// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//go:build js && wasm

package webui

import (
	"bufio"
	"bytes"
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"image"
	"io"
	"math"
	"syscall/js"

	"github.com/xiaoqidun/ofdgo"
)

// exportWriter 分块传递导出数据
type exportWriter struct {
	write js.Value
}

// Write 将数据块交给浏览器保存
// 入参: data 导出数据
// 返回: int 写入长度, error 错误信息
func (w exportWriter) Write(data []byte) (int, error) {
	size := len(data)
	for len(data) > 0 {
		n := min(len(data), 1<<20)
		if err := awaitExport(w.write, bytesToJS(data[:n])); err != nil {
			return size - len(data), err
		}
		data = data[n:]
	}
	return size, nil
}

// awaitExport 等待浏览器处理导出检查点
// 入参: fn 浏览器回调, args 回调参数
// 返回: error 写入错误或取消原因
func awaitExport(fn js.Value, args ...any) error {
	done := make(chan error)
	callback := js.FuncOf(func(this js.Value, args []js.Value) any {
		var err error
		if args[1].Bool() {
			err = context.Canceled
		} else if message := args[0].String(); message != "" {
			err = fmt.Errorf("%s", message)
		}
		done <- err
		return nil
	})
	defer callback.Release()
	fn.Invoke(append(args, callback)...)
	return <-done
}

// currentSession 当前WebUI文档会话
var currentSession *Session

// apiResult 浏览器接口返回结果
type apiResult struct {
	OK    bool   `json:"ok"`
	Error string `json:"error,omitempty"`
	Data  any    `json:"data,omitempty"`
}

// RunWASM 注册浏览器WASM接口并阻塞运行
func RunWASM() {
	registerCallback("ofdgoOpen", openDocument)
	registerCallback("ofdgoConfigure", configureDocument)
	registerCallback("ofdgoDocumentInfo", documentInfo)
	registerCallback("ofdgoRenderPage", renderPage)
	registerCallback("ofdgoSVGFontData", svgFontData)
	registerCallback("ofdgoSearchPage", searchPage)
	registerCallback("ofdgoPageTextString", pageTextString)
	registerCallback("ofdgoExportFormats", exportFormats)
	registerCallback("ofdgoParsePageRange", parsePageRange)
	registerExportCallback("ofdgoExportPage", exportPage)
	registerExportCallback("ofdgoExportDocument", exportDocument)
	registerExportCallback("ofdgoExportAttachment", exportAttachment)
	registerCallback("ofdgoMatchFontFiles", matchFontFiles)
	registerCallback("ofdgoCreateDocument", createDocument)
	registerCallback("ofdgoChangePage", changePage)
	registerCallback("ofdgoInsertText", insertText)
	registerCallback("ofdgoUpdateText", updateText)
	registerCallback("ofdgoInsertImage", insertImage)
	registerCallback("ofdgoTransformObject", transformObject)
	registerCallback("ofdgoCopyObject", copyObject)
	registerCallback("ofdgoMoveObject", moveObject)
	registerCallback("ofdgoDeleteObject", deleteObject)
	registerCallback("ofdgoUndo", func([]js.Value) (any, error) { return restoreEditor(false) })
	registerCallback("ofdgoRedo", func([]js.Value) (any, error) { return restoreEditor(true) })
	registerExportCallback("ofdgoSaveDocument", saveDocument)
	select {}
}

// registerCallback 注册浏览器回调函数
// 入参: name 回调名称, fn 回调函数
func registerCallback(name string, fn func([]js.Value) (any, error)) {
	cb := js.FuncOf(func(this js.Value, args []js.Value) any {
		return callbackResult(fn, args)
	})
	js.Global().Set(name, cb)
}

// registerExportCallback 异步导出，为浏览器处理数据块让出事件循环
// 入参: name 回调名称, fn 回调函数
func registerExportCallback(name string, fn func([]js.Value) (any, error)) {
	cb := js.FuncOf(func(this js.Value, args []js.Value) any {
		executor := js.FuncOf(func(this js.Value, callbacks []js.Value) any {
			resolve := callbacks[0]
			go func() {
				resolve.Invoke(callbackResult(fn, args))
			}()
			return nil
		})
		defer executor.Release()
		return js.Global().Get("Promise").New(executor)
	})
	js.Global().Set(name, cb)
}

// callbackResult 转换浏览器接口结果
// 入参: fn 回调函数, args 回调参数
// 返回: any 浏览器结果
func callbackResult(fn func([]js.Value) (any, error), args []js.Value) any {
	data, err := safeCall(fn, args)
	if err != nil {
		return encodeResult(apiResult{OK: false, Error: err.Error()})
	}
	if result, ok := data.(js.Value); ok {
		return result
	}
	return encodeResult(apiResult{OK: true, Data: data})
}

// safeCall 调用浏览器回调并转换异常
// 入参: fn 回调函数, args 回调参数
// 返回: any 回调结果, error 错误信息
func safeCall(fn func([]js.Value) (any, error), args []js.Value) (data any, err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("%v", r)
		}
	}()
	return fn(args)
}

// openDocument 打开OFD文档
// 入参: args 浏览器参数
// 返回: any 文档信息, error 错误信息
func openDocument(args []js.Value) (any, error) {
	if len(args) < 3 {
		return nil, fmt.Errorf("missing open arguments")
	}
	data, err := bytesFromJS(args[0])
	if err != nil {
		return nil, err
	}
	fonts, err := fontsFromJS(args[1])
	if err != nil {
		return nil, err
	}
	renderAnnotations := args[2].Bool()
	currentEditor = nil
	if currentSession != nil {
		_ = currentSession.Close()
		currentSession = nil
	}
	session, err := Open(data, OpenOptions{Fonts: fonts, RenderAnnotations: renderAnnotations})
	if err != nil {
		return nil, err
	}
	currentSession = session
	return currentSession.Summary(), nil
}

// configureDocument 更新当前会话的字体和注解设置
// 入参: args 浏览器参数
// 返回: any 文档信息, error 错误信息
func configureDocument(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	if !args[0].IsNull() && !args[0].IsUndefined() {
		fonts, err := fontsFromJS(args[0])
		if err != nil {
			return nil, err
		}
		if err := currentSession.SetFonts(fonts); err != nil {
			return nil, err
		}
	}
	if currentSession.Renderer.RenderAnnotations != args[1].Bool() {
		currentSession.Renderer.RenderAnnotations = args[1].Bool()
		clear(currentSession.textCache)
	}
	return currentSession.Summary(), nil
}

// documentInfo 获取首屏之后加载的字体统计和验签结果
// 入参: args 浏览器参数
// 返回: any 文档信息, error 错误信息
func documentInfo(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	return currentSession.Info(), nil
}

// exportAttachment 分块导出附件
// 入参: args 浏览器参数
// 返回: any 附件数据, error 错误信息
func exportAttachment(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	stream, err := currentSession.Reader.OpenAttachment(args[0].String())
	if err != nil {
		return nil, err
	}
	defer stream.Close()
	writer := bufio.NewWriterSize(exportWriter{write: args[1]}, 1<<20)
	if _, err := io.Copy(writer, stream); err != nil {
		return nil, err
	}
	if err := writer.Flush(); err != nil {
		return nil, err
	}
	return successResult(map[string]any{
		"mime": "application/octet-stream",
	}), nil
}

// svgFontData 读取SVG字体资源
// 入参: args 浏览器参数
// 返回: any 字体数据, error 错误信息
func svgFontData(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	data, err := currentSession.SVGFontData(args[0].String())
	if err != nil {
		return nil, err
	}
	return successResult(map[string]any{"bytes": bytesToJS(data)}), nil
}

// renderPage 渲染OFD页面
// 入参: args 浏览器参数
// 返回: any 页面SVG结果, error 错误信息
func renderPage(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	if len(args) == 0 {
		return nil, fmt.Errorf("missing page index")
	}
	page, err := currentSession.RenderPageSVG(args[0].Int())
	if err != nil {
		return nil, err
	}
	text, err := currentSession.PageText(args[0].Int())
	if err != nil {
		return nil, err
	}
	textData, err := json.Marshal(text)
	if err != nil {
		return nil, err
	}
	objects, err := editorObjects(args[0].Int(), text)
	if err != nil {
		return nil, err
	}
	links := make([]any, len(page.Links))
	for i, link := range page.Links {
		links[i] = map[string]any{
			"uri":    link.URI,
			"x":      link.Box.X,
			"y":      link.Box.Y,
			"width":  link.Box.W,
			"height": link.Box.H,
		}
	}
	fonts := make([]any, len(page.Fonts))
	for i, font := range page.Fonts {
		fonts[i] = map[string]any{"name": font.Name, "weight": font.Weight, "style": font.Style}
	}
	images := make([]any, len(page.Images))
	for i, image := range page.Images {
		images[i] = map[string]any{"name": image.Name, "mime": image.MIME, "bytes": bytesToJS(image.Data)}
	}
	return successResult(map[string]any{
		"index":   page.Index,
		"number":  page.Number,
		"id":      page.ID,
		"width":   page.Width,
		"height":  page.Height,
		"svg":     page.SVG,
		"links":   links,
		"fonts":   fonts,
		"images":  images,
		"text":    string(textData),
		"objects": objects,
	}), nil
}

// pageTextString 提取OFD页面原文
// 入参: args 浏览器参数
// 返回: any 页面原文, error 错误信息
func pageTextString(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	return currentSession.PageTextString(args[0].Int())
}

// searchPage 搜索OFD页面文字
// 入参: args 浏览器参数
// 返回: any 搜索结果, error 错误信息
func searchPage(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	return currentSession.SearchPage(args[0].Int(), args[1].String())
}

// exportFormats 获取导出格式
// 入参: args 浏览器参数
// 返回: any 导出格式, error 错误信息
func exportFormats(args []js.Value) (any, error) {
	return ExportFormats(), nil
}

// parsePageRange 解析当前文档的导出页码
// 入参: args 浏览器参数
// 返回: any 页面索引, error 错误信息
func parsePageRange(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	count, err := currentSession.Reader.PageCount()
	if err != nil {
		return nil, err
	}
	return ofdgo.ParsePageRange(args[0].String(), count)
}

// exportPage 导出OFD单页
// 入参: args 浏览器参数
// 返回: any 导出结果, error 错误信息
func exportPage(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	if len(args) < 4 {
		return nil, fmt.Errorf("missing export page arguments")
	}
	writer := bufio.NewWriterSize(exportWriter{write: args[3]}, 1<<20)
	format, err := currentSession.ExportPage(args[0].Int(), args[1].String(), args[2].Float(), writer)
	if err != nil {
		return nil, err
	}
	if err := writer.Flush(); err != nil {
		return nil, err
	}
	return successResult(map[string]any{
		"label": format.Label,
		"mime":  format.MIME,
	}), nil
}

// exportDocument 导出OFD文档
// 入参: args 浏览器参数
// 返回: any 导出结果, error 错误信息
func exportDocument(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	renderer := currentSession.Renderer
	renderer.OnExportProgress = func(completed, total int) error {
		return awaitExport(args[4], completed, total)
	}
	defer func() { renderer.OnExportProgress = nil }()
	var indices []int
	if !args[2].IsNull() {
		indices = make([]int, args[2].Length())
		for i := range indices {
			indices[i] = args[2].Index(i).Int()
		}
	}
	writer := bufio.NewWriterSize(exportWriter{write: args[3]}, 1<<20)
	format, err := currentSession.ExportDocument(args[0].String(), args[1].Float(), writer, indices...)
	if err != nil {
		return nil, err
	}
	if err := writer.Flush(); err != nil {
		return nil, err
	}
	return successResult(map[string]any{
		"label": format.Label,
		"mime":  format.MIME,
	}), nil
}

// successResult 创建成功接口结果
// 入参: data 返回数据
// 返回: js.Value 接口结果
func successResult(data any) js.Value {
	result := js.Global().Get("Object").New()
	result.Set("ok", true)
	result.Set("data", data)
	return result
}

// bytesToJS 将字节数据转换为Uint8Array
// 入参: data 字节数据
// 返回: js.Value Uint8Array对象
func bytesToJS(data []byte) js.Value {
	value := js.Global().Get("Uint8Array").New(len(data))
	js.CopyBytesToJS(value, data)
	return value
}

// matchFontFiles 匹配文档所需的字体文件
// 入参: args 浏览器参数
// 返回: any 匹配的字体文件名称, error 错误信息
func matchFontFiles(args []js.Value) (any, error) {
	if currentSession == nil {
		return nil, fmt.Errorf("ofd document is not opened")
	}
	return currentSession.Reader.MatchFontFiles(stringsFromJS(args[0]))
}

// bytesFromJS 从浏览器值读取二进制数据
// 入参: value 浏览器值
// 返回: []byte 二进制数据, error 错误信息
func bytesFromJS(value js.Value) ([]byte, error) {
	if value.IsUndefined() || value.IsNull() {
		return nil, fmt.Errorf("missing binary data")
	}
	uint8Array := js.Global().Get("Uint8Array")
	arrayBuffer := js.Global().Get("ArrayBuffer")
	if value.InstanceOf(arrayBuffer) {
		value = uint8Array.New(value)
	}
	if !value.InstanceOf(uint8Array) {
		return nil, fmt.Errorf("binary data must be Uint8Array or ArrayBuffer")
	}
	data := make([]byte, value.Get("byteLength").Int())
	if n := js.CopyBytesToGo(data, value); n != len(data) {
		return nil, fmt.Errorf("copied %d of %d bytes", n, len(data))
	}
	return data, nil
}

// fontsFromJS 从浏览器值读取字体文件
// 入参: value 浏览器值
// 返回: []FontFile 字体文件, error 错误信息
func fontsFromJS(value js.Value) ([]FontFile, error) {
	if value.IsUndefined() || value.IsNull() {
		return nil, nil
	}
	length := value.Get("length").Int()
	fonts := make([]FontFile, 0, length)
	for i := 0; i < length; i++ {
		item := value.Index(i)
		data, err := bytesFromJS(item.Get("data"))
		if err != nil {
			return nil, err
		}
		fonts = append(fonts, FontFile{Name: item.Get("name").String(), Data: data})
	}
	return fonts, nil
}

// stringsFromJS 从浏览器值读取字符串列表
// 入参: value 浏览器值
// 返回: []string 字符串列表
func stringsFromJS(value js.Value) []string {
	items := make([]string, value.Length())
	for i := range items {
		items[i] = value.Index(i).String()
	}
	return items
}

// encodeResult 编码浏览器接口返回结果
// 入参: result 返回结果
// 返回: string JSON字符串
func encodeResult(result apiResult) string {
	data, err := json.Marshal(result)
	if err != nil {
		fallback, _ := json.Marshal(apiResult{OK: false, Error: err.Error()})
		return string(fallback)
	}
	return string(data)
}

// currentEditor 当前新建文档
var currentEditor *ofdgo.Editor

// editorInfo 创作文档信息与操作状态
type editorInfo struct {
	DocumentInfo
	Revision uint64 `json:"revision"`
	CanUndo  bool   `json:"canUndo"`
	CanRedo  bool   `json:"canRedo"`
}

// editorPageInfo 页面操作结果与目标页面
type editorPageInfo struct {
	editorInfo
	PageIndex int `json:"pageIndex"`
}

// editorSummary 获取当前创作文档状态
// 返回: editorInfo 文档信息
func editorSummary() editorInfo {
	return editorInfo{currentSession.Summary(), currentEditor.Revision(), currentEditor.CanUndo(), currentEditor.CanRedo()}
}

// restoreEditor 撤销或重做并更新预览
// 入参: redo 是否重做
// 返回: any 文档信息, error 错误信息
func restoreEditor(redo bool) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	apply := currentEditor.Undo
	if redo {
		apply = currentEditor.Redo
	}
	if !apply() {
		return editorSummary(), nil
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// editorObjects 提供创作画布的对象命中区域
// 入参: index 页面索引, text 页面文字
// 返回: []any 对象区域, error 错误信息
func editorObjects(index int, text *ofdgo.PageText) ([]any, error) {
	objects := []any{}
	if currentEditor == nil {
		return objects, nil
	}
	page, err := currentSession.pageContent(index)
	if err != nil {
		return nil, err
	}
	textBoxes := make(map[string]ofdgo.Box)
	textValues := make(map[string]string)
	for _, run := range text.Runs {
		textValues[run.ID] += run.Text
		for _, box := range run.Boxes {
			if box.W <= 0 || box.H <= 0 {
				continue
			}
			prev, exists := textBoxes[run.ID]
			if !exists {
				textBoxes[run.ID] = box
				continue
			}
			x, y := math.Min(prev.X, box.X), math.Min(prev.Y, box.Y)
			textBoxes[run.ID] = ofdgo.Box{X: x, Y: y, W: math.Max(prev.X+prev.W, box.X+box.W) - x, H: math.Max(prev.Y+prev.H, box.Y+box.H) - y}
		}
	}
	fonts, err := currentSession.Reader.Fonts()
	if err != nil {
		return nil, err
	}
	fontNames := make(map[string]string, len(fonts))
	for _, font := range fonts {
		fontNames[font.ID] = font.FontName
	}
	for _, layer := range page.Content.Layer {
		for order, object := range layer.Objects {
			var id string
			var box ofdgo.Box
			switch object.Type {
			case "TextObject":
				id = object.TextObject.ID
				box = textBoxes[id]
			case "ImageObject":
				id = object.ImageObject.ID
				box, err = ofdgo.ParseBox(object.ImageObject.Boundary)
				if err != nil {
					return nil, err
				}
			default:
				continue
			}
			if box.W > 0 && box.H > 0 {
				item := map[string]any{"id": id, "image": object.Type == "ImageObject", "x": box.X, "y": box.Y, "width": box.W, "height": box.H, "order": order, "count": len(layer.Objects)}
				if object.Type == "TextObject" {
					item["text"], item["font"], item["fontName"], item["size"] = textValues[id], object.TextObject.Font, fontNames[object.TextObject.Font], object.TextObject.Size
					var r, g, b float64
					if fill := object.TextObject.FillColor; fill != nil {
						if _, err := fmt.Sscan(fill.Value, &r, &g, &b); err != nil {
							return nil, err
						}
					}
					item["color"] = fmt.Sprintf("#%02x%02x%02x", byte(r), byte(g), byte(b))
				}
				objects = append(objects, item)
			}
		}
	}
	return objects, nil
}

// transformObject 移动文字或等比缩放图片
// 入参: args 页码、对象标识、位移和缩放比例
// 返回: any 文档信息, error 错误信息
func transformObject(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	page, id := args[0].Int(), args[1].String()
	object, err := currentEditor.Object(page, id)
	if err != nil {
		return nil, err
	}
	scale := args[4].Float()
	var boundary *string
	switch object.Type {
	case "TextObject":
		if scale != 1 {
			return nil, fmt.Errorf("text resizing is not supported")
		}
		boundary = &object.TextObject.Boundary
	case "ImageObject":
		boundary = &object.ImageObject.Boundary
		object.ImageObject.CTM = ""
	default:
		return nil, fmt.Errorf("unsupported object type %q", object.Type)
	}
	box, err := ofdgo.ParseBox(*boundary)
	if err != nil {
		return nil, err
	}
	*boundary = fmt.Sprintf("%g %g %g %g", box.X+args[2].Float(), box.Y+args[3].Float(), box.W*scale, box.H*scale)
	if err := currentEditor.UpdateObject(page, id, object); err != nil {
		return nil, err
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// copyObject 复制选中对象并平移，复用字体和图片资源
// 入参: args 页码、对象标识和位移
// 返回: any 文档信息, error 错误信息
func copyObject(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	page := args[0].Int()
	object, err := currentEditor.Object(page, args[1].String())
	if err != nil {
		return nil, err
	}
	var boundary *string
	switch object.Type {
	case "TextObject":
		boundary = &object.TextObject.Boundary
	case "ImageObject":
		boundary = &object.ImageObject.Boundary
	default:
		return nil, fmt.Errorf("unsupported object type %q", object.Type)
	}
	box, err := ofdgo.ParseBox(*boundary)
	if err != nil {
		return nil, err
	}
	*boundary = fmt.Sprintf("%g %g %g %g", box.X+args[2].Float(), box.Y+args[3].Float(), box.W, box.H)
	if _, err := currentEditor.AddObject(page, object); err != nil {
		return nil, err
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// moveObject 调整选中对象的绘制顺序
// 入参: args 页码、对象标识和目标索引
// 返回: any 文档信息, error 错误信息
func moveObject(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	revision := currentEditor.Revision()
	if err := currentEditor.MoveObject(args[0].Int(), args[1].String(), args[2].Int()); err != nil {
		return nil, err
	}
	if currentEditor.Revision() == revision {
		return editorSummary(), nil
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// deleteObject 删除创作画布中选中的对象
// 入参: args 页码和对象标识
// 返回: any 文档信息, error 错误信息
func deleteObject(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	if err := currentEditor.DeleteObject(args[0].Int(), args[1].String()); err != nil {
		return nil, err
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// changePage 管理创作文档的页面
// 入参: args 操作、页面索引及尺寸或目标索引
// 返回: any 文档信息和目标页面, error 错误信息
func changePage(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	index := args[1].Int()
	revision := currentEditor.Revision()
	var err error
	switch action := args[0].String(); action {
	case "add":
		index, err = currentEditor.AddPage(args[2].Float(), args[3].Float())
	case "copy":
		index, err = currentEditor.CopyPage(index)
	case "delete":
		if currentEditor.PageCount() == 1 {
			return nil, fmt.Errorf("the document must contain at least one page")
		}
		err = currentEditor.DeletePage(index)
		index = min(index, currentEditor.PageCount()-1)
	case "move":
		target := args[2].Int()
		err = currentEditor.MovePage(index, target)
		index = target
	case "resize":
		err = currentEditor.ResizePage(index, args[2].Float(), args[3].Float())
	default:
		return nil, fmt.Errorf("unsupported page action %q", action)
	}
	if err != nil {
		return nil, err
	}
	if currentEditor.Revision() == revision {
		return editorPageInfo{editorSummary(), index}, nil
	}
	info, err := previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
	if err != nil {
		return nil, err
	}
	return editorPageInfo{info, index}, nil
}

// createDocument 新建单页文档
// 入参: args 标题、纸张宽高和注解设置
// 返回: any 文档信息, error 错误信息
func createDocument(args []js.Value) (any, error) {
	editor := ofdgo.NewEditor()
	editor.Info.Title = args[0].String()
	if _, err := editor.AddPage(args[1].Float(), args[2].Float()); err != nil {
		return nil, err
	}
	editor.SetHistoryLimit(100)
	return previewEditor(editor, args[3].Bool())
}

// previewEditor 通过内存快照更新预览，不生成中间压缩包
// 入参: editor 新建文档, annotations 是否显示注解
// 返回: editorInfo 文档信息, error 错误信息
func previewEditor(editor *ofdgo.Editor, annotations bool) (editorInfo, error) {
	reader, err := editor.Reader()
	if err != nil {
		return editorInfo{}, err
	}
	session, err := newSession(reader, OpenOptions{RenderAnnotations: annotations})
	if err != nil {
		return editorInfo{}, err
	}
	if currentSession != nil {
		_ = currentSession.Close()
	}
	currentSession = session
	currentEditor = editor
	return editorSummary(), nil
}

// updateText 修改文字，null内容保留排版，null字体数据和颜色沿用对象属性
// 入参: args 页码、对象标识、内容、字体数据、字号和颜色
// 返回: any 文档信息, error 错误信息
func updateText(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	page, id := args[0].Int(), args[1].String()
	object, err := currentEditor.Object(page, id)
	if err != nil {
		return nil, err
	}
	if object.Type != "TextObject" {
		return nil, fmt.Errorf("object %q is not text", id)
	}
	if !args[2].IsNull() {
		if !args[3].IsNull() {
			data, err := bytesFromJS(args[3])
			if err != nil {
				return nil, err
			}
			object.TextObject.Font, err = currentEditor.AddFont(FontFile{Data: data}, 0)
			if err != nil {
				return nil, err
			}
		}
		object.TextObject.Size = args[4].Float()
		if err := currentEditor.LayoutText(&object.TextObject, args[2].String()); err != nil {
			return nil, err
		}
	}
	if !args[5].IsNull() {
		if err := setTextColor(&object.TextObject, args[5].String()); err != nil {
			return nil, err
		}
	}
	revision := currentEditor.Revision()
	if err := currentEditor.UpdateObject(page, id, object); err != nil {
		return nil, err
	}
	if currentEditor.Revision() == revision {
		return editorSummary(), nil
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// setTextColor 将浏览器RGB色值写入文字对象，保留颜色透明度
// 入参: object 文字对象, value 十六进制色值
// 返回: error 错误信息
func setTextColor(object *ofdgo.TextObject, value string) error {
	if len(value) != 7 || value[0] != '#' {
		return fmt.Errorf("invalid RGB color %q", value)
	}
	rgb, err := hex.DecodeString(value[1:])
	if err != nil {
		return err
	}
	if object.FillColor == nil {
		object.FillColor = &ofdgo.FillColor{}
	}
	object.FillColor.Value = fmt.Sprintf("%d %d %d", rgb[0], rgb[1], rgb[2])
	return nil
}

// insertText 使用选定字体创建文字对象
// 入参: args 页码、内容、字体数据、横纵坐标、字号和颜色
// 返回: any 文档信息, error 错误信息
func insertText(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	data, err := bytesFromJS(args[2])
	if err != nil {
		return nil, err
	}
	fontID, err := currentEditor.AddFont(FontFile{Data: data}, 0)
	if err != nil {
		return nil, err
	}
	page := args[0].Int()
	content, err := currentSession.pageContent(page)
	if err != nil {
		return nil, err
	}
	box, err := currentSession.pageBox(page, content)
	if err != nil {
		return nil, err
	}
	x, y := args[3].Float(), args[4].Float()
	box = ofdgo.Box{X: x, Y: y, W: box.W - x, H: box.H - y}
	object := ofdgo.GraphicObject{Type: "TextObject", TextObject: ofdgo.TextObject{
		Boundary: fmt.Sprintf("%g %g %g %g", box.X, box.Y, box.W, box.H),
		Font:     fontID, Size: args[5].Float(),
	}}
	if err := currentEditor.LayoutText(&object.TextObject, args[1].String()); err != nil {
		return nil, err
	}
	if err := setTextColor(&object.TextObject, args[6].String()); err != nil {
		return nil, err
	}
	if _, err := currentEditor.AddObject(page, object); err != nil {
		return nil, err
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// insertImage 按原始比例创建图片对象
// 入参: args 页码、图片数据、横纵坐标和宽度
// 返回: any 文档信息, error 错误信息
func insertImage(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	data, err := bytesFromJS(args[1])
	if err != nil {
		return nil, err
	}
	resourceID, err := currentEditor.AddImage(data)
	if err != nil {
		return nil, err
	}
	config, _, err := image.DecodeConfig(bytes.NewReader(data))
	if err != nil {
		return nil, err
	}
	width := args[4].Float()
	box := ofdgo.Box{X: args[2].Float(), Y: args[3].Float(), W: width, H: width * float64(config.Height) / float64(config.Width)}
	content, err := currentSession.pageContent(args[0].Int())
	if err != nil {
		return nil, err
	}
	pageBox, err := currentSession.pageBox(args[0].Int(), content)
	if err != nil {
		return nil, err
	}
	if height := pageBox.H - box.Y*2; box.H > height {
		box.W *= height / box.H
		box.H = height
	}
	object := ofdgo.GraphicObject{Type: "ImageObject", ImageObject: ofdgo.ImageObject{
		ResourceID: resourceID, Boundary: fmt.Sprintf("%g %g %g %g", box.X, box.Y, box.W, box.H),
	}}
	if _, err := currentEditor.AddObject(args[0].Int(), object); err != nil {
		return nil, err
	}
	return previewEditor(currentEditor, currentSession.Renderer.RenderAnnotations)
}

// saveDocument 分块写出新建文档
// 入参: args 数据写出回调
// 返回: any 保存结果, error 错误信息
func saveDocument(args []js.Value) (any, error) {
	if currentEditor == nil {
		return nil, fmt.Errorf("no document is being created")
	}
	writer := bufio.NewWriterSize(exportWriter{write: args[0]}, 1<<20)
	if _, err := currentEditor.WriteTo(writer); err != nil {
		return nil, err
	}
	if err := writer.Flush(); err != nil {
		return nil, err
	}
	return successResult(map[string]any{"mime": "application/ofd", "label": "OFD"}), nil
}