// Package lobby forms games: an in-memory matchmaking pool that pairs two humans
// for an auto-match, and friend-game invitations (invite -> accept) that start a
// 2-4 player game once every invitee has accepted. Both produce a game through the
// game domain (a GameCreator); neither imports the engine. The matchmaking pool
// is in-memory and lost on restart (players re-queue); the robot that substitutes
// for a missing human after a short wait is added in a later stage.
package lobby

import (
	"context"
	"errors"

	"github.com/google/uuid"

	"scrabble/backend/internal/game"
)

// GameCreator is the slice of the game domain the lobby needs: starting a seated
// game. game.Service satisfies it.
type GameCreator interface {
	Create(ctx context.Context, params game.CreateParams) (game.Game, error)
}

// RobotProvider supplies a robot account to substitute for a missing human in
// auto-match. robot.Service satisfies it; it returns an error when no robot is
// available so the matchmaker can defer substitution.
type RobotProvider interface {
	Pick() (uuid.UUID, error)
}

// Blocker reports whether two accounts have a block between them (either
// direction). social.Service satisfies it; the lobby uses it to refuse
// invitations between blocked accounts.
type Blocker interface {
	IsBlocked(ctx context.Context, a, b uuid.UUID) (bool, error)
}

// Auto-match defaults: a casual two-player game on the longest move clock with one
// hint per player (docs/ARCHITECTURE.md §6). The drop-out tile disposition is moot
// for two players, so the engine default (remove) applies.
const (
	autoMatchHintsAllowed   = true
	autoMatchHintsPerPlayer = 1
)

// Sentinel errors returned by the lobby.
var (
	// ErrAlreadyQueued is returned when an account already waits in a pool.
	ErrAlreadyQueued = errors.New("lobby: account already in the matchmaking pool")
	// ErrInvalidInvitation is returned for a malformed invitation (bad player
	// count, duplicate or self invitee, or unacceptable settings).
	ErrInvalidInvitation = errors.New("lobby: invalid invitation")
	// ErrInvitationBlocked is returned when a block stands between the inviter and
	// an invitee.
	ErrInvitationBlocked = errors.New("lobby: invitation blocked between accounts")
	// ErrInvitationNotFound is returned when no invitation matches the lookup.
	ErrInvitationNotFound = errors.New("lobby: invitation not found")
	// ErrInvitationNotPending is returned when an invitation is no longer open.
	ErrInvitationNotPending = errors.New("lobby: invitation is not pending")
	// ErrInvitationExpired is returned when an invitation has passed its deadline.
	ErrInvitationExpired = errors.New("lobby: invitation has expired")
	// ErrNotInvited is returned when an account is not an invitee of the invitation.
	ErrNotInvited = errors.New("lobby: account was not invited")
	// ErrAlreadyResponded is returned when an invitee has already accepted or declined.
	ErrAlreadyResponded = errors.New("lobby: invitee has already responded")
	// ErrNotInviter is returned when a non-inviter tries to cancel an invitation.
	ErrNotInviter = errors.New("lobby: only the inviter may cancel")
)