Refactor to new framework (#98)

- Adjust directory structure
```text
├── internal
│   ├── app
│   │   ├── artifactcache
│   │   ├── cmd
│   │   ├── poll
│   │   └── run
│   └── pkg
│       ├── client
│       ├── config
│       ├── envcheck
│       ├── labels
│       ├── report
│       └── ver
└── main.go
```
- New pkg `labels` to parse label
- New pkg `report` to report logs to Gitea
- Remove pkg `engine`, use `envcheck` to check if docker running.
- Rewrite `runtime` to `run`
- Rewrite `poller` to `poll`
- Simplify some code and remove what's useless.

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/98
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Jason Song <i@wolfogre.com>
Co-committed-by: Jason Song <i@wolfogre.com>

internal/app/poll/poller.go

@@ -0,0 +1,82 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package poll
+
+import (
+	"context"
+	"errors"
+	"sync"
+	"time"
+
+	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
+	"github.com/bufbuild/connect-go"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/time/rate"
+
+	"gitea.com/gitea/act_runner/internal/app/run"
+	"gitea.com/gitea/act_runner/internal/pkg/client"
+	"gitea.com/gitea/act_runner/internal/pkg/config"
+)
+
+type Poller struct {
+	client   client.Client
+	runner   *run.Runner
+	capacity int
+}
+
+func New(cfg *config.Config, client client.Client, runner *run.Runner) *Poller {
+	return &Poller{
+		client:   client,
+		runner:   runner,
+		capacity: cfg.Runner.Capacity,
+	}
+}
+
+func (p *Poller) Poll(ctx context.Context) {
+	limiter := rate.NewLimiter(rate.Every(2*time.Second), 1)
+	wg := &sync.WaitGroup{}
+	for i := 0; i < p.capacity; i++ {
+		wg.Add(1)
+		go p.poll(ctx, wg, limiter)
+	}
+	wg.Wait()
+}
+
+func (p *Poller) poll(ctx context.Context, wg *sync.WaitGroup, limiter *rate.Limiter) {
+	defer wg.Done()
+	for {
+		if err := limiter.Wait(ctx); err != nil {
+			if ctx.Err() != nil {
+				log.WithError(err).Debug("limiter wait failed")
+			}
+			return
+		}
+		task, ok := p.fetchTask(ctx)
+		if !ok {
+			continue
+		}
+		if err := p.runner.Run(ctx, task); err != nil {
+			log.WithError(err).Error("failed to run task")
+		}
+	}
+}
+
+func (p *Poller) fetchTask(ctx context.Context) (*runnerv1.Task, bool) {
+	reqCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+
+	resp, err := p.client.FetchTask(reqCtx, connect.NewRequest(&runnerv1.FetchTaskRequest{}))
+	if errors.Is(err, context.DeadlineExceeded) {
+		err = nil
+	}
+	if err != nil {
+		log.WithError(err).Error("failed to fetch task")
+		return nil, false
+	}
+
+	if resp.Msg.Task == nil {
+		return nil, false
+	}
+	return resp.Msg.Task, true
+}