package web

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

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

// LaneReporter is the administrative page's whole window onto the running
// poller: one snapshot of Poll Lane state, copied out of memory on request.
// The Poller satisfies it in production and a fake with fixed values satisfies
// it in tests, so the page's tests need neither a poller nor a Site.
type LaneReporter interface {
	LaneStatus() latest.Status
}

// ownerWindow is the staleness boundary the Series list's "not checked in
// 12h" filter compares against. Declared once; later admin tickets read it.
const ownerWindow = 12 * time.Hour

// adminView is the shared shell data for an administrative page and the roster
// fragment returned after a Reader action.
type adminView struct {
	Page    string
	Readers []store.ReaderSummary
	// OwnerID travels with the roster so it can tell the owner's own row from
	// the Readers they may act on.
	OwnerID    int64
	Lanes      lanesView
	SeriesList seriesListView
}

// lanesView is the Lane status block: one row per Site that has run, plus the
// browser fact, which is shared by the three browser Sites rather than held
// once per Site.
type lanesView struct {
	Rows []laneRow
	// PollerOff means no poller is running at all (disabled by config, or its
	// client could not be built). The browser line must not answer "not
	// configured" then: the sidecar is not the reason nothing is polled.
	PollerOff         bool
	BrowserConfigured bool
	BrowserReachable  bool
}

// laneRow is one Lane formatted for reading rather than for arithmetic: the
// template renders strings and flags, and every judgement about what they mean
// is made here.
type laneRow struct {
	Site string
	Due  int
	Ran  string
	// Checked is how many Series the last pass read. Due without Checked is a
	// Lane that has stopped working; the two figures side by side are what
	// separate that from a Lane with nothing to do.
	Checked int
	// Gap is empty when no pass has reached the pace yet, so the row omits the
	// figure instead of stating a zero.
	Gap      string
	Clamped  bool
	Refusing bool
	// BrowserLost marks a Lane whose pages can only be read through the
	// sidecar while the sidecar is unreachable — including the case where none
	// is configured, which stops those Series just as completely.
	BrowserLost bool
	// Stalled marks a Lane with Series waiting that its last pass did not read
	// — the difference between a stopped Lane and a quiet one (story 13). A
	// browser Lane holding Chrome asleep under the wake thresholds is neither,
	// so it carries Asleep instead and never Stalled.
	Stalled bool
	Asleep  bool
	// Attention is the one flag the template colours on, so an unhealthy Lane
	// is found at a glance rather than read for.
	Attention bool
}

// adminRoute pairs a route pattern with its handler so the route list and the
// gate cannot drift apart.
type adminRoute struct {
	pattern string
	handler http.HandlerFunc
}

// adminRoutes is every route that reaches past the acting Reader. Register
// wraps each one in requireOwner, so a new administrative route is gated by
// being listed here rather than by remembering to write a check inside it.
func (h *Handler) adminRoutes() []adminRoute {
	return []adminRoute{
		{"GET /admin", h.admin},
		{"GET /admin/lanes", h.adminLanes},
		{"GET /admin/readers", h.adminReaders},
		{"GET /admin/series", h.adminSeries},
		{"GET /ui/admin/lanes", h.uiLanes},
		{"POST /readers/{id}/revoke", h.revokeReaderSessions},
		{"POST /readers/{id}/clear-marks", h.clearReaderMarks},
	}
}

// AdminPatterns names every administrative route, so one test can prove the
// owner gate covers all of them rather than one test per route. The receiver is
// nil because only the patterns are read; the bound handlers are never called.
func AdminPatterns() []string {
	routes := (*Handler)(nil).adminRoutes()
	out := make([]string, 0, len(routes))
	for _, rt := range routes {
		out = append(out, rt.pattern)
	}
	return out
}

// requireOwner is the owner test, in one place, layered on the session gate: no
// session is still 401, and a signed-in Reader who is not the owner gets 404
// rather than 403 — a refusal that confirms the address exists is a refusal
// that helps whoever is probing for it.
func (h *Handler) requireOwner(next http.HandlerFunc) http.HandlerFunc {
	return h.requireSession(func(w http.ResponseWriter, r *http.Request) {
		if readerOf(r) != h.store.OwnerID() {
			http.NotFound(w, r)
			return
		}
		next(w, r)
	})
}

// admin renders the Overview shell. Its data arrives in later admin tickets.
func (h *Handler) admin(w http.ResponseWriter, r *http.Request) {
	h.renderAdmin(w, adminView{Page: "overview"})
}

// adminLanes renders the page that hosts the live Lane fragment.
func (h *Handler) adminLanes(w http.ResponseWriter, r *http.Request) {
	h.renderAdmin(w, adminView{Page: "lanes", Lanes: h.lanesView()})
}

// adminReaders renders the Reader roster on its own bookmarkable page.
func (h *Handler) adminReaders(w http.ResponseWriter, r *http.Request) {
	readers, err := h.store.Readers()
	if err != nil {
		log.Printf("admin readers: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.renderAdmin(w, adminView{Page: "readers", Readers: readers, OwnerID: h.store.OwnerID()})
}

func (h *Handler) renderAdmin(w http.ResponseWriter, view adminView) {
	h.render(w, http.StatusOK, "admin", view)
}

// uiLanes answers the status block's own refresh. Only the block refreshes on a
// timer; the roster re-renders after an action, as it always has.
func (h *Handler) uiLanes(w http.ResponseWriter, r *http.Request) {
	h.render(w, http.StatusOK, "lanes", h.lanesView())
}

// lanesView copies the poller's snapshot into display form. A nil reporter (no
// poller running) and a poller no Lane has reported to yet are the same thing
// to the page: no data, which it must say rather than draw as confident zeroes
// — an empty page a few seconds after a restart must not read as a stopped one.
func (h *Handler) lanesView() lanesView {
	if h.lanes == nil {
		return lanesView{PollerOff: true}
	}
	snap := h.lanes.LaneStatus()
	v := lanesView{
		Rows:              make([]laneRow, 0, len(snap.Lanes)),
		BrowserConfigured: snap.BrowserConfigured,
		BrowserReachable:  snap.BrowserReachable,
	}
	now := time.Now()
	for _, l := range snap.Lanes {
		lost := l.Browser && !snap.BrowserReachable
		// Series waiting and none read is the shape of a Lane that has stopped
		// working, as distinct from one that is quiet for want of work — or one
		// deliberately leaving Chrome asleep until its group gathers.
		stalled := l.Due > 0 && l.Checked == 0 && !l.Asleep
		gap := ""
		if l.Gap > 0 {
			gap = l.Gap.Truncate(time.Second).String()
		}
		v.Rows = append(v.Rows, laneRow{
			Site:        l.Site,
			Due:         l.Due,
			Ran:         since(now, l.LastRun),
			Checked:     l.Checked,
			Gap:         gap,
			Clamped:     l.Clamped,
			Refusing:    l.Refusing,
			BrowserLost: lost,
			Stalled:     stalled,
			Asleep:      l.Asleep,
			Attention:   l.Clamped || l.Refusing || lost || stalled,
		})
	}
	return v
}

// since formats how long ago a Lane last ran, at second resolution: the block
// refreshes every thirty seconds, so anything finer is noise the owner would
// have to ignore.
func since(now, then time.Time) string {
	d := now.Sub(then).Truncate(time.Second)
	if d < time.Second {
		return "just now"
	}
	return d.String() + " ago"
}

// revokeReaderSessions logs one Reader out of every browser they are signed in
// on. The owner gate is the route's, not this handler's.
func (h *Handler) revokeReaderSessions(w http.ResponseWriter, r *http.Request) {
	target, ok := readerPathID(w, r)
	if !ok {
		return
	}
	// The owner is not one of the Readers this endpoint reaches: revoking
	// themselves would sign out the browser making the request, which is what
	// logout is for. The roster hides the button; this refuses the hand-rolled
	// POST behind it.
	if target == h.store.OwnerID() {
		http.NotFound(w, r)
		return
	}
	if err := h.store.DeleteReaderSessions(target); err != nil {
		log.Printf("revoke sessions: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.renderRoster(w, "revoke sessions")
}

// clearReaderMarks zeroes one Reader's Sighting counters. The guard those
// counters feed has one known false positive — a Site changing its page shape
// makes a correct adapter read a wrong high number and marks every honest
// Reader of that Site at once (issue #103) — and this is its remedy. It
// restores a privilege rather than destroying anything, so the control is
// confirmed but never wears the destruction accent.
func (h *Handler) clearReaderMarks(w http.ResponseWriter, r *http.Request) {
	target, ok := readerPathID(w, r)
	if !ok {
		return
	}
	if err := h.store.ClearReaderMarks(target); err != nil {
		log.Printf("clear marks: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.renderRoster(w, "clear marks")
}

// readerPathID reads the Reader a route names, answering the request itself
// when there is nobody to act on.
func readerPathID(w http.ResponseWriter, r *http.Request) (int64, bool) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.Error(w, "bad reader id", http.StatusBadRequest)
		return 0, false
	}
	return id, true
}

// renderRoster answers an action with the whole roster, so the counts and marks
// it shows cannot describe the state before the tap.
func (h *Handler) renderRoster(w http.ResponseWriter, what string) {
	readers, err := h.store.Readers()
	if err != nil {
		log.Printf("%s: %v", what, err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.render(w, http.StatusOK, "readers", adminView{Readers: readers, OwnerID: h.store.OwnerID()})
}