Add Conda package registry (#22262)

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

models/packages/conda/search.go

@@ -0,0 +1,63 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package conda
+
+import (
+	"context"
+	"strings"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/packages"
+	conda_module "code.gitea.io/gitea/modules/packages/conda"
+
+	"xorm.io/builder"
+)
+
+type FileSearchOptions struct {
+	OwnerID  int64
+	Channel  string
+	Subdir   string
+	Filename string
+}
+
+// SearchFiles gets all files matching the search options
+func SearchFiles(ctx context.Context, opts *FileSearchOptions) ([]*packages.PackageFile, error) {
+	var cond builder.Cond = builder.Eq{
+		"package.type":                packages.TypeConda,
+		"package.owner_id":            opts.OwnerID,
+		"package_version.is_internal": false,
+	}
+
+	if opts.Filename != "" {
+		cond = cond.And(builder.Eq{
+			"package_file.lower_name": strings.ToLower(opts.Filename),
+		})
+	}
+
+	var versionPropsCond builder.Cond = builder.Eq{
+		"package_property.ref_type": packages.PropertyTypePackage,
+		"package_property.name":     conda_module.PropertyChannel,
+		"package_property.value":    opts.Channel,
+	}
+
+	cond = cond.And(builder.In("package.id", builder.Select("package_property.ref_id").Where(versionPropsCond).From("package_property")))
+
+	var filePropsCond builder.Cond = builder.Eq{
+		"package_property.ref_type": packages.PropertyTypeFile,
+		"package_property.name":     conda_module.PropertySubdir,
+		"package_property.value":    opts.Subdir,
+	}
+
+	cond = cond.And(builder.In("package_file.id", builder.Select("package_property.ref_id").Where(filePropsCond).From("package_property")))
+
+	sess := db.GetEngine(ctx).
+		Select("package_file.*").
+		Table("package_file").
+		Join("INNER", "package_version", "package_version.id = package_file.version_id").
+		Join("INNER", "package", "package.id = package_version.package_id").
+		Where(cond)
+
+	pfs := make([]*packages.PackageFile, 0, 10)
+	return pfs, sess.Find(&pfs)
+}