package scraper

import (
	"bytes"
	"math/rand"
	"strconv"
	"sync"
	"time"

	"github.com/PuerkitoBio/goquery"
	"github.com/gocolly/colly/v2"

	"scrappr/internal/logx"
	"scrappr/internal/model"
)

type Scraper struct {
	cfg       Config
	collector *colly.Collector

	mu            sync.Mutex
	items         map[string]*model.Item
	effects       map[string]*model.Effect
	queued        map[string]bool
	completedURLs map[string]bool
	completed     int
	failed        int
	retried       int
	requestSeq    int
	spinnerIndex  int
	activeURL     string
	activeSince   time.Time
	lastEvent     time.Time
}

func New(cfg Config) *Scraper {
	return &Scraper{
		cfg:           cfg,
		items:         map[string]*model.Item{},
		effects:       map[string]*model.Effect{},
		queued:        map[string]bool{},
		completedURLs: map[string]bool{},
		lastEvent:     time.Now(),
	}
}

func (s *Scraper) Run() (model.Dataset, error) {
	if err := s.loadCheckpoint(); err != nil {
		return model.Dataset{}, err
	}

	s.collector = colly.NewCollector(
		colly.AllowedDomains(s.cfg.AllowedDomain),
		colly.MaxDepth(s.cfg.MaxDepth),
		colly.Async(true),
	)

	s.collector.SetRequestTimeout(s.cfg.RequestTimeout)
	s.collector.ParseHTTPErrorResponse = true

	if err := s.collector.Limit(&colly.LimitRule{
		DomainGlob:  "*" + s.cfg.AllowedDomain + "*",
		Parallelism: 1,
		Delay:       s.cfg.RequestDelay,
		RandomDelay: s.cfg.RequestJitter,
	}); err != nil {
		return model.Dataset{}, err
	}

	s.registerHandlers()

	done := make(chan struct{})
	defer close(done)
	s.startStatusLoop(done)
	s.startAutosaveLoop(done)

	s.resumeQueue()

	s.collector.Wait()

	if err := s.SaveCheckpoint("final"); err != nil {
		return model.Dataset{}, err
	}

	return model.Dataset{
		Items:   s.flattenItems(),
		Effects: s.flattenEffects(),
	}, nil
}

func (s *Scraper) registerHandlers() {
	s.collector.OnRequest(func(r *colly.Request) {
		s.applyBrowserHeaders(r)

		startedAt := time.Now()
		fromURL := r.Ctx.Get("from_url")
		if fromURL == "" {
			fromURL = "seed"
		}

		s.mu.Lock()
		s.requestSeq++
		reqID := s.requestSeq
		s.activeURL = r.URL.String()
		s.activeSince = startedAt
		s.lastEvent = startedAt
		s.mu.Unlock()

		r.Ctx.Put("request_id", strconv.Itoa(reqID))
		r.Ctx.Put("started_at_unix_nano", strconv.FormatInt(startedAt.UnixNano(), 10))

		logx.Eventf(
			"visit",
			"#%d depth=%d attempt=%d from=%s to=%s",
			reqID,
			r.Depth,
			s.retryAttempt(r.Ctx)+1,
			s.debugURLName(fromURL),
			r.URL.String(),
		)
	})

	s.collector.OnError(func(r *colly.Response, err error) {
		if r == nil || r.Request == nil {
			logx.Eventf("error", "request failed before response: %v", err)
			return
		}

		duration := s.requestDuration(r.Request)

		s.mu.Lock()
		s.failed++
		s.activeURL = ""
		s.activeSince = time.Time{}
		s.lastEvent = time.Now()
		s.mu.Unlock()

		logx.Eventf(
			"error",
			"#%s status=%d after=%s url=%s: %v",
			r.Request.Ctx.Get("request_id"),
			r.StatusCode,
			s.durationString(duration),
			r.Request.URL.String(),
			err,
		)

		if s.shouldRetry(r.StatusCode) {
			s.mu.Lock()
			s.retried++
			s.mu.Unlock()
			s.retryRequest(r, err)
		}
	})

	s.collector.OnResponse(func(r *colly.Response) {
		if r.StatusCode >= 400 {
			logx.Eventf("skip", "#%s status=%d url=%s", r.Request.Ctx.Get("request_id"), r.StatusCode, r.Request.URL.String())
			return
		}

		doc, err := goquery.NewDocumentFromReader(bytes.NewReader(r.Body))
		if err != nil {
			logx.Eventf("warn", "parse error for %s: %v", r.Request.URL.String(), err)
			return
		}

		title := s.clean(doc.Find("h1.page-header__title").First().Text())
		if title == "" {
			title = s.clean(doc.Find("h1").First().Text())
		}
		if title == "" {
			logx.Eventf("warn", "empty title for %s", r.Request.URL.String())
			return
		}

		pageURL := r.Request.URL.String()
		pagePath := r.Request.URL.Path
		categories := s.parseCategories(doc)
		lcCats := s.lowerSlice(categories)
		pageKind := s.pageKindForPath(pagePath)

		switch {
		case s.isEffectPage(pagePath, title, lcCats):
			effect := s.parseEffectPage(doc, title, pageURL, categories)
			if effect.Name != "" {
				s.mu.Lock()
				s.effects[effect.URL] = &effect
				s.mu.Unlock()

				pageKind = "effect"
				logx.Eventf("parsed", "#%s effect=%q", r.Request.Ctx.Get("request_id"), effect.Name)
			}
		case s.isLikelyItemPage(pagePath, title, lcCats, doc):
			item := s.parseItemPage(doc, title, pageURL, categories)

			s.mu.Lock()
			s.items[item.URL] = &item
			s.mu.Unlock()

			pageKind = "item"
			logx.Eventf(
				"parsed",
				"#%s item=%q effects=%d recipes=%d",
				r.Request.Ctx.Get("request_id"),
				item.Name,
				len(item.Effects),
				len(item.Recipes),
			)

			for _, effectLink := range item.EffectLinks {
				link := s.absoluteWikiURL(effectLink)
				if link == "" {
					continue
				}
				s.queueVisit(pageURL, link)
			}
		default:
			logx.Eventf("skip", "#%s page=%q kind=%s", r.Request.Ctx.Get("request_id"), title, pageKind)
		}

		logx.Eventf(
			"recv",
			"#%s status=%d bytes=%d kind=%s title=%q after=%s",
			r.Request.Ctx.Get("request_id"),
			r.StatusCode,
			len(r.Body),
			pageKind,
			title,
			s.durationString(s.requestDuration(r.Request)),
		)
	})

	s.collector.OnScraped(func(r *colly.Response) {
		s.mu.Lock()
		s.completed++
		if r != nil && r.Request != nil && r.StatusCode < 400 {
			s.completedURLs[r.Request.URL.String()] = true
		}
		s.activeURL = ""
		s.activeSince = time.Time{}
		s.lastEvent = time.Now()
		doneCount := s.completed
		queueLen := len(s.queued)
		s.mu.Unlock()

		logx.Eventf("done", "#%s total=%d queued=%d url=%s", r.Request.Ctx.Get("request_id"), doneCount, queueLen, r.Request.URL.String())

		if s.cfg.AutosavePages > 0 && doneCount%s.cfg.AutosavePages == 0 {
			if err := s.SaveCheckpoint("progress"); err != nil {
				logx.Eventf("warn", "autosave failed after %d pages: %v", doneCount, err)
			}
		}
	})

	s.collector.OnHTML(".mw-parser-output table a[href]", func(e *colly.HTMLElement) {
		href := e.Attr("href")
		link := e.Request.AbsoluteURL(href)
		if !s.shouldVisit(link) {
			return
		}

		if s.shouldQueueFromPage(e.Request.URL.Path, link) && s.shouldQueueTableLink(e) {
			s.queueVisit(e.Request.URL.String(), link)
			return
		}

		if s.looksLikeEffectLink(href, e.Text) {
			s.queueVisit(e.Request.URL.String(), link)
		}
	})
}

func (s *Scraper) startStatusLoop(done <-chan struct{}) {
	go func() {
		ticker := time.NewTicker(s.cfg.ProgressEvery)
		defer ticker.Stop()

		for {
			select {
			case <-done:
				return
			case <-ticker.C:
				s.mu.Lock()
				queueLen := len(s.queued)
				itemLen := len(s.items)
				effectLen := len(s.effects)
				currentURL := s.activeURL
				currentName := "-"
				currentFor := s.durationString(time.Since(s.activeSince))
				idleFor := s.durationString(time.Since(s.lastEvent))
				completedCount := s.completed
				failedCount := s.failed
				retriedCount := s.retried
				frame := s.spinnerFrame()
				s.mu.Unlock()

				if currentURL == "" {
					currentFor = "-"
				} else {
					currentName = s.debugURLName(currentURL)
				}

				logx.Statusf(
					frame,
					"queued=%d completed=%d failed=%d retries=%d items=%d effects=%d active=%s active_for=%s idle=%s",
					queueLen,
					completedCount,
					failedCount,
					retriedCount,
					itemLen,
					effectLen,
					currentName,
					currentFor,
					idleFor,
				)
			}
		}
	}()
}

func (s *Scraper) startAutosaveLoop(done <-chan struct{}) {
	if s.cfg.AutosaveEvery <= 0 {
		return
	}

	go func() {
		ticker := time.NewTicker(s.cfg.AutosaveEvery)
		defer ticker.Stop()

		for {
			select {
			case <-done:
				return
			case <-ticker.C:
				if err := s.SaveCheckpoint("timer"); err != nil {
					logx.Eventf("warn", "autosave failed: %v", err)
				}
			}
		}
	}()
}

func (s *Scraper) queueVisit(fromURL, toURL string) {
	if toURL == "" {
		return
	}

	s.mu.Lock()
	switch {
	case s.queued[toURL]:
		s.mu.Unlock()
		return
	case s.completedURLs[toURL]:
		s.mu.Unlock()
		return
	case len(s.queued) >= s.cfg.MaxQueuedPages:
		s.mu.Unlock()
		logx.Eventf("skip", "queue budget reached from=%s to=%s", s.debugURLName(fromURL), toURL)
		return
	default:
		s.queued[toURL] = true
		queueLen := len(s.queued)
		s.mu.Unlock()

		ctx := colly.NewContext()
		ctx.Put("from_url", fromURL)

		logx.Eventf("queue", "%d from=%s to=%s", queueLen, s.debugURLName(fromURL), toURL)
		if err := s.collector.Request("GET", toURL, nil, ctx, nil); err != nil {
			logx.Eventf("warn", "queue failed from=%s to=%s: %v", s.debugURLName(fromURL), toURL, err)
		}
	}
}

func (s *Scraper) spinnerFrame() string {
	if len(s.cfg.SpinnerFrames) == 0 {
		return "🌀"
	}

	frame := s.cfg.SpinnerFrames[s.spinnerIndex%len(s.cfg.SpinnerFrames)]
	s.spinnerIndex++
	return frame
}

func (s *Scraper) resumeQueue() {
	for _, seed := range append(append([]string{}, s.cfg.ItemSeeds...), s.cfg.CraftingSeeds...) {
		s.queueSeed(seed)
	}

	s.mu.Lock()
	items := make([]model.Item, 0, len(s.items))
	for _, item := range s.items {
		items = append(items, *item)
	}
	s.mu.Unlock()

	for _, item := range items {
		for _, effectLink := range item.EffectLinks {
			link := s.absoluteWikiURL(effectLink)
			if link == "" {
				continue
			}
			s.queueVisit(item.URL, link)
		}
	}
}

func (s *Scraper) queueSeed(toURL string) {
	if toURL == "" {
		return
	}

	s.mu.Lock()
	if s.queued[toURL] {
		s.mu.Unlock()
		return
	}
	s.queued[toURL] = true
	queueLen := len(s.queued)
	s.mu.Unlock()

	ctx := colly.NewContext()
	ctx.Put("from_url", "seed")

	logx.Eventf("queue", "%d from=%s to=%s", queueLen, "seed", toURL)
	if err := s.collector.Request("GET", toURL, nil, ctx, nil); err != nil {
		logx.Eventf("warn", "queue failed from=%s to=%s: %v", "seed", toURL, err)
	}
}

func (s *Scraper) shouldRetry(statusCode int) bool {
	return statusCode == 0 || statusCode == 408 || statusCode == 425 || statusCode == 429 || statusCode >= 500
}

func (s *Scraper) retryRequest(r *colly.Response, err error) {
	attempt := s.retryAttempt(r.Request.Ctx)

	if attempt >= s.cfg.MaxRetries {
		logx.Eventf("giveup", "url=%s attempts=%d: %v", r.Request.URL.String(), attempt, err)
		return
	}

	attempt++
	r.Request.Ctx.Put("retry_count", strconv.Itoa(attempt))

	wait := s.retryDelay(attempt)
	logx.Eventf("retry", "%d/%d %s after %s", attempt, s.cfg.MaxRetries, r.Request.URL.String(), wait)
	time.Sleep(wait)

	if retryErr := r.Request.Retry(); retryErr != nil {
		logx.Eventf("error", "retry failed for %s: %v (original error: %v)", r.Request.URL.String(), retryErr, err)
	}
}

func (s *Scraper) retryAttempt(ctx *colly.Context) int {
	attempt := 0
	if raw := ctx.Get("retry_count"); raw != "" {
		parsed, err := strconv.Atoi(raw)
		if err == nil {
			attempt = parsed
		}
	}
	return attempt
}

func (s *Scraper) retryDelay(attempt int) time.Duration {
	backoff := s.cfg.RetryBaseDelay * time.Duration(1<<(attempt-1))
	return backoff + s.jitter(500*time.Millisecond)
}

func (s *Scraper) jitter(max time.Duration) time.Duration {
	if max <= 0 {
		return 0
	}

	return time.Duration(rand.Int63n(int64(max)))
}

func (s *Scraper) requestDuration(r *colly.Request) time.Duration {
	raw := r.Ctx.Get("started_at_unix_nano")
	if raw == "" {
		return 0
	}

	startedAtUnixNano, err := strconv.ParseInt(raw, 10, 64)
	if err != nil {
		return 0
	}

	return time.Since(time.Unix(0, startedAtUnixNano))
}

func (s *Scraper) durationString(d time.Duration) string {
	if d <= 0 {
		return "0s"
	}

	return d.Round(100 * time.Millisecond).String()
}