package conversations

import (
	"fmt"
	"strings"
	"time"

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

type loadedConversation struct {
	conv      api.Conversation
	lastReply api.Message
}

type (
	// sent when conversation list is loaded
	msgConversationsLoaded ([]loadedConversation)
	// sent when a conversation is selected
	msgConversationSelected api.Conversation
	// sent when a conversation is deleted
	msgConversationDeleted struct{}
)

// Prompt payloads
type (
	deleteConversationPayload api.Conversation
)

type Model struct {
	shared.Shared
	shared.Sections

	conversations []loadedConversation
	cursor        int   // index of the currently selected conversation
	itemOffsets   []int // keeps track of the viewport y offset of each rendered item

	content viewport.Model

	confirmPrompt bubbles.ConfirmPrompt
}

func Conversations(shared shared.Shared) Model {
	m := Model{
		Shared:  shared,
		content: viewport.New(0, 0),
	}
	return m
}

func (m *Model) HandleInput(msg tea.KeyMsg) (bool, tea.Cmd) {
	if m.confirmPrompt.Focused() {
		var cmd tea.Cmd
		m.confirmPrompt, cmd = m.confirmPrompt.Update(msg)
		if cmd != nil {
			return true, cmd
		}
	}

	switch msg.String() {
	case "enter":
		if len(m.conversations) > 0 && m.cursor < len(m.conversations) {
			return true, func() tea.Msg {
				return msgConversationSelected(m.conversations[m.cursor].conv)
			}
		}
	case "j", "down":
		if m.cursor < len(m.conversations)-1 {
			m.cursor++
			if m.cursor == len(m.conversations)-1 {
				// if last conversation, simply scroll to the bottom
				m.content.GotoBottom()
			} else {
				// this hack positions the *next* conversatoin slightly
				// *off* the screen, ensuring the entire m.cursor is shown,
				// even if its height may not be constant due to wrapping.
				tuiutil.ScrollIntoView(&m.content, m.itemOffsets[m.cursor+1], -1)
			}
			m.content.SetContent(m.renderConversationList())
		} else {
			m.cursor = len(m.conversations) - 1
			m.content.GotoBottom()
		}
		return true, nil
	case "k", "up":
		if m.cursor > 0 {
			m.cursor--
			if m.cursor == 0 {
				m.content.GotoTop()
			} else {
				tuiutil.ScrollIntoView(&m.content, m.itemOffsets[m.cursor], 1)
			}
			m.content.SetContent(m.renderConversationList())
		} else {
			m.cursor = 0
			m.content.GotoTop()
		}
		return true, nil
	case "n":
		// new conversation
	case "d":
		if !m.confirmPrompt.Focused() && len(m.conversations) > 0 && m.cursor < len(m.conversations) {
			title := m.conversations[m.cursor].conv.Title
			if title == "" {
				title = "(untitled)"
			}
			m.confirmPrompt = bubbles.NewConfirmPrompt(
				fmt.Sprintf("Delete '%s'?", title),
				deleteConversationPayload(m.conversations[m.cursor].conv),
			)
			m.confirmPrompt.Style = lipgloss.NewStyle().
				Bold(true).
				Foreground(lipgloss.Color("3"))
			return true, nil
		}
	case "c":
		// copy/clone conversation
	case "r":
		// show prompt to rename conversation
	case "shift+r":
		// show prompt to generate name for conversation
	}
	return false, nil
}

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

func (m *Model) HandleResize(width, height int) {
	m.Width, m.Height = width, height
	m.content.Width = width
}

func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
	var cmds []tea.Cmd
	switch msg := msg.(type) {
	case shared.MsgViewEnter:
		cmds = append(cmds, m.loadConversations())
		m.content.SetContent(m.renderConversationList())
	case tea.WindowSizeMsg:
		m.HandleResize(msg.Width, msg.Height)
		m.content.SetContent(m.renderConversationList())
	case msgConversationsLoaded:
		m.conversations = msg
		m.cursor = max(0, min(len(m.conversations), m.cursor))
		m.content.SetContent(m.renderConversationList())
	case msgConversationSelected:
		m.Values.ConvShortname = msg.ShortName.String
		cmds = append(cmds, func() tea.Msg {
			return shared.MsgViewChange(shared.StateChat)
		})
	case bubbles.MsgConfirmPromptAnswered:
		m.confirmPrompt.Blur()
		if msg.Value {
			switch payload := msg.Payload.(type) {
			case deleteConversationPayload:
				cmds = append(cmds, m.deleteConversation(api.Conversation(payload)))
			}
		}
	case msgConversationDeleted:
		cmds = append(cmds, m.loadConversations())
	}

	var cmd tea.Cmd
	m.content, cmd = m.content.Update(msg)
	if cmd != nil {
		cmds = append(cmds, cmd)
	}

	if m.Width > 0 {
		wrap := lipgloss.NewStyle().Width(m.Width)
		m.Header = m.headerView()
		m.Footer = "" // TODO: "Press ? for help"
		if m.confirmPrompt.Focused() {
			m.Footer = wrap.Render(m.confirmPrompt.View())
		}
		m.Error = tuiutil.ErrorBanner(m.Err, m.Width)
		fixedHeight := tuiutil.Height(m.Header) + tuiutil.Height(m.Error) + tuiutil.Height(m.Footer)
		m.content.Height = m.Height - fixedHeight
		m.Content = m.content.View()
	}
	return m, tea.Batch(cmds...)
}

func (m *Model) loadConversations() tea.Cmd {
	return func() tea.Msg {
		messages, err := m.Ctx.Store.LatestConversationMessages()
		if err != nil {
			return shared.MsgError(fmt.Errorf("Could not load conversations: %v", err))
		}

		loaded := make([]loadedConversation, len(messages))
		for i, m := range messages {
			loaded[i].lastReply = m
			loaded[i].conv = *m.Conversation
		}

		return msgConversationsLoaded(loaded)
	}
}

func (m *Model) deleteConversation(conv api.Conversation) tea.Cmd {
	return func() tea.Msg {
		err := m.Ctx.Store.DeleteConversation(&conv)
		if err != nil {
			return shared.MsgError(fmt.Errorf("Could not delete conversation: %v", err))
		}
		return msgConversationDeleted{}
	}
}

func (m Model) View() string {
	if m.Width == 0 {
		return ""
	}
	sections := make([]string, 0, 6)

	if m.Header != "" {
		sections = append(sections, m.Header)
	}

	sections = append(sections, m.Content)
	if m.Error != "" {
		sections = append(sections, m.Error)
	}

	if m.Footer != "" {
		sections = append(sections, m.Footer)
	}

	return lipgloss.JoinVertical(lipgloss.Left, sections...)
}

func (m *Model) headerView() string {
	titleStyle := lipgloss.NewStyle().Bold(true)
	header := titleStyle.Render("Conversations")
	return styles.Header.Width(m.Width).Render(header)
}

func (m *Model) renderConversationList() string {
	now := time.Now()
	midnight := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	monthStart := time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location())
	dayOfWeek := int(now.Weekday())
	categories := []struct {
		name   string
		cutoff time.Duration
	}{
		{"Today", now.Sub(midnight)},
		{"Yesterday", now.Sub(midnight.AddDate(0, 0, -1))},
		{"This week", now.Sub(midnight.AddDate(0, 0, -dayOfWeek))},
		{"Last week", now.Sub(midnight.AddDate(0, 0, -(dayOfWeek + 7)))},
		{"This month", now.Sub(monthStart)},
		{"Last month", now.Sub(monthStart.AddDate(0, -1, 0))},
		{"2 Months ago", now.Sub(monthStart.AddDate(0, -2, 0))},
		{"3 Months ago", now.Sub(monthStart.AddDate(0, -3, 0))},
		{"4 Months ago", now.Sub(monthStart.AddDate(0, -4, 0))},
		{"5 Months ago", now.Sub(monthStart.AddDate(0, -5, 0))},
		{"6 Months ago", now.Sub(monthStart.AddDate(0, -6, 0))},
		{"Older", now.Sub(time.Time{})},
	}

	categoryStyle := lipgloss.NewStyle().
		MarginBottom(1).
		Foreground(lipgloss.Color("12")).
		PaddingLeft(1).
		Bold(true)

	itemStyle := lipgloss.NewStyle().
		MarginBottom(1)

	ageStyle := lipgloss.NewStyle().Faint(true).SetString()
	titleStyle := lipgloss.NewStyle().Bold(true)
	untitledStyle := lipgloss.NewStyle().Faint(true).Italic(true)
	selectedStyle := lipgloss.NewStyle().Faint(true).Foreground(lipgloss.Color("6"))

	var (
		currentOffset   int
		currentCategory string
		sb              strings.Builder
	)

	m.itemOffsets = make([]int, len(m.conversations))
	sb.WriteRune('\n')
	currentOffset += 1

	for i, c := range m.conversations {
		lastReplyAge := now.Sub(c.lastReply.CreatedAt)

		var category string
		for _, g := range categories {
			if lastReplyAge < g.cutoff {
				category = g.name
				break
			}
		}

		// print the category
		if category != currentCategory {
			currentCategory = category
			heading := categoryStyle.Render(currentCategory)
			sb.WriteString(heading)
			currentOffset += tuiutil.Height(heading)
			sb.WriteRune('\n')
		}

		tStyle := titleStyle.Copy()
		if c.conv.Title == "" {
			tStyle = tStyle.Inherit(untitledStyle).SetString("(untitled)")
		}
		if i == m.cursor {
			tStyle = tStyle.Inherit(selectedStyle)
		}

		title := tStyle.Width(m.Width - 3).PaddingLeft(2).Render(c.conv.Title)
		if i == m.cursor {
			title = ">" + title[1:]
		}

		m.itemOffsets[i] = currentOffset
		item := itemStyle.Render(fmt.Sprintf(
			"%s\n  %s",
			title,
			ageStyle.Render(util.HumanTimeElapsedSince(lastReplyAge)),
		))
		sb.WriteString(item)
		currentOffset += tuiutil.Height(item)
		if i < len(m.conversations)-1 {
			sb.WriteRune('\n')
		}
	}
	return sb.String()
}