package api

import (
	"context"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"github.com/google/uuid"

	"github.com/alchemistkay/guestguard/internal/auth"
	"github.com/alchemistkay/guestguard/internal/domain"
	"github.com/alchemistkay/guestguard/internal/natspub"
	"github.com/alchemistkay/guestguard/internal/storage"
)

type accessPublisher interface {
	PublishAccessAttempted(ctx context.Context, evt natspub.AccessAttempted) error
}

type invitationPublisher interface {
	PublishInvitationSend(ctx context.Context, evt natspub.InvitationSend) error
}

type tokenHandler struct {
	logger        *slog.Logger
	guests        *storage.GuestRepo
	tokens        *storage.TokenRepo
	events        *storage.EventRepo
	users         *storage.UserRepo
	accessLogs    *storage.AccessLogRepo
	gen           *auth.Generator
	ttl           time.Duration
	pub           accessPublisher
	invitations   invitationPublisher
	publicBaseURL string
}

type issueTokenResponse struct {
	Token            string        `json:"token"`
	TokenID          uuid.UUID     `json:"token_id"`
	Meta             *domain.Token `json:"meta"`
	InvitationQueued bool          `json:"invitation_queued"`
	InvitationLink   string        `json:"invitation_link"`
}

// POST /events/{id}/guests/{guest_id}/tokens — issue a token for the guest.
func (h *tokenHandler) issue(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	eventID, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	guestID, ok := parseIDParam(w, r, "guest_id")
	if !ok {
		return
	}
	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
	if !ok {
		return
	}

	guest, err := h.guests.Get(r.Context(), guestID)
	if err != nil {
		if errors.Is(err, domain.ErrGuestNotFound) {
			writeError(w, http.StatusNotFound, "guest not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load guest")
		return
	}
	if guest.EventID != eventID {
		writeError(w, http.StatusNotFound, "guest not found in event")
		return
	}

	raw, hash, err := h.gen.Generate()
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to generate token")
		return
	}

	tk, err := h.tokens.Create(r.Context(), storage.CreateTokenParams{
		GuestID:   guestID,
		TokenHash: hash,
		ExpiresAt: time.Now().UTC().Add(h.ttl),
	})
	if err != nil {
		writeError(w, http.StatusConflict, err.Error())
		return
	}

	link := h.invitationLink(raw)
	invitationQueued := h.queueInvitation(r.Context(), event, guest, tk, hostID, raw)

	writeJSON(w, http.StatusCreated, issueTokenResponse{
		Token:            raw,
		TokenID:          tk.ID,
		Meta:             tk,
		InvitationQueued: invitationQueued,
		InvitationLink:   link,
	})
}

// queueInvitation publishes an invitation.send event so the notifier can
// dispatch a branded email. Best-effort: if any step fails we log and
// return false rather than failing the whole token-issue request — the
// host still has the raw URL in the response and can re-trigger sending.
func (h *tokenHandler) queueInvitation(
	ctx context.Context,
	event *domain.Event,
	guest *domain.Guest,
	tk *domain.Token,
	hostID uuid.UUID,
	rawToken string,
) bool {
	if h.invitations == nil {
		return false
	}
	if guest.Email == nil || *guest.Email == "" {
		// Phone-only / nameless guests get no email — host shares the link
		// manually. Show that on the UI so it's not a silent surprise.
		return false
	}
	hostName := ""
	if h.users != nil {
		if host, err := h.users.GetByID(ctx, hostID); err == nil && host != nil {
			hostName = host.Name
		}
	}
	evt := natspub.InvitationSend{
		EventID:    event.ID,
		GuestID:    guest.ID,
		TokenID:    tk.ID,
		GuestName:  guest.Name,
		GuestEmail: *guest.Email,
		HostName:   hostName,
		EventName:  event.Name,
		Venue:      event.Venue,
		EventDate:  event.EventDate,
		Link:       h.invitationLink(rawToken),
		IssuedAt:   time.Now().UTC(),
	}
	if err := h.invitations.PublishInvitationSend(ctx, evt); err != nil {
		h.logger.Warn("publish invitation.send (continuing)", "err", err, "guest_id", guest.ID)
		return false
	}
	return true
}

// invitationLink renders the public RSVP URL the guest clicks from their
// inbox. publicBaseURL is the externally-reachable host (set via
// GG_PUBLIC_BASE_URL); access via /rsvp/<token> is intentional — the
// frontend page rsvp/[token].vue catches the raw token.
func (h *tokenHandler) invitationLink(raw string) string {
	base := h.publicBaseURL
	if base == "" {
		base = "http://localhost:3000"
	}
	return base + "/rsvp/" + raw
}

// bulkIssueRequest is the optional JSON body for the bulk-invite call.
// An empty body (or missing GuestIDs) means "every guest on the event
// who doesn't already have a token".
type bulkIssueRequest struct {
	GuestIDs []string `json:"guest_ids"`
}

type bulkIssueItemError struct {
	GuestID string `json:"guest_id"`
	Reason  string `json:"reason"`
}

// bulkIssueToken is one minted invitation. The raw token is returned so
// the host's UI can offer a "copy link" affordance after a bulk send
// (especially for guests with no email on file) without making another
// round-trip. Same data the per-guest issue endpoint already exposes,
// scoped to the host who owns the event.
type bulkIssueToken struct {
	GuestID          string `json:"guest_id"`
	Token            string `json:"token"`
	InvitationQueued bool   `json:"invitation_queued"`
	InvitationLink   string `json:"invitation_link"`
}

type bulkIssueResponse struct {
	Issued          int                  `json:"issued"`
	Queued          int                  `json:"queued"`
	SkippedExisting int                  `json:"skipped_existing"`
	SkippedNoEmail  int                  `json:"skipped_no_email"`
	Tokens          []bulkIssueToken     `json:"tokens,omitempty"`
	Errors          []bulkIssueItemError `json:"errors,omitempty"`
}

// POST /events/{id}/guests/invitations/bulk — generate tokens for every
// eligible guest (or the explicit subset) on the event and queue an
// invitation email for those with an address. Best-effort: any per-guest
// error is reported in the response and doesn't abort the rest.
func (h *tokenHandler) bulkIssue(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	eventID, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
	if !ok {
		return
	}

	var req bulkIssueRequest
	if r.ContentLength > 0 {
		// Body is optional; only decode when something was actually sent.
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			writeError(w, http.StatusBadRequest, "invalid json")
			return
		}
	}

	var onlyIDs []uuid.UUID
	if len(req.GuestIDs) > 0 {
		onlyIDs = make([]uuid.UUID, 0, len(req.GuestIDs))
		for _, raw := range req.GuestIDs {
			id, err := uuid.Parse(raw)
			if err != nil {
				writeError(w, http.StatusBadRequest, "invalid guest id: "+raw)
				return
			}
			onlyIDs = append(onlyIDs, id)
		}
	}

	guests, err := h.guests.ListGuestsForInvitation(r.Context(), eventID, onlyIDs)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to load guests")
		return
	}

	hostName := ""
	if h.users != nil {
		if host, err := h.users.GetByID(r.Context(), hostID); err == nil && host != nil {
			hostName = host.Name
		}
	}

	resp := bulkIssueResponse{}
	for _, g := range guests {
		if g.HasToken {
			resp.SkippedExisting++
			continue
		}
		raw, hash, err := h.gen.Generate()
		if err != nil {
			resp.Errors = append(resp.Errors, bulkIssueItemError{GuestID: g.ID.String(), Reason: "mint token failed"})
			continue
		}
		tk, err := h.tokens.Create(r.Context(), storage.CreateTokenParams{
			GuestID:   g.ID,
			TokenHash: hash,
			ExpiresAt: time.Now().UTC().Add(h.ttl),
		})
		if err != nil {
			// Likely a race against the unique constraint (someone else
			// issued in parallel) — surface but don't fail the batch.
			resp.Errors = append(resp.Errors, bulkIssueItemError{GuestID: g.ID.String(), Reason: err.Error()})
			continue
		}
		resp.Issued++
		link := h.invitationLink(raw)
		tokenInfo := bulkIssueToken{
			GuestID:        g.ID.String(),
			Token:          raw,
			InvitationLink: link,
		}

		if g.Email == "" {
			resp.SkippedNoEmail++
			resp.Tokens = append(resp.Tokens, tokenInfo)
			continue
		}
		evt := natspub.InvitationSend{
			EventID:    event.ID,
			GuestID:    g.ID,
			TokenID:    tk.ID,
			GuestName:  g.Name,
			GuestEmail: g.Email,
			HostName:   hostName,
			EventName:  event.Name,
			Venue:      event.Venue,
			EventDate:  event.EventDate,
			Link:       h.invitationLink(raw),
			IssuedAt:   time.Now().UTC(),
		}
		if h.invitations == nil {
			resp.Tokens = append(resp.Tokens, tokenInfo)
			continue
		}
		if err := h.invitations.PublishInvitationSend(r.Context(), evt); err != nil {
			h.logger.Warn("publish invitation.send (bulk, continuing)", "err", err, "guest_id", g.ID)
			resp.Errors = append(resp.Errors, bulkIssueItemError{GuestID: g.ID.String(), Reason: "publish failed"})
			resp.Tokens = append(resp.Tokens, tokenInfo)
			continue
		}
		resp.Queued++
		tokenInfo.InvitationQueued = true
		resp.Tokens = append(resp.Tokens, tokenInfo)
	}

	writeJSON(w, http.StatusOK, resp)
}

type rotateTokenRequest struct {
	// SendEmail asks the notifier to re-deliver the invitation. False
	// means "just give me a fresh link" — typical for phone-only guests
	// where the host shares the new URL via SMS.
	SendEmail bool `json:"send_email"`
}

// POST /events/{id}/guests/{guest_id}/tokens/rotate — invalidate the
// guest's existing invitation link and mint a fresh one. Optionally
// re-publishes invitation.send so the notifier re-delivers via email.
// The old URL stops working immediately.
func (h *tokenHandler) rotate(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	eventID, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	guestID, ok := parseIDParam(w, r, "guest_id")
	if !ok {
		return
	}
	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
	if !ok {
		return
	}

	guest, err := h.guests.Get(r.Context(), guestID)
	if err != nil {
		if errors.Is(err, domain.ErrGuestNotFound) {
			writeError(w, http.StatusNotFound, "guest not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load guest")
		return
	}
	if guest.EventID != eventID {
		writeError(w, http.StatusNotFound, "guest not found in event")
		return
	}

	var req rotateTokenRequest
	if r.ContentLength > 0 {
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			writeError(w, http.StatusBadRequest, "invalid json")
			return
		}
	}

	raw, hash, err := h.gen.Generate()
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to generate token")
		return
	}
	tk, err := h.tokens.RotateForGuest(r.Context(), storage.CreateTokenParams{
		GuestID:   guestID,
		TokenHash: hash,
		ExpiresAt: time.Now().UTC().Add(h.ttl),
	})
	if err != nil {
		h.logger.Error("rotate token", "err", err, "guest_id", guestID)
		writeError(w, http.StatusInternalServerError, "failed to rotate token")
		return
	}

	link := h.invitationLink(raw)
	invitationQueued := false
	if req.SendEmail {
		invitationQueued = h.queueInvitation(r.Context(), event, guest, tk, hostID, raw)
	}

	writeJSON(w, http.StatusOK, issueTokenResponse{
		Token:            raw,
		TokenID:          tk.ID,
		Meta:             tk,
		InvitationQueued: invitationQueued,
		InvitationLink:   link,
	})
}

type accessResponse struct {
	Guest      *domain.Guest `json:"guest"`
	Event      *domain.Event `json:"event"`
	Token      *domain.Token `json:"token"`
	AccessLog  uuid.UUID     `json:"access_log_id"`
}

// GET /access/{token} — validate token, log the access attempt, publish to NATS.
func (h *tokenHandler) access(w http.ResponseWriter, r *http.Request) {
	raw := r.PathValue("token")
	if err := auth.ValidateFormat(raw); err != nil {
		writeError(w, http.StatusBadRequest, "malformed token")
		return
	}

	tk, err := h.tokens.GetByHash(r.Context(), auth.HashToken(raw))
	if err != nil {
		if errors.Is(err, domain.ErrTokenNotFound) {
			writeError(w, http.StatusNotFound, "token not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load token")
		return
	}
	if err := tk.IsValid(time.Now().UTC()); err != nil {
		writeError(w, http.StatusGone, err.Error())
		return
	}

	guest, err := h.guests.Get(r.Context(), tk.GuestID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to load guest")
		return
	}
	event, err := h.events.Get(r.Context(), guest.EventID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to load event")
		return
	}

	fingerprint := collectFingerprint(r)
	ip := clientIP(r)

	accessLogID, err := h.accessLogs.Create(r.Context(), storage.CreateAccessLogParams{
		GuestID:     guest.ID,
		TokenID:     tk.ID,
		Fingerprint: fingerprint,
		IPAddress:   ip,
	})
	if err != nil {
		h.logger.Error("create access log", "err", err)
	}

	go func(evt natspub.AccessAttempted) {
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		if err := h.pub.PublishAccessAttempted(ctx, evt); err != nil {
			h.logger.Error("publish access.attempted", "err", err, "guest_id", evt.GuestID)
		}
	}(natspub.AccessAttempted{
		EventID:     event.ID,
		GuestID:     guest.ID,
		TokenID:     tk.ID,
		AccessLogID: accessLogID,
		Fingerprint: fingerprint,
		IPAddress:   ip,
		UserAgent:   r.UserAgent(),
		Referrer:    r.Referer(),
		OccurredAt:  time.Now().UTC(),
	})

	writeJSON(w, http.StatusOK, accessResponse{
		Guest:     guest,
		Event:     event,
		Token:     tk,
		AccessLog: accessLogID,
	})
}

func collectFingerprint(r *http.Request) map[string]any {
	fp := map[string]any{
		"user_agent":      r.UserAgent(),
		"accept_language": r.Header.Get("Accept-Language"),
		"accept_encoding": r.Header.Get("Accept-Encoding"),
	}
	if v := r.Header.Get("Sec-CH-UA-Platform"); v != "" {
		fp["platform"] = v
	}
	if v := r.Header.Get("X-Device-Fingerprint"); v != "" {
		fp["client_fingerprint"] = v
	}
	return fp
}

func clientIP(r *http.Request) string {
	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
		if i := strings.IndexByte(xff, ','); i > 0 {
			return strings.TrimSpace(xff[:i])
		}
		return strings.TrimSpace(xff)
	}
	if xr := r.Header.Get("X-Real-IP"); xr != "" {
		return strings.TrimSpace(xr)
	}
	host := r.RemoteAddr
	if i := strings.LastIndexByte(host, ':'); i > 0 {
		host = host[:i]
	}
	return host
}