Add CRAN package registry (#22331)

This PR adds a [CRAN](https://cran.r-project.org/) package registry.

![grafik](https://user-images.githubusercontent.com/1666336/210450039-d6fa6f77-20cd-4741-89a8-1624def267f7.png)

modules/packages/cran/metadata.go

@@ -0,0 +1,244 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package cran
+
+import (
+	"archive/tar"
+	"archive/zip"
+	"bufio"
+	"compress/gzip"
+	"io"
+	"path"
+	"regexp"
+	"strings"
+
+	"code.gitea.io/gitea/modules/util"
+)
+
+const (
+	PropertyType     = "cran.type"
+	PropertyPlatform = "cran.platform"
+	PropertyRVersion = "cran.rvserion"
+
+	TypeSource = "source"
+	TypeBinary = "binary"
+)
+
+var (
+	ErrMissingDescriptionFile = util.NewInvalidArgumentErrorf("DESCRIPTION file is missing")
+	ErrInvalidName            = util.NewInvalidArgumentErrorf("package name is invalid")
+	ErrInvalidVersion         = util.NewInvalidArgumentErrorf("package version is invalid")
+)
+
+var (
+	fieldPattern         = regexp.MustCompile(`\A\S+:`)
+	namePattern          = regexp.MustCompile(`\A[a-zA-Z][a-zA-Z0-9\.]*[a-zA-Z0-9]\z`)
+	versionPattern       = regexp.MustCompile(`\A[0-9]+(?:[.\-][0-9]+){1,3}\z`)
+	authorReplacePattern = regexp.MustCompile(`[\[\(].+?[\]\)]`)
+)
+
+// Package represents a CRAN package
+type Package struct {
+	Name          string
+	Version       string
+	FileExtension string
+	Metadata      *Metadata
+}
+
+// Metadata represents the metadata of a CRAN package
+type Metadata struct {
+	Title            string   `json:"title,omitempty"`
+	Description      string   `json:"description,omitempty"`
+	ProjectURL       []string `json:"project_url,omitempty"`
+	License          string   `json:"license,omitempty"`
+	Authors          []string `json:"authors,omitempty"`
+	Depends          []string `json:"depends,omitempty"`
+	Imports          []string `json:"imports,omitempty"`
+	Suggests         []string `json:"suggests,omitempty"`
+	LinkingTo        []string `json:"linking_to,omitempty"`
+	NeedsCompilation bool     `json:"needs_compilation"`
+}
+
+type ReaderReaderAt interface {
+	io.Reader
+	io.ReaderAt
+}
+
+// ParsePackage reads the package metadata from a CRAN package
+// .zip and .tar.gz/.tgz files are supported.
+func ParsePackage(r ReaderReaderAt, size int64) (*Package, error) {
+	magicBytes := make([]byte, 2)
+	if _, err := r.ReadAt(magicBytes, 0); err != nil {
+		return nil, err
+	}
+
+	if magicBytes[0] == 0x1F && magicBytes[1] == 0x8B {
+		return parsePackageTarGz(r)
+	}
+	return parsePackageZip(r, size)
+}
+
+func parsePackageTarGz(r io.Reader) (*Package, error) {
+	gzr, err := gzip.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	defer gzr.Close()
+
+	tr := tar.NewReader(gzr)
+	for {
+		hd, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		if hd.Typeflag != tar.TypeReg {
+			continue
+		}
+
+		if strings.Count(hd.Name, "/") > 1 {
+			continue
+		}
+
+		if path.Base(hd.Name) == "DESCRIPTION" {
+			p, err := ParseDescription(tr)
+			if p != nil {
+				p.FileExtension = ".tar.gz"
+			}
+			return p, err
+		}
+	}
+
+	return nil, ErrMissingDescriptionFile
+}
+
+func parsePackageZip(r io.ReaderAt, size int64) (*Package, error) {
+	zr, err := zip.NewReader(r, size)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, file := range zr.File {
+		if strings.Count(file.Name, "/") > 1 {
+			continue
+		}
+
+		if path.Base(file.Name) == "DESCRIPTION" {
+			f, err := zr.Open(file.Name)
+			if err != nil {
+				return nil, err
+			}
+			defer f.Close()
+
+			p, err := ParseDescription(f)
+			if p != nil {
+				p.FileExtension = ".zip"
+			}
+			return p, err
+		}
+	}
+
+	return nil, ErrMissingDescriptionFile
+}
+
+// ParseDescription parses a DESCRIPTION file to retrieve the metadata of a CRAN package
+func ParseDescription(r io.Reader) (*Package, error) {
+	p := &Package{
+		Metadata: &Metadata{},
+	}
+
+	scanner := bufio.NewScanner(r)
+
+	var b strings.Builder
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+		if !fieldPattern.MatchString(line) {
+			b.WriteRune(' ')
+			b.WriteString(line)
+			continue
+		}
+
+		if err := setField(p, b.String()); err != nil {
+			return nil, err
+		}
+
+		b.Reset()
+		b.WriteString(line)
+	}
+
+	if err := setField(p, b.String()); err != nil {
+		return nil, err
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return p, nil
+}
+
+func setField(p *Package, data string) error {
+	const listDelimiter = ", "
+
+	if data == "" {
+		return nil
+	}
+
+	parts := strings.SplitN(data, ":", 2)
+	if len(parts) != 2 {
+		return nil
+	}
+
+	name := strings.TrimSpace(parts[0])
+	value := strings.TrimSpace(parts[1])
+
+	switch name {
+	case "Package":
+		if !namePattern.MatchString(value) {
+			return ErrInvalidName
+		}
+		p.Name = value
+	case "Version":
+		if !versionPattern.MatchString(value) {
+			return ErrInvalidVersion
+		}
+		p.Version = value
+	case "Title":
+		p.Metadata.Title = value
+	case "Description":
+		p.Metadata.Description = value
+	case "URL":
+		p.Metadata.ProjectURL = splitAndTrim(value, listDelimiter)
+	case "License":
+		p.Metadata.License = value
+	case "Author":
+		p.Metadata.Authors = splitAndTrim(authorReplacePattern.ReplaceAllString(value, ""), listDelimiter)
+	case "Depends":
+		p.Metadata.Depends = splitAndTrim(value, listDelimiter)
+	case "Imports":
+		p.Metadata.Imports = splitAndTrim(value, listDelimiter)
+	case "Suggests":
+		p.Metadata.Suggests = splitAndTrim(value, listDelimiter)
+	case "LinkingTo":
+		p.Metadata.LinkingTo = splitAndTrim(value, listDelimiter)
+	case "NeedsCompilation":
+		p.Metadata.NeedsCompilation = value == "yes"
+	}
+
+	return nil
+}
+
+func splitAndTrim(s, sep string) []string {
+	items := strings.Split(s, sep)
+	for i := range items {
+		items[i] = strings.TrimSpace(items[i])
+	}
+	return items
+}