package catalogue

import (
	"fmt"
	"path"
	"strings"
)

// Item is one item a module contributes to a collection: its template in the module's repository, or, in the
// manifest the mesh holds, the template's text, read back from the build's templates archive like a file's.
//
// **Attributes, a capability and a name** (design 57 L3, issue 777): an item may carry `attributes` (string keys and
// values; `order`, a whole number 0–99 defaulting to 50, orders the items of one placeholder) and `if-capability`,
// the capability a machine must report for the item to be placed on it. A module may give several items to one
// collection, each then with a `name` unique within the module and the collection. A collector takes only the items
// whose attributes match, `${collected:<collection>:<k>=<v>,…}`, and all of them without the selector.
type Item struct {
	Collection   string            `json:"collection"`
	Name         string            `json:"name,omitempty"`
	Template     string            `json:"template,omitempty"`
	Content      string            `json:"content,omitempty"`
	Attributes   map[string]string `json:"attributes,omitempty"`
	IfCapability string            `json:"if-capability,omitempty"`
}

// ItemKey is an item's key among its module's: the collection, and `/<name>` for a named item.
func ItemKey(collection, name string) string {
	if name == "" {
		return collection
	}
	return collection + "/" + name
}

func (it Item) key() string { return ItemKey(it.Collection, it.Name) }

// OrderAttribute is the attribute that orders items.
const OrderAttribute = "order"

// Collection is one collection a module collects, and the comment its tool writes a line in: each contributor's item
// is introduced by `<comment> <contributor>`, and by nothing without one.
type Collection struct {
	Name    string `json:"name"`
	Comment string `json:"comment,omitempty"`
}

// CollectedNamespace is a collection's placeholder namespace, `${collected:<collection>}`.
const CollectedNamespace = "collected"

// EnvironmentCollection is the one collection of the session environment (design 57 L3, issue 795): its items are
// typed by attributes, a variable (`kind=variable`, `name`) or a PATH entry (`kind=path`, `at=start|end`), and the
// template's text is the value or the entry. A collector names the rendering, `${collected:environment:posix}` or
// `${collected:environment:systemd}`, which is not a selector.
const EnvironmentCollection = "environment"

// itemTemplateProblem is what is wrong with an item's template path, or "".
func itemTemplateProblem(m Manifest, name string) string {
	dir := m.TemplatesDir()
	if strings.HasPrefix(name, "/") || path.Clean(name) != name || !strings.HasPrefix(name, dir+"/") ||
		strings.Contains(name, "\\") {
		return fmt.Sprintf("the template %q is not a file under %s/ of its own repository: a template is %q, a "+
			"plain relative path, and the build packs only %s/", name, dir, dir+"/<name>", dir)
	}
	return ""
}