package common

import (
	"archive/zip"
	"io"
	"strings"
)

type docxParser struct{}

// Parse docx：解 zip 读 word/document.xml，按 <w:p> 段落提取文本
func (p *docxParser) Parse(path string) (string, error) {
	r, err := zip.OpenReader(path)
	if err != nil {
		return "", err
	}
	defer r.Close()

	var sb strings.Builder
	for _, f := range r.File {
		if f.Name != "word/document.xml" {
			continue
		}
		rc, err := f.Open()
		if err != nil {
			return "", err
		}
		body, err := io.ReadAll(rc)
		rc.Close()
		if err != nil {
			return "", err
		}
		extractDocxText(string(body), &sb)
		return sb.String(), nil
	}
	return "", nil
}

// extractDocxText 解析 document.xml：每个 <w:p> 一段，段内文本去 XML 标签
func extractDocxText(xml string, sb *strings.Builder) {
	for {
		start := strings.Index(xml, "<w:p")
		if start < 0 {
			break
		}
		end := findTagEnd(xml, start)
		if end < 0 {
			break
		}
		para := xml[start:end]
		xml = xml[end:]

		var paraSb strings.Builder
		texts := strings.Split(para, "<w:t")
		for i, seg := range texts {
			if i == 0 {
				continue
			}
			if !strings.HasPrefix(seg, ">") {
				continue
			}
			value := seg[1:]
			if j := strings.Index(value, "</w:t>"); j >= 0 {
				value = value[:j]
			}
			paraSb.WriteString(value)
		}
		line := strings.TrimSpace(paraSb.String())
		if line != "" {
			sb.WriteString(line)
			sb.WriteString("\n")
		}
	}
}

// findTagEnd 找到 <w:p ...> 对应的 </w:p> 结束位置（返回开标签之后的位置）
func findTagEnd(xml string, start int) int {
	openEnd := strings.Index(xml[start:], ">")
	if openEnd < 0 {
		return -1
	}
	closeTag := strings.Index(xml[start:], "</w:p>")
	if closeTag < 0 {
		return -1
	}
	return start + closeTag + len("</w:p>")
}