package web

import (
	"fmt"
	"log"
	"net/http"
	"slices"
	"time"

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

// lanesView is the Lane status block: one row per Site's latest durable pass,
// plus the browser fact derived from that same log. No poller is consulted —
// the page answers from the database, so it is complete thirty seconds after
// a deploy (issue #145).
type lanesView struct {
	Rows []laneRow
	// PollerOff means latest-chapter polling is switched off in this
	// deployment (LATEST_CHAPTER_POLL_ENABLED). It is a config fact, not a
	// poller answering "absent": the browser line must not blame the sidecar
	// when nothing polls.
	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
	Checked int
	// Gap is the last pass's pace, or "—" when no pass has reached one yet —
	// a refused Lane still reports the pace its last real pass chose, so a
	// zero here would be a figure the row never measured.
	Gap string
	Ran string
	// Chips are the named outcome counts over the owner's window, in the
	// taxonomy's fixed order. Empty writes "none observed".
	Chips    []chip
	HasChips bool
	// StatePhrase is the reason this Lane declined to work: a skipped pass's
	// own sentence, or the one true stall. Empty means the pass reached its
	// loop and read normally. StateGood marks a healthy way to do nothing
	// (paused, browser asleep, nothing eligible) rather than a fault.
	StatePhrase string
	StateGood   bool
	// Attention is the one flag the template colours on, so a Lane that
	// needs the owner is found at a glance rather than read for.
	Attention bool
	// Paused is the live pause state — the poll_lanes stamp the pass row
	// joins on, still in the future — not the pass's skip: the control must
	// offer Resume from the moment the owner presses Pause, with no pass
	// having run to record it (issue #147).
	Paused bool
}

// chip is one named outcome count over the owner's window.
type chip struct {
	Name  string
	Count int
}

// 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()})
}

// 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())
}

// pauseDurations are the offered pause lengths, by their wire value. A fixed
// allow-list rather than time.ParseDuration: the unoffered value must be
// refused, and a permissive parser turns the offered set into "anything Go
// can read" (issue #147).
var pauseDurations = map[string]time.Duration{
	"1h":  time.Hour,
	"6h":  6 * time.Hour,
	"24h": 24 * time.Hour,
}

// laneSite reads the Site a lane route names, answering the request itself
// when it is not a registry Site. The path value is client-supplied, so it
// is checked against the registry before it reaches the store.
func laneSite(w http.ResponseWriter, r *http.Request) (string, bool) {
	site := r.PathValue("site")
	if !slices.Contains(latest.SiteNames(), site) {
		http.Error(w, "unknown site", http.StatusBadRequest)
		return "", false
	}
	return site, true
}

// adminLanePause writes a bounded pause for one Site and answers with the
// freshly rendered Lanes block, so the figures describe the state after the
// press. The pause is a fact about the Site — the Lane's next pass reads it
// from the durable row, never from this process — so it survives a restart.
// The owner gate is the route's, not this handler's; the body is capped like
// the API path caps its bodies; the Site and the duration are validated
// here, before the store sees them (issue #147).
func (h *Handler) adminLanePause(w http.ResponseWriter, r *http.Request) {
	site, ok := laneSite(w, r)
	if !ok {
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, 1<<16)
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	d, ok := pauseDurations[r.PostFormValue("duration")]
	if !ok {
		http.Error(w, "unknown pause duration", http.StatusBadRequest)
		return
	}
	if err := h.store.PauseLane(site, time.Now().Add(d).UnixMilli()); err != nil {
		log.Printf("pause lane %s: %v", site, err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.render(w, http.StatusOK, "lanes", h.lanesView())
}

// adminLaneResume zeroes one Site's pause and answers with the freshly
// rendered Lanes block. Resume is the reversal of a bounded pause, so it
// fires instantly with no confirm row (issue #147).
func (h *Handler) adminLaneResume(w http.ResponseWriter, r *http.Request) {
	site, ok := laneSite(w, r)
	if !ok {
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, 1<<16)
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	if err := h.store.ResumeLane(site); err != nil {
		log.Printf("resume lane %s: %v", site, err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	h.render(w, http.StatusOK, "lanes", h.lanesView())
}

// lanesView builds the Lane status block from the durable pass log. Both
// reads are the store's latest-per-Site projection, so the page's seam is a
// seeded row rather than a fake poller; errors degrade to the empty state and
// are logged, never shown to the owner in detail.
func (h *Handler) lanesView() lanesView {
	v := lanesView{
		PollerOff:         !h.pollerEnabled,
		BrowserConfigured: h.browserConfigured,
	}
	passes, err := h.store.LatestLanePasses()
	if err != nil {
		log.Printf("admin lanes: latest passes: %v", err)
		// No evidence of a lost sidecar reads as reachable, per the same rule
		// browserReachable applies: a store failure must not condemn the
		// browser. The empty table already says no Lane has recorded a pass.
		v.BrowserReachable = true
		return v
	}
	now := time.Now()
	outcomes, err := h.store.LanePassOutcomes(now.Add(-ownerWindow).UnixMilli())
	if err != nil {
		// The rows are complete without the chips, so a failed outcome sum
		// must not blank the table into "no data yet" — that is the confident
		// wrong statement the page exists to avoid. Every row renders "none
		// observed" instead, which is honest.
		log.Printf("admin lanes: outcomes: %v", err)
		outcomes = nil
	}
	bySite := make(map[string]store.SiteOutcomes, len(outcomes))
	for _, o := range outcomes {
		bySite[o.Site] = o
	}
	v.Rows = make([]laneRow, 0, len(passes))
	v.BrowserReachable = browserReachable(passes, now)
	for _, p := range passes {
		v.Rows = append(v.Rows, buildLaneRow(p, bySite[p.Site], now))
	}
	return v
}

// browserReachable derives the sidecar's reachability from the pass log: a
// browser Site is down when its latest pass inside the refusal backoff is a
// sidecar loss, a missing fetcher, or an interrupted read. Only browser Sites
// ever produce those signals, so no Site registry leaks into the web layer.
// A configured browser with no such evidence reads as reachable; an unset
// BROWSER_WS_URL degrades identically to a browser that is down.
func browserReachable(passes []store.LanePass, now time.Time) bool {
	backoff := latest.RefuseBackoff
	for _, p := range passes {
		ran := time.UnixMilli(p.RanAt)
		if now.Sub(ran) >= backoff || ran.After(now) {
			continue
		}
		if p.Skip == latest.SkipSidecarDown || p.Skip == latest.SkipNoFetcher || p.Unreachable > 0 {
			return false
		}
	}
	return true
}

// buildLaneRow turns one Site's latest pass and window outcome sums into the
// row the template prints. The skip column is the authority on why a pass did
// nothing; the outcomes render named and unlinked, because the pass row holds
// counts and never identities.
func buildLaneRow(p store.LanePass, o store.SiteOutcomes, now time.Time) laneRow {
	row := laneRow{
		Site:    p.Site,
		Due:     p.Due,
		Checked: p.Checked,
		Gap:     "—",
		Ran:     since(now, time.UnixMilli(p.RanAt)),
	}
	if p.GapMS > 0 {
		row.Gap = (time.Duration(p.GapMS) * time.Millisecond).Truncate(time.Second).String()
	}
	row.Chips = outcomeChips(o)
	row.HasChips = len(row.Chips) > 0
	row.StatePhrase, row.StateGood, row.Attention = laneState(p, now)
	row.Paused = time.UnixMilli(p.PausedUntil).After(now)
	return row
}

// outcomeChips lists a Site's nonzero window sums in the taxonomy's fixed
// order, so the chips never reorder as the window changes. None observed is
// written by the template, not drawn as a confident zero count.
func outcomeChips(o store.SiteOutcomes) []chip {
	fixed := []struct {
		name  string
		count int
	}{
		{"refused", o.Refused},
		{"unreachable", o.Unreachable},
		{"no chapter", o.NoChapter},
		{"unfetchable", o.Unfetchable},
		{"not found", o.NotFound},
		{"errors", o.Errors},
	}
	var out []chip
	for _, f := range fixed {
		if f.count > 0 {
			out = append(out, chip{Name: f.name, Count: f.count})
		}
	}
	return out
}

// laneState renders the reason a Lane's last pass did nothing, in one sentence
// per skip value with the one true stall kept apart from every Lane that
// declined and said why. Good states — a pause, a sleeping browser, nothing
// eligible — carry no Attention: the mark must stay spendable on the faults
// that actually need the owner.
func laneState(p store.LanePass, now time.Time) (phrase string, good, attention bool) {
	// The pause phrase reads the live poll_lanes stamp the pass row joins
	// on, not the pass's skip: the owner's press must render as paused on
	// the very answer it gets, with no pass having run to record it. The
	// pause is a fact about the Site, and the join delivers it (issue #147).
	if pausedUntil := time.UnixMilli(p.PausedUntil); pausedUntil.After(now) {
		phrase = "paused · resumes in " + humanDuration(pausedUntil.Sub(now))
		good = true
		return phrase, good, attention
	}
	switch p.Skip {
	case latest.SkipPaused:
		// A paused pass whose stamp has since lapsed: the Lane still
		// declined with a reason, so it is never the one true stall.
		phrase = "paused · resumes in " + humanDuration(time.UnixMilli(p.PausedUntil).Sub(now))
		good = true
	case latest.SkipRefusing:
		phrase = "refusing"
		if until := time.UnixMilli(p.RefuseUntil); until.After(now) {
			phrase += " · backs off until " + until.Format("15:04")
		}
		attention = true
	case latest.SkipSidecarDown, latest.SkipNoFetcher:
		// Known false positive shipped per spec: a sibling Lane's Chrome loss
		// stamps this Site too, and the enum deliberately has no tenth value
		// to separate it (issue #141). Render it as written.
		phrase = "no browser"
		attention = true
	case latest.SkipAsleep:
		phrase = "browser asleep"
		good = true
	case latest.SkipDueQuery:
		phrase = "due query failed"
		attention = true
	case latest.SkipEligibleCount:
		phrase = "eligible count failed"
		attention = true
	case latest.SkipNothingEligible:
		phrase = "nothing eligible"
		good = true
	}
	if phrase == "" && p.Due > 0 && p.Checked == 0 {
		// The one true stall: the pass reached its loop, Series were waiting,
		// and none were read. Every skip above is a Lane that said why.
		phrase = "not checking"
		attention = true
	}
	return phrase, good, attention
}

// humanDuration renders a positive duration compactly for a "resumes in" clue
// at the pause and refusal scales — minutes under an hour, then h and h+m.
func humanDuration(d time.Duration) string {
	d = d.Round(time.Minute)
	if d <= 0 {
		return "soon"
	}
	if d < time.Hour {
		return fmt.Sprintf("%dm", int(d/time.Minute))
	}
	h := int(d / time.Hour)
	if m := int(d%time.Hour) / int(time.Minute); m == 0 {
		return fmt.Sprintf("%dh", h)
	} else {
		return fmt.Sprintf("%dh%dm", h, m)
	}
}

// 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"
}