Move migrations into services and base into modules/migration (#17663)

* Move migrtions into services and base into modules/migration

* Fix imports

* Fix lint

modules/migration/retry_downloader.go

@@ -0,0 +1,197 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migration
+
+import (
+	"context"
+	"time"
+)
+
+var (
+	_ Downloader = &RetryDownloader{}
+)
+
+// RetryDownloader retry the downloads
+type RetryDownloader struct {
+	Downloader
+	ctx        context.Context
+	RetryTimes int // the total execute times
+	RetryDelay int // time to delay seconds
+}
+
+// NewRetryDownloader creates a retry downloader
+func NewRetryDownloader(ctx context.Context, downloader Downloader, retryTimes, retryDelay int) *RetryDownloader {
+	return &RetryDownloader{
+		Downloader: downloader,
+		ctx:        ctx,
+		RetryTimes: retryTimes,
+		RetryDelay: retryDelay,
+	}
+}
+
+func (d *RetryDownloader) retry(work func() error) error {
+	var (
+		times = d.RetryTimes
+		err   error
+	)
+	for ; times > 0; times-- {
+		if err = work(); err == nil {
+			return nil
+		}
+		if IsErrNotSupported(err) {
+			return err
+		}
+		select {
+		case <-d.ctx.Done():
+			return d.ctx.Err()
+		case <-time.After(time.Second * time.Duration(d.RetryDelay)):
+		}
+	}
+	return err
+}
+
+// SetContext set context
+func (d *RetryDownloader) SetContext(ctx context.Context) {
+	d.ctx = ctx
+	d.Downloader.SetContext(ctx)
+}
+
+// GetRepoInfo returns a repository information with retry
+func (d *RetryDownloader) GetRepoInfo() (*Repository, error) {
+	var (
+		repo *Repository
+		err  error
+	)
+
+	err = d.retry(func() error {
+		repo, err = d.Downloader.GetRepoInfo()
+		return err
+	})
+
+	return repo, err
+}
+
+// GetTopics returns a repository's topics with retry
+func (d *RetryDownloader) GetTopics() ([]string, error) {
+	var (
+		topics []string
+		err    error
+	)
+
+	err = d.retry(func() error {
+		topics, err = d.Downloader.GetTopics()
+		return err
+	})
+
+	return topics, err
+}
+
+// GetMilestones returns a repository's milestones with retry
+func (d *RetryDownloader) GetMilestones() ([]*Milestone, error) {
+	var (
+		milestones []*Milestone
+		err        error
+	)
+
+	err = d.retry(func() error {
+		milestones, err = d.Downloader.GetMilestones()
+		return err
+	})
+
+	return milestones, err
+}
+
+// GetReleases returns a repository's releases with retry
+func (d *RetryDownloader) GetReleases() ([]*Release, error) {
+	var (
+		releases []*Release
+		err      error
+	)
+
+	err = d.retry(func() error {
+		releases, err = d.Downloader.GetReleases()
+		return err
+	})
+
+	return releases, err
+}
+
+// GetLabels returns a repository's labels with retry
+func (d *RetryDownloader) GetLabels() ([]*Label, error) {
+	var (
+		labels []*Label
+		err    error
+	)
+
+	err = d.retry(func() error {
+		labels, err = d.Downloader.GetLabels()
+		return err
+	})
+
+	return labels, err
+}
+
+// GetIssues returns a repository's issues with retry
+func (d *RetryDownloader) GetIssues(page, perPage int) ([]*Issue, bool, error) {
+	var (
+		issues []*Issue
+		isEnd  bool
+		err    error
+	)
+
+	err = d.retry(func() error {
+		issues, isEnd, err = d.Downloader.GetIssues(page, perPage)
+		return err
+	})
+
+	return issues, isEnd, err
+}
+
+// GetComments returns a repository's comments with retry
+func (d *RetryDownloader) GetComments(opts GetCommentOptions) ([]*Comment, bool, error) {
+	var (
+		comments []*Comment
+		isEnd    bool
+		err      error
+	)
+
+	err = d.retry(func() error {
+		comments, isEnd, err = d.Downloader.GetComments(opts)
+		return err
+	})
+
+	return comments, isEnd, err
+}
+
+// GetPullRequests returns a repository's pull requests with retry
+func (d *RetryDownloader) GetPullRequests(page, perPage int) ([]*PullRequest, bool, error) {
+	var (
+		prs   []*PullRequest
+		err   error
+		isEnd bool
+	)
+
+	err = d.retry(func() error {
+		prs, isEnd, err = d.Downloader.GetPullRequests(page, perPage)
+		return err
+	})
+
+	return prs, isEnd, err
+}
+
+// GetReviews returns pull requests reviews
+func (d *RetryDownloader) GetReviews(pullRequestContext IssueContext) ([]*Review, error) {
+	var (
+		reviews []*Review
+		err     error
+	)
+
+	err = d.retry(func() error {
+		reviews, err = d.Downloader.GetReviews(pullRequestContext)
+		return err
+	})
+
+	return reviews, err
+}