// Package todos: todo lists and items with assignment.
package todos

import (
	"context"
	"errors"
	"fmt"

	"atlas9.dev/c/core"
	"atlas9.dev/c/core/iam"
	"atlas9.dev/c/demo/lib/filter"
	"atlas9.dev/c/demo/lib/slack"
)

// List groups items. An item can belong to any number of lists
// within its tenant.
type List struct {
	ID     core.ID
	Tenant core.ID
	Name   string
}

type Item struct {
	ID     core.ID
	Tenant core.ID
	Title  string
	Notes  string
	Status Status
	// Assignee is the user assigned to the item. Empty means unassigned.
	// Assignees must be members of the item's tenant.
	Assignee core.ID
}

// ListEntry is a row of the item↔list join: one item's presence in one list.
// It is the read side of AddToList / RemoveFromList — list the entries for a
// set of items and group by Item.
type ListEntry struct {
	Tenant core.ID
	List   core.ID
	Item   core.ID
}

//atlas:enum Status Open InProgress Done

var (
	Cap_Todos_CreateList     = iam.NewCap("Todos_CreateList")
	Cap_Todos_UpdateList     = iam.NewCap("Todos_UpdateList")
	Cap_Todos_ReadList       = iam.NewCap("Todos_ReadList")
	Cap_Todos_DeleteList     = iam.NewCap("Todos_DeleteList")
	Cap_Todos_AddToList      = iam.NewCap("Todos_AddToList")
	Cap_Todos_RemoveFromList = iam.NewCap("Todos_RemoveFromList")

	Cap_Todos_CreateItem = iam.NewCap("Todos_CreateItem")
	Cap_Todos_UpdateItem = iam.NewCap("Todos_UpdateItem")
	Cap_Todos_ReadItem   = iam.NewCap("Todos_ReadItem")
	Cap_Todos_DeleteItem = iam.NewCap("Todos_DeleteItem")
)

var ErrAssigneeNotMember = errors.New("assignee is not a member of the tenant")

// Webhook event types emitted for item changes. Subscribers register these
// strings on an endpoint's EventTypes.
const (
	EventItemCreated = "Todos_ItemCreated"
	EventItemUpdated = "Todos_ItemUpdated"
)

// ItemCreated and ItemUpdated are the domain events emitted when a todo item
// changes. Each carries its own audit entry and channel renderings as methods;
// the dispatcher (demo/events) asserts those methods to route the event, so the
// per-event mapping lives here with the feature that owns it.
type ItemCreated struct{ Item Item }

func (ItemCreated) EventType() string { return EventItemCreated }

func (e ItemCreated) Audit() iam.AuditEntry {
	return iam.AuditEntry{
		Action: "Todos_CreateItem", 
		Resource: e.Item.ID.String(), 
		Detail: e.Item.Title,
	}
}

func (e ItemCreated) WebhookPayload() any { return e.Item }

func (e ItemCreated) SlackMessage() slack.Message {
	return slack.Message{
		Text: fmt.Sprintf("📝 New todo created: %q", e.Item.Title),
	}
}

type ItemUpdated struct{ Item Item }

func (ItemUpdated) EventType() string { return EventItemUpdated }

func (e ItemUpdated) Audit() iam.AuditEntry {
	return iam.AuditEntry{
		Action: "Todos_UpdateItem", 
		Resource: e.Item.ID.String(), 
		Detail: e.Item.Title,
	}
}

func (e ItemUpdated) WebhookPayload() any { return e.Item }

func (e ItemUpdated) SlackMessage() slack.Message {
	return slack.Message{
		Text: fmt.Sprintf("✏️ Todo updated: %q — %s", e.Item.Title, e.Item.Status),
	}
}

// ItemSchema declares the filterable fields for todo items.
var ItemSchema = filter.Schema{}.
	Enum("status", StatusUnknown).
	String("assignee").
	String("assignee_id").
	String("title").
	String("list").
	String("list_id").
	Default("title")

type Store interface {
	CreateList(ctx context.Context, list *List) error
	UpdateList(ctx context.Context, list *List) error
	GetList(ctx context.Context, tenant core.ID, id core.ID, out *List) error
	ListLists(ctx context.Context, tenant core.ID, page core.PageReq, out *core.Page[List]) error
	DeleteList(ctx context.Context, tenant core.ID, id core.ID) error

	AddToList(ctx context.Context, tenant core.ID, list core.ID, item core.ID) error
	RemoveFromList(ctx context.Context, tenant core.ID, list core.ID, item core.ID) error
	// ListEntriesByItems lists item↔list entries for a set of items, so a client
	// with a page of items resolves all their lists in one call. The result is
	// bounded by the caller's item set, so it is not itself paginated.
	ListEntriesByItems(ctx context.Context, tenant core.ID, items []core.ID, out *core.Page[ListEntry]) error

	CreateItem(ctx context.Context, item *Item) error
	UpdateItem(ctx context.Context, item *Item) error
	GetItem(ctx context.Context, tenant core.ID, id core.ID, out *Item) error
	ListItems(ctx context.Context, tenant core.ID, expr filter.Expr, page core.PageReq, out *core.Page[Item]) error
	DeleteItem(ctx context.Context, tenant core.ID, id core.ID) error
}