// Package invite defines the invite record domain model, status machine,
// and sentinel errors owned by Game Lobby Service for private-game
// enrollment.
package invite

import (
	"fmt"
	"strings"
	"time"

	"galaxy/lobby/internal/domain/common"
)

// Invite stores one durable invite record owned by Game Lobby Service.
// Invites are used exclusively by private games; public games use the
// application flow instead.
type Invite struct {
	// InviteID identifies the record.
	InviteID common.InviteID

	// GameID identifies the game this invite belongs to.
	GameID common.GameID

	// InviterUserID stores the platform user id of the private-game owner
	// who created the invite.
	InviterUserID string

	// InviteeUserID stores the platform user id of the invited user.
	InviteeUserID string

	// RaceName stores the invitee's chosen in-game name. It is empty until
	// the invite transitions to redeemed.
	RaceName string

	// Status stores the current lifecycle state.
	Status Status

	// CreatedAt stores when the record was created.
	CreatedAt time.Time

	// ExpiresAt stores the business deadline after which the invite is no
	// longer actionable. It equals enrollment_ends_at of the parent game
	// at creation time.
	ExpiresAt time.Time

	// DecidedAt stores when the record transitioned out of created. It is
	// nil while the invite is still created.
	DecidedAt *time.Time
}

// NewInviteInput groups all fields required to create an invite record.
type NewInviteInput struct {
	// InviteID identifies the new record.
	InviteID common.InviteID

	// GameID identifies the game the invitee is being invited to.
	GameID common.GameID

	// InviterUserID stores the platform user id of the private-game owner.
	InviterUserID string

	// InviteeUserID stores the platform user id of the invited user.
	InviteeUserID string

	// Now stores the creation wall-clock used for CreatedAt.
	Now time.Time

	// ExpiresAt stores the business deadline propagated from the parent
	// game's enrollment_ends_at.
	ExpiresAt time.Time
}

// New validates input and returns a created Invite record. Validation
// errors are returned verbatim so callers can surface them as
// invalid_request.
func New(input NewInviteInput) (Invite, error) {
	if err := input.Validate(); err != nil {
		return Invite{}, err
	}

	record := Invite{
		InviteID:      input.InviteID,
		GameID:        input.GameID,
		InviterUserID: strings.TrimSpace(input.InviterUserID),
		InviteeUserID: strings.TrimSpace(input.InviteeUserID),
		Status:        StatusCreated,
		CreatedAt:     input.Now.UTC(),
		ExpiresAt:     input.ExpiresAt.UTC(),
	}

	if err := record.Validate(); err != nil {
		return Invite{}, err
	}

	return record, nil
}

// Validate reports whether input satisfies the frozen invite-record
// invariants required to construct a created record.
func (input NewInviteInput) Validate() error {
	if err := input.InviteID.Validate(); err != nil {
		return fmt.Errorf("invite id: %w", err)
	}
	if err := input.GameID.Validate(); err != nil {
		return fmt.Errorf("game id: %w", err)
	}
	if strings.TrimSpace(input.InviterUserID) == "" {
		return fmt.Errorf("inviter user id must not be empty")
	}
	if strings.TrimSpace(input.InviteeUserID) == "" {
		return fmt.Errorf("invitee user id must not be empty")
	}
	if strings.TrimSpace(input.InviterUserID) == strings.TrimSpace(input.InviteeUserID) {
		return fmt.Errorf("inviter and invitee must not be the same user")
	}
	if input.Now.IsZero() {
		return fmt.Errorf("now must not be zero")
	}
	if input.ExpiresAt.IsZero() {
		return fmt.Errorf("expires at must not be zero")
	}
	if !input.ExpiresAt.After(input.Now) {
		return fmt.Errorf("expires at must be after now")
	}
	return nil
}

// Validate reports whether record satisfies the full invariants.
// Every marshal and unmarshal round-trip calls Validate to guarantee that
// the Redis store never exposes malformed records.
func (record Invite) Validate() error {
	if err := record.InviteID.Validate(); err != nil {
		return fmt.Errorf("invite id: %w", err)
	}
	if err := record.GameID.Validate(); err != nil {
		return fmt.Errorf("game id: %w", err)
	}
	if strings.TrimSpace(record.InviterUserID) == "" {
		return fmt.Errorf("inviter user id must not be empty")
	}
	if strings.TrimSpace(record.InviteeUserID) == "" {
		return fmt.Errorf("invitee user id must not be empty")
	}
	if !record.Status.IsKnown() {
		return fmt.Errorf("status %q is unsupported", record.Status)
	}
	if record.CreatedAt.IsZero() {
		return fmt.Errorf("created at must not be zero")
	}
	if record.ExpiresAt.IsZero() {
		return fmt.Errorf("expires at must not be zero")
	}
	if record.ExpiresAt.Before(record.CreatedAt) {
		return fmt.Errorf("expires at must not be before created at")
	}
	switch record.Status {
	case StatusCreated:
		if record.DecidedAt != nil {
			return fmt.Errorf("decided at must be nil for created invites")
		}
		if record.RaceName != "" {
			return fmt.Errorf("race name must be empty for created invites")
		}
	case StatusRedeemed:
		if strings.TrimSpace(record.RaceName) == "" {
			return fmt.Errorf("race name must not be empty for redeemed invites")
		}
		if record.DecidedAt == nil {
			return fmt.Errorf("decided at must not be nil for redeemed invites")
		}
	default:
		if record.RaceName != "" {
			return fmt.Errorf("race name must be empty for %q invites", record.Status)
		}
		if record.DecidedAt == nil {
			return fmt.Errorf("decided at must not be nil for %q invites", record.Status)
		}
	}
	if record.DecidedAt != nil {
		if record.DecidedAt.IsZero() {
			return fmt.Errorf("decided at must not be zero when present")
		}
		if record.DecidedAt.Before(record.CreatedAt) {
			return fmt.Errorf("decided at must not be before created at")
		}
	}
	return nil
}