package live

import (
	"context"
	"errors"
	"strings"
	"time"
)

const (
	MaxStreams    = 20
	StatusWaiting = "waiting"
	StatusLive    = "live"
)

var (
	ErrInvalidStreamID    = errors.New("invalid stream id")
	ErrMaxStreams         = errors.New("maximum live streams reached")
	ErrPublisherExists    = errors.New("publisher already exists")
	ErrPublisherNotFound  = errors.New("publisher not found")
	ErrSubscriberExists   = errors.New("subscriber already exists")
	ErrSubscriberNotFound = errors.New("subscriber not found")
)

type Stream struct {
	StreamID        string
	PublisherID     uint
	PublisherOnline bool
	SubscriberCount int
	LikeCount       int
	StartedAt       time.Time
	UpdatedAt       time.Time
}

type StreamRepo interface {
	Get(context.Context, string) (*Stream, error)
	List(context.Context) ([]*Stream, error)
	RegisterPublisher(context.Context, string, uint) (*Stream, error)
	UnregisterPublisher(context.Context, string, uint) error
	RegisterSubscriber(context.Context, string, uint) (*Stream, error)
	UnregisterSubscriber(context.Context, string, uint) error
	Like(context.Context, string) (int, error)
}

type StreamUsecase struct{ repo StreamRepo }

func NewStreamUsecase(repo StreamRepo) *StreamUsecase { return &StreamUsecase{repo: repo} }

func (uc *StreamUsecase) List(ctx context.Context) ([]*Stream, error) {
	return uc.repo.List(ctx)
}

func (uc *StreamUsecase) Get(ctx context.Context, streamID string) (*Stream, error) {
	streamID = normalizeStreamID(streamID)
	if streamID == "" {
		return nil, ErrInvalidStreamID
	}
	return uc.repo.Get(ctx, streamID)
}

func (uc *StreamUsecase) RegisterPublisher(ctx context.Context, streamID string, userID uint) (*Stream, error) {
	streamID = normalizeStreamID(streamID)
	if streamID == "" || userID == 0 {
		return nil, ErrInvalidStreamID
	}
	return uc.repo.RegisterPublisher(ctx, streamID, userID)
}

func (uc *StreamUsecase) UnregisterPublisher(ctx context.Context, streamID string, userID uint) error {
	return uc.repo.UnregisterPublisher(ctx, normalizeStreamID(streamID), userID)
}

func (uc *StreamUsecase) RegisterSubscriber(ctx context.Context, streamID string, userID uint) (*Stream, error) {
	streamID = normalizeStreamID(streamID)
	if streamID == "" || userID == 0 {
		return nil, ErrInvalidStreamID
	}
	return uc.repo.RegisterSubscriber(ctx, streamID, userID)
}

func (uc *StreamUsecase) UnregisterSubscriber(ctx context.Context, streamID string, userID uint) error {
	return uc.repo.UnregisterSubscriber(ctx, normalizeStreamID(streamID), userID)
}

func (uc *StreamUsecase) Like(ctx context.Context, streamID string) (int, error) {
	streamID = normalizeStreamID(streamID)
	if streamID == "" {
		return 0, ErrInvalidStreamID
	}
	return uc.repo.Like(ctx, streamID)
}

func normalizeStreamID(value string) string {
	return strings.TrimSpace(value)
}