package conversations

import (
	"fmt"
	"strings"
	"time"

	"git.mlow.ca/mlow/lmcli/pkg/conversation"
	"git.mlow.ca/mlow/lmcli/pkg/tui/bubbles"
	"git.mlow.ca/mlow/lmcli/pkg/tui/model"
	"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 (
	// sent when conversation list is loaded
	msgConversationsLoaded conversation.ConversationList
	// sent when a single conversation is loaded
	msgConversationLoaded conversation.Conversation
	// sent when a conversation is deleted
	msgConversationDeleted struct{}
)

type Model struct {
	App    *model.AppModel
	width  int
	height int

	cursor      int
	itemOffsets []int // conversation y offsets

	content       viewport.Model
	confirmPrompt bubbles.ConfirmPrompt
}

func Conversations(app *model.AppModel) *Model {
	viewport.New(0, 0)
	m := Model{
		App:     app,
		content: viewport.New(0, 0),
	}
	return &m
}

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

	conversations := m.App.Conversations.Items

	switch msg.String() {
	case "enter":
		if len(conversations) > 0 && m.cursor < len(conversations) {
			return m.loadConversation(conversations[m.cursor].ID)
		}
	case "j", "down":
		if m.cursor < len(conversations)-1 {
			m.cursor++
			if m.cursor == len(conversations)-1 {
				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(conversations) - 1
			m.content.GotoBottom()
		}
		return shared.KeyHandled(msg)
	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 shared.KeyHandled(msg)
	case "n":
		m.App.NewConversation()
		return shared.ChangeView(shared.ViewChat)
	case "d":
		if !m.confirmPrompt.Focused() && len(conversations) > 0 && m.cursor < len(conversations) {
			title := conversations[m.cursor].Title
			if title == "" {
				title = "(untitled)"
			}
			m.confirmPrompt = bubbles.NewConfirmPrompt(
				fmt.Sprintf("Delete '%s'?", title),
				conversations[m.cursor],
			)
			m.confirmPrompt.Style = lipgloss.NewStyle().
				Bold(true).
				Foreground(lipgloss.Color("3"))
			return shared.KeyHandled(msg)
		}
	case "c":
		// copy/clone conversation
	case "r":
		// show prompt to rename conversation
	case "shift+r":
		// show prompt to generate name for conversation
	}
	return nil
}

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

func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
	isInput := false
	inputHandled := false

	var cmds []tea.Cmd
	switch msg := msg.(type) {
	case tea.KeyMsg:
		isInput = true
		cmd := m.handleInput(msg)
		if cmd != nil {
			cmds = append(cmds, cmd)
			inputHandled = true
		}
	case shared.MsgViewEnter:
		cmds = append(cmds, m.loadConversations())
		m.content.SetContent(m.renderConversationList())
	case tea.WindowSizeMsg:
		m.width, m.height = msg.Width, msg.Height
		m.content.SetContent(m.renderConversationList())
	case msgConversationsLoaded:
		m.App.Conversations = conversation.ConversationList(msg)
		m.cursor = max(0, min(len(m.App.Conversations.Items), m.cursor))
		m.content.SetContent(m.renderConversationList())
	case msgConversationLoaded:
		m.App.ClearConversation()
		m.App.Conversation = conversation.Conversation(msg)
		cmds = append(cmds, func() tea.Msg {
			return shared.MsgViewChange(shared.ViewChat)
		})
	case bubbles.MsgConfirmPromptAnswered:
		m.confirmPrompt.Blur()
		if msg.Value {
			conv, ok := msg.Payload.(conversation.ConversationListItem)
			if ok {
				cmds = append(cmds, m.deleteConversation(conv))
			}
		}
	case msgConversationDeleted:
		cmds = append(cmds, m.loadConversations())
	}

	if !isInput || !inputHandled {
		content, cmd := m.content.Update(msg)
		m.content = content
		if cmd != nil {
			cmds = append(cmds, cmd)
		}
	}

	if len(cmds) > 0 {
		return m, tea.Batch(cmds...)
	}

	return m, nil
}

func (m *Model) loadConversations() tea.Cmd {
	return func() tea.Msg {
		list, err := m.App.Ctx.Conversations.LoadConversationList()
		if err != nil {
			return shared.AsMsgError(fmt.Errorf("Could not load conversations: %v", err))
		}
		return msgConversationsLoaded(list)
	}
}

func (m *Model) loadConversation(conversationID uint) tea.Cmd {
	return func() tea.Msg {
		conversation, err := m.App.Ctx.Conversations.GetConversationByID(conversationID)
		if err != nil {
			return shared.AsMsgError(fmt.Errorf("Could not load conversation %d: %v", conversationID, err))
		}
		return msgConversationLoaded(*conversation)
	}
}

func (m *Model) deleteConversation(conv conversation.ConversationListItem) tea.Cmd {
	return func() tea.Msg {
		err := m.App.Ctx.Conversations.DeleteConversationById(conv.ID)
		if err != nil {
			return shared.AsMsgError(fmt.Errorf("Could not delete conversation: %v", err))
		}
		return msgConversationDeleted{}
	}
}

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

func (m *Model) Content(width int, height int, errors string) string {
	m.content.Width, m.content.Height = width, height
	content := m.content.View()
	if errors != "" {
		content += errors
	}
	return content
}

func (m *Model) Footer(width int) string {
	if m.confirmPrompt.Focused() {
		return lipgloss.NewStyle().Width(width).Render(m.confirmPrompt.View())
	}
	return ""
}

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.App.Conversations.Items))
	sb.WriteRune('\n')
	currentOffset += 1

	for i, c := range m.App.Conversations.Items {
		lastReplyAge := now.Sub(c.LastMessageAt)

		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
		if c.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.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.App.Conversations.Items)-1 {
			sb.WriteRune('\n')
		}
	}
	return sb.String()
}