package ui

import (
	"fmt"
	"os"
	"strings"

	"github.com/charmbracelet/bubbles/key"
	"github.com/charmbracelet/bubbles/list"
	"github.com/charmbracelet/bubbles/textinput"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"

	"task/internal/command"
	"task/internal/config"
	"task/internal/project"
	"task/internal/ticket"
	"task/internal/ui/views"
	"task/internal/version"
)

// editorFinishedMsg is sent after the external $EDITOR exits.
type editorFinishedMsg struct {
	ticketID string
	path     string
	err      error
}

// Mode is the active UI mode.
type Mode int

const (
	ModeList Mode = iota
	ModeCreate
	ModeSearch
	ModeProjects
	ModeStatus
	ModeBoard
)

// Model is the root Bubble Tea model.
type Model struct {
	cfg      *config.Config
	store    ticket.Store
	projects project.Store
	exec     command.Executor

	mode            Mode
	tickets         views.TicketList
	projectList     list.Model
	statusMenu      views.StatusMenu
	boardMenu       views.BoardMenu
	boardList       ticket.BoardList
	input           textinput.Model
	width           int
	height          int
	status          string
	statusIsError   bool
	filter          string
	keys            KeyMap
	styles          Styles
	version         string
	allTickets      []ticket.Ticket
	creatingProject bool
}

// New creates the root UI model.
func New(cfg *config.Config, store ticket.Store, projects project.Store, exec command.Executor) Model {
	styles := DefaultStyles()
	if exec == nil {
		exec = command.NewHistory()
	}

	m := Model{
		cfg:       cfg,
		store:     store,
		projects:  projects,
		exec:      exec,
		mode:      ModeList,
		boardList: ticket.ParseBoardList(cfg.ActiveBoardList(cfg.ActiveProject)),
		tickets: views.TicketList{
			Styles: views.TicketListStyles{
				Card:         styles.Card,
				CardSelected: styles.CardSelected,
				StatusOPEN:   styles.StatusTodo,
				StatusWIP:    styles.StatusWIP,
				StatusDONE:   styles.StatusDone,
				Headline:     styles.Headline,
			},
		},
		input:   views.NewCreateInput(),
		keys:    DefaultKeyMap(),
		styles:  styles,
		version: version.BuildVersion,
	}
	_ = m.reloadTickets()
	return m
}

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

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

	case editorFinishedMsg:
		return m.handleEditorFinished(msg)

	case tea.KeyMsg:
		switch m.mode {
		case ModeCreate, ModeSearch:
			return m.updateInput(msg)
		case ModeProjects:
			return m.updateProjects(msg)
		case ModeStatus:
			return m.updateStatus(msg)
		case ModeBoard:
			return m.updateBoard(msg)
		default:
			return m.updateList(msg)
		}
	}

	var cmd tea.Cmd
	switch m.mode {
	case ModeProjects:
		m.projectList, cmd = m.projectList.Update(msg)
	case ModeCreate, ModeSearch:
		m.input, cmd = m.input.Update(msg)
	}
	return m, cmd
}

// View implements tea.Model.
func (m Model) View() string {
	if m.width == 0 {
		return "loading…"
	}
	header := m.renderHeader()
	footer := m.renderFooter()
	bodyH := m.height - lipgloss.Height(header) - lipgloss.Height(footer)
	if bodyH < 1 {
		bodyH = 1
	}
	body := m.renderBody(bodyH)
	return lipgloss.JoinVertical(lipgloss.Left, header, body, footer)
}

func (m *Model) resizeLists() {
	headerH := 1
	footerH := 1
	bodyH := m.height - headerH - footerH
	if bodyH < 1 {
		bodyH = 1
	}
	m.tickets.SetSize(m.width, bodyH)
	if m.mode == ModeProjects {
		m.projectList.SetSize(m.width, bodyH)
	}
	m.input.Width = max(10, m.width-4)
	m.statusMenu.Width = m.width
	m.boardMenu.Width = m.width
}

func (m Model) updateList(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch {
	case key.Matches(msg, m.keys.Quit):
		return m, tea.Quit

	case key.Matches(msg, m.keys.New):
		m.clearStatus()
		m.creatingProject = false
		m.mode = ModeCreate
		m.input = views.NewCreateInput()
		m.input.Focus()
		return m, textinput.Blink

	case key.Matches(msg, m.keys.Search):
		m.clearStatus()
		m.creatingProject = false
		m.mode = ModeSearch
		m.input = views.NewSearchInput()
		m.input.SetValue(m.filter)
		m.input.Focus()
		return m, textinput.Blink

	case key.Matches(msg, m.keys.Project):
		m.clearStatus()
		if err := m.openProjects(); err != nil {
			m.setError(err)
			return m, nil
		}
		m.mode = ModeProjects
		return m, nil

	case key.Matches(msg, m.keys.Board):
		m.clearStatus()
		m.boardMenu = views.NewBoardMenu(m.boardList, m.width, views.StatusMenuStyles{
			Box:      m.styles.StatusMenuBox,
			Title:    m.styles.StatusMenuTitle,
			Selected: m.styles.StatusMenuSelected,
			Normal:   m.styles.StatusMenuNormal,
		})
		m.mode = ModeBoard
		return m, nil

	case key.Matches(msg, m.keys.Delete):
		m.clearStatus()
		if err := m.deleteSelected(); err != nil {
			m.setError(err)
		} else {
			m.setStatus("deleted")
		}
		return m, nil

	case key.Matches(msg, m.keys.Undo):
		m.clearStatus()
		if err := m.undo(); err != nil {
			m.setError(err)
		}
		return m, nil

	case key.Matches(msg, m.keys.Redo):
		m.clearStatus()
		if err := m.redo(); err != nil {
			m.setError(err)
		}
		return m, nil

	case key.Matches(msg, m.keys.Edit):
		m.clearStatus()
		cmd, err := m.openEditorForSelected()
		if err != nil {
			m.setError(err)
			return m, nil
		}
		return m, cmd

	case key.Matches(msg, m.keys.Status):
		m.clearStatus()
		t, ok := m.tickets.Selected()
		if !ok {
			m.setError(fmt.Errorf("no ticket selected"))
			return m, nil
		}
		m.statusMenu = views.NewStatusMenu(t.Status, m.width, views.StatusMenuStyles{
			Box:      m.styles.StatusMenuBox,
			Title:    m.styles.StatusMenuTitle,
			Selected: m.styles.StatusMenuSelected,
			Normal:   m.styles.StatusMenuNormal,
		})
		m.mode = ModeStatus
		return m, nil

	case key.Matches(msg, m.keys.Down):
		m.tickets.MoveDown()
		return m, nil

	case key.Matches(msg, m.keys.Up):
		m.tickets.MoveUp()
		return m, nil
	}

	return m, nil
}

func (m Model) updateStatus(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch {
	case key.Matches(msg, m.keys.Escape):
		m.mode = ModeList
		m.clearStatus()
		return m, nil

	case key.Matches(msg, m.keys.Enter):
		if err := m.applyStatus(m.statusMenu.Selected()); err != nil {
			m.setError(err)
			return m, nil
		}
		m.mode = ModeList
		return m, nil

	case key.Matches(msg, m.keys.Down):
		m.statusMenu.MoveDown()
		return m, nil

	case key.Matches(msg, m.keys.Up):
		m.statusMenu.MoveUp()
		return m, nil
	}
	return m, nil
}

func (m Model) updateBoard(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch {
	case key.Matches(msg, m.keys.Escape):
		m.mode = ModeList
		m.clearStatus()
		return m, nil

	case key.Matches(msg, m.keys.Enter):
		if err := m.applyBoardList(m.boardMenu.Selected()); err != nil {
			m.setError(err)
			return m, nil
		}
		m.mode = ModeList
		return m, nil

	case key.Matches(msg, m.keys.Down):
		m.boardMenu.MoveDown()
		return m, nil

	case key.Matches(msg, m.keys.Up):
		m.boardMenu.MoveUp()
		return m, nil
	}
	return m, nil
}

func (m Model) updateInput(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch {
	case key.Matches(msg, m.keys.Escape):
		wasProject := m.creatingProject
		m.creatingProject = false
		m.input.Blur()
		m.clearStatus()
		if wasProject {
			m.mode = ModeProjects
		} else {
			m.mode = ModeList
		}
		return m, nil

	case key.Matches(msg, m.keys.Enter):
		value := strings.TrimSpace(m.input.Value())
		if m.mode == ModeCreate {
			if value == "" {
				m.setError(fmt.Errorf("name required"))
				return m, nil
			}
			if m.creatingProject {
				id := sanitizeProjectID(value)
				if err := m.projects.Ensure(id); err != nil {
					m.setError(err)
					return m, nil
				}
				if err := m.switchProject(id); err != nil {
					m.setError(err)
					return m, nil
				}
				m.creatingProject = false
				m.mode = ModeList
				m.input.Blur()
				m.setStatus(fmt.Sprintf("created project %s", id))
				return m, nil
			}
			if err := m.createTicket(value); err != nil {
				m.setError(err)
				return m, nil
			}
			m.mode = ModeList
			m.input.Blur()
			m.setStatus("created")
			return m, nil
		}
		m.filter = value
		m.applyFilter()
		m.mode = ModeList
		m.input.Blur()
		if value == "" {
			m.setStatus("filter cleared")
		} else {
			m.setStatus(fmt.Sprintf("filter: %q", value))
		}
		return m, nil
	}

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

func (m Model) updateProjects(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch {
	case key.Matches(msg, m.keys.Escape):
		m.mode = ModeList
		m.clearStatus()
		return m, nil

	case key.Matches(msg, m.keys.New):
		m.clearStatus()
		m.creatingProject = true
		m.mode = ModeCreate
		m.input = views.NewCreateInput()
		m.input.Placeholder = "Project name…"
		m.input.Focus()
		return m, textinput.Blink

	case key.Matches(msg, m.keys.Enter):
		item, ok := m.projectList.SelectedItem().(views.ProjectItem)
		if !ok {
			return m, nil
		}
		if err := m.switchProject(item.Project.ID); err != nil {
			m.setError(err)
			return m, nil
		}
		m.mode = ModeList
		m.setStatus(fmt.Sprintf("switched to %s", item.Project.ID))
		return m, nil
	}

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

func (m Model) openEditorForSelected() (tea.Cmd, error) {
	t, ok := m.tickets.Selected()
	if !ok {
		return nil, fmt.Errorf("no ticket selected")
	}
	path, err := ticket.WriteEditFile(t)
	if err != nil {
		return nil, err
	}
	c := ticket.EditorCmd(path)
	ticketID := t.ID
	return tea.ExecProcess(c, func(err error) tea.Msg {
		return editorFinishedMsg{ticketID: ticketID, path: path, err: err}
	}), nil
}

func (m Model) handleEditorFinished(msg editorFinishedMsg) (tea.Model, tea.Cmd) {
	defer func() { _ = os.Remove(msg.path) }()

	if msg.err != nil {
		m.setError(fmt.Errorf("editor: %w", msg.err))
		return m, nil
	}

	data, err := os.ReadFile(msg.path)
	if err != nil {
		m.setError(fmt.Errorf("read edited file: %w", err))
		return m, nil
	}
	title, description, err := ticket.ParseEditDocument(string(data))
	if err != nil {
		m.setError(err)
		return m, nil
	}

	before, err := m.store.Get(msg.ticketID)
	if err != nil {
		m.setError(err)
		return m, nil
	}
	after := before
	after.Title = title
	after.Description = description
	if err := m.exec.Do(&command.UpdateTicket{
		Store:  m.store,
		Before: before,
		After:  after,
	}); err != nil {
		m.setError(err)
		return m, nil
	}
	idx := m.tickets.CursorIndex()
	if err := m.reloadTickets(); err != nil {
		m.setError(err)
		return m, nil
	}
	if idx < m.tickets.Len() {
		m.tickets.Select(idx)
	}
	m.setStatus("saved")
	return m, nil
}

func (m *Model) createTicket(title string) error {
	cmd := &command.CreateTicket{
		Store: m.store,
		Ticket: ticket.Ticket{
			Title:     title,
			ProjectID: m.cfg.ActiveProject,
			Status:    m.boardList.DefaultStatus(),
		},
	}
	if err := m.exec.Do(cmd); err != nil {
		return err
	}
	return m.reloadTickets()
}

func (m *Model) deleteSelected() error {
	t, ok := m.tickets.Selected()
	if !ok {
		return fmt.Errorf("no ticket selected")
	}
	idx := m.tickets.CursorIndex()
	if err := m.exec.Do(&command.DeleteTicket{Store: m.store, Snapshot: t}); err != nil {
		return err
	}
	if err := m.reloadTickets(); err != nil {
		return err
	}
	if idx >= m.tickets.Len() && m.tickets.Len() > 0 {
		m.tickets.Select(m.tickets.Len() - 1)
	} else if idx < m.tickets.Len() {
		m.tickets.Select(idx)
	}
	return nil
}

func (m *Model) applyStatus(st ticket.Status) error {
	t, ok := m.tickets.Selected()
	if !ok {
		return fmt.Errorf("no ticket selected")
	}
	after := t
	after.Status = st
	if err := m.exec.Do(&command.UpdateTicket{
		Store:  m.store,
		Before: t,
		After:  after,
	}); err != nil {
		return err
	}
	idx := m.tickets.CursorIndex()
	if err := m.reloadTickets(); err != nil {
		return err
	}
	if idx < m.tickets.Len() {
		m.tickets.Select(idx)
	}
	m.setStatus(fmt.Sprintf("status → %s", st.Label()))
	return nil
}

func (m *Model) undo() error {
	name := m.exec.LastUndoName()
	if err := m.exec.Undo(); err != nil {
		return err
	}
	if err := m.reloadTickets(); err != nil {
		return err
	}
	if name != "" {
		m.setStatus("undo: " + name)
	} else {
		m.setStatus("undo")
	}
	return nil
}

func (m *Model) redo() error {
	name := m.exec.LastRedoName()
	if err := m.exec.Redo(); err != nil {
		return err
	}
	if err := m.reloadTickets(); err != nil {
		return err
	}
	if name != "" {
		m.setStatus("redo: " + name)
	} else {
		m.setStatus("redo")
	}
	return nil
}

func (m *Model) applyBoardList(bl ticket.BoardList) error {
	m.boardList = bl
	m.cfg.SetActiveBoardList(m.cfg.ActiveProject, string(bl))
	if err := config.Save(m.cfg); err != nil {
		return err
	}
	m.applyFilter()
	m.setStatus(fmt.Sprintf("list → %s", bl.Label()))
	return nil
}

func (m *Model) switchProject(id string) error {
	if err := m.projects.Ensure(id); err != nil {
		return err
	}
	m.cfg.ActiveProject = id
	m.boardList = ticket.ParseBoardList(m.cfg.ActiveBoardList(id))
	if err := config.Save(m.cfg); err != nil {
		return err
	}
	m.filter = ""
	return m.reloadTickets()
}

func (m *Model) openProjects() error {
	projects, err := m.projects.List()
	if err != nil {
		return err
	}
	if len(projects) == 0 {
		if err := m.projects.Ensure(m.cfg.ActiveProject); err != nil {
			return err
		}
		projects, err = m.projects.List()
		if err != nil {
			return err
		}
	}
	headerH, footerH := 1, 1
	bodyH := m.height - headerH - footerH
	if bodyH < 1 {
		bodyH = 1
	}
	m.projectList = views.NewProjectList(projects, m.cfg.ActiveProject, m.width, bodyH)
	return nil
}

func (m *Model) reloadTickets() error {
	tickets, err := m.store.List(m.cfg.ActiveProject)
	if err != nil {
		return err
	}
	m.allTickets = tickets
	m.applyFilter()
	return nil
}

func (m *Model) applyFilter() {
	filtered := make([]ticket.Ticket, 0, len(m.allTickets))
	for _, t := range m.allTickets {
		if m.boardList.Matches(t.Status) {
			filtered = append(filtered, t)
		}
	}
	filtered = views.FilterTickets(filtered, m.filter)
	cursor := m.tickets.CursorIndex()
	m.tickets.SetItems(filtered)
	if cursor < m.tickets.Len() {
		m.tickets.Select(cursor)
	}
}

func (m Model) ticketCount() int {
	return m.tickets.Len()
}

func (m *Model) setStatus(s string) {
	m.status = s
	m.statusIsError = false
}

func (m *Model) setError(err error) {
	m.status = err.Error()
	m.statusIsError = true
}

func (m *Model) clearStatus() {
	m.status = ""
	m.statusIsError = false
}

func sanitizeProjectID(name string) string {
	name = strings.TrimSpace(strings.ToLower(name))
	var b strings.Builder
	for _, r := range name {
		switch {
		case r >= 'a' && r <= 'z', r >= '0' && r <= '9', r == '-', r == '_':
			b.WriteRune(r)
		case r == ' ':
			b.WriteRune('-')
		}
	}
	id := b.String()
	if id == "" {
		return "project"
	}
	return id
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}