Add Conda package registry (#22262)

This PR adds a [Conda](https://conda.io/) package registry.

modules/packages/conda/metadata.go

@@ -0,0 +1,243 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package conda
+
+import (
+	"archive/tar"
+	"archive/zip"
+	"compress/bzip2"
+	"io"
+	"strings"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/modules/validation"
+
+	"github.com/klauspost/compress/zstd"
+)
+
+var (
+	ErrInvalidStructure = util.SilentWrap{Message: "package structure is invalid", Err: util.ErrInvalidArgument}
+	ErrInvalidName      = util.SilentWrap{Message: "package name is invalid", Err: util.ErrInvalidArgument}
+	ErrInvalidVersion   = util.SilentWrap{Message: "package version is invalid", Err: util.ErrInvalidArgument}
+)
+
+const (
+	PropertyName     = "conda.name"
+	PropertyChannel  = "conda.channel"
+	PropertySubdir   = "conda.subdir"
+	PropertyMetadata = "conda.metdata"
+)
+
+// Package represents a Conda package
+type Package struct {
+	Name            string
+	Version         string
+	Subdir          string
+	VersionMetadata *VersionMetadata
+	FileMetadata    *FileMetadata
+}
+
+// VersionMetadata represents the metadata of a Conda package
+type VersionMetadata struct {
+	Description      string `json:"description,omitempty"`
+	Summary          string `json:"summary,omitempty"`
+	ProjectURL       string `json:"project_url,omitempty"`
+	RepositoryURL    string `json:"repository_url,omitempty"`
+	DocumentationURL string `json:"documentation_url,omitempty"`
+	License          string `json:"license,omitempty"`
+	LicenseFamily    string `json:"license_family,omitempty"`
+}
+
+// FileMetadata represents the metadata of a Conda package file
+type FileMetadata struct {
+	IsCondaPackage bool     `json:"is_conda"`
+	Architecture   string   `json:"architecture,omitempty"`
+	NoArch         string   `json:"noarch,omitempty"`
+	Build          string   `json:"build,omitempty"`
+	BuildNumber    int64    `json:"build_number,omitempty"`
+	Dependencies   []string `json:"dependencies,omitempty"`
+	Platform       string   `json:"platform,omitempty"`
+	Timestamp      int64    `json:"timestamp,omitempty"`
+}
+
+type index struct {
+	Name          string   `json:"name"`
+	Version       string   `json:"version"`
+	Architecture  string   `json:"arch"`
+	NoArch        string   `json:"noarch"`
+	Build         string   `json:"build"`
+	BuildNumber   int64    `json:"build_number"`
+	Dependencies  []string `json:"depends"`
+	License       string   `json:"license"`
+	LicenseFamily string   `json:"license_family"`
+	Platform      string   `json:"platform"`
+	Subdir        string   `json:"subdir"`
+	Timestamp     int64    `json:"timestamp"`
+}
+
+type about struct {
+	Description      string `json:"description"`
+	Summary          string `json:"summary"`
+	ProjectURL       string `json:"home"`
+	RepositoryURL    string `json:"dev_url"`
+	DocumentationURL string `json:"doc_url"`
+}
+
+type ReaderAndReaderAt interface {
+	io.Reader
+	io.ReaderAt
+}
+
+// ParsePackageBZ2 parses the Conda package file compressed with bzip2
+func ParsePackageBZ2(r io.Reader) (*Package, error) {
+	gzr := bzip2.NewReader(r)
+
+	return parsePackageTar(gzr)
+}
+
+// ParsePackageConda parses the Conda package file compressed with zip and zstd
+func ParsePackageConda(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.HasPrefix(file.Name, "info-") && strings.HasSuffix(file.Name, ".tar.zst") {
+			f, err := zr.Open(file.Name)
+			if err != nil {
+				return nil, err
+			}
+			defer f.Close()
+
+			dec, err := zstd.NewReader(f)
+			if err != nil {
+				return nil, err
+			}
+			defer dec.Close()
+
+			p, err := parsePackageTar(dec)
+			if p != nil {
+				p.FileMetadata.IsCondaPackage = true
+			}
+			return p, err
+		}
+	}
+
+	return nil, ErrInvalidStructure
+}
+
+func parsePackageTar(r io.Reader) (*Package, error) {
+	var i *index
+	var a *about
+
+	tr := tar.NewReader(r)
+	for {
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		if hdr.Typeflag != tar.TypeReg {
+			continue
+		}
+
+		if hdr.Name == "info/index.json" {
+			if err := json.NewDecoder(tr).Decode(&i); err != nil {
+				return nil, err
+			}
+
+			if !checkName(i.Name) {
+				return nil, ErrInvalidName
+			}
+
+			if !checkVersion(i.Version) {
+				return nil, ErrInvalidVersion
+			}
+
+			if a != nil {
+				break // stop loop if both files were found
+			}
+		} else if hdr.Name == "info/about.json" {
+			if err := json.NewDecoder(tr).Decode(&a); err != nil {
+				return nil, err
+			}
+
+			if !validation.IsValidURL(a.ProjectURL) {
+				a.ProjectURL = ""
+			}
+			if !validation.IsValidURL(a.RepositoryURL) {
+				a.RepositoryURL = ""
+			}
+			if !validation.IsValidURL(a.DocumentationURL) {
+				a.DocumentationURL = ""
+			}
+
+			if i != nil {
+				break // stop loop if both files were found
+			}
+		}
+	}
+
+	if i == nil {
+		return nil, ErrInvalidStructure
+	}
+	if a == nil {
+		a = &about{}
+	}
+
+	return &Package{
+		Name:    i.Name,
+		Version: i.Version,
+		Subdir:  i.Subdir,
+		VersionMetadata: &VersionMetadata{
+			License:          i.License,
+			LicenseFamily:    i.LicenseFamily,
+			Description:      a.Description,
+			Summary:          a.Summary,
+			ProjectURL:       a.ProjectURL,
+			RepositoryURL:    a.RepositoryURL,
+			DocumentationURL: a.DocumentationURL,
+		},
+		FileMetadata: &FileMetadata{
+			Architecture: i.Architecture,
+			NoArch:       i.NoArch,
+			Build:        i.Build,
+			BuildNumber:  i.BuildNumber,
+			Dependencies: i.Dependencies,
+			Platform:     i.Platform,
+			Timestamp:    i.Timestamp,
+		},
+	}, nil
+}
+
+// https://github.com/conda/conda-build/blob/db9a728a9e4e6cfc895637ca3221117970fc2663/conda_build/metadata.py#L1393
+func checkName(name string) bool {
+	if name == "" {
+		return false
+	}
+	if name != strings.ToLower(name) {
+		return false
+	}
+	return !checkBadCharacters(name, "!")
+}
+
+// https://github.com/conda/conda-build/blob/db9a728a9e4e6cfc895637ca3221117970fc2663/conda_build/metadata.py#L1403
+func checkVersion(version string) bool {
+	if version == "" {
+		return false
+	}
+	return !checkBadCharacters(version, "-")
+}
+
+func checkBadCharacters(s, additional string) bool {
+	if strings.ContainsAny(s, "=@#$%^&*:;\"'\\|<>?/ ") {
+		return true
+	}
+	return strings.ContainsAny(s, additional)
+}