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

import (
	"fmt"
	"strings"

	"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/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
)

// 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

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

	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)
)

// 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

	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,
		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},
		}),
		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)
}

// 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
}

// 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 tea.KeyMsg:
		if m.input != inputNone {
			return m.updateInput(msg)
		}
		return m.updateNormal(msg)
	}
	return m, nil
}

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)

	// 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 "tab":
		m.view = (m.view + 1) % 3
		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":
		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":
		res, err := importer.Run(m.root, m.db, m.accounts, m.engine, importer.Options{})
		if err != nil {
			m.err = err
			return m, nil
		}
		_, added, skipped := res.Total()
		m.status = fmt.Sprintf("imported: %d new, %d duplicate", added, skipped)
		if failures := res.Errs(); len(failures) > 0 {
			m.err = fmt.Errorf("%s: %w", failures[0].Path, failures[0].Err)
		}
		m.err = m.reload()
		return m, nil
	}

	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()) + "\n")

	switch m.view {
	case viewAccounts:
		b.WriteString(m.accountTable.View())
	case viewTxns:
		b.WriteString(m.txnTable.View())
	case viewReport:
		b.WriteString(m.reportTable.View())
	}
	b.WriteString("\n")

	switch {
	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()
}

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 viewReport:
		return "money · report · " + scope + " · transfers excluded"
	default:
		return fmt.Sprintf("money · transactions · %s · %d rows", scope, len(m.txns))
	}
}

func (m *Model) help() string {
	if m.input != inputNone {
		return "enter confirm · esc cancel"
	}
	switch m.view {
	case viewAccounts:
		return "enter open · 2 transactions · 3 report · i import · r retag · q quit"
	case viewReport:
		return "1 accounts · 2 transactions · u untagged · a all accounts · q quit"
	default:
		return "t tag · x transfer · c clear · / search · u untagged · a all · i import · r retag · 1 accounts · 3 report · q quit"
	}
}