package web

import (
	"fmt"
	"html/template"
	"net/http"
	"net/url"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/i18n"
	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
	"gitea.dooplex.hu/admin/felhom-controller/internal/util"
)

// ── i18n (v0.247.0) — the dashboard in more than one language ──────────────────────────────────
//
// Design: felhom.eu/documentation/architecture/10-localisation.md. Hungarian is the default and the
// only language a household sees unless it switches. The Hungarian page is byte-identical to what it
// was before this file existed — pinned by i18n_parity_test.go against fixtures captured from the
// unconverted templates.

// ── Go-side copy (v0.252.0, slice 2 — R-557) ───────────────────────────────────────────────────
//
// A handler builds sentences the template never sees: flash lines, page data, JSON answers. Those go
// through these three helpers, never through a Hungarian literal, so they follow the request's
// language exactly as the template does.
//
// The Hungarian text is the SAME BYTES the literal carried, which scripts/i18n_go_parity.py measures
// against a frozen capture of the base commit. So a handler that reads
//
//	data["Msg"] = s.msg(r, "backup.window_updated")
//
// renders, for a Hungarian household, the literal that used to sit at that line and nothing else.

// bundle returns the message bundle for these helpers.
//
// It falls back to the process-wide i18n.Shared() when the Server has none. That is not defensive
// clutter: `s.i18n` is set by loadTemplates, so any Server built WITHOUT going through it — a test
// fixture, a future construction path — would otherwise render raw KEYS onto a page, which is the one
// outcome §4 of the localisation design forbids ("never a key, never a blank"). The bundle is
// embedded in the binary, so the fallback cannot fail for any reason a running box can reach; if it
// somehow does, the caller still gets the key rather than a panic.
func (s *Server) bundle() *i18n.Bundle {
	if s.i18n != nil {
		return s.i18n
	}
	b, err := i18n.Shared()
	if err != nil {
		return nil
	}
	return b
}

// msg returns a Go-side message in the request's language, with the message's own printf verbs
// filled in from a.
func (s *Server) msg(r *http.Request, key string, a ...interface{}) string {
	return s.msgLang(s.langFor(r), key, a...)
}

// msgLang is msg for a language that is already known — a background run reading the box's setting
// (internal/settings GetLanguage), or a handler that resolved the language once for several lines.
func (s *Server) msgLang(lang, key string, a ...interface{}) string {
	b := s.bundle()
	if b == nil {
		return key
	}
	if len(a) == 0 {
		return b.Msg(lang, key)
	}
	return b.Msgf(lang, key, a...)
}

// msgN returns a count-dependent message in the request's language. Hungarian carries one form under
// the key itself; English carries key+".one" and key+".other" (i18n.Bundle.Plural).
func (s *Server) msgN(r *http.Request, key string, n int) string {
	b := s.bundle()
	if b == nil {
		return key
	}
	return b.Plural(s.langFor(r), key, n)
}

// ── Errors on a page (v0.253.0, slice 2 release B) ─────────────────────────────────────────────
//
// An error is MADE deep in a package that has no request, and PRINTED by a handler that has one.
// util.MsgError carries the key across that gap; errText is the handler side of it.
//
// A plain error — restic, docker, ssh, the Go stdlib — prints verbatim, in both languages, because
// that sentence is not ours (10-localisation.md §9). So this is safe to put in front of EVERY
// err.Error() on a display path, converted or not, and that is exactly what release B does.

// errText renders an error in the request's language: its bundle message when it carries one, its own
// text otherwise.
func (s *Server) errText(r *http.Request, err error) string {
	return util.ErrText(s.langFor(r), err)
}

// errTextLang is errText for a language already resolved (a background run, or a handler that
// resolved it once).
func (s *Server) errTextLang(lang string, err error) string {
	return util.ErrText(lang, err)
}

// ── Flash lines (v0.252.0) ─────────────────────────────────────────────────────────────────────
//
// A flash travels to the page INSIDE THE REDIRECT URL (`?flash=…`), so it is rendered by a DIFFERENT
// request from the one that wrote it — and until now it travelled as Hungarian text, which is the
// language of whoever redirected. It now travels as a bundle KEY plus its parameters, and the reader
// renders it in its own language.
//
// Backward compatibility is not a nicety here: a customer's open tab, a bookmark or a browser's
// back-forward cache can replay a URL minted by the previous version, and a mail client can carry
// one. So the rule is: a value the bundle knows as a key is a MESSAGE; anything else is TEXT and is
// shown verbatim, exactly as it was before. That also covers a hand-typed `?flash=<script>` — which
// html/template escapes, as it always did.

// flashForErr turns an error into what a flash carries: its bundle KEY plus its parameters when it
// has one, and its own text otherwise.
//
// The second half is what makes this safe to use everywhere: a restic, docker or ssh sentence goes
// into the URL as text and is shown verbatim by flashText, exactly as it was before v0.252.0.
func flashForErr(err error) (string, []string) {
	if err == nil {
		return "", nil
	}
	if m, ok := util.AsMsg(err); ok {
		return m.Key(), m.Args()
	}
	return err.Error(), nil
}

// flashArgParam is the repeated query parameter carrying a flash message's parameters, in order.
const flashArgParam = "fa"

// flashQuery builds the query fragment for a flash: the key, then one `fa` per parameter.
// It returns "flash=…" (or "flash_error=…") WITHOUT a leading separator, because the callers differ
// on whether the destination already carries a query.
func flashQuery(param, key string, args ...string) string {
	q := url.Values{}
	q.Set(param, key)
	for _, a := range args {
		q.Add(flashArgParam, a)
	}
	return q.Encode()
}

// flashText resolves a flash query value for display.
//
// A value that names a key in the bundle is rendered in lang, with the `fa` parameters filled in.
// Anything else — a sentence minted by an older controller, or something a person typed — is
// returned unchanged. It is never dropped and never shown as a raw key.
func (s *Server) flashText(r *http.Request, v string) string {
	if v == "" {
		return ""
	}
	b := s.bundle()
	if b == nil {
		return v
	}
	lang := s.langFor(r)
	if !b.Has(i18n.Default, v) {
		return v // legacy text, or not ours: verbatim
	}
	var args []interface{}
	if r != nil {
		for _, a := range r.URL.Query()[flashArgParam] {
			args = append(args, a)
		}
	}
	if len(args) == 0 {
		return b.Msg(lang, v)
	}
	return b.Msgf(lang, v, args...)
}

// flashFrom reads one flash parameter off the request and resolves it. Empty when absent.
func (s *Server) flashFrom(r *http.Request, param string) string {
	if r == nil {
		return ""
	}
	return s.flashText(r, strings.TrimSpace(r.URL.Query().Get(param)))
}

// addLanguageData puts the request's language and the switch state into a page's data.
//
// The switch is on every dashboard page, in every language (v0.250.0, slice 1 release C). Until then it
// was hidden from Hungarian pages without ?lang=, because English covered only part of the dashboard;
// every template is converted now, so the offer no longer leads to a half-English page. Pinned by
// TestLanguageSwitch_EndToEnd (a Hungarian household with no ?lang= sees the form).
func (s *Server) addLanguageData(data map[string]interface{}, r *http.Request, lang string) {
	data["Lang"] = lang
	if r != nil {
		data["LangSwitch"] = true
		data["LangSwitchBack"] = r.URL.Path
		// v0.254.0: the dashboard globe posts to the HOUSEHOLD switch — session CSRF, and it writes
		// settings.json. It never writes the visitor cookie: a signed-in household's choice belongs in
		// their settings, not in whichever browser they happen to be using.
		addLangOptions(data, lang, "/settings/language", r.URL.Path, s.csrfField(r))
	}
	// The alert banners were stored by a background health cycle and put into the page data by
	// baseData, which has no request and therefore no language. Re-rendered here, where the language
	// is known. Idempotent: an Alert keeps its key, so rendering it twice is rendering it once.
	if alerts, ok := data["Alerts"].([]Alert); ok {
		for i := range alerts {
			alerts[i] = alerts[i].rendered(lang)
		}
	}
	// A page title is Go-side copy. The handler names its key; the Hungarian title the handler set is
	// left untouched, so a Hungarian page cannot change here.
	//
	// TitleArgs (v0.252.0, R-566) carries the app name for the three titles built around one: „<app>
	// — Naplók", „<app> — Telepítés"/„— Beállítások" and „2. mentés beállítása — <app>". Their page
	// BODIES were English from slice 1 while the browser tab stayed Hungarian, because one static
	// message cannot hold a name. The message now carries a `%s` and the handler supplies the name.
	if key, ok := data["TitleKey"].(string); ok && lang != i18n.Default && s.i18n != nil {
		if args, ok := data["TitleArgs"].([]interface{}); ok && len(args) > 0 {
			data["Title"] = s.i18n.Msgf(lang, key, args...)
		} else {
			data["Title"] = s.i18n.Msg(lang, key)
		}
	}
}

// LangOption is one entry in the globe menu. Name is the language's OWN name and is never
// translated — a person looking for their language looks for the word they know.
type LangOption struct {
	Code    string
	Name    string
	Current bool
}

// langNativeNames — a language's own name, in itself. Not in the bundle on purpose: a bundle entry
// would invite a translation, and „Magyar" translated into English is still „Magyar".
var langNativeNames = map[string]string{"hu": "Magyar", "en": "English"}

// addLangOptions puts everything the lang_globe partial needs into a page's data.
//
// `csrf` is template.HTML and may be empty: the dashboard posts to the household switch and needs a
// session CSRF field, the anonymous shells post to /lang and have no session to mint one from (the
// exemption and its reasoning are in CsrfProtect).
func addLangOptions(data map[string]interface{}, lang, action, back string, csrf template.HTML) {
	opts := make([]LangOption, 0, len(i18n.Supported))
	for _, code := range i18n.Supported {
		name := langNativeNames[code]
		if name == "" {
			name = code
		}
		opts = append(opts, LangOption{Code: code, Name: name, Current: code == lang})
	}
	data["LangOptions"] = opts
	data["LangAction"] = action
	data["LangBack"] = back
	data["LangCSRF"] = csrf
}

// languageSwitchHandler stores the household's language (POST /settings/language) and goes back to
// the page it came from. CSRF is enforced by the CsrfProtect middleware wrapping "/" (main.go), as for
// every other dashboard form; the switch form carries {{.CSRFField}}.
func (s *Server) languageSwitchHandler(w http.ResponseWriter, r *http.Request) {
	lang := r.FormValue("lang")
	if !i18n.IsSupported(lang) {
		http.Error(w, "unsupported language", http.StatusBadRequest)
		return
	}
	if err := s.settings.SetLanguage(lang); err != nil {
		s.logger.Printf("[ERROR] [web] language switch: save failed: %v", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
		return
	}
	s.logger.Printf("[INFO] [web] language switch: household language set to %s", lang)
	s.reportTriggerNow() // the hub learns the language on the next report, in seconds rather than minutes
	http.Redirect(w, r, stripLangQuery(redirectBackTo(r, "/launcher")), http.StatusFound)
}

// stripLangQuery keeps a ?lang= override from pinning the page after the setting has been saved.
func stripLangQuery(p string) string {
	if i := strings.Index(p, "?"); i >= 0 {
		return p[:i]
	}
	return p
}

// localeFuncs returns the template funcs whose OUTPUT is copy, re-implemented from the bundle, for
// every language except Hungarian. Hungarian gets nothing here: its funcs stay the ones in
// templateFuncMap, untouched, which is the parity guarantee for Go-side helper text.
// TestLocaleFuncsHungarianBundleMatchesFuncMap pins that hu.json carries the same words the Hungarian
// funcs return, so the bundle can become the single source in slice 1 without a byte moving.
func (s *Server) localeFuncs(lang string) template.FuncMap {
	if lang == i18n.Default {
		return nil
	}
	b, err := i18n.Shared()
	if err != nil {
		return nil
	}
	loc := getTimezone()
	ago := func(d time.Duration) string {
		switch {
		case d < time.Minute:
			return b.Msg(lang, "func.time.now")
		case d < time.Hour:
			return b.Plural(lang, "func.time.minutes_ago", int(d.Minutes()))
		case d < 24*time.Hour:
			return b.Plural(lang, "func.time.hours_ago", int(d.Hours()))
		case d < 48*time.Hour:
			return b.Msg(lang, "func.time.yesterday")
		default:
			return b.Plural(lang, "func.time.days_ago", int(d.Hours()/24))
		}
	}
	return template.FuncMap{
		"stateLabel": func(state stacks.ContainerState) string {
			return b.Msg(lang, stateLabelKey(state))
		},
		"timeAgo": func(t time.Time) string {
			if t.IsZero() {
				return "–"
			}
			return ago(time.Now().In(loc).Sub(t.In(loc)))
		},
		"timeAgoStr": func(str string) string {
			t, err := time.Parse(time.RFC3339, str)
			if err != nil {
				return str
			}
			return ago(time.Now().In(loc).Sub(t.In(loc)))
		},
		"nextRunLabel": func(t time.Time) string {
			if t.IsZero() {
				return "–"
			}
			lt := t.In(loc)
			now := time.Now().In(loc)
			hm := lt.Format("15:04")
			if lt.Year() == now.Year() && lt.YearDay() == now.YearDay() {
				return fmt.Sprintf(b.Msg(lang, "func.time.today_at"), hm)
			}
			if lt.Year() == now.Year() && lt.YearDay() == now.YearDay()+1 {
				return fmt.Sprintf(b.Msg(lang, "func.time.tomorrow_at"), hm)
			}
			return lt.Format("2006-01-02") + " " + hm
		},
		// infraMeta: the protected infra stacks' curated identity (inframeta.go). Names that are product
		// names stay; descriptions — and samba's display name — come from the bundle.
		"infraMeta": func(name string) *InfraMeta {
			m := infraMetaFor(name)
			if m == nil {
				return nil
			}
			out := *m
			if v, _, ok := b.Text(lang, "func.infra."+name+".description"); ok {
				out.Description = v
			}
			if v, _, ok := b.Text(lang, "func.infra."+name+".display"); ok {
				out.DisplayName = v
			}
			return &out
		},
		// updateBadge / lifecycleBadge (R-589, v0.258.0) — the two *MetaBadge builders. Their
		// Hungarian forms in templateFuncMap are UNTOUCHED, which is the parity guarantee; these
		// rebuild the same badge from the bundle, reusing compareInstalledToTemplate and
		// EffectiveLifecycle so the DECISION cannot drift between the two languages — only the
		// words do. TestLocaleFuncsHungarianBundleMatchesFuncMap pins that hu.json says what the
		// Hungarian funcs say.
		//
		// Found live on 2026-09-20: on an English app page the only Felhom-authored Hungarian left
		// was this badge, „Naprakész", with a Hungarian tooltip under it.
		"updateBadge": func(st stacks.Stack) *MetaBadge {
			switch compareInstalledToTemplate(st) {
			case updateCurrent:
				return &MetaBadge{
					Label: b.Msg(lang, "badge.update.current"),
					Class: "tag-ok",
					Title: b.Msg(lang, "badge.update.current.title"),
				}
			case updateAhead:
				// R-524's twin. Same word, same class as updateCurrent — see updatebadge.go.
				return &MetaBadge{
					Label: b.Msg(lang, "badge.update.current"),
					Class: "tag-ok",
					Title: b.Msg(lang, "badge.update.ahead.title"),
				}
			case updateBehind:
				label := b.Msg(lang, "badge.update.behind")
				if days, ok := st.Meta.CatalogSinceAge(time.Now().UTC()); ok {
					if days == 0 {
						label += b.Msg(lang, "badge.update.behind.today")
					} else {
						label += b.Plural(lang, "badge.update.behind.days", days)
					}
				}
				return &MetaBadge{Label: label, Class: "tag-warn", Title: b.Msg(lang, "badge.update.behind.title")}
			default:
				// UNKNOWN renders nothing, in every language — see updatebadge.go.
				return nil
			}
		},
		"lifecycleBadge": func(m stacks.Metadata) *MetaBadge {
			if m.EffectiveLifecycle() != stacks.LifecycleAbandoned {
				return nil
			}
			return &MetaBadge{
				Label: b.Msg(lang, "badge.lifecycle.abandoned"),
				Class: "tag-warn",
				Title: b.Msg(lang, "badge.lifecycle.abandoned.title"),
			}
		},
		"statusText": func(status string) string {
			switch status {
			case "pending", "restoring", "done", "failed", "skipped":
				return b.Msg(lang, "func.restore_status."+status)
			default:
				return status
			}
		},
	}
}

// stateLabelKey maps a container state to its bundle key. The default arm mirrors templateFuncMap's
// "Ismeretlen" default, so an unmapped state is labelled unknown in every language.
func stateLabelKey(state stacks.ContainerState) string {
	switch state {
	case stacks.StateRunning:
		return "func.state.running"
	case stacks.StateStarting:
		return "func.state.starting"
	case stacks.StateDeploying:
		return "func.state.deploying"
	case stacks.StateUnhealthy:
		return "func.state.unhealthy"
	case stacks.StateDegraded:
		return "func.state.degraded"
	case stacks.StateStopped, stacks.StateExited:
		return "func.state.stopped"
	case stacks.StateRestarting:
		return "func.state.restarting"
	case stacks.StateNotDeployed:
		return "func.state.not_deployed"
	case stacks.StatePaused:
		return "func.state.paused"
	default:
		return "func.state.unknown"
	}
}

// ── The visitor's language, for a page with no household signed in (v0.254.0, R-557 release C) ──
//
// The sign-in, claim and recovery pages are met by someone who has not signed in. They have no
// setting to read, and they must not be able to write the household's: a box's sign-in page is
// reachable by anyone who can reach the box, and changing what the HOUSEHOLD reads from there would
// be an anonymous write to something they own. Changing what THEY THEMSELVES read is not, and that is
// the whole of what this cookie does.
//
// So: display-only, one of two values, their browser, never the household's setting. `langFor` reads
// it only when there is no session (server.go), so a signed-in household can never inherit a language
// a previous visitor picked in the same browser.

// langCookiePath is the anonymous switch's route.
const langCookiePath = "/lang"

// langCookieName is the visitor's display-language cookie.
const langCookieName = "felhom_lang"

// langCookieMaxAge — a year. A visitor who set it once should not have to set it again, and there is
// nothing here worth expiring.
const langCookieMaxAge = 365 * 24 * 60 * 60

// langCookieHandler serves POST /lang: the anonymous language switch.
//
// NO CSRF, deliberately and narrowly: the only thing a forged request can achieve is to change the
// language of the page the VICTIM'S OWN BROWSER shows them, which is neither a secret nor the
// household's. The handler cannot touch settings.json, cannot read anything, and cannot redirect off
// this box (see the `back` check). If it ever gains a second effect, it needs CSRF that day.
func (s *Server) langCookieHandler(w http.ResponseWriter, r *http.Request) {
	_ = r.ParseForm()
	lang := r.FormValue("lang")
	if !i18n.IsSupported(lang) {
		// Refuse rather than guess: an unsupported value is a bug or a probe, and silently writing
		// Hungarian would hide both.
		http.Error(w, "unsupported language", http.StatusBadRequest)
		return
	}
	http.SetCookie(w, &http.Cookie{
		Name:     langCookieName,
		Value:    lang,
		Path:     "/",
		HttpOnly: true, // nothing on the page needs to read it; the server does
		SameSite: http.SameSiteLaxMode,
		Secure:   r.TLS != nil || r.Header.Get("X-Forwarded-Proto") == "https",
		MaxAge:   langCookieMaxAge,
	})
	http.Redirect(w, r, safeBackPath(r.FormValue("back")), http.StatusSeeOther)
}

// safeBackPath keeps an open redirect out of the one handler that takes a destination from an
// anonymous request.
//
// Only a same-origin PATH is allowed. `//evil.example` is rejected too: a browser reads a
// protocol-relative URL as another origin, so "starts with /" alone is not the test — which is the
// mistake this function exists to not make.
func safeBackPath(back string) string {
	if back == "" || !strings.HasPrefix(back, "/") || strings.HasPrefix(back, "//") {
		return "/"
	}
	if strings.Contains(back, "\\") || strings.ContainsAny(back, "\r\n") {
		return "/"
	}
	return back
}

// ── Saved notes (v0.254.0, release C) ──────────────────────────────────────────────────────────
//
// A restore runs in a goroutine with no request and finishes minutes later; its outcome is SAVED and
// read on a page afterwards. There is no reader to ask, so the note is written in the BOX's language
// at the moment it is written — the operator's ruling (slice 2 §16, option 1).
//
// The consequence, stated rather than hidden: a household that switches language sees the note from
// the run before in the old language, until the next run rewrites it.

// boxLang is the language a SAVED note is written in.
func (s *Server) boxLang() string {
	if s.settings == nil {
		return i18n.Default
	}
	return s.settings.GetLanguage()
}

// note renders a saved note in the box's language.
func (s *Server) note(key string, args ...interface{}) string {
	return util.Text(s.boxLang(), key, args...)
}

// noteErr renders an error into a saved note in the box's language: its bundle message when it
// carries one (release B), its own text otherwise.
func (s *Server) noteErr(err error) string { return util.ErrText(s.boxLang(), err) }