package list

import (
	"fmt"
	"strings"

	"git.mlow.ca/mlow/lmcli/pkg/tui/shared"
	tuiutil "git.mlow.ca/mlow/lmcli/pkg/tui/util"
	"github.com/charmbracelet/bubbles/textinput"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

type Option struct {
	Label string
	Value interface{}
}

type OptionGroup struct {
	Name    string
	Options []Option
}

type Model struct {
	ID            int
	HeaderStyle   lipgloss.Style
	ItemStyle     lipgloss.Style
	SelectedStyle lipgloss.Style
	ItemRender    func(Option, bool) string

	Width  int
	Height int

	optionGroups    []OptionGroup
	selected        int
	filterInput     textinput.Model
	filteredIndices []filteredIndex
	content         viewport.Model
	itemYOffsets    []int
}

type filteredIndex struct {
	groupIndex  int
	optionIndex int
}

type MsgOptionSelected struct {
	ID     int
	Option Option
}

func New(opts []Option) Model {
	return NewWithGroups([]OptionGroup{{Options: opts}})
}

func NewWithGroups(groups []OptionGroup) Model {
	ti := textinput.New()
	ti.Prompt = "/"
	ti.PromptStyle = lipgloss.NewStyle().Faint(true)

	m := Model{
		HeaderStyle:   lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("12")).Padding(1, 0, 1, 1),
		ItemStyle:     lipgloss.NewStyle(),
		SelectedStyle: lipgloss.NewStyle().Faint(true).Foreground(lipgloss.Color("6")),

		optionGroups:    groups,
		selected:        0,
		filterInput:     ti,
		filteredIndices: make([]filteredIndex, 0),
		content:         viewport.New(0, 0),
		itemYOffsets:    make([]int, 0),
	}

	m.filterItems()
	m.content.SetContent(m.renderList())
	return m
}

func (m *Model) Focused() {
	m.filterInput.Focused()
}

func (m *Model) Focus() {
	m.filterInput.Focus()
}

func (m *Model) Blur() {
	m.filterInput.Blur()
}

func (m *Model) filterItems() {
	filterText := strings.ToLower(m.filterInput.Value())

	var prevSelection *filteredIndex
	if m.selected <= len(m.filteredIndices)-1 {
		prevSelection = &m.filteredIndices[m.selected]
	}

	m.filteredIndices = make([]filteredIndex, 0)

	for groupIndex, group := range m.optionGroups {
		for optionIndex, option := range group.Options {
			if filterText == "" ||
				strings.Contains(strings.ToLower(option.Label), filterText) ||
				(group.Name != "" && strings.Contains(strings.ToLower(group.Name), filterText)) {
				m.filteredIndices = append(m.filteredIndices, filteredIndex{groupIndex, optionIndex})
			}
		}
	}

	found := false
	if len(m.filteredIndices) > 0 && prevSelection != nil {
		// Preserve previous selection if possible
		for i, filterIdx := range m.filteredIndices {
			if prevSelection.groupIndex == filterIdx.groupIndex {
				if prevSelection.optionIndex == filterIdx.optionIndex {
					m.selected = i
					found = true
					break
				}
			}
		}
	}
	if !found {
		m.selected = 0
	}
}

func (m *Model) Update(msg tea.Msg) (Model, tea.Cmd) {
	var cmd tea.Cmd

	switch msg := msg.(type) {
	case tea.KeyMsg:
		if m.filterInput.Focused() {
			switch msg.String() {
			case "esc":
				m.filterInput.Blur()
				m.filterInput.SetValue("")
				m.filterItems()
				m.refreshContent()
				return *m, shared.KeyHandled(msg)
			case "enter":
				m.filterInput.Blur()
				m.refreshContent()
				break
			case "up", "down":
				break
			default:
				m.filterInput, cmd = m.filterInput.Update(msg)
				m.filterItems()
				m.refreshContent()
				return *m, cmd
			}
		}

		switch msg.String() {
		case "up", "k":
			m.moveSelection(-1)
			return *m, shared.KeyHandled(msg)
		case "down", "j":
			m.moveSelection(1)
			return *m, shared.KeyHandled(msg)
		case "enter":
			return *m, func() tea.Msg {
				idx := m.filteredIndices[m.selected]
				return MsgOptionSelected{
					ID: m.ID,
					Option: m.optionGroups[idx.groupIndex].Options[idx.optionIndex],
				}
			}
		case "/":
			m.filterInput.Focus()
			return *m, textinput.Blink
		}
	}

	m.content, cmd = m.content.Update(msg)
	return *m, cmd
}

func (m *Model) refreshContent() {
	m.content.SetContent(m.renderList())
	m.ensureSelectedVisible()
}

func (m *Model) ensureSelectedVisible() {
	if m.selected == 0 {
		m.content.GotoTop()
	} else if m.selected == len(m.filteredIndices)-1 {
		m.content.GotoBottom()
	} else {
		tuiutil.ScrollIntoView(&m.content, m.itemYOffsets[m.selected], 0)
	}
}

func (m *Model) moveSelection(delta int) {
	prev := m.selected
	m.selected = min(len(m.filteredIndices)-1, max(0, m.selected+delta))
	if prev != m.selected {
		m.refreshContent()
	}
}

func (m *Model) View() string {
	filter := ""
	if m.filterInput.Focused() {
		m.filterInput.Width = m.Width
		filter = m.filterInput.View()
	}

	contentHeight := m.Height - tuiutil.Height(filter)
	m.content.Width, m.content.Height = m.Width, contentHeight

	parts := []string{m.content.View()}
	if filter != "" {
		parts = append(parts, filter)
	}
	return lipgloss.JoinVertical(lipgloss.Left, parts...)
}

func (m *Model) renderList() string {
	var sb strings.Builder
	yOffset := 0
	lastGroupIndex := -1
	m.itemYOffsets = make([]int, len(m.filteredIndices))

	for i, idx := range m.filteredIndices {
		if idx.groupIndex != lastGroupIndex {
			group := m.optionGroups[idx.groupIndex].Name
			if group != "" {
				headingStr := m.HeaderStyle.Render(group)
				yOffset += tuiutil.Height(headingStr)
				sb.WriteString(headingStr)
				sb.WriteRune('\n')
			}
			lastGroupIndex = idx.groupIndex
		}

		m.itemYOffsets[i] = yOffset
		option := m.optionGroups[idx.groupIndex].Options[idx.optionIndex]
		var item string
		if m.ItemRender != nil {
			item = m.ItemRender(option, i == m.selected)
		} else {
			prefix := "  "
			if i == m.selected {
				prefix = "> "
				item = m.SelectedStyle.Render(option.Label)
			} else {
				item = m.ItemStyle.Render(option.Label)
			}
			item = fmt.Sprintf("%s%s", prefix, item)
		}
		sb.WriteString(item)
		yOffset += tuiutil.Height(item)
		if i < len(m.filteredIndices)-1 {
			sb.WriteRune('\n')
		}
	}

	return sb.String()
}