package ui

import (
	"image/color"
	"strings"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/canvas"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/theme"
	"fyne.io/fyne/v2/widget"
)

// bubbleKind 区分气泡样式。
type bubbleKind int

const (
	bubbleUser bubbleKind = iota
	bubbleBot
	bubbleError
)

func colorFor(k bubbleKind) color.Color {
	switch k {
	case bubbleUser:
		return colorUserBubble()
	case bubbleError:
		return colorErrBubble()
	default:
		return colorBotBubble()
	}
}

// bubble 是一条消息气泡：圆角背景 + 角色标题 + 正文。
// 流式阶段用 Label 追加文本，结束后换成 RichText 以获得 Markdown 排版。
type bubble struct {
	root *fyne.Container
	bg   *canvas.Rectangle
	body *fyne.Container
	head *widget.Label
	live *widget.Label
	text strings.Builder
}

func newBubble(role string, kind bubbleKind) *bubble {
	bg := canvas.NewRectangle(colorFor(kind))
	bg.CornerRadius = 10
	bg.StrokeColor = colorBorder()
	bg.StrokeWidth = 1

	head := widget.NewLabelWithStyle(role, fyne.TextAlignLeading, fyne.TextStyle{Bold: true})
	head.Importance = widget.LowImportance

	live := widget.NewLabel("…")
	live.Wrapping = fyne.TextWrapWord

	body := container.NewVBox(head, live)
	root := container.NewStack(bg, container.New(innerPadLayout{}, body))

	return &bubble{root: root, bg: bg, body: body, head: head, live: live}
}

// append 追加流式文本。
func (b *bubble) append(delta string) {
	b.text.WriteString(delta)
	b.live.SetText(b.text.String())
}

// finish 结束流式状态；err 非空时展示错误。
func (b *bubble) finish(err error) {
	if err != nil {
		b.live.SetText("⚠ " + err.Error())
		b.bg.FillColor = colorErrBubble()
		b.bg.Refresh()
		return
	}
	text := strings.TrimSpace(b.text.String())
	if text == "" {
		text = "（没有返回内容）"
	}
	rt := widget.NewRichTextFromMarkdown(text)
	rt.Wrapping = fyne.TextWrapWord
	b.body.Objects = []fyne.CanvasObject{b.head, rt}
	b.body.Refresh()
}

// innerPadLayout 给气泡留内边距。
type innerPadLayout struct{}

func (innerPadLayout) MinSize(objs []fyne.CanvasObject) fyne.Size {
	// 宽度不参与最小尺寸计算：气泡宽度由滚动区的视口决定，
	// 否则长文本会把聊天区撑宽，导致换行宽度算大、右侧文字被截断。
	h := float32(0)
	for _, o := range objs {
		h = fyne.Max(h, o.MinSize().Height)
	}
	pad := theme.Padding() * 2
	return fyne.NewSize(0, h+pad)
}

func (innerPadLayout) Layout(objs []fyne.CanvasObject, size fyne.Size) {
	pad := theme.Padding() * 2
	w := fyne.Max(size.Width-pad*2, 1)
	h := fyne.Max(size.Height-pad, 1)
	for _, o := range objs {
		o.Move(fyne.NewPos(pad, pad/2))
		o.Resize(fyne.NewSize(w, h))
	}
}

// chatView 是消息列表：可滚动，支持流式追加与自动滚底。
type chatView struct {
	list    *fyne.Container
	scroll  *container.Scroll
	current *bubble
}

func newChatView() *chatView {
	list := container.NewVBox()
	scroll := container.NewScroll(list)
	scroll.Direction = container.ScrollVerticalOnly
	scroll.SetMinSize(fyne.NewSize(380, 300))
	return &chatView{list: list, scroll: scroll}
}

// object 返回可嵌入界面的对象。
func (c *chatView) object() fyne.CanvasObject { return c.scroll }

func (c *chatView) appendBubble(b *bubble) {
	c.list.Add(b.root)
	c.scroll.ScrollToBottom()
}

// addUser 添加一条用户消息。
func (c *chatView) addUser(text string, withImage bool) {
	if withImage {
		text += "\n（已附带区域截图）"
	}
	b := newBubble("你", bubbleUser)
	b.append(text)
	b.finish(nil)
	c.appendBubble(b)
}

// beginAssistant 开始一条助手消息。
func (c *chatView) beginAssistant(auto bool) {
	role := "助手"
	if auto {
		role = "助手 · 自动识别"
	}
	c.current = newBubble(role, bubbleBot)
	c.appendBubble(c.current)
}

// appendDelta 追加流式文本。
func (c *chatView) appendDelta(delta string) {
	if c.current == nil {
		c.beginAssistant(false)
	}
	c.current.append(delta)
	c.scroll.ScrollToBottom()
}

// endAssistant 结束当前助手消息。
func (c *chatView) endAssistant(err error) {
	if c.current == nil {
		return
	}
	c.current.finish(err)
	c.current = nil
	c.scroll.ScrollToBottom()
}

// addNotice 插入一条系统提示。
func (c *chatView) addNotice(text string) {
	b := newBubble("系统", bubbleError)
	b.append(text)
	b.finish(nil)
	c.appendBubble(b)
}

// clear 清空消息列表。
func (c *chatView) clear() {
	c.list.Objects = nil
	c.current = nil
	c.list.Refresh()
}