// 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.

package ofdgo

import (
	"archive/zip"
	"bytes"
	"encoding/hex"
	"encoding/xml"
	"fmt"
	"io"
	"strconv"
	"time"
)

const ofdNamespace = "http://www.ofdspec.org/2016"

// WriteTo 逐个条目写出OFD，仅包含实际引用的资源，不关闭调用方输出流，出错时应丢弃本次输出
// 入参: writer 输出流
// 返回: int64 已写入字节数, error 错误信息
func (e *Editor) WriteTo(writer io.Writer) (int64, error) {
	if err := e.validate(); err != nil {
		return 0, err
	}
	output := &ofdCountingWriter{writer: writer}
	archive := zip.NewWriter(output)
	err := e.writeParts(func(name string, data []byte, compressed bool) error {
		method := uint16(zip.Deflate)
		if compressed {
			method = zip.Store
		}
		entry, err := archive.CreateHeader(&zip.FileHeader{Name: name, Method: method})
		if err != nil {
			return err
		}
		_, err = entry.Write(data)
		return err
	})
	if err == nil {
		err = archive.Close()
	}
	return output.count, err
}

// Reader 获取当前文档的独立内存快照，不进行ZIP压缩，后续修改不影响已有快照
// 返回的Reader可用于现有渲染、搜索和导出接口，仅包含实际引用的资源，二进制数据内部共享只读
// 返回: *Reader 阅读器, error 错误信息
func (e *Editor) Reader() (*Reader, error) {
	if err := e.validate(); err != nil {
		return nil, err
	}
	r := &Reader{files: make(map[string][]byte)}
	if err := e.writeParts(func(name string, data []byte, _ bool) error {
		r.files[name] = data
		return nil
	}); err != nil {
		return nil, err
	}
	if err := r.initRoot(); err != nil {
		return nil, err
	}
	if _, err := r.Doc(); err != nil {
		return nil, err
	}
	return r, nil
}

// validate 校验文档保存条件
// 返回: error 错误信息
func (e *Editor) validate() error {
	if len(e.pages) == 0 {
		return fmt.Errorf("document must contain at least one page")
	}
	if data, err := hex.DecodeString(e.Info.DocID); err != nil || len(data) != 16 {
		return fmt.Errorf("DocID must contain 32 hexadecimal characters")
	}
	for _, date := range []string{e.Info.CreationDate, e.Info.ModDate} {
		if date != "" {
			if _, err := time.Parse("2006-01-02", date); err != nil {
				return fmt.Errorf("invalid document date: %w", err)
			}
		}
	}
	return nil
}

// writeParts 生成根节点、文档、资源索引、页面及二进制资源
// 入参: write 条目写入方法
// 返回: error 错误信息
func (e *Editor) writeParts(write func(string, []byte, bool) error) error {
	fonts, images := e.usedResources()
	writeXML := func(name string, encode func(*ofdXML)) error {
		data, err := encodeOFDXML(encode)
		if err != nil {
			return err
		}
		return write(name, data, false)
	}
	if err := writeXML("OFD.xml", func(x *ofdXML) {
		x.root("OFD", ofdAttrs{{Name: xml.Name{Local: "Version"}, Value: "1.0"}, {Name: xml.Name{Local: "DocType"}, Value: "OFD"}})
		x.start("DocBody", nil)
		x.start("DocInfo", nil)
		for _, field := range [][2]string{
			{"DocID", e.Info.DocID}, {"Title", e.Info.Title}, {"Author", e.Info.Author},
			{"Subject", e.Info.Subject}, {"Abstract", e.Info.Abstract},
			{"CreationDate", e.Info.CreationDate}, {"ModDate", e.Info.ModDate},
			{"Creator", "xiaoqidun/ofdgo"},
		} {
			if field[1] != "" {
				x.text(field[0], field[1])
			}
		}
		if e.Info.CustomDatas != nil && len(e.Info.CustomDatas.CustomData) != 0 {
			x.start("CustomDatas", nil)
			for _, item := range e.Info.CustomDatas.CustomData {
				attrs := ofdAttrs{{Name: xml.Name{Local: "Name"}, Value: item.Name}}
				x.start("CustomData", attrs)
				x.token(xml.CharData(item.Value))
				x.end("CustomData")
			}
			x.end("CustomDatas")
		}
		x.end("DocInfo")
		x.text("DocRoot", "Doc_0/Document.xml")
		x.end("DocBody")
		x.end("OFD")
	}); err != nil {
		return err
	}
	if err := writeXML("Doc_0/Document.xml", func(x *ofdXML) {
		x.root("Document", nil)
		x.start("CommonData", nil)
		x.text("MaxUnitID", strconv.Itoa(e.maxID))
		x.start("PageArea", nil)
		x.text("PhysicalBox", e.pages[0].Area.PhysicalBox)
		x.end("PageArea")
		if len(fonts)+len(images) != 0 {
			x.text("DocumentRes", "DocumentRes.xml")
		}
		x.end("CommonData")
		x.start("Pages", nil)
		for i, page := range e.pages {
			var attrs ofdAttrs
			attrs.add("ID", page.ID)
			attrs.add("BaseLoc", fmt.Sprintf("Pages/%d/Content.xml", i+1))
			x.start("Page", attrs)
			x.end("Page")
		}
		x.end("Pages")
		x.end("Document")
	}); err != nil {
		return err
	}
	if len(fonts)+len(images) != 0 {
		if err := writeXML("Doc_0/DocumentRes.xml", func(x *ofdXML) { x.resources(fonts, images) }); err != nil {
			return err
		}
	}
	for i, page := range e.pages {
		if err := writeXML(fmt.Sprintf("Doc_0/Pages/%d/Content.xml", i+1), func(x *ofdXML) {
			x.page(page)
		}); err != nil {
			return err
		}
	}
	for _, resources := range [][]editorResource{fonts, images} {
		for _, resource := range resources {
			if err := write(resource.name, resource.data, resource.image != nil); err != nil {
				return err
			}
		}
	}
	return nil
}

// usedResources 按注册顺序筛选当前页面引用的字体和图片，不修改资源池
// 返回: []editorResource 字体资源, []editorResource 图片资源
func (e *Editor) usedResources() (fonts, images []editorResource) {
	used := make(map[string]bool)
	for _, page := range e.pages {
		for _, layer := range page.Content.Layer {
			for _, object := range layer.Objects {
				switch object.Type {
				case "TextObject":
					used[object.TextObject.Font] = true
				case "ImageObject":
					used[object.ImageObject.ResourceID] = true
					if object.ImageObject.ImageMask != "" {
						used[object.ImageObject.ImageMask] = true
					}
				}
			}
		}
	}
	for _, resource := range e.resources {
		if resource.font != nil && used[resource.font.ID] {
			fonts = append(fonts, resource)
		}
		if resource.image != nil && used[resource.image.ID] {
			images = append(images, resource)
		}
	}
	return fonts, images
}

// page 写出页面尺寸、图层和对象
// 入参: page 页面内容
func (x *ofdXML) page(page PageContent) {
	x.root("Page", nil)
	x.start("Area", nil)
	x.text("PhysicalBox", page.Area.PhysicalBox)
	x.end("Area")
	x.start("Content", nil)
	for _, layer := range page.Content.Layer {
		var attrs ofdAttrs
		attrs.add("ID", layer.ID)
		attrs.add("Type", layer.Type)
		x.start("Layer", attrs)
		for _, object := range layer.Objects {
			x.object(object, false)
		}
		x.end("Layer")
	}
	x.end("Content")
	x.end("Page")
}

// resources 写出文档资源索引
// 入参: fonts 字体资源, images 图片资源
func (x *ofdXML) resources(fonts, images []editorResource) {
	x.root("Res", ofdAttrs{{Name: xml.Name{Local: "BaseLoc"}, Value: "Res"}})
	if len(fonts) != 0 {
		x.start("Fonts", nil)
		for _, resource := range fonts {
			font := resource.font
			var attrs ofdAttrs
			attrs.add("ID", font.ID)
			attrs.add("FontName", font.FontName)
			attrs.add("FamilyName", font.FamilyName)
			attrs.add("Charset", font.Charset)
			if font.Bold {
				attrs.add("Bold", "true")
			}
			if font.Italic {
				attrs.add("Italic", "true")
			}
			if font.FixedWidth {
				attrs.add("FixedWidth", "true")
			}
			x.start("Font", attrs)
			x.text("FontFile", font.FontFile)
			x.end("Font")
		}
		x.end("Fonts")
	}
	if len(images) != 0 {
		x.start("MultiMedias", nil)
		for _, resource := range images {
			image := resource.image
			var attrs ofdAttrs
			attrs.add("ID", image.ID)
			attrs.add("Type", image.Type)
			attrs.add("Format", image.Format)
			x.start("MultiMedia", attrs)
			x.text("MediaFile", image.MediaFile)
			x.end("MultiMedia")
		}
		x.end("MultiMedias")
	}
	x.end("Res")
}

// ofdCountingWriter 记录实际输出字节数
type ofdCountingWriter struct {
	writer io.Writer
	count  int64
}

// Write 写入并累计字节数
// 入参: data 数据
// 返回: int 字节数, error 错误信息
func (w *ofdCountingWriter) Write(data []byte) (int, error) {
	n, err := w.writer.Write(data)
	w.count += int64(n)
	if err == nil && n != len(data) {
		err = io.ErrShortWrite
	}
	return n, err
}

// ofdXML 使用标准ofd命名空间写出XML
type ofdXML struct {
	encoder *xml.Encoder
	err     error
}

// newOFDXML 创建XML编码器
// 入参: writer 输出流
// 返回: *ofdXML 编码器
func newOFDXML(writer io.Writer) *ofdXML {
	_, err := io.WriteString(writer, xml.Header)
	return &ofdXML{encoder: xml.NewEncoder(writer), err: err}
}

// token 写入XML标记并保留首个错误
// 入参: token XML标记
func (x *ofdXML) token(token xml.Token) {
	if x.err == nil {
		x.err = x.encoder.EncodeToken(token)
	}
}

// root 写入声明命名空间的根节点
// 入参: name 节点名, attrs 属性
func (x *ofdXML) root(name string, attrs ofdAttrs) {
	attrs.add("xmlns:ofd", ofdNamespace)
	x.start(name, attrs)
}

// start 写入节点起始标记
// 入参: name 节点名, attrs 属性
func (x *ofdXML) start(name string, attrs ofdAttrs) {
	x.token(xml.StartElement{Name: xml.Name{Local: "ofd:" + name}, Attr: attrs})
}

// end 写入节点结束标记
// 入参: name 节点名
func (x *ofdXML) end(name string) {
	x.token(xml.EndElement{Name: xml.Name{Local: "ofd:" + name}})
}

// text 写入文本节点
// 入参: name 节点名, value 文本
func (x *ofdXML) text(name, value string) {
	x.start(name, nil)
	x.token(xml.CharData(value))
	x.end(name)
}

// finish 完成XML输出
// 返回: error 错误信息
func (x *ofdXML) finish() error {
	if x.err != nil {
		return x.err
	}
	return x.encoder.Close()
}

// ofdAttrs OFD节点属性
type ofdAttrs []xml.Attr

// add 添加非空属性
// 入参: name 属性名, value 属性值
func (a *ofdAttrs) add(name, value string) {
	if value != "" {
		*a = append(*a, xml.Attr{Name: xml.Name{Local: name}, Value: value})
	}
}

// number 添加非零数值属性
// 入参: name 属性名, value 数值
func (a *ofdAttrs) number(name string, value float64) {
	if value != 0 {
		a.add(name, ofdNumber(value))
	}
}

// flag 添加显式布尔属性
// 入参: name 属性名, value 布尔值
func (a *ofdAttrs) flag(name string, value *bool) {
	if value != nil {
		a.add(name, strconv.FormatBool(*value))
	}
}

// alpha 添加显式透明度
// 入参: value 透明度
func (a *ofdAttrs) alpha(value *int) {
	if value != nil {
		a.add("Alpha", strconv.Itoa(*value))
	}
}

// encodeOFDXML 编码文档节点，用于保存和独立副本
// 入参: encode 节点写入方法
// 返回: []byte XML数据, error 错误信息
func encodeOFDXML(encode func(*ofdXML)) ([]byte, error) {
	var data bytes.Buffer
	x := newOFDXML(&data)
	encode(x)
	if err := x.finish(); err != nil {
		return nil, err
	}
	return data.Bytes(), nil
}

// object 按OFD规定顺序写出基本对象
// 入参: object 图形对象, root 是否为根节点
func (x *ofdXML) object(object GraphicObject, root bool) {
	var attrs ofdAttrs
	var fill, stroke *FillColor
	if root {
		attrs.add("xmlns:ofd", ofdNamespace)
	}
	switch object.Type {
	case "TextObject":
		obj := object.TextObject
		attrs.add("ID", obj.ID)
		attrs.add("Boundary", obj.Boundary)
		attrs.add("CTM", obj.CTM)
		attrs.add("Font", obj.Font)
		attrs.number("Size", obj.Size)
		attrs.number("HScale", obj.HScale)
		attrs.number("Weight", float64(obj.Weight))
		attrs.number("ReadDirection", float64(obj.ReadDirection))
		attrs.number("CharDirection", float64(obj.CharDirection))
		attrs.number("LineWidth", obj.LineWidth)
		attrs.number("MiterLimit", obj.MiterLimit)
		attrs.add("Join", obj.Join)
		if obj.Italic {
			attrs.add("Italic", "true")
		}
		attrs.flag("Visible", obj.Visible)
		attrs.flag("Stroke", obj.Stroke)
		attrs.flag("Fill", obj.Fill)
		attrs.alpha(obj.Alpha)
		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
	case "PathObject", "Path":
		obj := object.PathObject
		attrs.add("ID", obj.ID)
		attrs.add("Boundary", obj.Boundary)
		attrs.add("CTM", obj.CTM)
		attrs.number("LineWidth", obj.LineWidth)
		attrs.number("MiterLimit", obj.MiterLimit)
		attrs.add("Join", obj.Join)
		attrs.add("Cap", obj.Cap)
		attrs.add("Rule", obj.Rule)
		attrs.add("DashPattern", obj.DashPattern)
		if obj.DashOffset != nil {
			attrs.add("DashOffset", ofdNumber(*obj.DashOffset))
		}
		attrs.flag("Visible", obj.Visible)
		attrs.flag("Stroke", obj.Stroke)
		attrs.flag("Fill", obj.Fill)
		attrs.alpha(obj.Alpha)
		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
	case "ImageObject":
		obj := object.ImageObject
		attrs.add("ID", obj.ID)
		attrs.add("Boundary", obj.Boundary)
		attrs.add("CTM", obj.CTM)
		attrs.add("ResourceID", obj.ResourceID)
		attrs.add("ImageMask", obj.ImageMask)
		attrs.flag("Visible", obj.Visible)
		attrs.alpha(obj.Alpha)
	}
	x.start(object.Type, attrs)
	if object.Type == "ImageObject" {
		x.clips(object.ImageObject.Clips)
	} else if object.Type == "PathObject" || object.Type == "Path" {
		x.color("StrokeColor", stroke)
		x.color("FillColor", fill)
		x.text("AbbreviatedData", object.PathObject.AbbreviatedData)
	} else if object.Type == "TextObject" {
		x.color("FillColor", fill)
		x.color("StrokeColor", stroke)
		for _, code := range object.TextObject.TextCode {
			var attrs ofdAttrs
			attrs.add("X", code.X)
			attrs.add("Y", code.Y)
			attrs.add("DeltaX", code.DeltaX)
			attrs.add("DeltaY", code.DeltaY)
			x.textCode(code.Value, attrs)
		}
	}
	x.end(object.Type)
}

// clips 写出图片路径裁剪，保留裁剪集合、区域及路径的变换
// 入参: clips 裁剪集合，nil不输出节点
func (x *ofdXML) clips(clips *Clips) {
	if clips == nil {
		return
	}
	var attrs ofdAttrs
	attrs.flag("TransFlag", clips.TransFlag)
	x.start("Clips", attrs)
	for _, clip := range clips.Clip {
		x.start("Clip", nil)
		for _, area := range clip.Area {
			var attrs ofdAttrs
			attrs.add("CTM", area.CTM)
			x.start("Area", attrs)
			for _, path := range area.Path {
				x.object(GraphicObject{Type: "Path", PathObject: path}, false)
			}
			x.end("Area")
		}
		x.end("Clip")
	}
	x.end("Clips")
}

// textCode 使用XML字符引用转义空格，避免依赖阅读器保留原始空白
// 入参: value OFD文字内容, attrs 文字定位属性
func (x *ofdXML) textCode(value string, attrs ofdAttrs) {
	if x.err != nil {
		return
	}
	var escaped bytes.Buffer
	if x.err = xml.EscapeText(&escaped, []byte(value)); x.err != nil {
		return
	}
	content := struct {
		Text []byte `xml:",innerxml"`
	}{Text: bytes.ReplaceAll(escaped.Bytes(), []byte(" "), []byte(" "))}
	x.err = x.encoder.EncodeElement(content, xml.StartElement{Name: xml.Name{Local: "ofd:TextCode"}, Attr: attrs})
}

// color 写出基本颜色
// 入参: name 节点名, color 颜色
func (x *ofdXML) color(name string, color *FillColor) {
	if color == nil {
		return
	}
	var attrs ofdAttrs
	attrs.add("Value", color.Value)
	attrs.alpha(color.Alpha)
	x.start(name, attrs)
	x.end(name)
}