package chat

import (
	"strings"
	"time"

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

func (m *Model) setMessage(i int, msg conversation.Message) {
	if i >= len(m.App.Messages) {
		panic("i out of range")
	}
	m.App.Messages[i] = msg
	m.messageCache[i] = m.renderMessage(i)
}

func (m *Model) addMessage(msg conversation.Message) {
	m.App.Messages = append(m.App.Messages, msg)
	m.messageCache = append(m.messageCache, m.renderMessage(len(m.App.Messages)-1))
}

func (m *Model) setMessageContents(i int, content string) {
	if i >= len(m.App.Messages) {
		panic("i out of range")
	}
	m.App.Messages[i].Content = content
	m.messageCache[i] = m.renderMessage(i)
}

func (m *Model) rebuildMessageCache() {
	m.messageCache = make([]string, len(m.App.Messages))
	for i := range m.App.Messages {
		m.messageCache[i] = m.renderMessage(i)
	}
}

func (m *Model) updateContent() {
	atBottom := m.content.AtBottom()
	m.content.SetContent(m.conversationMessagesView())
	if atBottom {
		m.content.GotoBottom()
	}
}

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

	var cmds []tea.Cmd
	switch msg := msg.(type) {
	case tea.KeyMsg:
		cmd := m.handleInput(msg)
		if cmd != nil {
			inputHandled = true
			cmds = append(cmds, cmd)
		}
	case tea.WindowSizeMsg:
		m.Width, m.Height = msg.Width, msg.Height
		m.content.Width = msg.Width
		m.input.SetWidth(msg.Width - m.input.FocusedStyle.Base.GetHorizontalFrameSize())
		if len(m.App.Messages) > 0 {
			m.rebuildMessageCache()
			m.updateContent()
		}
	case shared.MsgViewEnter:
		// wake up spinners and cursors
		cmds = append(cmds, cursor.Blink, m.spinner.Tick)

		// Refresh view
		m.rebuildMessageCache()
		m.updateContent()

		if m.App.Conversation.ID > 0 {
			// (re)load conversation contents
			cmds = append(cmds, m.loadConversationMessages())
		}
	case tuiutil.MsgTempfileEditorClosed:
		contents := string(msg)
		switch m.editorTarget {
		case input:
			m.input.SetValue(contents)
		case selectedMessage:
			toEdit := m.App.Messages[m.selectedMessage]
			if toEdit.Content != contents {
				toEdit.Content = contents
				m.setMessage(m.selectedMessage, toEdit)
				if m.persistence && toEdit.ID > 0 {
					// create clone of message with its new contents
					cmds = append(cmds, m.cloneMessage(toEdit, true))
				}
			}
		}
	case msgConversationMessagesLoaded:
		m.App.Messages = msg.messages
		if m.selectedMessage == -1 {
			m.selectedMessage = len(msg.messages) - 1
		} else {
			m.selectedMessage = min(m.selectedMessage, len(m.App.Messages))
		}
		m.rebuildMessageCache()
		m.updateContent()
	case msgChatResponseChunk:
		cmds = append(cmds, m.waitForResponseChunk()) // wait for the next chunk

		if msg.Content == "" {
			// skip empty chunks
			break
		}

		last := len(m.App.Messages) - 1
		if last >= 0 && m.App.Messages[last].Role.IsAssistant() {
			// append chunk to existing message
			m.setMessageContents(last, m.App.Messages[last].Content+msg.Content)
		} else {
			// use chunk in a new message
			m.addMessage(conversation.Message{
				Role:    api.MessageRoleAssistant,
				Content: msg.Content,
			})
		}
		m.updateContent()

		// show cursor and reset blink interval (simulate typing)
		m.replyCursor.Blink = false
		cmds = append(cmds, m.replyCursor.BlinkCmd())

		m.tokenCount += msg.TokenCount
		m.elapsed = time.Now().Sub(m.startTime)
	case msgChatResponse:
		m.state = idle

		reply := conversation.Message(msg)
		reply.Content = strings.TrimSpace(reply.Content)

		last := len(m.App.Messages) - 1
		if last < 0 {
			panic("Unexpected empty messages handling msgAssistantReply")
		}

		if m.App.Messages[last].Role.IsAssistant() {
			// TODO: handle continuations gracefully - only some models support them
			m.setMessage(last, reply)
		} else {
			m.addMessage(reply)
		}

		if reply.Role == api.MessageRoleToolCall {
			// TODO: user confirmation before execution
			// m.state = confirmToolUse
			cmds = append(cmds, m.executeToolCalls(reply.ToolCalls))
		}

		if m.persistence {
			cmds = append(cmds, m.persistConversation())
		}

		if m.App.Conversation.Title == "" && len(m.App.Messages) > 0 {
			cmds = append(cmds, m.generateConversationTitle())
		}
	case msgChatResponseCanceled:
		m.state = idle
		m.updateContent()
	case msgChatResponseError:
		m.state = idle
		m.updateContent()
		return m, shared.WrapError(msg.Err)
	case msgToolResults:
		last := len(m.App.Messages) - 1
		if last < 0 {
			panic("Unexpected empty messages handling msgAssistantReply")
		}

		if m.App.Messages[last].Role != api.MessageRoleToolCall {
			panic("Previous message not a tool call, unexpected")
		}

		m.addMessage(conversation.Message{
			Role:        api.MessageRoleToolResult,
			ToolResults: conversation.ToolResults(msg),
		})

		if m.persistence {
			cmds = append(cmds, m.persistConversation())
		}

		m.updateContent()
	case msgConversationTitleGenerated:
		title := string(msg)
		m.App.Conversation.Title = title
		if m.persistence && m.App.Conversation.ID > 0 {
			cmds = append(cmds, m.persistConversation())
		}
	case cursor.BlinkMsg:
		if m.state == pendingResponse {
			// ensure we show the updated "wait for response" cursor blink state
			last := len(m.App.Messages) - 1
			m.messageCache[last] = m.renderMessage(last)
			m.updateContent()
		}
	case msgConversationPersisted:
		m.App.Conversation = conversation.Conversation(msg)
		cmds = append(cmds, m.persistMessages())
	case msgMessagesPersisted:
		m.App.Messages = msg
		m.rebuildMessageCache()
		m.updateContent()
	case msgMessageCloned:
		cmds = append(cmds, m.loadConversationMessages())
	case msgSelectedRootCycled, msgSelectedReplyCycled, msgMessageUpdated:
		cmds = append(cmds, m.loadConversationMessages())
	}

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

	prevInputLineCnt := m.input.LineCount()

	if !inputHandled {
		m.input, cmd = m.input.Update(msg)
		if cmd != nil {
			inputHandled = true
			cmds = append(cmds, cmd)
		}
	}

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

	// this is a pretty nasty hack to ensure the input area viewport doesn't
	// scroll below its content, which can happen when the input viewport
	// height has grown, or previously entered lines have been deleted
	if prevInputLineCnt != m.input.LineCount() {
		// dist is the distance we'd need to scroll up from the current cursor
		// position to position the last input line at the bottom of the
		// viewport. if negative, we're already scrolled above the bottom
		dist := m.input.Line() - (m.input.LineCount() - m.input.Height())
		if dist > 0 {
			for i := 0; i < dist; i++ {
				// move cursor up until content reaches the bottom of the viewport
				m.input.CursorUp()
			}
			m.input, _ = m.input.Update(nil)
			for i := 0; i < dist; i++ {
				// move cursor back down to its previous position
				m.input.CursorDown()
			}
			m.input, _ = m.input.Update(nil)
		}
	}

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