package api

import (
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/alchemistkay/guestguard/internal/domain"
	"github.com/alchemistkay/guestguard/internal/storage"
	"github.com/alchemistkay/guestguard/internal/uploads"
)

// brandingHandler owns the per-event customisation row plus image uploads.
// Tier 2 Block D. Reads are viewer+; writes (PUT + image upload) are
// editor+. The role check uses the standard requireRole helper.
type brandingHandler struct {
	logger  *slog.Logger
	events  *storage.EventRepo
	collabs *storage.CollaboratorRepo
	repo    *storage.BrandingRepo
	store   uploads.ImageStore
}

type brandingResponse struct {
	*domain.Branding
	// AllowedFonts is echoed back on every GET so the frontend's picker
	// stays in sync with the server's allowlist without a separate
	// /branding/fonts endpoint.
	AllowedFonts []string `json:"allowed_fonts"`
}

// GET /events/{id}/branding — viewer+. Missing row is rendered as
// "defaults" (200 with nulls) rather than 404 so the frontend doesn't
// need a special-case loader.
func (h *brandingHandler) get(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	eventID, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleViewer); !ok {
		return
	}
	b, err := h.repo.Get(r.Context(), eventID)
	if err != nil && !errors.Is(err, domain.ErrBrandingNotFound) {
		writeError(w, http.StatusInternalServerError, "failed to load branding")
		return
	}
	if b == nil {
		b = &domain.Branding{EventID: eventID}
	}
	writeJSON(w, http.StatusOK, brandingResponse{Branding: b, AllowedFonts: domain.AllowedFonts})
}

type updateBrandingRequest struct {
	// Pointer-typed so omitted JSON keys map to nil = "leave unchanged",
	// while empty-string maps to "clear the field". The repo's Upsert
	// honours this distinction.
	PrimaryColor    *string `json:"primary_color"`
	AccentColor     *string `json:"accent_color"`
	LogoURL         *string `json:"logo_url"`
	CoverImageURL   *string `json:"cover_image_url"`
	FontFamily      *string `json:"font_family"`
	GreetingMessage *string `json:"greeting_message"`
}

// PUT /events/{id}/branding — editor+. Validates each field server-side
// (the allowlist for fonts, hex shape for colours, our-CDN-only for image
// URLs to prevent the host smuggling an `<img>` from an arbitrary origin
// into the guest-facing page).
func (h *brandingHandler) put(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	eventID, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
		return
	}
	var req updateBrandingRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return
	}
	if req.PrimaryColor != nil && !domain.IsValidHexColor(*req.PrimaryColor) {
		writeError(w, http.StatusBadRequest, "primary_color: "+domain.ErrInvalidColor.Error())
		return
	}
	if req.AccentColor != nil && !domain.IsValidHexColor(*req.AccentColor) {
		writeError(w, http.StatusBadRequest, "accent_color: "+domain.ErrInvalidColor.Error())
		return
	}
	if req.FontFamily != nil && !domain.IsAllowedFont(*req.FontFamily) {
		writeError(w, http.StatusBadRequest, domain.ErrUnknownFont.Error())
		return
	}
	if !validImageURL(req.LogoURL) {
		writeError(w, http.StatusBadRequest, "logo_url must be a previously-uploaded image URL")
		return
	}
	if !validImageURL(req.CoverImageURL) {
		writeError(w, http.StatusBadRequest, "cover_image_url must be a previously-uploaded image URL")
		return
	}
	b, err := h.repo.Upsert(r.Context(), storage.UpsertBrandingParams{
		EventID:         eventID,
		PrimaryColor:    req.PrimaryColor,
		AccentColor:     req.AccentColor,
		LogoURL:         req.LogoURL,
		CoverImageURL:   req.CoverImageURL,
		FontFamily:      req.FontFamily,
		GreetingMessage: req.GreetingMessage,
	})
	if err != nil {
		h.logger.Error("upsert branding", "err", err)
		writeError(w, http.StatusInternalServerError, "failed to save branding")
		return
	}
	writeJSON(w, http.StatusOK, brandingResponse{Branding: b, AllowedFonts: domain.AllowedFonts})
}

// validImageURL accepts nil / "" / any URL whose path begins with
// /uploads/ — i.e. the host must have run the bytes through our own
// /uploads/image endpoint. This prevents `logo_url=https://evil/x.png`
// from rendering attacker-controlled content on every RSVP page.
func validImageURL(p *string) bool {
	if p == nil || *p == "" {
		return true
	}
	u, err := url.Parse(*p)
	if err != nil {
		return false
	}
	return strings.HasPrefix(u.Path, "/uploads/")
}

// uploadHandler is split out so the route can sit at /uploads/image without
// being tied to an event id (a single host may upload before deciding
// which of their events to attach the image to).
type uploadHandler struct {
	logger *slog.Logger
	store  uploads.ImageStore
}

type uploadResponse struct {
	URL string `json:"url"`
}

// POST /uploads/image — authed. multipart "file" or raw body. Validates
// size + format, re-encodes to strip EXIF, stores under a random name.
// The response URL is what the host pastes into the branding PUT body.
func (h *uploadHandler) post(w http.ResponseWriter, r *http.Request) {
	if _, ok := hostFromContext(w, r); !ok {
		return
	}

	// Cap the read so a hostile client can't OOM the API even on a slow
	// connection. The +1 lets DecodeAndReencode report "exceeds limit"
	// distinctly from "exactly the limit".
	r.Body = http.MaxBytesReader(w, r.Body, uploads.MaxUploadBytes+1024)

	body, err := readImageUpload(r)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	out, format, err := uploads.DecodeAndReencode(body)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	publicURL, err := h.store.Save(r.Context(), out, format)
	if err != nil {
		h.logger.Error("save upload", "err", err)
		writeError(w, http.StatusInternalServerError, "failed to save upload")
		return
	}
	writeJSON(w, http.StatusCreated, uploadResponse{URL: publicURL})
}

// readImageUpload accepts either a multipart upload (the drag-drop UI's
// shape) or a raw body (curl-friendly).
func readImageUpload(r *http.Request) ([]byte, error) {
	if err := r.ParseMultipartForm(uploads.MaxUploadBytes + 1024); err == nil && r.MultipartForm != nil {
		files := r.MultipartForm.File["file"]
		if len(files) > 0 {
			f, err := files[0].Open()
			if err != nil {
				return nil, err
			}
			defer f.Close()
			return uploads.PeekReader(f)
		}
	}
	defer r.Body.Close()
	return uploads.PeekReader(r.Body)
}

// GET /uploads/{filename} — serves the bytes the LocalFSStore wrote. In
// production a CDN would handle this; in dev the API streams them.
func (h *uploadHandler) serve(w http.ResponseWriter, r *http.Request) {
	name := r.PathValue("filename")
	if name == "" {
		writeError(w, http.StatusBadRequest, "missing filename")
		return
	}
	local, ok := h.store.(*uploads.LocalFSStore)
	if !ok {
		writeError(w, http.StatusNotFound, "upload not found")
		return
	}
	path, err := local.FilePath(name)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid filename")
		return
	}
	f, err := os.Open(path)
	if err != nil {
		writeError(w, http.StatusNotFound, "upload not found")
		return
	}
	defer f.Close()
	if strings.HasSuffix(name, ".png") {
		w.Header().Set("Content-Type", "image/png")
	} else {
		w.Header().Set("Content-Type", "image/jpeg")
	}
	// Branding images don't change once uploaded (host gets a new URL on
	// re-upload), so long cache lifetime is safe.
	w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
	if _, err := io.Copy(w, f); err != nil {
		h.logger.Warn("serve upload", "err", err, "name", name)
	}
}