numerus/pkg/payments.go

package pkg

import (
	"context"
	"fmt"
	"github.com/julienschmidt/httprouter"
	"html/template"
	"math"
	"net/http"
	"time"
)

const (
	PaymentTypePayment    = "P"
	PaymentTypeCollection = "C"
)

func servePaymentIndex(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	conn := getConn(r)
	company := mustGetCompany(r)
	locale := getLocale(r)

	page := NewPaymentIndexPage(r.Context(), conn, company, locale)
	page.MustRender(w, r)
}

func serveExpensePaymentIndex(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	expenseSlug := params[0].Value
	conn := getConn(r)
	company := mustGetCompany(r)
	locale := getLocale(r)

	expense := mustGetPaymentExpense(r.Context(), conn, expenseSlug)
	if expense == nil {
		http.NotFound(w, r)
		return
	}
	page := NewPaymentIndexPageForExpense(r.Context(), conn, company, locale, expense)
	page.MustRender(w, r)
}

func serveInvoiceCollectionIndex(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	invoiceSlug := params[0].Value
	conn := getConn(r)
	company := mustGetCompany(r)
	locale := getLocale(r)

	invoice := mustGetCollectionInvoice(r.Context(), conn, invoiceSlug)
	if invoice == nil {
		http.NotFound(w, r)
		return
	}
	page := NewPaymentIndexPageForInvoice(r.Context(), conn, company, locale, invoice)
	page.MustRender(w, r)
}

type PaymentIndexPage struct {
	Payments []*PaymentEntry
	BaseURI  string
	Expense  *PaymentExpense
	Invoice  *CollectionInvoice
}

func NewPaymentIndexPage(ctx context.Context, conn *Conn, company *Company, locale *Locale) *PaymentIndexPage {
	return &PaymentIndexPage{
		Payments: mustCollectPaymentEntries(ctx, conn, company, locale, "", 0),
		BaseURI:  companyURI(company, "/payments"),
	}
}

func NewPaymentIndexPageForExpense(ctx context.Context, conn *Conn, company *Company, locale *Locale, expense *PaymentExpense) *PaymentIndexPage {
	return &PaymentIndexPage{
		Payments: mustCollectPaymentEntries(ctx, conn, company, locale, PaymentTypePayment, expense.Id),
		BaseURI:  expense.BaseURI(company),
		Expense:  expense,
	}
}

func NewPaymentIndexPageForInvoice(ctx context.Context, conn *Conn, company *Company, locale *Locale, invoice *CollectionInvoice) *PaymentIndexPage {
	return &PaymentIndexPage{
		Payments: mustCollectPaymentEntries(ctx, conn, company, locale, PaymentTypeCollection, invoice.Id),
		BaseURI:  invoice.BaseURI(company),
		Invoice:  invoice,
	}
}

func (page *PaymentIndexPage) MustRender(w http.ResponseWriter, r *http.Request) {
	mustRenderMainTemplate(w, r, "payments/index.gohtml", page)
}

type PaymentExpense struct {
	Id            int
	Slug          string
	InvoiceNumber string
}

func mustGetPaymentExpense(ctx context.Context, conn *Conn, expenseSlug string) *PaymentExpense {
	if !ValidUuid(expenseSlug) {
		return nil
	}

	expense := &PaymentExpense{}
	if notFoundErrorOrPanic(conn.QueryRow(ctx, `
		select expense_id
		     , slug
		     , coalesce(nullif(invoice_number, ''), slug::text)
		from expense
		where expense.slug = $1
	`, expenseSlug).Scan(
		&expense.Id,
		&expense.Slug,
		&expense.InvoiceNumber)) {
		return nil
	}
	return expense
}

func (expense *PaymentExpense) BaseURI(company *Company) string {
	return companyURI(company, "/expenses/"+expense.Slug+"/payments")
}

func (expense *PaymentExpense) calcRemainingPaymentAmount(ctx context.Context, conn *Conn) string {
	return conn.MustGetText(ctx, "", `
		select to_price(greatest(0, expense.amount + tax_amount - paid_amount)::int, decimal_digits)
		from (
		    select coalesce (sum(payment.amount), 0) as paid_amount
			from expense_payment
			join payment using (payment_id)
			where expense_payment.expense_id = $1
		) as payment
		cross join (
		    select coalesce (sum(amount), 0) as tax_amount
			from expense_tax_amount
			where expense_id = $1
		) as tax
		cross join (
		    select amount, decimal_digits
			from expense
			join currency using (currency_code)
			where expense_id = $1
		) as expense
`, expense.Id)
}

type CollectionInvoice struct {
	Id            int
	Slug          string
	InvoiceNumber string
}

func mustGetCollectionInvoice(ctx context.Context, conn *Conn, invoiceSlug string) *CollectionInvoice {
	if !ValidUuid(invoiceSlug) {
		return nil
	}

	invoice := &CollectionInvoice{}
	if notFoundErrorOrPanic(conn.QueryRow(ctx, `
		select invoice_id
		     , slug
		     , invoice_number
		from invoice
		where invoice.slug = $1
	`, invoiceSlug).Scan(
		&invoice.Id,
		&invoice.Slug,
		&invoice.InvoiceNumber)) {
		return nil
	}
	return invoice
}

func (invoice *CollectionInvoice) BaseURI(company *Company) string {
	return companyURI(company, "/invoices/"+invoice.Slug+"/collections")
}

func (invoice *CollectionInvoice) calcRemainingPaymentAmount(ctx context.Context, conn *Conn) string {
	return conn.MustGetText(ctx, "", `
		select to_price(greatest(0, invoice_amount.total - collected_amount)::int, decimal_digits)
		from (
		    select coalesce (sum(collection.amount), 0) as collected_amount
			from invoice_collection
			join collection using (collection_id)
			where invoice_collection.invoice_id = $1
		) as collection
		cross join (
            select total
			     , decimal_digits
			from invoice_amount
			join invoice using (invoice_id)
			join currency using (currency_code)
			where invoice_id = $1
		) as invoice_amount
`, invoice.Id)
}

type PaymentEntry struct {
	ID               int
	Type             string
	Slug             string
	PaymentDate      time.Time
	Description      string
	DocumentSlug     string
	InvoiceNumber    string
	Total            string
	OriginalFileName string
	Tags             []string
	Status           string
	StatusLabel      string
}

func mustCollectPaymentEntries(ctx context.Context, conn *Conn, company *Company, locale *Locale, paymentType string, documentId int) []*PaymentEntry {
	rows := conn.MustQuery(ctx, `
			select $5 as type
			     , payment_id
			     , payment.slug
			     , payment_date
			     , description
			     , to_price(payment.amount, decimal_digits) as total
			     , payment.tags
			     , payment.payment_status
			     , psi18n.name
			     , coalesce(attachment.original_filename, '')
			     , coalesce(expense.slug::text, '')
			     , coalesce(expense.invoice_number, '')
			from payment
			join payment_status_i18n psi18n on payment.payment_status = psi18n.payment_status and psi18n.lang_tag = $1
			join currency using (currency_code)
			left join payment_attachment as attachment using (payment_id)
			left join expense_payment using (payment_id)
			left join expense using (expense_id)
			where payment.company_id = $2
			  and ($3 = '' or ($3 = $5 and expense_id = $4))
		union all
			select $6 as type
			     , collection_id
			     , collection.slug
			     , collection_date as payment_date
			     , description
			     , to_price(collection.amount, decimal_digits) as total
			     , collection.tags
			     , collection.payment_status
			     , psi18n.name
			     , coalesce(attachment.original_filename, '')
			     , coalesce(invoice.slug::text, '')
			     , coalesce(invoice.invoice_number, '')
			from collection
			join payment_status_i18n psi18n on collection.payment_status = psi18n.payment_status and psi18n.lang_tag = $1
			join currency using (currency_code)
			left join collection_attachment as attachment using (collection_id)
			left join invoice_collection using (collection_id)
			left join invoice using (invoice_id)
			where collection.company_id = $2
			  and ($3 = '' or ($3 = $6 and invoice_id = $4))
		order by payment_date desc, total desc
	`, locale.Language, company.Id, paymentType, documentId, PaymentTypePayment, PaymentTypeCollection)
	defer rows.Close()

	var entries []*PaymentEntry
	for rows.Next() {
		entry := &PaymentEntry{}
		if err := rows.Scan(&entry.Type, &entry.ID, &entry.Slug, &entry.PaymentDate, &entry.Description, &entry.Total, &entry.Tags, &entry.Status, &entry.StatusLabel, &entry.OriginalFileName, &entry.DocumentSlug, &entry.InvoiceNumber); err != nil {
			panic(err)
		}
		entries = append(entries, entry)
	}
	if rows.Err() != nil {
		panic(rows.Err())
	}

	return entries
}

func servePaymentForm(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	form := newPaymentForm(r.Context(), conn, locale, company)
	slug := params[0].Value
	if slug == "new" {
		form.PaymentDate.Val = time.Now().Format("2006-01-02")
		form.MustRender(w, r)
		return
	}
	if !ValidUuid(slug) {
		http.NotFound(w, r)
		return
	}
	if !form.MustFillFromDatabase(r.Context(), conn, slug) {
		http.NotFound(w, r)
		return
	}
	form.MustRender(w, r)
}

func serveExpensePaymentForm(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	expenseSlug := params[0].Value
	expense := mustGetPaymentExpense(r.Context(), conn, expenseSlug)
	if expense == nil {
		http.NotFound(w, r)
		return
	}
	form := newPaymentFormForExpense(r.Context(), conn, locale, company, expense)
	paymentSlug := params[1].Value
	if paymentSlug == "new" {
		form.PaymentDate.Val = time.Now().Format("2006-01-02")
		form.Description.Val = fmt.Sprintf(gettext("Payment of %s", locale), form.Expense.InvoiceNumber)
		form.Amount.Val = form.Expense.calcRemainingPaymentAmount(r.Context(), conn)
		form.MustRender(w, r)
		return
	}
	if !ValidUuid(paymentSlug) {
		http.NotFound(w, r)
		return
	}
	if !form.MustFillFromDatabase(r.Context(), conn, paymentSlug) {
		http.NotFound(w, r)
		return
	}
	form.MustRender(w, r)
}

func serveInvoiceCollectionForm(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	invoiceSlug := params[0].Value
	invoice := mustGetCollectionInvoice(r.Context(), conn, invoiceSlug)
	if invoice == nil {
		http.NotFound(w, r)
		return
	}
	form := newPaymentFormForInvoice(r.Context(), conn, locale, company, invoice)
	paymentSlug := params[1].Value
	if paymentSlug == "new" {
		form.PaymentDate.Val = time.Now().Format("2006-01-02")
		form.Description.Val = fmt.Sprintf(gettext("Collection of %s", locale), form.Invoice.InvoiceNumber)
		form.Amount.Val = form.Invoice.calcRemainingPaymentAmount(r.Context(), conn)
		form.MustRender(w, r)
		return
	}
	if !ValidUuid(paymentSlug) {
		http.NotFound(w, r)
		return
	}
	if !form.MustFillFromDatabase(r.Context(), conn, paymentSlug) {
		http.NotFound(w, r)
		return
	}
	form.MustRender(w, r)
}

type PaymentForm struct {
	locale         *Locale
	company        *Company
	Slug           string
	BaseURI        string
	Expense        *PaymentExpense
	Invoice        *CollectionInvoice
	Type           *SelectField
	Description    *InputField
	PaymentDate    *InputField
	PaymentAccount *SelectField
	Amount         *InputField
	File           *FileField
	Tags           *TagsField
}

func newPaymentForm(ctx context.Context, conn *Conn, locale *Locale, company *Company) *PaymentForm {
	return &PaymentForm{
		locale:  locale,
		company: company,
		BaseURI: companyURI(company, "/payments"),
		Type: &SelectField{
			Name:     "type",
			Label:    pgettext("input", "Type", locale),
			Required: true,
			Options: []*SelectOption{
				{Value: PaymentTypePayment, Label: pgettext("payment type", "Payment", locale)},
				{Value: PaymentTypeCollection, Label: pgettext("payment type", "Collection", locale)},
			},
		},
		Description: &InputField{
			Name:     "description",
			Label:    pgettext("input", "Description", locale),
			Required: true,
			Type:     "text",
		},
		PaymentDate: &InputField{
			Name:     "payment_date",
			Label:    pgettext("input", "Payment Date", locale),
			Required: true,
			Type:     "date",
		},
		PaymentAccount: &SelectField{
			Name:     "payment_account",
			Label:    pgettext("input", "Account", locale),
			Required: true,
			Options:  MustGetOptions(ctx, conn, "select payment_account_id::text, name from payment_account where company_id = $1 order by name", company.Id),
		},
		Amount: &InputField{
			Name:     "amount",
			Label:    pgettext("input", "Amount", locale),
			Type:     "number",
			Required: true,
			Attributes: []template.HTMLAttr{
				`min="0"`,
				template.HTMLAttr(fmt.Sprintf(`step="%v"`, company.MinCents())),
			},
		},
		File: &FileField{
			Name:    "file",
			Label:   pgettext("input", "File", locale),
			MaxSize: 1 << 20,
		},
		Tags: &TagsField{
			Name:  "tags",
			Label: pgettext("input", "Tags", locale),
		},
	}
}

func newPaymentFormForExpense(ctx context.Context, conn *Conn, locale *Locale, company *Company, expense *PaymentExpense) *PaymentForm {
	form := newPaymentForm(ctx, conn, locale, company)
	form.Type.Selected = []string{PaymentTypePayment}
	form.BaseURI = expense.BaseURI(company)
	form.Expense = expense
	return form
}

func newPaymentFormForInvoice(ctx context.Context, conn *Conn, locale *Locale, company *Company, invoice *CollectionInvoice) *PaymentForm {
	form := newPaymentForm(ctx, conn, locale, company)
	form.Type.Selected = []string{PaymentTypeCollection}
	form.BaseURI = invoice.BaseURI(company)
	form.Invoice = invoice
	return form
}

func (f *PaymentForm) MustRender(w http.ResponseWriter, r *http.Request) {
	if f.Slug == "" {
		f.Type.EmptyLabel = gettext("Select a type.", f.locale)
		f.PaymentAccount.EmptyLabel = gettext("Select an account.", f.locale)
		mustRenderMainTemplate(w, r, "payments/new.gohtml", f)
	} else {
		mustRenderMainTemplate(w, r, "payments/edit.gohtml", f)
	}
}

func (f *PaymentForm) MustFillFromDatabase(ctx context.Context, conn *Conn, slug string) bool {
	selectedType := f.Type.Selected
	selectedPaymentAccount := f.PaymentAccount.Selected
	f.PaymentAccount.Clear()
	if notFoundErrorOrPanic(conn.QueryRow(ctx, `
			select $2 as type
			     , description
			     , payment_date
			     , payment_account_id::text
			     , to_price(amount, decimal_digits)
			     , tags
			from payment
			join currency using (currency_code)
			where payment.slug = $1
		union all
			select $3 as type
			     , description
			     , collection_date
			     , payment_account_id::text
			     , to_price(amount, decimal_digits)
			     , tags
			from collection
			join currency using (currency_code)
			where collection.slug = $1
	`, slug, PaymentTypePayment, PaymentTypeCollection).Scan(
		f.Type,
		f.Description,
		f.PaymentDate,
		f.PaymentAccount,
		f.Amount,
		f.Tags)) {
		f.Type.Selected = selectedType
		f.PaymentAccount.Selected = selectedPaymentAccount
		return false
	}
	f.Slug = slug
	return true
}

func (f *PaymentForm) Parse(r *http.Request) error {
	if err := r.ParseMultipartForm(f.File.MaxSize); err != nil {
		return err
	}
	f.Type.FillValue(r)
	f.Description.FillValue(r)
	f.PaymentDate.FillValue(r)
	f.PaymentAccount.FillValue(r)
	f.Amount.FillValue(r)
	if err := f.File.FillValue(r); err != nil {
		return err
	}
	f.Tags.FillValue(r)
	return nil
}

func (f *PaymentForm) Validate() bool {
	validator := newFormValidator()
	validator.CheckValidSelectOption(f.Type, gettext("Selected payment type is not valid.", f.locale))
	validator.CheckRequiredInput(f.Description, gettext("Description can not be empty.", f.locale))
	validator.CheckValidSelectOption(f.PaymentAccount, gettext("Selected payment account is not valid.", f.locale))
	validator.CheckValidDate(f.PaymentDate, gettext("Payment date must be a valid date.", f.locale))
	if validator.CheckRequiredInput(f.Amount, gettext("Amount can not be empty.", f.locale)) {
		validator.CheckValidDecimal(f.Amount, f.company.MinCents(), math.MaxFloat64, gettext("Amount must be a number greater than zero.", f.locale))
	}
	return validator.AllOK()
}

func handleAddPayment(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	form := newPaymentForm(r.Context(), conn, locale, company)
	handleAddPaymentForm(w, r, conn, company, form)
}

func handleAddPaymentForm(w http.ResponseWriter, r *http.Request, conn *Conn, company *Company, form *PaymentForm) {
	if err := form.Parse(r); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if err := verifyCsrfTokenValid(r); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}
	if !form.Validate() {
		w.WriteHeader(http.StatusUnprocessableEntity)
		form.MustRender(w, r)
		return
	}
	var documentId any
	if form.Type.String() == PaymentTypePayment {
		if form.Expense != nil {
			documentId = form.Expense.Id
		}
		slug := conn.MustGetText(r.Context(), "", "select add_payment($1, $2, $3, $4, $5, $6, $7)", company.Id, documentId, form.PaymentDate, form.PaymentAccount, form.Description, form.Amount, form.Tags)
		if len(form.File.Content) > 0 {
			conn.MustQuery(r.Context(), "select attach_to_payment($1, $2, $3, $4)", slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
		}
	} else {
		if form.Invoice != nil {
			documentId = form.Invoice.Id
		}
		slug := conn.MustGetText(r.Context(), "", "select add_collection($1, $2, $3, $4, $5, $6, $7)", company.Id, documentId, form.PaymentDate, form.PaymentAccount, form.Description, form.Amount, form.Tags)
		if len(form.File.Content) > 0 {
			conn.MustQuery(r.Context(), "select attach_to_collection($1, $2, $3, $4)", slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
		}
	}
	htmxRedirect(w, r, form.BaseURI)
}

func handleAddExpensePayment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	expenseSlug := params[0].Value
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	expense := mustGetPaymentExpense(r.Context(), conn, expenseSlug)
	if expense == nil {
		http.NotFound(w, r)
		return
	}

	form := newPaymentFormForExpense(r.Context(), conn, locale, company, expense)
	handleAddPaymentForm(w, r, conn, company, form)
}

func handleAddInvoiceCollection(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	invoiceSlug := params[0].Value
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	invoice := mustGetCollectionInvoice(r.Context(), conn, invoiceSlug)
	if invoice == nil {
		http.NotFound(w, r)
		return
	}

	form := newPaymentFormForInvoice(r.Context(), conn, locale, company, invoice)
	handleAddPaymentForm(w, r, conn, company, form)
}

func handleEditPayment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	locale := getLocale(r)
	company := mustGetCompany(r)
	form := newPaymentForm(r.Context(), conn, locale, company)
	form.Slug = params[0].Value
	handleEditPaymentForm(w, r, conn, form)
}

func handleEditPaymentForm(w http.ResponseWriter, r *http.Request, conn *Conn, form *PaymentForm) {
	if !ValidUuid(form.Slug) {
		http.NotFound(w, r)
		return
	}
	if err := form.Parse(r); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if err := verifyCsrfTokenValid(r); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}
	if !form.Validate() {
		w.WriteHeader(http.StatusUnprocessableEntity)
		form.MustRender(w, r)
		return
	}
	if form.Type.String() == PaymentTypePayment {
		if found := conn.MustGetText(r.Context(), "", "select edit_payment($1, $2, $3, $4, $5, $6)", form.Slug, form.PaymentDate, form.PaymentAccount, form.Description, form.Amount, form.Tags); found == "" {
			http.NotFound(w, r)
			return
		}
		if len(form.File.Content) > 0 {
			conn.MustQuery(r.Context(), "select attach_to_payment($1, $2, $3, $4)", form.Slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
		}
	} else {
		if found := conn.MustGetText(r.Context(), "", "select edit_collection($1, $2, $3, $4, $5, $6)", form.Slug, form.PaymentDate, form.PaymentAccount, form.Description, form.Amount, form.Tags); found == "" {
			http.NotFound(w, r)
			return
		}
		if len(form.File.Content) > 0 {
			conn.MustQuery(r.Context(), "select attach_to_collection($1, $2, $3, $4)", form.Slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
		}
	}
	htmxRedirect(w, r, form.BaseURI)
}

func handleEditExpensePayment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	locale := getLocale(r)
	company := mustGetCompany(r)
	expenseSlug := params[0].Value
	expense := mustGetPaymentExpense(r.Context(), conn, expenseSlug)
	if expense == nil {
		http.NotFound(w, r)
		return
	}

	form := newPaymentFormForExpense(r.Context(), conn, locale, company, expense)
	form.Slug = params[1].Value
	handleEditPaymentForm(w, r, conn, form)
}

func handleEditInvoiceCollection(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	locale := getLocale(r)
	company := mustGetCompany(r)
	invoiceSlug := params[0].Value
	invoice := mustGetCollectionInvoice(r.Context(), conn, invoiceSlug)
	if invoice == nil {
		http.NotFound(w, r)
		return
	}

	form := newPaymentFormForInvoice(r.Context(), conn, locale, company, invoice)
	form.Slug = params[1].Value
	handleEditPaymentForm(w, r, conn, form)
}

func handleRemovePayment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	company := mustGetCompany(r)
	removePayment(w, r, params[0].Value, companyURI(company, "/payments"))
}

func removePayment(w http.ResponseWriter, r *http.Request, slug string, backURI string) {
	if !ValidUuid(slug) {
		http.NotFound(w, r)
		return
	}
	if err := verifyCsrfTokenValid(r); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}

	conn := getConn(r)
	conn.MustExec(r.Context(), "select remove_payment($1), remove_collection($1)", slug)

	htmxRedirect(w, r, backURI)
}

func handleRemoveExpensePayment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	expenseSlug := params[0].Value
	expense := mustGetPaymentExpense(r.Context(), conn, expenseSlug)
	if expense == nil {
		http.NotFound(w, r)
		return
	}

	company := mustGetCompany(r)
	removePayment(w, r, params[1].Value, expense.BaseURI(company))
}

func handleRemoveInvoiceCollection(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	invoiceSlug := params[0].Value
	invoice := mustGetCollectionInvoice(r.Context(), conn, invoiceSlug)
	if invoice == nil {
		http.NotFound(w, r)
		return
	}

	company := mustGetCompany(r)
	removePayment(w, r, params[1].Value, invoice.BaseURI(company))
}

func servePaymentAttachment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	serveAttachment(w, r, params, `
			select mime_type
			     , content
			from payment
			join payment_attachment using (payment_id)
			where slug = $1
		union all
			select mime_type
			     , content
			from collection
			join collection_attachment using (collection_id)
			where slug = $1
`)
}

func servePaymentTagsEditForm(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	serveTagsEditForm(w, r, params, "/payments/", "select tags from payment where slug = $1 union all select tags from collection where slug = $1")
}

func handleUpdatePaymentTags(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	handleUpdateTags(w, r, params, "/payments/", "with p as (update payment set tags = $1 where slug = $2 returning slug), c as (update collection set tags = $1 where slug = $2 returning slug) select p.slug from p union all select c.slug from c")
}