Support asciicast files as new markup (#22448)

Support [asciicast
files](https://github.com/asciinema/asciinema/blob/develop/doc/asciicast-v2.md)
as a new markup via
[asciinema-player](https://github.com/asciinema/asciinema-player). For
more on asciinema, see the [introduction](https://asciinema.org/).

So users can use asciinema recorder to generate an asciicast file (or
you can download a sample file from
https://asciinema.org/a/335480.cast?dl=1), then upload it to Gitea and
play it on Gitea.

Snapshots:
<details>

## Upload asciicast files

<img width="1134" alt="image"
src="https://user-images.githubusercontent.com/9418365/212461061-cc2c7181-0e14-4534-af55-1ec60a639fd1.png">

## Open an asciicast file

<img width="1137" alt="image"
src="https://user-images.githubusercontent.com/9418365/212461090-a3b5141f-4894-430d-a2b4-ea257801a0ed.png">

## Play it

<img width="1144" alt="image"
src="https://user-images.githubusercontent.com/9418365/212461157-4e82db69-0e41-471d-928f-ac1fe0737105.png">

## Copy contents from the "video"

<img width="1145" alt="image"
src="https://user-images.githubusercontent.com/9418365/212461286-211612bc-15d6-427a-89a9-6abff5c6a0a5.png">


## View the source

<img width="1140" alt="image"
src="https://user-images.githubusercontent.com/9418365/212461187-05473b2d-ba3d-4072-84a6-4aa1e7d82182.png">


</details>

Known issue:

Don't support the [v1 version asciicast
files](https://github.com/asciinema/asciinema/blob/develop/doc/asciicast-v1.md),
it's a poorly designed version, it does not specify the file extension
and uses `*.json` usually, so it's impossible to recognize the files.

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/modules/markup/asciicast/asciicast.go b/modules/markup/asciicast/asciicast.go
new file mode 100644
index 0000000000..0678062340
--- /dev/null
+++ b/modules/markup/asciicast/asciicast.go
@@ -0,0 +1,64 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package asciicast
+
+import (
+	"fmt"
+	"io"
+	"net/url"
+	"regexp"
+
+	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+func init() {
+	markup.RegisterRenderer(Renderer{})
+}
+
+// Renderer implements markup.Renderer for asciicast files.
+// See https://github.com/asciinema/asciinema/blob/develop/doc/asciicast-v2.md
+type Renderer struct{}
+
+// Name implements markup.Renderer
+func (Renderer) Name() string {
+	return "asciicast"
+}
+
+// Extensions implements markup.Renderer
+func (Renderer) Extensions() []string {
+	return []string{".cast"}
+}
+
+const (
+	playerClassName = "asciinema-player-container"
+	playerSrcAttr   = "data-asciinema-player-src"
+)
+
+// SanitizerRules implements markup.Renderer
+func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
+	return []setting.MarkupSanitizerRule{
+		{Element: "div", AllowAttr: "class", Regexp: regexp.MustCompile(playerClassName)},
+		{Element: "div", AllowAttr: playerSrcAttr},
+	}
+}
+
+// Render implements markup.Renderer
+func (Renderer) Render(ctx *markup.RenderContext, _ io.Reader, output io.Writer) error {
+	rawURL := fmt.Sprintf("%s/%s/%s/raw/%s/%s",
+		setting.AppSubURL,
+		url.PathEscape(ctx.Metas["user"]),
+		url.PathEscape(ctx.Metas["repo"]),
+		ctx.Metas["BranchNameSubURL"],
+		url.PathEscape(ctx.RelativePath),
+	)
+
+	_, err := io.WriteString(output, fmt.Sprintf(
+		`<div class="%s" %s="%s"></div>`,
+		playerClassName,
+		playerSrcAttr,
+		rawURL,
+	))
+	return err
+}