package collect

import (
	"context"
	"os"
	"path/filepath"
	"sync"
	"testing"
	"time"

	"git.opencomputing.cn/yumoqing/host-metrics-collector/internal/checkpoint"
	"git.opencomputing.cn/yumoqing/host-metrics-collector/internal/model"
)

func writeTempLog(t *testing.T, content string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "app.log")
	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
		t.Fatalf("write temp log: %v", err)
	}
	return path
}

func TestLogTailReadOnceEmitsCompleteLines(t *testing.T) {
	path := writeTempLog(t, "line one\nline two\n")

	var mu sync.Mutex
	var got []model.LogRecord
	tail := NewLogTail(path, checkpoint.NewMemoryStore(), time.Second, func(r model.LogRecord) {
		mu.Lock()
		defer mu.Unlock()
		got = append(got, r)
	})

	offset, partial := tail.readOnce(0, nil)
	if offset != int64(len("line one\nline two\n")) {
		t.Fatalf("offset = %d", offset)
	}
	if len(partial) != 0 {
		t.Fatalf("partial = %q, want empty", partial)
	}

	mu.Lock()
	defer mu.Unlock()
	if len(got) != 2 || got[0].Message != "line one" || got[1].Message != "line two" {
		t.Fatalf("records = %+v", got)
	}
	if got[0].Level != "INFO" {
		t.Fatalf("level = %q, want INFO", got[0].Level)
	}
}

func TestLogTailReadOnceKeepsPartialLine(t *testing.T) {
	path := writeTempLog(t, "partial line")

	tail := NewLogTail(path, checkpoint.NewMemoryStore(), time.Second, nil)
	offset, partial := tail.readOnce(0, nil)
	if offset != 0 {
		t.Fatalf("offset = %d, want 0 (no newline yet)", offset)
	}
	if string(partial) != "partial line" {
		t.Fatalf("partial = %q", partial)
	}
}

func TestLogTailReadOnceHandlesTruncation(t *testing.T) {
	path := writeTempLog(t, "old content longer\n")
	tail := NewLogTail(path, checkpoint.NewMemoryStore(), time.Second, nil)

	// 模拟文件被轮转/截断：offset 超出文件大小，应从头读取。
	if err := os.WriteFile(path, []byte("new\n"), 0o644); err != nil {
		t.Fatalf("truncate: %v", err)
	}
	offset, partial := tail.readOnce(100, []byte("tail"))
	if offset != int64(len("new\n")) {
		t.Fatalf("offset = %d, want %d", offset, len("new\n"))
	}
	if len(partial) != 0 {
		t.Fatalf("partial = %q", partial)
	}
}

func TestLogTailRunStopsOnContextCancel(t *testing.T) {
	path := writeTempLog(t, "hello\n")
	tail := NewLogTail(path, checkpoint.NewMemoryStore(), 10*time.Millisecond, nil)

	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan struct{})
	go func() {
		tail.Run(ctx)
		close(done)
	}()

	// 等它至少消费一轮，再取消。
	time.Sleep(50 * time.Millisecond)
	cancel()

	select {
	case <-done:
	case <-time.After(2 * time.Second):
		t.Fatalf("LogTail.Run did not stop after cancel")
	}
}