package pkg

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

type ExpenseEntry struct {
	ID               int
	Slug             string
	InvoiceDate      time.Time
	InvoiceNumber    string
	Amount           string
	Taxes            map[string]string
	Total            string
	InvoicerName     string
	OriginalFileName string
	Tags             []string
	Status           string
	StatusLabel      string
}

type expensesIndexPage struct {
	Expenses        []*ExpenseEntry
	SumAmount       string
	SumTaxes        map[string]string
	SumTotal        string
	Filters         *expenseFilterForm
	TaxClasses      []string
	ExpenseStatuses map[string]string
}

func IndexExpenses(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	conn := getConn(r)
	locale := getLocale(r)
	company := mustGetCompany(r)
	filters := newExpenseFilterForm(r.Context(), conn, locale, company)
	if err := filters.Parse(r); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	page := &expensesIndexPage{
		Expenses:        mustCollectExpenseEntries(r.Context(), conn, locale, filters),
		ExpenseStatuses: mustCollectExpenseStatuses(r.Context(), conn, locale),
		TaxClasses:      mustCollectTaxClasses(r.Context(), conn, company),
		Filters:         filters,
	}
	page.mustComputeExpensesTotalAmount(r.Context(), conn, filters)
	mustRenderMainTemplate(w, r, "expenses/index.gohtml", page)
}

func mustCollectExpenseEntries(ctx context.Context, conn *Conn, locale *Locale, filters *expenseFilterForm) []*ExpenseEntry {
	where, args := filters.BuildQuery([]interface{}{locale.Language.String()})
	rows := conn.MustQuery(ctx, fmt.Sprintf(`
		select expense_id
		     , expense.slug
		     , invoice_date
		     , invoice_number
		     , to_price(expense.amount, decimal_digits) as amount
		     , array_agg(array[tax_class.name, to_price(coalesce(expense_tax.amount, 0), decimal_digits)]) filter (where tax_class.name is not null)
		     , to_price(expense.amount + coalesce(sum(expense_tax.amount)::integer, 0), decimal_digits) as total
		     , contact.name
		     , coalesce(attachment.original_filename, '')
		     , expense.tags
		     , expense.expense_status
		     , esi18n.name
		from expense
	    left join expense_attachment as attachment using (expense_id)
	    left join expense_tax_amount as expense_tax using (expense_id)
		left join tax using (tax_id)
		left join tax_class using (tax_class_id)
		join contact using (contact_id)
		join expense_status_i18n esi18n on expense.expense_status = esi18n.expense_status and esi18n.lang_tag = $1
		join currency using (currency_code)
		where (%s)
		group by expense_id
		       , expense.slug
		       , invoice_date
		       , invoice_number
		       , expense.amount
		       , decimal_digits
		       , contact.name
		       , attachment.original_filename
		       , expense.tags
		       , expense.expense_status
		       , esi18n.name
		order by invoice_date desc, contact.name, total desc
	`, where), args...)
	defer rows.Close()

	var entries []*ExpenseEntry
	for rows.Next() {
		entry := &ExpenseEntry{
			Taxes: make(map[string]string),
		}
		var taxes [][]string
		if err := rows.Scan(&entry.ID, &entry.Slug, &entry.InvoiceDate, &entry.InvoiceNumber, &entry.Amount, &taxes, &entry.Total, &entry.InvoicerName, &entry.OriginalFileName, &entry.Tags, &entry.Status, &entry.StatusLabel); err != nil {
			panic(err)
		}
		for _, tax := range taxes {
			entry.Taxes[tax[0]] = tax[1]
		}
		entries = append(entries, entry)
	}
	if rows.Err() != nil {
		panic(rows.Err())
	}

	return entries
}

func mustCollectExpenseStatuses(ctx context.Context, conn *Conn, locale *Locale) map[string]string {
	rows := conn.MustQuery(ctx, `
		select expense_status.expense_status
		     , esi18n.name
		from expense_status
		    join expense_status_i18n esi18n using(expense_status)
		where esi18n.lang_tag = $1
		order by expense_status`, locale.Language.String())
	defer rows.Close()

	statuses := map[string]string{}
	for rows.Next() {
		var key, name string
		if err := rows.Scan(&key, &name); err != nil {
			panic(err)
		}
		statuses[key] = name
	}
	if rows.Err() != nil {
		panic(rows.Err())
	}

	return statuses
}

func (page *expensesIndexPage) mustComputeExpensesTotalAmount(ctx context.Context, conn *Conn, filters *expenseFilterForm) {
	where, args := filters.BuildQuery(nil)
	row := conn.QueryRow(ctx, fmt.Sprintf(`
		select to_price(sum(subtotal)::integer, decimal_digits)
		     , to_price(sum(subtotal + taxes)::integer, decimal_digits)
		from (
		    select expense_id
		         , expense.amount as subtotal
		         , coalesce(sum(tax.amount)::integer, 0) as taxes
		         , currency_code
			from expense
	    		left join expense_tax_amount as tax using (expense_id)
			where (%s)	
			group by expense_id
			       , expense.amount
			       , currency_code
		) as expense
		join currency using (currency_code)
		group by decimal_digits
	`, where), args...)
	if notFoundErrorOrPanic(row.Scan(&page.SumAmount, &page.SumTotal)) {
		page.SumAmount = "0.0"
		page.SumTotal = "0.0"
	}

	row = conn.QueryRow(ctx, fmt.Sprintf(`
		select array_agg(array[tax_class_name, to_price(coalesce(tax_amount, 0), decimal_digits)]) filter (where tax_class_name is not null)
		from (
		    select tax_class.name as tax_class_name
		         , coalesce(sum(expense_tax.amount)::integer, 0) as tax_amount
		         , currency_code
		    from expense
	    		left join expense_tax_amount as expense_tax using (expense_id)
				left join tax using (tax_id)
				left join tax_class using (tax_class_id)
			where (%s)
			group by tax_class.name
			       , currency_code
		) as tax
		join currency using (currency_code)
	    group by decimal_digits
	`, where), args...)
	var taxes [][]string
	if notFoundErrorOrPanic(row.Scan(&taxes)) {
		// well, nothing to do
	}
	page.SumTaxes = make(map[string]string)
	for _, tax := range taxes {
		page.SumTaxes[tax[0]] = tax[1]
	}
}

func mustCollectTaxClasses(ctx context.Context, conn *Conn, company *Company) []string {
	rows := conn.MustQuery(ctx, "select name from tax_class where company_id = $1", company.Id)
	defer rows.Close()

	var taxClasses []string
	for rows.Next() {
		var taxClass string
		if err := rows.Scan(&taxClass); err != nil {
			panic(err)
		}
		taxClasses = append(taxClasses, taxClass)
	}
	return taxClasses
}

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

func mustRenderNewExpenseForm(w http.ResponseWriter, r *http.Request, form *expenseForm) {
	locale := getLocale(r)
	form.Invoicer.EmptyLabel = gettext("Select a contact.", locale)
	page := newNewExpensePage(form, r)
	mustRenderMainTemplate(w, r, "expenses/new.gohtml", page)
}

type newExpensePage struct {
	Form  *expenseForm
	Taxes [][]string
	Total string
}

func newNewExpensePage(form *expenseForm, r *http.Request) *newExpensePage {
	page := &newExpensePage{
		Form: form,
	}
	conn := getConn(r)
	company := mustGetCompany(r)
	err := conn.QueryRow(r.Context(), "select taxes, total from compute_new_expense_amount($1, $2, $3)", company.Id, form.Amount, form.Tax.Selected).Scan(&page.Taxes, &page.Total)
	if err != nil {
		panic(err)
	}
	return page
}

func mustRenderEditExpenseForm(w http.ResponseWriter, r *http.Request, slug string, form *expenseForm) {
	page := &editExpensePage{
		newNewExpensePage(form, r),
		slug,
	}
	mustRenderMainTemplate(w, r, "expenses/edit.gohtml", page)
}

type editExpensePage struct {
	*newExpensePage
	Slug string
}

type expenseForm struct {
	locale        *Locale
	company       *Company
	Invoicer      *SelectField
	InvoiceNumber *InputField
	InvoiceDate   *InputField
	Tax           *SelectField
	Amount        *InputField
	File          *FileField
	Tags          *TagsField
}

func newExpenseForm(ctx context.Context, conn *Conn, locale *Locale, company *Company) *expenseForm {
	triggerRecompute := template.HTMLAttr(`data-hx-on="change: this.dispatchEvent(new CustomEvent('recompute', {bubbles: true}))"`)
	return &expenseForm{
		locale:  locale,
		company: company,
		Invoicer: &SelectField{
			Name:     "invoicer",
			Label:    pgettext("input", "Contact", locale),
			Required: true,
			Options:  mustGetContactOptions(ctx, conn, company),
		},
		InvoiceNumber: &InputField{
			Name:  "invoice_number",
			Label: pgettext("input", "Invoice number", locale),
			Type:  "text",
		},
		InvoiceDate: &InputField{
			Name:     "invoice_date",
			Label:    pgettext("input", "Invoice Date", locale),
			Required: true,
			Type:     "date",
		},
		Tax: &SelectField{
			Name:     "tax",
			Label:    pgettext("input", "Taxes", locale),
			Multiple: true,
			Options:  mustGetTaxOptions(ctx, conn, company),
			Attributes: []template.HTMLAttr{
				triggerRecompute,
			},
		},
		Amount: &InputField{
			Name:     "amount",
			Label:    pgettext("input", "Amount", locale),
			Type:     "number",
			Required: true,
			Attributes: []template.HTMLAttr{
				triggerRecompute,
				`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 mustGetExpenseStatusOptions(ctx context.Context, conn *Conn, locale *Locale) []*SelectOption {
	return MustGetOptions(ctx, conn, `
		select expense_status.expense_status
		     , esi18n.name
		from expense_status
		    join expense_status_i18n esi18n using(expense_status)
		where esi18n.lang_tag = $1
		order by expense_status`, locale.Language.String())
}

func (form *expenseForm) Parse(r *http.Request) error {
	if err := r.ParseMultipartForm(form.File.MaxSize); err != nil {
		return err
	}
	form.Invoicer.FillValue(r)
	form.InvoiceNumber.FillValue(r)
	form.InvoiceDate.FillValue(r)
	form.Tax.FillValue(r)
	form.Amount.FillValue(r)
	if err := form.File.FillValue(r); err != nil {
		return err
	}
	form.Tags.FillValue(r)
	return nil
}

func (form *expenseForm) Validate() bool {
	validator := newFormValidator()
	validator.CheckValidSelectOption(form.Invoicer, gettext("Selected contact is not valid.", form.locale))
	validator.CheckValidDate(form.InvoiceDate, gettext("Invoice date must be a valid date.", form.locale))
	validator.CheckValidSelectOption(form.Tax, gettext("Selected tax is not valid.", form.locale))
	validator.CheckAtMostOneOfEachGroup(form.Tax, gettext("You can only select a tax of each class.", form.locale))
	if validator.CheckRequiredInput(form.Amount, gettext("Amount can not be empty.", form.locale)) {
		validator.CheckValidDecimal(form.Amount, form.company.MinCents(), math.MaxFloat64, gettext("Amount must be a number greater than zero.", form.locale))
	}
	return validator.AllOK()
}

func (form *expenseForm) MustFillFromDatabase(ctx context.Context, conn *Conn, slug string) bool {
	if notFoundErrorOrPanic(conn.QueryRow(ctx, `
		select contact_id
		     , invoice_number
		     , invoice_date
		     , to_price(amount, decimal_digits)
		     , array_agg(tax_id) filter ( where tax_id is not null )
		     , tags
		from expense
		left join expense_tax using (expense_id)
		join currency using (currency_code)
		where expense.slug = $1
		group by contact_id
		       , invoice_number
		       , invoice_date
		       , amount
		       , decimal_digits
		       , tags
	`, slug).Scan(
		form.Invoicer,
		form.InvoiceNumber,
		form.InvoiceDate,
		form.Amount,
		form.Tax,
		form.Tags)) {
		return false
	}
	if len(form.Tax.Selected) == 1 && form.Tax.Selected[0] == "" {
		form.Tax.Selected = nil
	}
	return true
}
func HandleUpdateExpense(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	conn := getConn(r)
	locale := getLocale(r)
	company := mustGetCompany(r)
	form := newExpenseForm(r.Context(), conn, locale, company)
	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
	}
	slug := params[0].Value
	if !ValidUuid(slug) {
		http.NotFound(w, r)
		return
	}
	if !form.Validate() {
		w.WriteHeader(http.StatusUnprocessableEntity)
		mustRenderEditExpenseForm(w, r, slug, form)
		return
	}
	taxes := mustSliceAtoi(form.Tax.Selected)
	if found := conn.MustGetText(r.Context(), "", "select edit_expense($1, $2, $3, $4, $5, $6, $7)", slug, form.InvoiceDate, form.Invoicer, form.InvoiceNumber, form.Amount, taxes, form.Tags); found == "" {
		http.NotFound(w, r)
		return
	}
	if len(form.File.Content) > 0 {
		conn.MustQuery(r.Context(), "select attach_to_expense($1, $2, $3, $4)", slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
	}
	htmxRedirect(w, r, companyURI(company, "/expenses"))
}

type expenseFilterForm struct {
	locale        *Locale
	company       *Company
	Contact       *SelectField
	InvoiceNumber *InputField
	FromDate      *InputField
	ToDate        *InputField
	ExpenseStatus *SelectField
	Tags          *TagsField
	TagsCondition *ToggleField
}

func newExpenseFilterForm(ctx context.Context, conn *Conn, locale *Locale, company *Company) *expenseFilterForm {
	return &expenseFilterForm{
		locale:  locale,
		company: company,
		Contact: &SelectField{
			Name:       "contact",
			Label:      pgettext("input", "Contact", locale),
			EmptyLabel: gettext("All contacts", locale),
			Options:    mustGetContactOptions(ctx, conn, company),
		},
		InvoiceNumber: &InputField{
			Name:  "number",
			Label: pgettext("input", "Invoice Number", locale),
			Type:  "search",
		},
		FromDate: &InputField{
			Name:  "from_date",
			Label: pgettext("input", "From Date", locale),
			Type:  "date",
		},
		ToDate: &InputField{
			Name:  "to_date",
			Label: pgettext("input", "To Date", locale),
			Type:  "date",
		},
		Tags: &TagsField{
			Name:  "tags",
			Label: pgettext("input", "Tags", locale),
		},
		ExpenseStatus: &SelectField{
			Name:       "expense_status",
			Label:      pgettext("input", "Expense Status", locale),
			EmptyLabel: gettext("All status", locale),
			Options:    mustGetExpenseStatusOptions(ctx, conn, locale),
		},
		TagsCondition: &ToggleField{
			Name:     "tags_condition",
			Label:    pgettext("input", "Tags Condition", locale),
			Selected: "and",
			FirstOption: &ToggleOption{
				Value:       "and",
				Label:       pgettext("tag condition", "All", locale),
				Description: gettext("Invoices must have all the specified labels.", locale),
			},
			SecondOption: &ToggleOption{
				Value:       "or",
				Label:       pgettext("tag condition", "Any", locale),
				Description: gettext("Invoices must have at least one of the specified labels.", locale),
			},
		},
	}
}

func (form *expenseFilterForm) Parse(r *http.Request) error {
	if err := r.ParseForm(); err != nil {
		return err
	}
	form.Contact.FillValue(r)
	form.InvoiceNumber.FillValue(r)
	form.FromDate.FillValue(r)
	form.ToDate.FillValue(r)
	form.ExpenseStatus.FillValue(r)
	form.Tags.FillValue(r)
	form.TagsCondition.FillValue(r)
	return nil
}

func (form *expenseFilterForm) HasValue() bool {
	return form.Contact.HasValue() ||
		form.InvoiceNumber.HasValue() ||
		form.FromDate.HasValue() ||
		form.ToDate.HasValue() ||
		form.ExpenseStatus.HasValue() ||
		form.Tags.HasValue()
}

func (form *expenseFilterForm) BuildQuery(args []interface{}) (string, []interface{}) {
	var where []string
	appendWhere := func(expression string, value interface{}) {
		args = append(args, value)
		where = append(where, fmt.Sprintf(expression, len(args)))
	}
	maybeAppendWhere := func(expression string, value string, conv func(string) interface{}) {
		if value != "" {
			if conv == nil {
				appendWhere(expression, value)
			} else {
				appendWhere(expression, conv(value))
			}
		}
	}

	appendWhere("expense.company_id = $%d", form.company.Id)
	maybeAppendWhere("contact_id = $%d", form.Contact.String(), func(v string) interface{} {
		customerId, _ := strconv.Atoi(form.Contact.Selected[0])
		return customerId
	})
	maybeAppendWhere("expense.expense_status = $%d", form.ExpenseStatus.String(), nil)
	maybeAppendWhere("invoice_number = $%d", form.InvoiceNumber.String(), nil)
	maybeAppendWhere("invoice_date >= $%d", form.FromDate.String(), nil)
	maybeAppendWhere("invoice_date <= $%d", form.ToDate.String(), nil)
	if len(form.Tags.Tags) > 0 {
		if form.TagsCondition.Selected == "and" {
			appendWhere("expense.tags @> $%d", form.Tags)
		} else {
			appendWhere("expense.tags && $%d", form.Tags)
		}
	}

	return strings.Join(where, ") AND ("), args
}

func ServeEditExpenseTags(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	serveTagsEditForm(w, r, params, "/expenses/", "select tags from expense where slug = $1")
}

func HandleUpdateExpenseTags(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	handleUpdateTags(w, r, params, "/expenses/", "update expense set tags = $1 where slug = $2 returning slug")
}

func ServeExpenseAttachment(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	serveAttachment(w, r, params, `
		select mime_type
		     , content
		from expense
		join expense_attachment using (expense_id)
		where slug = $1
`)
}

func HandleEditExpenseAction(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	slug := params[0].Value
	switch slug {
	case "batch":
		HandleBatchExpenseAction(w, r, params)
	default:
		if !ValidUuid(slug) {
			http.NotFound(w, r)
			return
		}
		actionUri := fmt.Sprintf("/invoices/%s/edit", slug)
		handleExpenseAction(w, r, actionUri, func(w http.ResponseWriter, r *http.Request, form *expenseForm) {
			mustRenderEditExpenseForm(w, r, slug, form)
		})
	}
}

func HandleNewExpenseAction(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
	handleExpenseAction(w, r, "/expenses", mustRenderNewExpenseForm)
}

type renderExpenseFormFunc func(w http.ResponseWriter, r *http.Request, form *expenseForm)

func handleExpenseAction(w http.ResponseWriter, r *http.Request, action string, renderForm renderExpenseFormFunc) {
	locale := getLocale(r)
	conn := getConn(r)
	company := mustGetCompany(r)
	form := newExpenseForm(r.Context(), conn, locale, company)
	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
	}
	actionField := r.Form.Get("action")
	switch actionField {
	case "update":
		// Nothing else to do
		w.WriteHeader(http.StatusOK)
		renderForm(w, r, form)
	case "add":
		if !form.Validate() {
			w.WriteHeader(http.StatusUnprocessableEntity)
			renderForm(w, r, form)
			return
		}
		taxes := mustSliceAtoi(form.Tax.Selected)
		slug := conn.MustGetText(r.Context(), "", "select add_expense($1, $2, $3, $4, $5, $6, $7)", company.Id, form.InvoiceDate, form.Invoicer, form.InvoiceNumber, form.Amount, taxes, form.Tags)
		if len(form.File.Content) > 0 {
			conn.MustQuery(r.Context(), "select attach_to_expense($1, $2, $3, $4)", slug, form.File.OriginalFileName, form.File.ContentType, form.File.Content)
		}
		htmxRedirect(w, r, companyURI(company, action))
	default:
		http.Error(w, gettext("Invalid action", locale), http.StatusBadRequest)
	}
}

func HandleBatchExpenseAction(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if err := verifyCsrfTokenValid(r); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}
	locale := getLocale(r)
	switch r.Form.Get("action") {
	case "export":
		conn := getConn(r)
		company := getCompany(r)
		filters := newExpenseFilterForm(r.Context(), conn, locale, company)
		if err := filters.Parse(r); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		entries := mustCollectExpenseEntries(r.Context(), conn, locale, filters)
		vatin := mustCollectExpenseEntriesVATIN(r.Context(), conn, entries)
		taxes := mustCollectExpenseEntriesTaxes(r.Context(), conn, entries)
		taxColumns := mustCollectTaxColumns(r.Context(), conn, company)
		ods := mustWriteExpensesOds(entries, vatin, taxes, taxColumns, locale, company)
		writeOdsResponse(w, ods, gettext("expenses.ods", locale))
	default:
		http.Error(w, gettext("Invalid action", locale), http.StatusBadRequest)
	}
}

func mustCollectExpenseEntriesTaxes(ctx context.Context, conn *Conn, entries []*ExpenseEntry) map[int]taxMap {
	ids := mustMakeIDArray(entries, func(entry *ExpenseEntry) int {
		return entry.ID
	})
	return mustMakeTaxMap(ctx, conn, ids, `
		select expense_id
		     , tax_id
		     , to_price(tax.amount, decimal_digits)
		from expense_tax_amount as tax
		    join expense using (expense_id)
			join currency using (currency_code)
		where expense_id = any ($1)	
	`)
}

func mustCollectExpenseEntriesVATIN(ctx context.Context, conn *Conn, entries []*ExpenseEntry) map[int]string {
	ids := mustMakeIDArray(entries, func(entry *ExpenseEntry) int {
		return entry.ID
	})
	return mustMakeVATINMap(ctx, conn, ids, `
		select expense_id
		     , vatin::text
		from contact_tax_details as tax
		    join expense using (contact_id)
		where expense_id = any ($1)	
	`)
}