package logic

import (
	"context"
	"errors"
	"math/rand"
	"net/http"
	"strings"
	"time"

	"go.uber.org/zap"

	squarelogic "spark-server/internal/module/square/logic"
	userentity "spark-server/internal/module/user/entity"
	"spark-server/internal/pkg/errs"
)

// Options configures the square media bot worker.
type Options struct {
	Enabled    bool
	Interval   time.Duration
	TTL        time.Duration
	Feeds      []string
	BotIndexes []int
	HTTPClient *http.Client
}

// Users resolves seeded robot accounts.
type Users interface {
	GetByEmail(ctx context.Context, email string) (*userentity.User, error)
}

// Square publishes and expires bot posts.
type Square interface {
	PublishBotMedia(ctx context.Context, userID int64, in *squarelogic.BotPublishInput) (*squarelogic.View, error)
	ExpireBotPosts(ctx context.Context, now time.Time, limit int) (int, error)
}

// Locker is an optional distributed tick lock (e.g. Redis SETNX).
type Locker interface {
	TryLock(ctx context.Context, key string, ttl time.Duration) (bool, error)
}

// Service runs one RSS publish + TTL cleanup tick.
type Service struct {
	log     *zap.Logger
	square  Square
	users   Users
	locker  Locker
	opts    Options
	client  *http.Client
	rand    *rand.Rand
	lockKey string
}

func NewService(log *zap.Logger, square Square, users Users, locker Locker, opts Options) *Service {
	if log == nil {
		log = zap.NewNop()
	}
	opts = normalizeOptions(opts)
	client := opts.HTTPClient
	if client == nil {
		client = &http.Client{Timeout: rssTimeout}
	}
	return &Service{
		log: log, square: square, users: users, locker: locker, opts: opts,
		client: client, rand: rand.New(rand.NewSource(time.Now().UnixNano())),
		lockKey: "squarebot:tick",
	}
}

func normalizeOptions(o Options) Options {
	if o.Interval <= 0 {
		o.Interval = 5 * time.Minute
	}
	if o.TTL <= 0 {
		o.TTL = 15 * 24 * time.Hour
	}
	if len(o.Feeds) == 0 {
		o.Feeds = DefaultFeeds()
	}
	if len(o.BotIndexes) == 0 {
		o.BotIndexes = defaultBotIndexes()
	}
	return o
}

// DefaultFeeds are public overseas mainstream media RSS endpoints (title/summary/link only).
func DefaultFeeds() []string {
	return []string{
		"https://feeds.bbci.co.uk/news/world/rss.xml",
		"https://www.theguardian.com/world/rss",
		"https://feeds.npr.org/1004/rss.xml",
		"https://www.aljazeera.com/xml/rss/all.xml",
		"https://rss.nytimes.com/services/xml/rss/nyt/World.xml",
		"https://www.reutersagency.com/feed/?best-topics=world-including-us&post_type=best",
	}
}

func defaultBotIndexes() []int {
	out := make([]int, 0, userentity.BotCount)
	for i := 1; i <= userentity.BotCount; i++ {
		out = append(out, i)
	}
	return out
}

func (s *Service) Enabled() bool {
	return s != nil && s.opts.Enabled && s.square != nil && s.users != nil
}

func (s *Service) Interval() time.Duration {
	if s == nil {
		return 5 * time.Minute
	}
	return s.opts.Interval
}

// Tick expires old bot posts then publishes one new RSS item via a random bot.
func (s *Service) Tick(ctx context.Context) error {
	if !s.Enabled() {
		return nil
	}
	if s.locker != nil {
		ok, err := s.locker.TryLock(ctx, s.lockKey, s.opts.Interval)
		if err != nil {
			s.log.Warn("squarebot lock", zap.Error(err))
		} else if !ok {
			return nil
		}
	}
	if n, err := s.square.ExpireBotPosts(ctx, time.Now(), 200); err != nil {
		s.log.Warn("squarebot expire", zap.Error(err))
	} else if n > 0 {
		s.log.Info("squarebot expired", zap.Int("count", n))
	}
	bot, err := s.pickBot(ctx)
	if err != nil {
		return err
	}
	item, err := s.pickItem(ctx)
	if err != nil {
		return err
	}
	text := FormatPostText(item)
	view, err := s.square.PublishBotMedia(ctx, bot.ID, &squarelogic.BotPublishInput{
		Text: text, SourceURL: item.Link, TTL: s.opts.TTL,
	})
	if err != nil {
		if errors.Is(err, errs.ErrDuplicate) {
			s.log.Info("squarebot skip duplicate", zap.String("url", item.Link))
			return nil
		}
		return err
	}
	s.log.Info("squarebot posted",
		zap.Int64("bot_uid", bot.ID),
		zap.String("bot", bot.Nickname),
		zap.Int64("post_id", view.ID),
		zap.String("url", item.Link),
	)
	return nil
}

func (s *Service) pickBot(ctx context.Context) (*userentity.User, error) {
	indexes := append([]int(nil), s.opts.BotIndexes...)
	s.rand.Shuffle(len(indexes), func(i, j int) { indexes[i], indexes[j] = indexes[j], indexes[i] })
	var last error
	for _, idx := range indexes {
		email := userentity.BotEmail(idx)
		if email == "" {
			continue
		}
		u, err := s.users.GetByEmail(ctx, email)
		if err != nil {
			last = err
			continue
		}
		if u != nil && u.ID > 0 {
			return u, nil
		}
	}
	if last != nil {
		return nil, last
	}
	return nil, errs.ErrNotFound
}

func (s *Service) pickItem(ctx context.Context) (FeedItem, error) {
	feeds := append([]string(nil), s.opts.Feeds...)
	s.rand.Shuffle(len(feeds), func(i, j int) { feeds[i], feeds[j] = feeds[j], feeds[i] })
	var last error
	for _, feed := range feeds {
		feed = strings.TrimSpace(feed)
		if feed == "" {
			continue
		}
		items, err := FetchFeed(ctx, s.client, feed)
		if err != nil {
			last = err
			s.log.Warn("squarebot feed", zap.String("feed", feed), zap.Error(err))
			continue
		}
		if len(items) == 0 {
			continue
		}
		return items[s.rand.Intn(len(items))], nil
	}
	if last != nil {
		return FeedItem{}, last
	}
	return FeedItem{}, errs.ErrNotFound
}