// Package tui is the terminal interface: browse accounts, tag transactions,
// mark transfers by hand, and see where the money went.
package tui

import (
	"fmt"
	"sort"
	"strings"

	"github.com/charmbracelet/bubbles/spinner"
	"github.com/charmbracelet/bubbles/table"
	"github.com/charmbracelet/bubbles/textinput"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"

	"git.petrovv.com/nikola/money/internal/config"
	"git.petrovv.com/nikola/money/internal/glob"
	"git.petrovv.com/nikola/money/internal/importer"
	"git.petrovv.com/nikola/money/internal/model"
	"git.petrovv.com/nikola/money/internal/report"
	"git.petrovv.com/nikola/money/internal/rules"
	"git.petrovv.com/nikola/money/internal/store"
)

type view int

const (
	viewAccounts view = iota
	viewTxns
	viewReport
	viewRules
	viewRuleList

	viewCount = 5
)

// confirmation is a pending destructive action awaiting a y/n answer.
// Deleting rewrites a file the user maintains by hand, so it is never done on
// a single keypress.
type confirmation int

const (
	confirmNone confirmation = iota
	confirmDeleteRule
	confirmPruneRules
)

// input is the modal state: the transaction list is read-only until the user
// starts typing a tag or a search.
type input int

const (
	inputNone input = iota
	inputTag
	inputSearch
)

// Model is the root Bubble Tea model.
type Model struct {
	root     string
	db       *store.DB
	accounts []*config.Account
	engine   *rules.Engine

	view  view
	input input

	accountTable table.Model
	txnTable     table.Model
	reportTable  table.Model
	text         textinput.Model
	spinner      spinner.Model

	// importing is set while an import runs in the background, so the UI keeps
	// redrawing instead of freezing on a slow PDF.
	importing bool

	txns []model.Transaction // rows currently shown in txnTable

	// Rule builder: three inputs on the left, and a live preview on the right
	// of which untagged descriptions the glob would catch.
	ruleGlob    textinput.Model
	ruleAccount textinput.Model
	ruleTag     textinput.Model
	ruleFocus   int // which of the three inputs has the cursor
	ruleTable   table.Model
	ruleReturn  view // the view to go back to on esc
	untagged    []descGroup
	ruleMatches int // untagged descriptions the current glob matches

	// Rule list: every rule with the number of transactions it actually
	// claims, so dead ones can be found and removed.
	ruleListTable table.Model
	ruleUsage     []int
	confirm       confirmation

	filter       store.Filter
	onlyUntagged bool

	status string
	err    error
	width  int
	height int
}

var (
	titleStyle  = lipgloss.NewStyle().Bold(true).Padding(0, 1)
	statusStyle = lipgloss.NewStyle().Faint(true).Padding(0, 1)
	errStyle    = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("9")).Padding(0, 1)
	helpStyle   = lipgloss.NewStyle().Faint(true).Padding(0, 1)
	emptyStyle  = lipgloss.NewStyle().Padding(1, 2)

	labelStyle        = lipgloss.NewStyle().Faint(true)
	focusedLabelStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("62"))
	// Both boxes are pinned to the same width: a focused input renders one
	// extra cell for the cursor, which would otherwise shift the border as
	// the cursor moves between fields.
	boxStyle = lipgloss.NewStyle().Border(lipgloss.RoundedBorder()).
			BorderForeground(lipgloss.Color("240")).Padding(0, 1).Width(ruleInputWidth + 2)
	focusedBoxStyle = lipgloss.NewStyle().Border(lipgloss.RoundedBorder()).
			BorderForeground(lipgloss.Color("62")).Padding(0, 1).Width(ruleInputWidth + 2)
	hintStyle       = lipgloss.NewStyle().Faint(true).PaddingLeft(2)
	matchCountStyle = lipgloss.NewStyle().Bold(true).PaddingLeft(2)
	ruleFormStyle   = lipgloss.NewStyle().Width(ruleFormWidth)
)

// Run starts the interface.
func Run(root string, db *store.DB, accounts []*config.Account, engine *rules.Engine) error {
	m := New(root, db, accounts, engine)
	if err := m.reload(); err != nil {
		return err
	}
	_, err := tea.NewProgram(m, tea.WithAltScreen()).Run()
	return err
}

// New builds the root model.
func New(root string, db *store.DB, accounts []*config.Account, engine *rules.Engine) *Model {
	ti := textinput.New()
	ti.Prompt = ""
	ti.CharLimit = 64

	newInput := func(placeholder string) textinput.Model {
		in := textinput.New()
		in.Prompt = ""
		in.CharLimit = 80
		in.Width = ruleInputWidth
		in.Placeholder = placeholder
		return in
	}

	sp := spinner.New()
	sp.Spinner = spinner.Dot
	sp.Style = lipgloss.NewStyle().Foreground(lipgloss.Color("62"))

	styles := table.DefaultStyles()
	styles.Header = styles.Header.Bold(true)
	styles.Selected = styles.Selected.Bold(true).Foreground(lipgloss.Color("15")).Background(lipgloss.Color("62"))

	newTable := func(cols []table.Column) table.Model {
		return table.New(table.WithColumns(cols), table.WithFocused(true),
			table.WithHeight(15), table.WithStyles(styles))
	}

	return &Model{
		root:     root,
		db:       db,
		accounts: accounts,
		engine:   engine,
		view:     viewAccounts,
		text:     ti,
		spinner:  sp,
		accountTable: newTable([]table.Column{
			{Title: "Account", Width: 20},
			{Title: "Balance", Width: 14},
			{Title: "Cur", Width: 4},
			{Title: "Txns", Width: 6},
		}),
		txnTable: newTable([]table.Column{
			{Title: "Date", Width: 10},
			{Title: "Account", Width: 12},
			{Title: "Amount", Width: 12},
			{Title: "Tag", Width: 14},
			{Title: "T", Width: 1},
			{Title: "Description", Width: 40},
		}),
		ruleGlob:    newInput("*LIDL*"),
		ruleAccount: newInput("blank = every account"),
		ruleTag:     newInput("groceries"),
		ruleTable: newTable([]table.Column{
			{Title: " ", Width: 1},
			{Title: "Untagged description", Width: 44},
			{Title: "N", Width: 4},
		}),
		ruleListTable: newTable([]table.Column{
			{Title: "#", Width: 3},
			{Title: " ", Width: 1},
			{Title: "Pattern", Width: 34},
			{Title: "Account", Width: 12},
			{Title: "Tag", Width: 14},
			{Title: "T", Width: 1},
			{Title: "Txns", Width: 6},
		}),
		reportTable: newTable([]table.Column{
			{Title: "Tag", Width: 20},
			{Title: "Cur", Width: 4},
			{Title: "Out", Width: 14},
			{Title: "In", Width: 14},
			{Title: "Net", Width: 14},
			{Title: "N", Width: 5},
		}),
	}
}

// Init implements tea.Model.
func (m *Model) Init() tea.Cmd { return nil }

// reload refreshes whichever view is active from the index.
func (m *Model) reload() error {
	if err := m.reloadAccounts(); err != nil {
		return err
	}
	return m.reloadTxns()
}

func (m *Model) reloadAccounts() error {
	accounts, err := m.db.Accounts()
	if err != nil {
		return err
	}
	rows := make([]table.Row, 0, len(accounts))
	for _, a := range accounts {
		bal, err := m.db.Balance(a.ID)
		if err != nil {
			return err
		}
		n, err := m.db.Count(a.ID)
		if err != nil {
			return err
		}
		rows = append(rows, table.Row{
			a.Name, model.FormatMinor(bal, a.MinorDigits), a.Currency, fmt.Sprintf("%d", n),
		})
	}
	m.accountTable.SetRows(rows)
	return nil
}

func (m *Model) reloadTxns() error {
	f := m.filter
	f.Untagged = m.onlyUntagged
	txns, err := m.db.Transactions(f)
	if err != nil {
		return err
	}
	m.txns = txns

	rows := make([]table.Row, 0, len(txns))
	for _, t := range txns {
		transfer := ""
		if t.IsTransfer() {
			transfer = "T"
		}
		tag := t.Tag()
		if tag != "" && t.ManualTag != "" {
			tag += "*" // marks a manual override
		}
		rows = append(rows, table.Row{
			t.Date, t.AccountSlug, t.FormatAmount(), tag, transfer, t.Description,
		})
	}
	// Keep the cursor in range after the row count shrinks (e.g. tagging the
	// last untagged row while the untagged filter is on).
	cursor := m.txnTable.Cursor()
	m.txnTable.SetRows(rows)
	if cursor >= len(rows) {
		cursor = len(rows) - 1
	}
	if cursor < 0 {
		cursor = 0
	}
	m.txnTable.SetCursor(cursor)

	m.reloadReport(txns)
	return nil
}

func (m *Model) reloadReport(txns []model.Transaction) {
	rows := report.ByTag(txns)
	out := make([]table.Row, 0, len(rows)+2)
	for _, r := range rows {
		out = append(out, table.Row{
			r.Tag, r.Currency,
			model.FormatMinor(r.Out, r.Digits),
			model.FormatMinor(r.In, r.Digits),
			model.FormatMinor(r.Net(), r.Digits),
			fmt.Sprintf("%d", r.Count),
		})
	}
	for _, c := range report.Totals(rows) {
		out = append(out, table.Row{
			"TOTAL", c.Currency,
			model.FormatMinor(c.Out, c.Digits),
			model.FormatMinor(c.In, c.Digits),
			model.FormatMinor(c.Net(), c.Digits),
			"",
		})
	}
	m.reportTable.SetRows(out)
}

// ruleFormWidth is the width of the rule builder's left-hand form, and
// ruleInputWidth the editable area inside its boxes. The form must stay wider
// than a box plus its border, padding and the block cursor, or lipgloss wraps
// the border and the panel falls apart.
const (
	ruleInputWidth = 26
	ruleFormWidth  = ruleInputWidth + 12
)

// descGroup is one distinct untagged description and how often it occurs.
// Grouping matters: a statement holds the same payee dozens of times, and a
// rule is written against the description, not against individual rows.
type descGroup struct {
	Description string
	Accounts    map[string]bool
	Count       int
}

// reloadUntagged rebuilds the alphabetical list of untagged descriptions that
// the rule builder previews against.
func (m *Model) reloadUntagged() error {
	txns, err := m.db.Transactions(store.Filter{Untagged: true})
	if err != nil {
		return err
	}

	byDesc := map[string]*descGroup{}
	for _, t := range txns {
		key := model.NormalizeDescription(t.Description)
		g, ok := byDesc[key]
		if !ok {
			g = &descGroup{Description: t.Description, Accounts: map[string]bool{}}
			byDesc[key] = g
		}
		g.Accounts[t.AccountSlug] = true
		g.Count++
	}

	m.untagged = make([]descGroup, 0, len(byDesc))
	for _, g := range byDesc {
		m.untagged = append(m.untagged, *g)
	}
	sort.Slice(m.untagged, func(i, j int) bool {
		a := model.NormalizeDescription(m.untagged[i].Description)
		b := model.NormalizeDescription(m.untagged[j].Description)
		if a != b {
			return a < b
		}
		return m.untagged[i].Description < m.untagged[j].Description
	})

	m.refreshRulePreview()
	return nil
}

// refreshRulePreview re-marks the preview against whatever is typed right now.
// It runs on every keystroke, so the glob is checked against descriptions only,
// never against the database.
func (m *Model) refreshRulePreview() {
	var (
		pattern = strings.TrimSpace(m.ruleGlob.Value())
		account = strings.TrimSpace(m.ruleAccount.Value())
		rows    = make([]table.Row, 0, len(m.untagged))
	)
	m.ruleMatches = 0

	for _, g := range m.untagged {
		// An account filter narrows the preview the same way the saved rule
		// will narrow its matching.
		if account != "" && !g.Accounts[account] {
			continue
		}
		marker := " "
		if pattern != "" && glob.Match(pattern, model.NormalizeDescription(g.Description)) {
			marker = "▸"
			m.ruleMatches++
		}
		rows = append(rows, table.Row{marker, g.Description, fmt.Sprintf("%d", g.Count)})
	}

	cursor := m.ruleTable.Cursor()
	m.ruleTable.SetRows(rows)
	if cursor >= len(rows) {
		cursor = len(rows) - 1
	}
	if cursor < 0 {
		cursor = 0
	}
	m.ruleTable.SetCursor(cursor)
}

// saveRule appends the composed rule to rules.toml, reloads the engine and
// retags, so the effect is visible immediately.
func (m *Model) saveRule() error {
	r := config.Rule{
		Match:   strings.TrimSpace(m.ruleGlob.Value()),
		Account: strings.TrimSpace(m.ruleAccount.Value()),
		Tag:     strings.TrimSpace(m.ruleTag.Value()),
	}
	if r.Match == "" {
		return fmt.Errorf("enter a glob first, e.g. *LIDL*")
	}
	if r.Tag == "" {
		return fmt.Errorf("enter a tag to apply")
	}
	if r.Account != "" && !m.knownAccount(r.Account) {
		return fmt.Errorf("no account called %q; leave it blank to apply to every account", r.Account)
	}

	if err := config.AppendRule(m.root, r); err != nil {
		return err
	}

	// Re-read the file rather than appending to the in-memory engine, so what
	// runs is exactly what is now on disk.
	loaded, err := config.LoadRules(m.root)
	if err != nil {
		return fmt.Errorf("rule saved, but re-reading rules.toml failed: %w", err)
	}
	m.engine = rules.New(loaded)

	n, err := m.engine.Retag(m.db)
	if err != nil {
		return err
	}

	m.status = fmt.Sprintf("saved rule %s → %s, %d transactions retagged", r.Match, r.Tag, n)
	m.ruleGlob.SetValue("")
	m.ruleTag.SetValue("")
	m.setRuleFocus(0)
	return m.reload()
}

func (m *Model) knownAccount(slug string) bool {
	for _, a := range m.accounts {
		if a.Slug == slug {
			return true
		}
	}
	// Fall back to the index, so accounts work even when the caller passed no
	// config (as the tests do).
	accounts, err := m.db.Accounts()
	if err != nil {
		return false
	}
	for _, a := range accounts {
		if a.Slug == slug {
			return true
		}
	}
	return false
}

// reloadRuleList counts, for every rule, how many transactions it actually
// claims. A rule can match nothing because no description fits it, or because
// an earlier rule already took everything it would have caught; both show up
// here as a zero.
func (m *Model) reloadRuleList() error {
	txns, err := m.db.Transactions(store.Filter{})
	if err != nil {
		return err
	}
	rs := m.engine.Rules()
	m.ruleUsage = m.engine.Usage(txns)

	rows := make([]table.Row, 0, len(rs))
	for i, r := range rs {
		marker := " "
		if m.ruleUsage[i] == 0 {
			marker = "✗"
		}
		transfer := ""
		if r.Transfer {
			transfer = "T"
		}
		account := r.Account
		if account == "" {
			account = "(all)"
		}
		rows = append(rows, table.Row{
			fmt.Sprintf("%d", i+1), marker, rulePattern(r), account, r.Tag, transfer,
			fmt.Sprintf("%d", m.ruleUsage[i]),
		})
	}

	cursor := m.ruleListTable.Cursor()
	m.ruleListTable.SetRows(rows)
	if cursor >= len(rows) {
		cursor = len(rows) - 1
	}
	if cursor < 0 {
		cursor = 0
	}
	m.ruleListTable.SetCursor(cursor)
	return nil
}

// rulePattern renders whichever patterns a rule sets, labelled so a
// counterparty or type rule is not mistaken for a description one.
func rulePattern(r config.Rule) string {
	var parts []string
	if r.Match != "" {
		parts = append(parts, r.Match)
	}
	if r.Counterparty != "" {
		parts = append(parts, "counterparty:"+r.Counterparty)
	}
	if r.Type != "" {
		parts = append(parts, "type:"+r.Type)
	}
	return strings.Join(parts, " + ")
}

// unusedRules lists the positions of every rule claiming no transactions.
func (m *Model) unusedRules() []int {
	var out []int
	for i, n := range m.ruleUsage {
		if n == 0 {
			out = append(out, i)
		}
	}
	return out
}

// deleteRules removes rules from rules.toml, then reloads and retags so the
// counts on screen reflect the new file.
func (m *Model) deleteRules(positions []int) error {
	n, err := config.DeleteRules(m.root, positions)
	if err != nil {
		return err
	}

	loaded, err := config.LoadRules(m.root)
	if err != nil {
		return fmt.Errorf("rules deleted, but re-reading rules.toml failed: %w", err)
	}
	m.engine = rules.New(loaded)

	retagged, err := m.engine.Retag(m.db)
	if err != nil {
		return err
	}
	m.status = fmt.Sprintf("deleted %d rule(s), %d transactions retagged", n, retagged)

	if err := m.reload(); err != nil {
		return err
	}
	return m.reloadRuleList()
}

// openRuleList switches to the rule list, remembering where to return to.
func (m *Model) openRuleList() {
	if m.view != viewRuleList {
		m.ruleReturn = m.view
	}
	m.view = viewRuleList
	m.confirm = confirmNone
	if err := m.reloadRuleList(); err != nil {
		m.err = err
	}
}

// updateRuleList drives the rule list, including the delete confirmations.
func (m *Model) updateRuleList(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	if m.confirm != confirmNone {
		pending := m.confirm
		m.confirm = confirmNone
		if msg.String() != "y" {
			m.status = "cancelled"
			return m, nil
		}
		m.err = nil
		switch pending {
		case confirmDeleteRule:
			if i := m.ruleListTable.Cursor(); i >= 0 && i < len(m.ruleUsage) {
				if err := m.deleteRules([]int{i}); err != nil {
					m.err = err
				}
			}
		case confirmPruneRules:
			if err := m.deleteRules(m.unusedRules()); err != nil {
				m.err = err
			}
		}
		return m, nil
	}

	switch msg.String() {
	case "q", "ctrl+c":
		return m, tea.Quit
	case "esc":
		m.view = m.ruleReturn
		return m, nil
	case "1":
		m.view = viewAccounts
		return m, nil
	case "2":
		m.view = viewTxns
		return m, nil
	case "3":
		m.view = viewReport
		return m, nil
	case "4":
		return m, m.openRuleBuilder()

	case "d":
		i := m.ruleListTable.Cursor()
		rs := m.engine.Rules()
		if i < 0 || i >= len(rs) {
			return m, nil
		}
		m.confirm = confirmDeleteRule
		m.status = fmt.Sprintf("delete rule %d (%s → %s), used by %d transactions? y/n",
			i+1, rulePattern(rs[i]), rs[i].Tag, m.ruleUsage[i])
		return m, nil

	case "p":
		unused := m.unusedRules()
		if len(unused) == 0 {
			m.status = "no unused rules to prune"
			return m, nil
		}
		m.confirm = confirmPruneRules
		m.status = fmt.Sprintf("delete all %d rules that match nothing? y/n", len(unused))
		return m, nil

	case "r":
		m.err = m.reloadRuleList()
		m.status = "counts refreshed"
		return m, nil
	}

	var cmd tea.Cmd
	m.ruleListTable, cmd = m.ruleListTable.Update(msg)
	return m, cmd
}

// openRuleBuilder switches to the rule builder, remembering where to return to
// and seeding the account field from whatever account is being browsed.
func (m *Model) openRuleBuilder() tea.Cmd {
	if m.view != viewRules {
		m.ruleReturn = m.view
	}
	m.view = viewRules
	if m.ruleAccount.Value() == "" && m.filter.AccountSlug != "" {
		m.ruleAccount.SetValue(m.filter.AccountSlug)
	}
	m.setRuleFocus(0)
	if err := m.reloadUntagged(); err != nil {
		m.err = err
	}
	return textinput.Blink
}

// ruleInputs lists the form fields in tab order.
func (m *Model) ruleInputs() []*textinput.Model {
	return []*textinput.Model{&m.ruleGlob, &m.ruleAccount, &m.ruleTag}
}

// setRuleFocus moves the cursor between the form fields, wrapping around.
func (m *Model) setRuleFocus(i int) {
	inputs := m.ruleInputs()
	n := len(inputs)
	m.ruleFocus = ((i % n) + n) % n
	for j, in := range inputs {
		if j == m.ruleFocus {
			in.Focus()
			in.CursorEnd()
			continue
		}
		in.Blur()
	}
}

// selected returns the transaction under the cursor, if any.
func (m *Model) selected() (model.Transaction, bool) {
	i := m.txnTable.Cursor()
	if i < 0 || i >= len(m.txns) {
		return model.Transaction{}, false
	}
	return m.txns[i], true
}

// importDoneMsg carries the outcome of a background import back to the model.
type importDoneMsg struct {
	res importer.Result
	err error
}

// importCmd runs the import off the event loop. Only values are captured, and
// the model is left untouched until the result comes back as a message.
func (m *Model) importCmd() tea.Cmd {
	root, db, accounts, engine := m.root, m.db, m.accounts, m.engine
	return func() tea.Msg {
		res, err := importer.Run(root, db, accounts, engine, importer.Options{})
		return importDoneMsg{res: res, err: err}
	}
}

// Update implements tea.Model.
func (m *Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.width, m.height = msg.Width, msg.Height
		m.resize()
		return m, nil

	case spinner.TickMsg:
		if !m.importing {
			return m, nil // a stale tick from a finished import
		}
		var cmd tea.Cmd
		m.spinner, cmd = m.spinner.Update(msg)
		return m, cmd

	case importDoneMsg:
		return m.finishImport(msg)

	case tea.KeyMsg:
		if m.input != inputNone {
			return m.updateInput(msg)
		}
		// The rule builder is a form: every printable key belongs to the
		// focused input, so the global single-letter keymap cannot apply.
		if m.view == viewRules {
			return m.updateRules(msg)
		}
		if m.view == viewRuleList {
			return m.updateRuleList(msg)
		}
		return m.updateNormal(msg)
	}
	return m, nil
}

// updateRules drives the rule builder form.
func (m *Model) updateRules(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch msg.String() {
	case "ctrl+c":
		return m, tea.Quit
	case "esc":
		m.view = m.ruleReturn
		return m, nil
	case "tab", "down":
		m.setRuleFocus(m.ruleFocus + 1)
		return m, nil
	case "shift+tab", "up":
		m.setRuleFocus(m.ruleFocus - 1)
		return m, nil
	case "pgdown":
		m.ruleTable.MoveDown(10)
		return m, nil
	case "pgup":
		m.ruleTable.MoveUp(10)
		return m, nil
	case "enter":
		m.err = nil
		if err := m.saveRule(); err != nil {
			m.err = err
			return m, nil
		}
		if err := m.reloadUntagged(); err != nil {
			m.err = err
		}
		return m, nil
	}

	var cmd tea.Cmd
	inputs := m.ruleInputs()
	*inputs[m.ruleFocus], cmd = inputs[m.ruleFocus].Update(msg)
	m.refreshRulePreview()
	return m, cmd
}

func (m *Model) finishImport(msg importDoneMsg) (tea.Model, tea.Cmd) {
	m.importing = false
	if msg.err != nil {
		m.err = msg.err
		m.status = "import failed"
		return m, nil
	}

	_, added, skipped := msg.res.Total()
	m.status = fmt.Sprintf("imported: %d new, %d duplicate", added, skipped)

	// A failed file and a warning are both worth surfacing, but the status
	// line only has room for the first thing that went wrong.
	if failures := msg.res.Errs(); len(failures) > 0 {
		m.err = fmt.Errorf("%s: %w", failures[0].Path, failures[0].Err)
	} else if warnings := firstWarning(msg.res); warnings != "" {
		m.status += " · " + warnings
	}

	if err := m.reload(); err != nil {
		m.err = err
	}
	return m, nil
}

func firstWarning(res importer.Result) string {
	total := 0
	first := ""
	for _, f := range res.Files {
		for _, w := range f.Warnings {
			if first == "" {
				first = fmt.Sprintf("%s: %s", f.Path, w)
			}
			total++
		}
	}
	if total > 1 {
		return fmt.Sprintf("%s (+%d more warnings)", first, total-1)
	}
	return first
}

func (m *Model) resize() {
	h := m.height - 6 // title, status, help, padding
	if h < 3 {
		h = 3
	}
	m.accountTable.SetHeight(h)
	m.txnTable.SetHeight(h)
	m.reportTable.SetHeight(h)
	m.ruleTable.SetHeight(h)
	m.ruleListTable.SetHeight(h)

	// The preview list gets whatever the form does not use.
	if m.width > 0 {
		cols := m.ruleTable.Columns()
		desc := m.width - ruleFormWidth - cols[0].Width - cols[2].Width - 10
		if desc < 20 {
			desc = 20
		}
		cols[1].Width = desc
		m.ruleTable.SetColumns(cols)
	}

	// Give the description column whatever is left over.
	if m.width > 0 {
		cols := m.txnTable.Columns()
		fixed := 0
		for _, c := range cols[:len(cols)-1] {
			fixed += c.Width + 2
		}
		desc := m.width - fixed - 4
		if desc < 20 {
			desc = 20
		}
		cols[len(cols)-1].Width = desc
		m.txnTable.SetColumns(cols)
	}
}

// updateInput handles typing into the tag or search prompt.
func (m *Model) updateInput(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch msg.Type {
	case tea.KeyEsc:
		m.input = inputNone
		m.text.Blur()
		m.text.SetValue("")
		return m, nil
	case tea.KeyEnter:
		value := strings.TrimSpace(m.text.Value())
		mode := m.input
		m.input = inputNone
		m.text.Blur()
		m.text.SetValue("")

		switch mode {
		case inputTag:
			t, ok := m.selected()
			if !ok {
				return m, nil
			}
			if err := m.db.SetManualTag(t.ID, value); err != nil {
				m.err = err
				return m, nil
			}
			if value == "" {
				m.status = "cleared manual tag"
			} else {
				m.status = "tagged as " + value
			}
		case inputSearch:
			m.filter.Search = value
			m.status = "search: " + value
			if value == "" {
				m.status = "search cleared"
			}
		}
		m.err = m.reloadTxns()
		return m, nil
	}

	var cmd tea.Cmd
	m.text, cmd = m.text.Update(msg)
	return m, cmd
}

// updateNormal handles the main keymap.
func (m *Model) updateNormal(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch msg.String() {
	case "q", "ctrl+c":
		return m, tea.Quit

	case "1":
		m.view = viewAccounts
		return m, nil
	case "2":
		m.view = viewTxns
		return m, nil
	case "3":
		m.view = viewReport
		return m, nil
	case "4":
		return m, m.openRuleBuilder()
	case "5":
		m.openRuleList()
		return m, nil
	case "tab":
		m.view = (m.view + 1) % viewCount
		switch m.view {
		case viewRules:
			return m, m.openRuleBuilder()
		case viewRuleList:
			m.openRuleList()
		}
		return m, nil

	case "enter":
		// From the account list, drill into that account's transactions.
		if m.view == viewAccounts {
			accounts, err := m.db.Accounts()
			if err != nil {
				m.err = err
				return m, nil
			}
			i := m.accountTable.Cursor()
			if i >= 0 && i < len(accounts) {
				m.filter.AccountSlug = accounts[i].Slug
				m.status = "account: " + accounts[i].Slug
				m.view = viewTxns
				m.err = m.reloadTxns()
			}
		}
		return m, nil

	case "a":
		m.filter.AccountSlug = ""
		m.status = "all accounts"
		m.err = m.reloadTxns()
		return m, nil

	case "u":
		m.onlyUntagged = !m.onlyUntagged
		if m.onlyUntagged {
			m.status = "showing untagged only"
			m.view = viewTxns
		} else {
			m.status = "showing all transactions"
		}
		m.err = m.reloadTxns()
		return m, nil

	case "t":
		if m.view != viewTxns {
			return m, nil
		}
		t, ok := m.selected()
		if !ok {
			return m, nil
		}
		m.input = inputTag
		m.text.SetValue(t.ManualTag)
		m.text.CursorEnd()
		m.text.Focus()
		return m, nil

	case "/":
		m.view = viewTxns
		m.input = inputSearch
		m.text.SetValue(m.filter.Search)
		m.text.CursorEnd()
		m.text.Focus()
		return m, nil

	case "x":
		// Toggle the manual transfer override away from whatever is in effect.
		if m.view != viewTxns {
			return m, nil
		}
		t, ok := m.selected()
		if !ok {
			return m, nil
		}
		v := !t.IsTransfer()
		if err := m.db.SetManualTransfer(t.ID, &v); err != nil {
			m.err = err
			return m, nil
		}
		if v {
			m.status = "marked as transfer"
		} else {
			m.status = "unmarked as transfer"
		}
		m.err = m.reloadTxns()
		return m, nil

	case "c":
		// Drop manual overrides and fall back to what the rules say.
		if m.view != viewTxns {
			return m, nil
		}
		t, ok := m.selected()
		if !ok {
			return m, nil
		}
		if err := m.db.ClearOverrides(t.ID); err != nil {
			m.err = err
			return m, nil
		}
		m.status = "manual overrides cleared"
		m.err = m.reloadTxns()
		return m, nil

	case "r":
		if m.importing {
			m.status = "import in progress…"
			return m, nil
		}
		n, err := m.engine.Retag(m.db)
		if err != nil {
			m.err = err
			return m, nil
		}
		m.status = fmt.Sprintf("rules re-applied, %d rows changed", n)
		m.err = m.reload()
		return m, nil

	case "i":
		if m.importing {
			return m, nil // already running; ignore the repeat press
		}
		m.importing = true
		m.err = nil
		m.status = ""
		return m, tea.Batch(m.spinner.Tick, m.importCmd())
	}

	var cmd tea.Cmd
	switch m.view {
	case viewAccounts:
		m.accountTable, cmd = m.accountTable.Update(msg)
	case viewTxns:
		m.txnTable, cmd = m.txnTable.Update(msg)
	case viewReport:
		m.reportTable, cmd = m.reportTable.Update(msg)
	}
	return m, cmd
}

// View implements tea.Model.
func (m *Model) View() string {
	var b strings.Builder

	b.WriteString(titleStyle.Render(m.title()))
	b.WriteString("\n")

	// An empty table is just a bare header, which says nothing about why it is
	// empty or what to do next.
	if empty := m.emptyMessage(); empty != "" {
		b.WriteString(emptyStyle.Render(empty))
	} else {
		switch m.view {
		case viewAccounts:
			b.WriteString(m.accountTable.View())
		case viewTxns:
			b.WriteString(m.txnTable.View())
		case viewReport:
			b.WriteString(m.reportTable.View())
		case viewRules:
			b.WriteString(m.rulesView())
		case viewRuleList:
			b.WriteString(m.ruleListTable.View())
		}
	}
	b.WriteString("\n")

	switch {
	case m.importing:
		b.WriteString(statusStyle.Render(m.spinner.View() + m.importingLabel()))
	case m.input == inputTag:
		b.WriteString(statusStyle.Render("tag: ") + m.text.View())
	case m.input == inputSearch:
		b.WriteString(statusStyle.Render("search: ") + m.text.View())
	case m.err != nil:
		b.WriteString(errStyle.Render("error: " + m.err.Error()))
	default:
		b.WriteString(statusStyle.Render(m.status))
	}
	b.WriteString("\n")
	b.WriteString(helpStyle.Render(m.help()))
	return b.String()
}

// rulesView puts the form on the left and the live preview on the right.
func (m *Model) rulesView() string {
	return lipgloss.JoinHorizontal(lipgloss.Top, m.ruleFormView(), m.ruleTable.View())
}

func (m *Model) ruleFormView() string {
	field := func(i int, label, help string) string {
		name := labelStyle.Render("  " + label)
		box := boxStyle.Render(m.ruleInputs()[i].View())
		if i == m.ruleFocus {
			name = focusedLabelStyle.Render("▸ " + label)
			box = focusedBoxStyle.Render(m.ruleInputs()[i].View())
		}
		return name + "\n" + box + "\n" + hintStyle.Render(help) + "\n"
	}

	var b strings.Builder
	b.WriteString(field(0, "glob", "vs. the description"))
	b.WriteString("\n")
	b.WriteString(field(1, "account", "blank = all accounts"))
	b.WriteString("\n")
	b.WriteString(field(2, "tag", "applied to matches"))
	b.WriteString("\n")

	// The count is the whole point of the preview: it says what the rule will
	// do before it is written to disk.
	summary := fmt.Sprintf("%d of %d descriptions match", m.ruleMatches, len(m.ruleTable.Rows()))
	if strings.TrimSpace(m.ruleGlob.Value()) == "" {
		summary = fmt.Sprintf("%d untagged descriptions", len(m.ruleTable.Rows()))
	}
	b.WriteString(matchCountStyle.Render(summary))

	return ruleFormStyle.Render(b.String())
}

// emptyMessage explains an empty view and names the key that fixes it, or
// returns "" when there is something to show.
func (m *Model) emptyMessage() string {
	switch m.view {
	case viewAccounts:
		if len(m.accountTable.Rows()) > 0 {
			return ""
		}
		// An account.toml on disk is not enough: folders are only registered
		// in the index by an import, so say that rather than showing nothing.
		if n := len(m.accounts); n > 0 {
			return fmt.Sprintf(
				"No accounts imported yet.\n\n"+
					"%d account folder(s) configured in %s.\n"+
					"Press i to import their statements (same as running `money import`).",
				n, m.root)
		}
		return fmt.Sprintf(
			"No account folders found in %s.\n\n"+
				"An account is a folder containing an account.toml.\n"+
				"Create one, drop statements in, then press i to import.",
			m.root)

	case viewTxns:
		if len(m.txns) > 0 {
			return ""
		}
		switch {
		case m.filter.Search != "":
			return fmt.Sprintf("No transactions match /%s.\n\nPress / to change the search.", m.filter.Search)
		case m.onlyUntagged:
			return "Nothing untagged.\n\nEvery transaction here has a tag. Press u to see them all."
		case m.filter.AccountSlug != "":
			return fmt.Sprintf(
				"No transactions in %s.\n\nPress i to import, or a to see every account.",
				m.filter.AccountSlug)
		}
		return "No transactions yet.\n\nPress i to import (same as running `money import`)."

	case viewReport:
		if len(m.reportTable.Rows()) > 0 {
			return ""
		}
		return "Nothing to report yet.\n\nPress i to import some statements first."

	case viewRuleList:
		if len(m.ruleListTable.Rows()) > 0 {
			return ""
		}
		return "No rules yet.\n\nPress 4 to build one, or write rules.toml by hand."
	}
	return ""
}

func (m *Model) title() string {
	scope := "all accounts"
	if m.filter.AccountSlug != "" {
		scope = m.filter.AccountSlug
	}
	if m.onlyUntagged {
		scope += " · untagged"
	}
	if m.filter.Search != "" {
		scope += " · /" + m.filter.Search
	}

	switch m.view {
	case viewAccounts:
		return "money · accounts"
	case viewRules:
		return "money · rule builder · writes to rules.toml"
	case viewRuleList:
		unused := len(m.unusedRules())
		if unused == 0 {
			return fmt.Sprintf("money · rules · %d rules, all in use", len(m.engine.Rules()))
		}
		return fmt.Sprintf("money · rules · %d rules · %d match nothing", len(m.engine.Rules()), unused)
	case viewReport:
		return "money · report · " + scope + " · transfers excluded"
	default:
		return fmt.Sprintf("money · transactions · %s · %d rows", scope, len(m.txns))
	}
}

// importingLabel names what the import is working through, since extracting
// text from PDFs is where the wait actually comes from.
func (m *Model) importingLabel() string {
	if n := len(m.accounts); n > 0 {
		return fmt.Sprintf("importing %d account(s)… parsing statements can take a while for PDFs", n)
	}
	return "importing…"
}

func (m *Model) help() string {
	if m.importing {
		return "importing… · q quit"
	}
	if m.input != inputNone {
		return "enter confirm · esc cancel"
	}
	switch m.view {
	case viewAccounts:
		return "enter open · 2 transactions · 3 report · 4 rules · i import · r retag · q quit"
	case viewRules:
		return "tab/↑↓ field · pgup/pgdn scroll list · enter save rule · esc back · ctrl+c quit"
	case viewRuleList:
		if m.confirm != confirmNone {
			return "y confirm · any other key cancels"
		}
		return "d delete rule · p prune all unused · r refresh counts · 4 rule builder · esc back · q quit"
	case viewReport:
		return "1 accounts · 2 transactions · 4 rules · u untagged · a all accounts · q quit"
	default:
		return "t tag · x transfer · c clear · / search · u untagged · a all · i import · r retag · 4 rules · 1 accounts · 3 report · q quit"
	}
}