package web

import (
	"fmt"
	"log"
	"net/http"
	"net/url"
	"strconv"
	"time"

	"bookmarkmanager/backend/internal/latest"
	"bookmarkmanager/backend/internal/store"
)

// seriesPageSize matches the store's row-read page length: the pager's range
// must agree with the LIMIT the store applies or the "of N" figure describes
// the wrong page. The store does not export it (#140).
const seriesPageSize = 50

// seriesFilterLabels names every hygiene filter for the Series list select,
// keyed by the wire constant the URL carries. The render order is
// seriesFilterOrder; the labels are read by later admin tickets too, so the
// map and the constants cannot drift apart.
var seriesFilterLabels = map[string]string{
	store.SeriesFilterAll:          "All series",
	store.SeriesFilterNoURL:        "No series URL",
	store.SeriesFilterNoChapter:    "Never read a chapter",
	store.SeriesFilterNoReaders:    "No Readers",
	store.SeriesFilterNeverChecked: "Never checked",
	store.SeriesFilterStale:        "Not checked in 12h",
	store.SeriesFilterNoCover:      "No cover",
	store.SeriesFilterReaderReport: "Latest from a Reader",
}

// seriesFilterOrder is the select's render order: All first, then the
// permanent repairs, then the fixable ones (issue #140).
var seriesFilterOrder = []string{
	store.SeriesFilterAll,
	store.SeriesFilterNoURL,
	store.SeriesFilterNoChapter,
	store.SeriesFilterNoReaders,
	store.SeriesFilterNeverChecked,
	store.SeriesFilterStale,
	store.SeriesFilterNoCover,
	store.SeriesFilterReaderReport,
}

// seriesListView is the Series list page's data. The template renders strings
// and flags, and every judgement about what a value means is made here.
type seriesListView struct {
	Filters     []seriesFilterOption
	Sites       []string
	Site        string // "" = every Site
	Kind        string // "" = both libraries
	FilterLabel string
	Rows        []seriesRowView
	Total       int
	// KindBoth / KindManga / KindNovel are the Library segment links, and
	// PrevHref / NextHref the pager's, all carrying the active filter, Site
	// and Kind so narrowing never drops state.
	KindBoth  string
	KindManga string
	KindNovel string
	PrevHref  string
	NextHref  string
	Range     string
}

// seriesFilterOption is one entry of the Show select: its wire value, its
// rendered label with the library-wide count, and whether it is the active
// filter.
type seriesFilterOption struct {
	Name     string
	Label    string
	Count    int
	Selected bool
}

// seriesRowView is one Series row formatted for the template. Band carries
// the alternating row tint by class rather than nth-of-type, so the confirm
// rows later tickets add are row siblings without breaking the alternation.
// Attention tints the title patina: a row with any hygiene chip needs one.
type seriesRowView struct {
	Key       string
	Title     string
	Site      string
	Ch        string // chapter number; "—" until first captured
	Age       string // checked age; "never" until first check
	Readers   int
	Notes     []string // chips, capped at two
	More      int      // chips past the cap, rendered as a +N tail
	Band      bool
	Attention bool
}

// adminSeries renders the filterable, bookmarkable Series list: filter, Site,
// Library and page all live in the query string, so the list's state is an
// address rather than a click path.
func (h *Handler) adminSeries(w http.ResponseWriter, r *http.Request) {
	view, err := h.seriesListView(r)
	if err != nil {
		log.Printf("admin series: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.renderAdmin(w, adminView{Page: "series", SeriesList: view})
}

// seriesListView assembles one Series list view from the request's query
// string. An unknown filter value is the absent All case, never an error: the
// select's options are not the only way this URL can be reached.
func (h *Handler) seriesListView(r *http.Request) (seriesListView, error) {
	q := r.URL.Query()
	filter := q.Get("filter")
	if _, ok := seriesFilterLabels[filter]; !ok {
		filter = store.SeriesFilterAll
	}
	site := q.Get("site")
	kind := q.Get("kind")
	if kind != store.KindManga && kind != store.KindNovel {
		kind = ""
	}
	page := 1
	if p, err := strconv.Atoi(q.Get("page")); err == nil && p > 1 {
		page = p
	}

	sf := store.SeriesFilter{
		Site:   site,
		Kind:   kind,
		Name:   filter,
		Cutoff: time.Now().Add(-ownerWindow).UnixMilli(),
		Page:   page,
	}
	data, err := h.store.SeriesPage(sf)
	if err != nil {
		return seriesListView{}, err
	}
	// A page past the end is not an empty list: the store's window count runs
	// over the rows the result set carries, so an overflow page reports zero
	// rows and zero total, and the list re-reads at page 1 to know the truth.
	if len(data.Rows) == 0 && page > 1 {
		page = 1
		sf.Page = 1
		data, err = h.store.SeriesPage(sf)
		if err != nil {
			return seriesListView{}, err
		}
	}

	view := seriesListView{
		Site:        site,
		Kind:        kind,
		FilterLabel: seriesFilterLabels[filter],
		Rows:        make([]seriesRowView, 0, len(data.Rows)),
		Total:       data.Total,
		Sites:       latest.SiteNames(),
	}
	now := time.Now()
	for i, a := range data.Rows {
		view.Rows = append(view.Rows, seriesRow(a, i, now))
	}
	view.Filters, err = h.seriesFilterOptions(filter)
	if err != nil {
		return seriesListView{}, err
	}
	view.KindBoth = seriesListHref(filter, site, "", 0)
	view.KindManga = seriesListHref(filter, site, store.KindManga, 0)
	view.KindNovel = seriesListHref(filter, site, store.KindNovel, 0)
	if page > 1 {
		view.PrevHref = seriesListHref(filter, site, kind, page-1)
	}
	if last := (data.Total + seriesPageSize - 1) / seriesPageSize; page < last {
		view.NextHref = seriesListHref(filter, site, kind, page+1)
	}
	view.Range = pagerRange(data.Total, len(data.Rows), page)
	return view, nil
}

// seriesFilterOptions renders every hygiene filter with its library-wide
// count, one SeriesShapes pass per filter summed in Go — the shipped surface
// offers eight grouped passes, not a single stats query (#140). The counts
// are library-wide because the select sits next to the Site narrowing and
// must not shift as the owner narrows the list itself.
func (h *Handler) seriesFilterOptions(selected string) ([]seriesFilterOption, error) {
	out := make([]seriesFilterOption, 0, len(seriesFilterOrder))
	for _, name := range seriesFilterOrder {
		shapes, err := h.store.SeriesShapes(store.SeriesFilter{Name: name})
		if err != nil {
			return nil, err
		}
		count := 0
		for _, sh := range shapes {
			count += sh.Total
		}
		out = append(out, seriesFilterOption{
			Name:     name,
			Label:    seriesFilterLabels[name],
			Count:    count,
			Selected: name == selected,
		})
	}
	return out, nil
}

// seriesRow formats one store row for the template. The note chips are the
// row's own hygiene facts, capped at two with a +N tail; attention marks a
// row that carries any.
func seriesRow(a store.AdminSeries, i int, now time.Time) seriesRowView {
	row := seriesRowView{
		Key:     a.Key(),
		Title:   a.Title,
		Site:    a.Site,
		Readers: a.ReaderCount,
		Band:    i%2 == 1,
	}
	if a.LatestChapterNum != nil {
		row.Ch = strconv.FormatFloat(*a.LatestChapterNum, 'f', -1, 64)
	} else {
		row.Ch = "—"
	}
	row.Age = checkedAge(now, a.LatestCheckedAt)
	notes := seriesNotes(a, now)
	if n := len(notes); n > 2 {
		row.Notes, row.More = notes[:2], n-2
	} else {
		row.Notes = notes
	}
	row.Attention = len(notes) > 0
	return row
}

// seriesNotes are a row's hygiene chips in the design's order: no URL, no
// cover, orphan, stale, reader sighting.
func seriesNotes(a store.AdminSeries, now time.Time) []string {
	notes := []string{}
	if a.SeriesURL == "" {
		notes = append(notes, "no URL")
	}
	if a.CoverAddress == "" {
		notes = append(notes, "no cover")
	}
	if a.ReaderCount == 0 {
		notes = append(notes, "orphan")
	}
	if a.LatestCheckedAt > 0 && a.LatestCheckedAt < now.Add(-ownerWindow).UnixMilli() {
		notes = append(notes, "stale")
	}
	if a.RaisedByReader {
		notes = append(notes, "reader sighting")
	}
	return notes
}

// checkedAge formats how long ago a Series was last checked, at the
// granularity the list reads at — minutes, hours, days. Zero means never.
func checkedAge(now time.Time, ts int64) string {
	if ts == 0 {
		return "never"
	}
	d := now.Sub(time.UnixMilli(ts))
	switch {
	case d < time.Hour:
		m := int(d / time.Minute)
		if m < 1 {
			m = 1
		}
		return fmt.Sprintf("%dm ago", m)
	case d < 24*time.Hour:
		return fmt.Sprintf("%dh ago", int(d/time.Hour))
	default:
		return fmt.Sprintf("%dd ago", int(d/(24*time.Hour)))
	}
}

// pagerRange is the pager's "1–50 of 120" line. Zero rows reads as "0 of 0":
// the empty state carries the page then, and a window number for a list that
// rendered nothing would be a number nothing points at.
func pagerRange(total, rows, page int) string {
	if rows == 0 {
		return "0 of 0"
	}
	from := (page-1)*seriesPageSize + 1
	return fmt.Sprintf("%d–%d of %d", from, from+rows-1, total)
}

// seriesListHref is one Series list address carrying the filter, Site, Kind
// and page. The All filter and page 1 are the absent cases and stay out of
// the URL, so the default address is the shortest one.
func seriesListHref(filter, site, kind string, page int) string {
	q := url.Values{}
	if filter != "" && filter != store.SeriesFilterAll {
		q.Set("filter", filter)
	}
	if site != "" {
		q.Set("site", site)
	}
	if kind != "" {
		q.Set("kind", kind)
	}
	if page > 1 {
		q.Set("page", strconv.Itoa(page))
	}
	if len(q) == 0 {
		return "/admin/series"
	}
	return "/admin/series?" + q.Encode()
}