package services

// 用户手册文档站:docs/user-guide/*.md 按 manifest.json 分组,
// 服务端 goldmark 渲染 + 三栏布局(侧栏/内容/本页目录)+ 顶栏搜索。
// 布局与交互参考 opsxapi/opsxshell 文档站,换 LokiStack 品牌绿。
import (
	"encoding/json"
	"fmt"
	"html/template"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/parser"
)

// DocsManifest docs/user-guide/manifest.json
type DocsManifest struct {
	ProductVersion string `json:"productVersion"`
	Groups         []struct {
		Name  string `json:"name"`
		Pages []struct {
			File    string `json:"file"`
			Slug    string `json:"slug"`
			Title   string `json:"title"`
			Updated string `json:"updated"`
		} `json:"pages"`
	} `json:"groups"`
}

// DocsPage 渲染一页所需的数据
type DocsPage struct {
	Title   string
	Group   string
	Updated string
	Slug    string
	Content template.HTML
	TOC     []DocsTOCItem
	Prev    *DocsNav
	Next    *DocsNav
}

type DocsTOCItem struct {
	Level int
	ID    string
	Text  string
}

type DocsNav struct {
	Slug  string
	Title string
}

var (
	docsManifestCache *DocsManifest
	docsBasePath      string
	docsMD            = goldmark.New(goldmark.WithExtensions(extension.Table), goldmark.WithParserOptions(parser.WithAutoHeadingID()))
	docsTOCPattern    = regexp.MustCompile(`<h([23]) id="([^"]+)"[^>]*>([^<]+)</h[23]>`)
)

// DocsBaseDir 定位 docs 根(含 user-guide/manifest.json);找不到返回空
func DocsBaseDir() string {
	if docsBasePath != "" {
		return docsBasePath
	}
	for _, p := range []string{"docs", "../docs", "../../docs"} {
		abs, err := filepath.Abs(p)
		if err != nil {
			continue
		}
		if _, err := os.Stat(filepath.Join(abs, "user-guide", "manifest.json")); err == nil {
			docsBasePath = abs
			return abs
		}
	}
	return ""
}

// DocsLoadManifest 解析(并缓存)manifest
func DocsLoadManifest() (*DocsManifest, error) {
	if docsManifestCache != nil {
		return docsManifestCache, nil
	}
	base := DocsBaseDir()
	if base == "" {
		return nil, fmt.Errorf("docs 目录不存在")
	}
	data, err := os.ReadFile(filepath.Join(base, "user-guide", "manifest.json"))
	if err != nil {
		return nil, err
	}
	var m DocsManifest
	if err := json.Unmarshal(data, &m); err != nil {
		return nil, err
	}
	docsManifestCache = &m
	return docsManifestCache, nil
}

// DocsFlat 顺序展开全部页面(slug 定位与上下页)
func DocsFlat(m *DocsManifest) []struct {
	Group   string
	File    string
	Slug    string
	Title   string
	Updated string
} {
	var out []struct {
		Group   string
		File    string
		Slug    string
		Title   string
		Updated string
	}
	for _, g := range m.Groups {
		for _, p := range g.Pages {
			out = append(out, struct {
				Group   string
				File    string
				Slug    string
				Title   string
				Updated string
			}{g.Name, p.File, p.Slug, p.Title, p.Updated})
		}
	}
	return out
}

// DocsRenderPage 渲染指定 slug;含 TOC 与上一页/下一页
func DocsRenderPage(slug string) (*DocsPage, *DocsManifest, error) {
	m, err := DocsLoadManifest()
	if err != nil {
		return nil, nil, err
	}
	flat := DocsFlat(m)
	idx := -1
	for i, p := range flat {
		if p.Slug == slug {
			idx = i
			break
		}
	}
	if idx < 0 {
		return nil, nil, fmt.Errorf("页面不存在")
	}
	cur := flat[idx]
	data, err := os.ReadFile(filepath.Join(DocsBaseDir(), "user-guide", cur.File))
	if err != nil {
		return nil, nil, err
	}
	var sb strings.Builder
	if err := docsMD.Convert(data, &sb); err != nil {
		return nil, nil, err
	}
	html := sb.String()
	// 页面头已渲染标题,剥掉正文首个 H1 避免重复
	if i := strings.Index(html, "<h1"); i >= 0 {
		if j := strings.Index(html[i:], "</h1>"); j >= 0 {
			html = html[:i] + html[i+j+len("</h1>"):]
		}
	}

	page := &DocsPage{Title: cur.Title, Group: cur.Group, Updated: cur.Updated, Slug: cur.Slug, Content: template.HTML(html)}
	for _, m2 := range docsTOCPattern.FindAllStringSubmatch(html, -1) {
		page.TOC = append(page.TOC, DocsTOCItem{Level: int(m2[1][0] - '0'), ID: m2[2], Text: m2[3]})
	}
	if idx > 0 {
		page.Prev = &DocsNav{Slug: flat[idx-1].Slug, Title: flat[idx-1].Title}
	}
	if idx < len(flat)-1 {
		page.Next = &DocsNav{Slug: flat[idx+1].Slug, Title: flat[idx+1].Title}
	}
	return page, m, nil
}

// DocsSearchData 顶栏搜索索引(标题 + 纯文本摘要)
func DocsSearchData() ([]map[string]string, error) {
	m, err := DocsLoadManifest()
	if err != nil {
		return nil, err
	}
	var out []map[string]string
	for _, p := range DocsFlat(m) {
		data, err := os.ReadFile(filepath.Join(DocsBaseDir(), "user-guide", p.File))
		if err != nil {
			continue
		}
		text := regexp.MustCompile(`<[^>]+>`).ReplaceAllString(string(data), " ")
		text = strings.Join(strings.Fields(text), " ")
		if len(text) > 4000 {
			text = text[:4000]
		}
		out = append(out, map[string]string{"slug": p.Slug, "title": p.Title, "group": p.Group, "text": text})
	}
	return out, nil
}

// DocsFirstSlug 首页重定向目标
func DocsFirstSlug() string {
	m, err := DocsLoadManifest()
	if err != nil || len(m.Groups) == 0 || len(m.Groups[0].Pages) == 0 {
		return "readme"
	}
	return m.Groups[0].Pages[0].Slug
}