package tui

// The terminal UI for lmcli, launched from the `lmcli chat` command
// TODO:
// - mode/focus changing between input and message selection
// - binding to open selected message/input in $EDITOR

import (
	"context"
	"fmt"
	"strings"

	"git.mlow.ca/mlow/lmcli/pkg/lmcli"
	models "git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
	"git.mlow.ca/mlow/lmcli/pkg/lmcli/tools"
	"github.com/charmbracelet/bubbles/textarea"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

type model struct {
	ctx           *lmcli.Context
	convShortname string

	// application state
	conversation *models.Conversation
	messages     []models.Message
	replyChan    chan string
	err          error

	// ui state
	isWaiting     bool
	confirmPrompt bool

	// ui elements
	content viewport.Model
	input   textarea.Model
	footer  string
}

type message struct {
	role    string
	content string
}

// custom tea.Msg types
type (
	// sent on each chunk received from LLM
	msgResponseChunk string
	// sent when response is finished being received
	msgResponseEnd string
	// sent when a conversation is (re)loaded
	msgConversationLoaded *models.Conversation
	// send when a conversation's messages are laoded
	msgMessagesLoaded []models.Message
	// sent when an error occurs
	msgError error
)

// styles
var (
	inputStyle     = lipgloss.NewStyle().Foreground(lipgloss.Color("#ff0000"))
	contentStyle   = lipgloss.NewStyle().PaddingLeft(2)
	userStyle      = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("10"))
	assistantStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("12"))
	footerStyle    = lipgloss.NewStyle().
			BorderTop(true).
			BorderStyle(lipgloss.NormalBorder())
)

func (m model) Init() tea.Cmd {
	return tea.Batch(
		textarea.Blink,
		m.loadConversation(m.convShortname),
		waitForChunk(m.replyChan),
	)
}

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

	switch msg := msg.(type) {
	case tea.KeyMsg:
		cmd = m.handleKeyMsg(msg)
	case tea.WindowSizeMsg:
		m.content.Width = msg.Width
		m.content.Height = msg.Height - m.input.Height() - lipgloss.Height(m.footerView())
		m.input.SetWidth(msg.Width - 1)
		m.updateContent()
	case msgConversationLoaded:
		c := (*models.Conversation)(msg)
		cmd = m.loadMessages(c)
	case msgMessagesLoaded:
		m.messages = []models.Message(msg)
		m.updateContent()
	case msgResponseChunk:
		chunk := string(msg)
		if len(m.messages) > 0 {
			i := len(m.messages) - 1
			switch m.messages[i].Role {
			case models.MessageRoleAssistant:
				m.messages[i].Content += chunk
			default:
				m.messages = append(m.messages, models.Message{
					Role:            models.MessageRoleAssistant,
					Content: chunk,
				})
			}
			m.updateContent()
		}
		cmd = waitForChunk(m.replyChan) // wait for the next chunk
	case msgResponseEnd:
		m.isWaiting = false
		m.footer = "Press Ctrl+S to send, Ctrl+C or 'q' to quit"
	}

	if cmd != nil {
		return m, cmd
	}

	m.input, cmd = m.input.Update(msg)
	if cmd != nil {
		return m, cmd
	}

	m.content, cmd = m.content.Update(msg)
	if cmd != nil {
		return m, cmd
	}

	return m, cmd
}

func (m model) View() string {
	return lipgloss.JoinVertical(
		lipgloss.Left,
		m.content.View(),
		m.inputView(),
		m.footerView(),
	)
}

func initialModel(ctx *lmcli.Context, convShortname string) model {
	m := model{
		ctx:           ctx,
		convShortname: convShortname,

		replyChan: make(chan string),

		isWaiting:     false,
		confirmPrompt: false,
	}

	m.content = viewport.New(0, 0)

	m.input = textarea.New()
	m.input.Placeholder = "Enter a message"

	m.input.FocusedStyle.CursorLine = lipgloss.NewStyle()
	m.input.ShowLineNumbers = false
	m.input.Focus()

	m.updateContent()

	m.footer = "Press Ctrl+S to send, Ctrl+C or 'q' to quit"

	return m
}

func (m *model) handleKeyMsg(msg tea.KeyMsg) tea.Cmd {
	switch msg.String() {
	case "ctrl+c", "q":
		return tea.Quit
	case "ctrl+s":
		if !m.isWaiting && !m.confirmPrompt {
			m.confirmPrompt = true
			m.footer = "Press 'y' to confirm sending the message, 'n' to cancel"
			return nil
		}
	case "y":
		if m.confirmPrompt {
			userInput := m.input.Value()
			m.input.SetValue("")
			m.messages = append(m.messages, models.Message{
				Role:            models.MessageRoleUser,
				Content: userInput,
			})
			m.updateContent()
			m.content.GotoBottom()
			m.isWaiting = true
			m.confirmPrompt = false
			m.footer = "Waiting for response... (Press 's' to stop)"
			return m.promptLLM()
		}
	case "n":
		if m.confirmPrompt {
			m.confirmPrompt = false
			m.footer = "Press Ctrl+S to send, Ctrl+C or 'q' to quit"
			return nil
		}
	case "s":
		if m.isWaiting {
			m.isWaiting = false
			m.footer = "Response generation stopped. Press Ctrl+S to send, Ctrl+C or 'q' to quit"
			return nil
		}
	}

	return nil
}

func (m *model) loadConversation(shortname string) tea.Cmd {
	return func() tea.Msg {
		if shortname == "" {
			return nil
		}
		c, err := m.ctx.Store.ConversationByShortName(shortname)
		if err != nil {
			return msgError(fmt.Errorf("Could not lookup conversation: %v\n", err))
		}
		if c.ID == 0 {
			return msgError(fmt.Errorf("Conversation not found with short name: %s\n", shortname))
		}
		return msgConversationLoaded(c)
	}
}

func (m *model) loadMessages(c *models.Conversation) tea.Cmd {
	return func() tea.Msg {
		messages, err := m.ctx.Store.Messages(c)
		if err != nil {
			return msgError(fmt.Errorf("Could not load conversation messages: %v\n", err))
		}
		return msgMessagesLoaded(messages)
	}
}

func waitForChunk(ch chan string) tea.Cmd {
	return func() tea.Msg {
		return msgResponseChunk(<-ch)
	}
}

func (m *model) promptLLM() tea.Cmd {
	return func() tea.Msg {
		completionProvider, err := m.ctx.GetCompletionProvider(*m.ctx.Config.Defaults.Model)
		if err != nil {
			return msgError(err)
		}

		var toolBag []models.Tool
		for _, toolName := range *m.ctx.Config.Tools.EnabledTools {
			tool, ok := tools.AvailableTools[toolName]
			if ok {
				toolBag = append(toolBag, tool)
			}
		}

		requestParams := models.RequestParameters{
			Model:       *m.ctx.Config.Defaults.Model,
			MaxTokens:   *m.ctx.Config.Defaults.MaxTokens,
			Temperature: *m.ctx.Config.Defaults.Temperature,
			ToolBag:     toolBag,
		}

		// TODO: supply a reply callback and handle error
		resp, _ := completionProvider.CreateChatCompletionStream(
			context.Background(), requestParams, m.messages, nil, m.replyChan,
		)

		return msgResponseEnd(resp)
	}
}

func (m *model) updateContent() {
	sb := strings.Builder{}
	msgCnt := len(m.messages)
	for i, message := range m.messages {
		var style lipgloss.Style
		if message.Role == models.MessageRoleUser {
			style = userStyle
		} else {
			style = assistantStyle
		}

		sb.WriteString(fmt.Sprintf("%s:\n\n", style.Render(string(message.Role))))

		highlighted, _ := m.ctx.Chroma.HighlightS(message.Content)
		sb.WriteString(contentStyle.Width(m.content.Width - 5).Render(highlighted))
		if i < msgCnt-1 {
			sb.WriteString("\n\n")
		}
	}
	m.content.SetContent(sb.String())
}

func (m model) inputView() string {
	var inputView string
	if m.isWaiting {
		inputView = inputStyle.Faint(true).Render(m.input.View())
	} else {
		inputView = inputStyle.Render(m.input.View())
	}
	return inputView
}

func (m model) footerView() string {
	return footerStyle.
		Width(m.content.Width).
		Align(lipgloss.Center).
		Render(m.footer)
}

func Launch(ctx *lmcli.Context, convShortname string) error {
	p := tea.NewProgram(initialModel(ctx, convShortname), tea.WithAltScreen())
	if _, err := p.Run(); err != nil {
		return fmt.Errorf("Error running program: %v", err)
	}
	return nil
}