package web

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"git.arnef.de/arnef/nidus/internal/store"
	"git.arnef.de/arnef/nidus/internal/web/templates"
	vcard "github.com/emersion/go-vcard"
)

// contactIDRe validates a contact's object ID as it appears in a URL path
// segment: a filename like "3f9a2b8c1d4e5f60ab12cd34ef56ab78.vcf" produced
// by newContactID.
var contactIDRe = regexp.MustCompile(`^[a-zA-Z0-9_-]{1,128}\.vcf$`)

// brokenMultiTypeRe matches a malformed TYPE parameter value seen in some
// exported vCards (e.g. from certain Nextcloud Contacts versions): a
// comma-separated pair of quoted strings where the quote characters
// themselves were mistakenly emitted as RFC 6868 caret-encoded quotes
// (^') rather than actually delimiting the two values, e.g.
// `TYPE="WORK^'","^'VOICE"`. go-vcard's decoder can't parse this as a
// valid parameter and silently drops the whole field (no error), which is
// why phone numbers using this pattern vanish on import. The intended
// value is simply the two types joined by a comma, so it's rewritten to
// the unambiguous, valid form TYPE=WORK,VOICE before decoding.
var brokenMultiTypeRe = regexp.MustCompile(`TYPE="([A-Za-z0-9]+)\^'","\^'([A-Za-z0-9]+)"`)

// sanitizeVCardBytes repairs known-malformed-but-recoverable syntax
// produced by some real-world vCard exporters before handing the data to
// go-vcard, so fields that would otherwise be silently dropped survive
// import.
func sanitizeVCardBytes(data []byte) []byte {
	return brokenMultiTypeRe.ReplaceAll(data, []byte(`TYPE=$1,$2`))
}

// newContactID generates a random filename for a new contact object,
// mirroring the "<id>.vcf" convention used by the CardDAV backend
// (internal/carddav).
func newContactID() (string, error) {
	buf := make([]byte, 16)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf) + ".vcf", nil
}

// ownsAddressBook reports whether book is one of username's own address
// books (never a book shared with them by another user — the web contacts
// UI only manages a user's own books, consistent with the file browser and
// dashboard resource cards).
func (s *Server) ownsAddressBook(username, book string) (bool, error) {
	if !resourceNameRe.MatchString(book) {
		return false, nil
	}
	names, err := s.dbase.ListAddressBooks(username)
	if err != nil {
		return false, err
	}
	for _, n := range names {
		if n == book {
			return true, nil
		}
	}
	return false, nil
}

func (s *Server) handleContactsHome(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		w.Header().Set("Allow", "GET")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	names, err := s.dbase.ListAddressBooks(username)
	if err != nil {
		s.logger.Error("listing address books", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	sort.Strings(names)

	var books []templates.AddressBookSummary
	for _, name := range names {
		ids, err := s.store.ListObjects(username, "card-"+name)
		if err != nil {
			s.logger.Warn("listing contacts", "book", name, "error", err)
		}
		books = append(books, templates.AddressBookSummary{Name: name, Count: len(ids)})
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ContactsHome(username, books).Render(context.Background(), w)
}

func (s *Server) handleContactsList(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		w.Header().Set("Allow", "GET")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok {
		http.NotFound(w, r)
		return
	}

	ids, err := s.store.ListObjects(username, "card-"+book)
	if err != nil {
		s.logger.Error("listing contacts", "book", book, "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	var contacts []templates.ContactSummary
	for _, id := range ids {
		data, err := s.store.GetObject(username, "card-"+book, id)
		if err != nil {
			continue
		}
		contacts = append(contacts, summarizeCard(id, data))
	}
	sort.Slice(contacts, func(i, j int) bool {
		return strings.ToLower(contacts[i].FullName) < strings.ToLower(contacts[j].FullName)
	})

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ContactsList(username, book, contacts).Render(context.Background(), w)
}

func summarizeCard(id string, data []byte) templates.ContactSummary {
	dec := vcard.NewDecoder(bytes.NewReader(data))
	card, err := dec.Decode()
	if err != nil {
		return templates.ContactSummary{ID: id, FullName: id}
	}
	fullName := card.PreferredValue(vcard.FieldFormattedName)
	if fullName == "" {
		fullName = id
	}
	return templates.ContactSummary{
		ID:           id,
		FullName:     fullName,
		Organization: card.PreferredValue(vcard.FieldOrganization),
		Phone:        card.PreferredValue(vcard.FieldTelephone),
		Email:        card.PreferredValue(vcard.FieldEmail),
		PhotoDataURL: photoDataURL(card),
	}
}

func (s *Server) handleContactNew(w http.ResponseWriter, r *http.Request) {
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok {
		http.NotFound(w, r)
		return
	}

	switch r.Method {
	case http.MethodGet:
		form := templates.ContactFormData{
			Book:      book,
			Phones:    ensureAtLeastOne[templates.LabeledValue](nil),
			Emails:    ensureAtLeastOne[templates.LabeledValue](nil),
			Addresses: ensureAtLeastOne[templates.AddressValue](nil),
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_ = templates.ContactForm(username, form, "").Render(context.Background(), w)
	case http.MethodPost:
		s.saveContactFromForm(w, r, username, book, "")
	default:
		w.Header().Set("Allow", "GET, POST")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func (s *Server) handleContactEdit(w http.ResponseWriter, r *http.Request) {
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	id := r.PathValue("id")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok || !contactIDRe.MatchString(id) {
		http.NotFound(w, r)
		return
	}

	switch r.Method {
	case http.MethodGet:
		data, err := s.store.GetObject(username, "card-"+book, id)
		if err != nil {
			http.NotFound(w, r)
			return
		}
		form, err := contactFormFromCard(book, id, data)
		if err != nil {
			s.logger.Error("decoding contact", "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_ = templates.ContactForm(username, form, "").Render(context.Background(), w)
	case http.MethodPost:
		s.saveContactFromForm(w, r, username, book, id)
	default:
		w.Header().Set("Allow", "GET, POST")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}

// contactFormInput holds the parsed, validated-ish values submitted by the
// contact form, before they're translated into vCard fields.
type contactFormInput struct {
	Forename     string
	Surname      string
	Organization string
	Note         string
	Birthday     string
	Phones       []templates.LabeledValue
	Emails       []templates.LabeledValue
	Addresses    []templates.AddressValue
	PhotoData    []byte
	PhotoMime    string
	RemovePhoto  bool
}

// ensureAtLeastOne returns items unchanged if non-empty, or a single
// zero-value element otherwise, so the repeatable-row UI always renders at
// least one row per section.
func ensureAtLeastOne[T any](items []T) []T {
	if len(items) > 0 {
		return items
	}
	var zero T
	return []T{zero}
}

func formValue(values []string, i int) string {
	if i < 0 || i >= len(values) {
		return ""
	}
	return values[i]
}

// parseContactForm reads the multipart contact form (required because it
// may include a photo upload) into a contactFormInput, zipping the
// parallel type/value fields for phones, emails, and addresses by index.
func parseContactForm(r *http.Request) (contactFormInput, error) {
	if err := r.ParseMultipartForm(maxUploadMemory); err != nil {
		return contactFormInput{}, err
	}

	var form map[string][]string
	if r.MultipartForm != nil {
		form = r.MultipartForm.Value
	}
	get := func(key string) []string { return form[key] }

	in := contactFormInput{
		Forename:     strings.TrimSpace(formValue(get("forename"), 0)),
		Surname:      strings.TrimSpace(formValue(get("surname"), 0)),
		Organization: strings.TrimSpace(formValue(get("organization"), 0)),
		Note:         strings.TrimSpace(formValue(get("note"), 0)),
		Birthday:     strings.TrimSpace(formValue(get("birthday"), 0)),
		RemovePhoto:  formValue(get("remove_photo"), 0) != "",
	}

	phoneTypes, phoneValues := get("phone_type"), get("phone_value")
	for i, v := range phoneValues {
		v = strings.TrimSpace(v)
		if v == "" {
			continue
		}
		in.Phones = append(in.Phones, templates.LabeledValue{Type: formValue(phoneTypes, i), Value: v})
	}

	emailTypes, emailValues := get("email_type"), get("email_value")
	for i, v := range emailValues {
		v = strings.TrimSpace(v)
		if v == "" {
			continue
		}
		in.Emails = append(in.Emails, templates.LabeledValue{Type: formValue(emailTypes, i), Value: v})
	}

	addrTypes := get("address_type")
	streets := get("address_street")
	cities := get("address_city")
	postalCodes := get("address_postal_code")
	regions := get("address_region")
	countries := get("address_country")
	for i := range streets {
		street := strings.TrimSpace(formValue(streets, i))
		city := strings.TrimSpace(formValue(cities, i))
		postalCode := strings.TrimSpace(formValue(postalCodes, i))
		region := strings.TrimSpace(formValue(regions, i))
		country := strings.TrimSpace(formValue(countries, i))
		if street == "" && city == "" && postalCode == "" && region == "" && country == "" {
			continue
		}
		in.Addresses = append(in.Addresses, templates.AddressValue{
			Type: formValue(addrTypes, i), Street: street, City: city,
			Region: region, PostalCode: postalCode, Country: country,
		})
	}

	if r.MultipartForm != nil {
		if files := r.MultipartForm.File["photo"]; len(files) > 0 {
			fh := files[0]
			f, err := fh.Open()
			if err == nil {
				defer f.Close()
				data, err := io.ReadAll(io.LimitReader(f, 10<<20))
				if err == nil && len(data) > 0 {
					in.PhotoData = data
					in.PhotoMime = fh.Header.Get("Content-Type")
				}
			}
		}
	}

	return in, nil
}

// saveContactFromForm handles both contact creation (id == "") and
// editing (id preserves the existing contact's ID and any vCard fields
// not set from the form, such as UID and an unchanged photo).
func (s *Server) saveContactFromForm(w http.ResponseWriter, r *http.Request, username, book, id string) {
	in, err := parseContactForm(r)
	if err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}

	if in.Forename == "" && in.Surname == "" {
		form := templates.ContactFormData{
			Book:         book,
			ID:           id,
			Forename:     in.Forename,
			Surname:      in.Surname,
			Organization: in.Organization,
			Note:         in.Note,
			Birthday:     in.Birthday,
			Phones:       ensureAtLeastOne(in.Phones),
			Emails:       ensureAtLeastOne(in.Emails),
			Addresses:    ensureAtLeastOne(in.Addresses),
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_ = templates.ContactForm(username, form, "Name is required").Render(context.Background(), w)
		return
	}

	var uid, existingPhoto string
	if id == "" {
		newID, err := newContactID()
		if err != nil {
			s.logger.Error("generating contact id", "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		id = newID
		uid = strings.TrimSuffix(id, ".vcf")
	} else {
		data, err := s.store.GetObject(username, "card-"+book, id)
		if err != nil {
			http.NotFound(w, r)
			return
		}
		dec := vcard.NewDecoder(bytes.NewReader(data))
		existing, err := dec.Decode()
		if err != nil {
			s.logger.Error("decoding existing contact", "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		uid = existing.Value(vcard.FieldUID)
		existingPhoto = existing.Value(vcard.FieldPhoto)
	}

	card := buildCard(uid, in, existingPhoto)
	if err := s.saveCard(username, book, id, card); err != nil {
		s.logger.Error("saving contact", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, "/web/contacts/"+book, http.StatusSeeOther)
}

// buildCard builds a fresh vCard from the submitted form input. uid and
// existingPhoto (both optional) are carried over from an existing contact
// when editing, so re-saving doesn't drop its identity or a previously
// uploaded photo the user didn't change.
func buildCard(uid string, in contactFormInput, existingPhoto string) vcard.Card {
	card := make(vcard.Card)
	card.SetValue(vcard.FieldVersion, "4.0")
	if uid != "" {
		card.SetValue(vcard.FieldUID, uid)
	}
	if fn := strings.TrimSpace(in.Forename + " " + in.Surname); fn != "" {
		card.SetValue(vcard.FieldFormattedName, fn)
	}
	name := &vcard.Name{GivenName: in.Forename, FamilyName: in.Surname}
	card.SetName(name)

	if in.Organization != "" {
		card.SetValue(vcard.FieldOrganization, in.Organization)
	}
	if in.Note != "" {
		card.SetValue(vcard.FieldNote, in.Note)
	}
	if in.Birthday != "" {
		card.SetValue(vcard.FieldBirthday, in.Birthday)
	}

	for _, p := range in.Phones {
		f := &vcard.Field{Value: p.Value}
		if p.Type != "" {
			f.Params = vcard.Params{vcard.ParamType: {p.Type}}
		}
		card.Add(vcard.FieldTelephone, f)
	}
	for _, e := range in.Emails {
		f := &vcard.Field{Value: e.Value}
		if e.Type != "" {
			f.Params = vcard.Params{vcard.ParamType: {e.Type}}
		}
		card.Add(vcard.FieldEmail, f)
	}
	for _, a := range in.Addresses {
		addr := &vcard.Address{
			Field:         &vcard.Field{},
			StreetAddress: a.Street,
			Locality:      a.City,
			Region:        a.Region,
			PostalCode:    a.PostalCode,
			Country:       a.Country,
		}
		if a.Type != "" {
			addr.Params = vcard.Params{vcard.ParamType: {a.Type}}
		}
		card.AddAddress(addr)
	}

	switch {
	case in.RemovePhoto:
		// Leave PHOTO unset.
	case len(in.PhotoData) > 0:
		mime := in.PhotoMime
		if mime == "" {
			mime = http.DetectContentType(in.PhotoData)
		}
		encoded := base64.StdEncoding.EncodeToString(in.PhotoData)
		card.SetValue(vcard.FieldPhoto, "data:"+mime+";base64,"+encoded)
	case existingPhoto != "":
		card.SetValue(vcard.FieldPhoto, existingPhoto)
	}

	return card
}

func (s *Server) saveCard(username, book, id string, card vcard.Card) error {
	var buf strings.Builder
	enc := vcard.NewEncoder(&buf)
	if err := enc.Encode(card); err != nil {
		return fmt.Errorf("encoding vcard: %w", err)
	}
	return s.store.PutObject(username, "card-"+book, id, []byte(buf.String()))
}

// photoDataURL returns card's PHOTO value if it's already a data: URI
// (how we always store newly uploaded photos), so it can be used directly
// as an <img src>. Legacy vCards may store photos differently (e.g. a bare
// base64 blob with an ENCODING param, or a remote http(s) URL); those are
// preserved on save but not rendered as a preview.
func photoDataURL(card vcard.Card) string {
	v := card.Value(vcard.FieldPhoto)
	if strings.HasPrefix(v, "data:") {
		return v
	}
	return ""
}

func labeledValues(card vcard.Card, key string) []templates.LabeledValue {
	fields := card[key]
	out := make([]templates.LabeledValue, 0, len(fields))
	for _, f := range fields {
		typ := ""
		if f.Params != nil {
			typ = f.Params.Get(vcard.ParamType)
		}
		out = append(out, templates.LabeledValue{Type: typ, Value: f.Value})
	}
	return out
}

func addressValues(card vcard.Card) []templates.AddressValue {
	addrs := card.Addresses()
	out := make([]templates.AddressValue, 0, len(addrs))
	for _, a := range addrs {
		typ := ""
		if a.Params != nil {
			typ = a.Params.Get(vcard.ParamType)
		}
		out = append(out, templates.AddressValue{
			Type: typ, Street: a.StreetAddress, City: a.Locality,
			Region: a.Region, PostalCode: a.PostalCode, Country: a.Country,
		})
	}
	return out
}

func contactFormFromCard(book, id string, data []byte) (templates.ContactFormData, error) {
	dec := vcard.NewDecoder(bytes.NewReader(data))
	card, err := dec.Decode()
	if err != nil {
		return templates.ContactFormData{}, err
	}
	var forename, surname string
	if n := card.Name(); n != nil && (n.GivenName != "" || n.FamilyName != "") {
		forename, surname = n.GivenName, n.FamilyName
	} else if fn := strings.TrimSpace(card.PreferredValue(vcard.FieldFormattedName)); fn != "" {
		parts := strings.Fields(fn)
		if len(parts) > 1 {
			forename, surname = parts[0], strings.Join(parts[1:], " ")
		} else {
			forename = parts[0]
		}
	}
	return templates.ContactFormData{
		Book:         book,
		ID:           id,
		Forename:     forename,
		Surname:      surname,
		Organization: card.PreferredValue(vcard.FieldOrganization),
		Note:         card.PreferredValue(vcard.FieldNote),
		Birthday:     card.PreferredValue(vcard.FieldBirthday),
		PhotoDataURL: photoDataURL(card),
		Phones:       ensureAtLeastOne(labeledValues(card, vcard.FieldTelephone)),
		Emails:       ensureAtLeastOne(labeledValues(card, vcard.FieldEmail)),
		Addresses:    ensureAtLeastOne(addressValues(card)),
	}, nil
}

func (s *Server) handleContactDelete(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.Header().Set("Allow", "POST")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	id := r.PathValue("id")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok || !contactIDRe.MatchString(id) {
		http.NotFound(w, r)
		return
	}
	if err := s.store.DeleteObject(username, "card-"+book, id); err != nil && !errors.Is(err, store.ErrNotFound) {
		s.logger.Error("deleting contact", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/web/contacts/"+book, http.StatusSeeOther)
}

func (s *Server) handleContactExportOne(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		w.Header().Set("Allow", "GET")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	id := r.PathValue("id")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok || !contactIDRe.MatchString(id) {
		http.NotFound(w, r)
		return
	}
	data, err := s.store.GetObject(username, "card-"+book, id)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/vcard; charset=utf-8")
	w.Header().Set("Content-Disposition", `attachment; filename="`+id+`"`)
	_, _ = w.Write(data)
}

func (s *Server) handleContactExportAll(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		w.Header().Set("Allow", "GET")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok {
		http.NotFound(w, r)
		return
	}

	ids, err := s.store.ListObjects(username, "card-"+book)
	if err != nil {
		s.logger.Error("listing contacts", "book", book, "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "text/vcard; charset=utf-8")
	w.Header().Set("Content-Disposition", `attachment; filename="`+book+`.vcf"`)
	for _, id := range ids {
		data, err := s.store.GetObject(username, "card-"+book, id)
		if err != nil {
			continue
		}
		// Each stored object is already a complete, self-contained vCard
		// (ending in "END:VCARD"), so concatenating their raw bytes
		// produces a valid multi-card .vcf file.
		_, _ = w.Write(data)
	}
}

func (s *Server) handleContactImport(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.Header().Set("Allow", "POST")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	book := r.PathValue("book")
	ok, err := s.ownsAddressBook(username, book)
	if err != nil {
		s.logger.Error("checking address book ownership", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok {
		http.NotFound(w, r)
		return
	}

	if err := r.ParseMultipartForm(maxUploadMemory); err != nil {
		http.Error(w, "invalid upload", http.StatusBadRequest)
		return
	}
	file, _, err := r.FormFile("file")
	if err != nil {
		http.Error(w, "no file provided", http.StatusBadRequest)
		return
	}
	defer file.Close()

	body, err := io.ReadAll(file)
	if err != nil {
		s.logger.Error("reading import file", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	body = sanitizeVCardBytes(body)

	dec := vcard.NewDecoder(bytes.NewReader(body))
	imported := 0
	for {
		card, err := dec.Decode()
		if errors.Is(err, io.EOF) {
			break
		}
		if err != nil {
			s.logger.Warn("stopping vcard import on parse error", "book", book, "error", err)
			break
		}
		id, err := newContactID()
		if err != nil {
			s.logger.Error("generating contact id", "error", err)
			continue
		}
		if err := s.saveCard(username, book, id, card); err != nil {
			s.logger.Warn("saving imported contact", "error", err)
			continue
		}
		imported++
	}

	http.Redirect(w, r, "/web/contacts/"+book+"?imported="+strconv.Itoa(imported), http.StatusSeeOther)
}