package main

import (
	"fmt"
	"strings"
	"time"

	"github.com/gdamore/tcell/v2"
	"github.com/rivo/tview"
)

// Buffer holds messages for a channel/DM/status window.
type Buffer struct {
	Name   string
	Lines  []string
	Unread int
}

// UI manages the terminal interface.
type UI struct {
	app       *tview.Application
	messages  *tview.TextView
	statusBar *tview.TextView
	input     *tview.InputField
	layout    *tview.Flex

	buffers       []*Buffer
	currentBuffer int

	onInput func(string)
}

// NewUI creates the tview-based IRC-like UI.
func NewUI() *UI {
	ui := &UI{
		app: tview.NewApplication(),
		buffers: []*Buffer{
			{Name: "(status)", Lines: nil},
		},
	}

	// Message area.
	ui.messages = tview.NewTextView().
		SetDynamicColors(true).
		SetScrollable(true).
		SetWordWrap(true).
		SetChangedFunc(func() {
			ui.app.Draw()
		})
	ui.messages.SetBorder(false)

	// Status bar.
	ui.statusBar = tview.NewTextView().
		SetDynamicColors(true)
	ui.statusBar.SetBackgroundColor(tcell.ColorNavy)
	ui.statusBar.SetTextColor(tcell.ColorWhite)

	// Input field.
	ui.input = tview.NewInputField().
		SetFieldBackgroundColor(tcell.ColorBlack).
		SetFieldTextColor(tcell.ColorWhite)
	ui.input.SetDoneFunc(func(key tcell.Key) {
		if key == tcell.KeyEnter {
			text := ui.input.GetText()
			if text == "" {
				return
			}
			ui.input.SetText("")
			if ui.onInput != nil {
				ui.onInput(text)
			}
		}
	})

	// Capture Alt+N for window switching.
	ui.app.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
		if event.Modifiers()&tcell.ModAlt != 0 {
			r := event.Rune()
			if r >= '0' && r <= '9' {
				idx := int(r - '0')
				ui.SwitchBuffer(idx)
				return nil
			}
		}
		return event
	})

	// Layout: messages on top, status bar, input at bottom.
	ui.layout = tview.NewFlex().SetDirection(tview.FlexRow).
		AddItem(ui.messages, 0, 1, false).
		AddItem(ui.statusBar, 1, 0, false).
		AddItem(ui.input, 1, 0, true)

	ui.app.SetRoot(ui.layout, true)
	ui.app.SetFocus(ui.input)

	return ui
}

// Run starts the UI event loop (blocks).
func (ui *UI) Run() error {
	return ui.app.Run()
}

// Stop stops the UI.
func (ui *UI) Stop() {
	ui.app.Stop()
}

// OnInput sets the callback for user input.
func (ui *UI) OnInput(fn func(string)) {
	ui.onInput = fn
}

// AddLine adds a line to the specified buffer.
func (ui *UI) AddLine(bufferName string, line string) {
	ui.app.QueueUpdateDraw(func() {
		buf := ui.getOrCreateBuffer(bufferName)
		buf.Lines = append(buf.Lines, line)

		// Mark unread if not currently viewing this buffer.
		if ui.buffers[ui.currentBuffer] != buf {
			buf.Unread++
			ui.refreshStatus()
		}

		// If viewing this buffer, append to display.
		if ui.buffers[ui.currentBuffer] == buf {
			fmt.Fprintln(ui.messages, line)
		}
	})
}

// AddStatus adds a line to the status buffer (buffer 0).
func (ui *UI) AddStatus(line string) {
	ts := time.Now().Format("15:04")
	ui.AddLine("(status)", fmt.Sprintf("[gray]%s[white] %s", ts, line))
}

// SwitchBuffer switches to the buffer at index n.
func (ui *UI) SwitchBuffer(n int) {
	ui.app.QueueUpdateDraw(func() {
		if n < 0 || n >= len(ui.buffers) {
			return
		}
		ui.currentBuffer = n
		buf := ui.buffers[n]
		buf.Unread = 0
		ui.messages.Clear()
		for _, line := range buf.Lines {
			fmt.Fprintln(ui.messages, line)
		}
		ui.messages.ScrollToEnd()
		ui.refreshStatus()
	})
}

// SwitchToBuffer switches to the named buffer, creating it if needed.
func (ui *UI) SwitchToBuffer(name string) {
	ui.app.QueueUpdateDraw(func() {
		buf := ui.getOrCreateBuffer(name)
		for i, b := range ui.buffers {
			if b == buf {
				ui.currentBuffer = i
				break
			}
		}
		buf.Unread = 0
		ui.messages.Clear()
		for _, line := range buf.Lines {
			fmt.Fprintln(ui.messages, line)
		}
		ui.messages.ScrollToEnd()
		ui.refreshStatus()
	})
}

// SetStatus updates the status bar text.
func (ui *UI) SetStatus(nick, target, connStatus string) {
	ui.app.QueueUpdateDraw(func() {
		ui.refreshStatusWith(nick, target, connStatus)
	})
}

func (ui *UI) refreshStatus() {
	// Will be called from the main goroutine via QueueUpdateDraw parent.
	// Rebuild status from app state — caller must provide context.
}

func (ui *UI) refreshStatusWith(nick, target, connStatus string) {
	var unreadParts []string
	for i, buf := range ui.buffers {
		if buf.Unread > 0 {
			unreadParts = append(unreadParts, fmt.Sprintf("%d:%s(%d)", i, buf.Name, buf.Unread))
		}
	}
	unread := ""
	if len(unreadParts) > 0 {
		unread = " [Act: " + strings.Join(unreadParts, ",") + "]"
	}

	bufInfo := fmt.Sprintf("[%d:%s]", ui.currentBuffer, ui.buffers[ui.currentBuffer].Name)

	ui.statusBar.Clear()
	fmt.Fprintf(ui.statusBar, " [%s] %s %s %s%s",
		connStatus, nick, bufInfo, target, unread)
}

func (ui *UI) getOrCreateBuffer(name string) *Buffer {
	for _, buf := range ui.buffers {
		if buf.Name == name {
			return buf
		}
	}
	buf := &Buffer{Name: name}
	ui.buffers = append(ui.buffers, buf)
	return buf
}

// BufferCount returns the number of buffers.
func (ui *UI) BufferCount() int {
	return len(ui.buffers)
}

// BufferIndex returns the index of a named buffer, or -1.
func (ui *UI) BufferIndex(name string) int {
	for i, buf := range ui.buffers {
		if buf.Name == name {
			return i
		}
	}
	return -1
}