package cabana

import (
	"context"
	"sort"

	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/phrasebook"
)

// NavigationEntry is one permission-filtered backend navigation item.
type NavigationEntry struct {
	Code       string            `json:"code"`
	Label      string            `json:"label"`
	Icon       string            `json:"icon"`
	Order      int               `json:"order"`
	Controller string            `json:"controller"`
	SideMenu   []NavigationEntry `json:"sideMenu"`
}

// SettingsEntry is one permission-filtered settings-list item.
type SettingsEntry struct {
	Code        string   `json:"code"`
	Label       string   `json:"label"`
	Description string   `json:"description"`
	Category    string   `json:"category"`
	Icon        string   `json:"icon"`
	Order       int      `json:"order"`
	Keywords    []string `json:"keywords"`
	Model       string   `json:"model"`
}

// Metadata returns only entries the backend principal may open. Denied
// entries are removed before any response value is constructed.
func (r *Registry) Metadata(ctx context.Context, principal *bouncer.Principal, tr *phrasebook.Translator) ([]NavigationEntry, []SettingsEntry) {
	navigation := make([]NavigationEntry, 0)
	settings := make([]SettingsEntry, 0)
	if r == nil || principal == nil || !principal.Backend {
		return navigation, settings
	}
	for _, item := range r.navigation {
		// Like Winter's NavigationManager, a main item the principal may not
		// open is dropped whatever its children allow, so a denied parent
		// never leaks its label or target controller.
		if !Allows(principal, item.Permissions) {
			continue
		}
		children := make([]NavigationEntry, 0)
		for _, child := range item.SideMenu {
			if !Allows(principal, child.Permissions) {
				continue
			}
			children = append(children, navigationView(ctx, tr, child, nil))
		}
		view := navigationView(ctx, tr, item, children)
		view.Controller = r.openableTarget(principal, item, children)
		navigation = append(navigation, view)
	}
	sort.SliceStable(navigation, func(i, j int) bool {
		if navigation[i].Order == navigation[j].Order {
			return navigation[i].Code < navigation[j].Code
		}
		return navigation[i].Order < navigation[j].Order
	})
	for _, compiled := range r.settings {
		item := compiled.Item
		if !Allows(principal, item.Permissions) {
			continue
		}
		keywords := append([]string(nil), item.Keywords...)
		if keywords == nil {
			keywords = []string{}
		}
		settings = append(settings, SettingsEntry{
			Code: item.Code, Label: translateKey(ctx, tr, item.Label),
			Description: translateKey(ctx, tr, item.Description),
			Category:    translateKey(ctx, tr, item.Category), Icon: item.Icon,
			Order: item.Order, Keywords: keywords, Model: item.Model,
		})
	}
	sort.SliceStable(settings, func(i, j int) bool {
		if settings[i].Order == settings[j].Order {
			return settings[i].Code < settings[j].Code
		}
		return settings[i].Order < settings[j].Order
	})
	return navigation, settings
}

// openableTarget returns the controller a main item should link to. It is the
// item's own controller unless the principal cannot open it, in which case it
// is the first side-menu entry the principal can, so the menu never links to a
// page that answers 403. It is empty when nothing is openable.
func (r *Registry) openableTarget(principal *bouncer.Principal, item pact.NavigationItem, children []NavigationEntry) string {
	if item.Controller == "" || r.canOpen(principal, item.Controller) {
		return item.Controller
	}
	for _, child := range children {
		if child.Controller != "" && r.canOpen(principal, child.Controller) {
			return child.Controller
		}
	}
	return ""
}

// canOpen reports whether principal passes a registered controller's required
// permissions. A controller the registry does not know is not blocked here:
// the guard answers for it when it is opened.
func (r *Registry) canOpen(principal *bouncer.Principal, controller string) bool {
	cc, ok := r.Get(controller)
	if !ok {
		return true
	}
	return Allows(principal, requiredOf(cc.Controller))
}

func navigationView(ctx context.Context, tr *phrasebook.Translator, item pact.NavigationItem, children []NavigationEntry) NavigationEntry {
	if children == nil {
		children = []NavigationEntry{}
	}
	return NavigationEntry{
		Code: item.Code, Label: translateKey(ctx, tr, item.Label), Icon: item.Icon,
		Order: item.Order, Controller: item.Controller, SideMenu: children,
	}
}