Implement code frequency graph (#29191)

### Overview
This is the implementation of Code Frequency page. This feature was
mentioned on these issues: #18262, #7392.


It adds another tab to Activity page called Code Frequency. Code
Frequency tab shows additions and deletions over time since the
repository existed.


Before:
<img width="1296" alt="image"
src="https://github.com/go-gitea/gitea/assets/32161460/2603504f-aee7-4929-a8c4-fb3412a7a0f6">

After:
<img width="1296" alt="image"
src="https://github.com/go-gitea/gitea/assets/32161460/58c03721-729f-4536-a663-9f337f240963">

---


#### Features
- See additions deletions over time since repository existed
- Click on "Additions" or "Deletions" legend to show only one type of
contribution
- Use the same cache from Contributors page so that the loading of data
will be fast once it is cached by visiting either one of the pages

---------

Co-authored-by: Giteabot <teabot@gitea.io>

2 files changed, 45 insertions, 0 deletions

diff --git a/routers/web/repo/code_frequency.go b/routers/web/repo/code_frequency.go
new file mode 100644
index 0000000000..48ade655b7
--- /dev/null
+++ b/routers/web/repo/code_frequency.go
@@ -0,0 +1,41 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repo
+
+import (
+	"errors"
+	"net/http"
+
+	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/context"
+	contributors_service "code.gitea.io/gitea/services/repository"
+)
+
+const (
+	tplCodeFrequency base.TplName = "repo/activity"
+)
+
+// CodeFrequency renders the page to show repository code frequency
+func CodeFrequency(ctx *context.Context) {
+	ctx.Data["Title"] = ctx.Tr("repo.activity.navbar.code_frequency")
+
+	ctx.Data["PageIsActivity"] = true
+	ctx.Data["PageIsCodeFrequency"] = true
+	ctx.PageData["repoLink"] = ctx.Repo.RepoLink
+
+	ctx.HTML(http.StatusOK, tplCodeFrequency)
+}
+
+// CodeFrequencyData returns JSON of code frequency data
+func CodeFrequencyData(ctx *context.Context) {
+	if contributorStats, err := contributors_service.GetContributorStats(ctx, ctx.Cache, ctx.Repo.Repository, ctx.Repo.CommitID); err != nil {
+		if errors.Is(err, contributors_service.ErrAwaitGeneration) {
+			ctx.Status(http.StatusAccepted)
+			return
+		}
+		ctx.ServerError("GetCodeFrequencyData", err)
+	} else {
+		ctx.JSON(http.StatusOK, contributorStats["total"].Weeks)
+	}
+}
diff --git a/routers/web/web.go b/routers/web/web.go
index 77c8319f06..5e18aac67d 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -1403,6 +1403,10 @@ func registerRoutes(m *web.Route) {
 				m.Get("", repo.Contributors)
 				m.Get("/data", repo.ContributorsData)
 			})
+			m.Group("/code-frequency", func() {
+				m.Get("", repo.CodeFrequency)
+				m.Get("/data", repo.CodeFrequencyData)
+			})
 		}, context.RepoRef(), repo.MustBeNotEmpty, context.RequireRepoReaderOr(unit.TypePullRequests, unit.TypeIssues, unit.TypeReleases))
 
 		m.Group("/activity_author_data", func() {