":"c"}]`)
	if len(out) != 2 {
		t.Fatalf("want 2 servers, got %d", len(out))
	}
	if len(out[0].URLs) != 1 || out[0].URLs[0] != "stun:a:1" {
		t.Errorf("server0 urls wrong: %+v", out[0].URLs)
	}
	if len(out[1].URLs) != 2 || out[1].Username != "u" {
		t.Errorf("server1 wrong: %+v", out[1])
	}
}