package handlers

import (
	"html/template"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/yuin/goldmark"
)

// docsCategories are the only subdirectories served under /docs -- a
// whitelist, not a filesystem listing, so an unexpected file dropped into
// DocsDir doesn't unintentionally become servable.
var docsCategories = []string{"specs", "plans"}

type docsEntry struct {
	Name string // filename, e.g. "2026-07-14-foo-design.md"
	URL  string
}

type docsCategoryListing struct {
	Name    string
	Entries []docsEntry
}

// HandleDocsIndex lists every markdown file under each whitelisted category
// subdirectory of cfg.DocsDir, newest first (filenames are date-prefixed,
// so reverse-alphabetical is reverse-chronological).
func (h *Handler) HandleDocsIndex(w http.ResponseWriter, r *http.Request) {
	var categories []docsCategoryListing
	for _, cat := range docsCategories {
		files, err := os.ReadDir(filepath.Join(h.config.DocsDir, cat))
		if err != nil {
			continue
		}
		var entries []docsEntry
		for _, f := range files {
			if f.IsDir() || !strings.HasSuffix(f.Name(), ".md") {
				continue
			}
			entries = append(entries, docsEntry{
				Name: f.Name(),
				URL:  "/docs/" + cat + "/" + f.Name(),
			})
		}
		sort.Slice(entries, func(i, j int) bool { return entries[i].Name > entries[j].Name })
		categories = append(categories, docsCategoryListing{Name: cat, Entries: entries})
	}

	if err := h.renderer.Render(w, "docs-index.html", struct {
		Categories []docsCategoryListing
	}{categories}); err != nil {
		http.Error(w, "Failed to render template", http.StatusInternalServerError)
	}
}

// HandleDocsView renders a single markdown file to HTML. category and
// filename both come from the URL and are validated against a whitelist /
// base-name check before touching the filesystem, so a request can't
// escape DocsDir via "..": chi's {filename} route param never contains a
// literal "/", and Go's filepath.Base further strips any residual path
// separators before the read.
func (h *Handler) HandleDocsView(w http.ResponseWriter, r *http.Request) {
	category := chi.URLParam(r, "category")
	if !isValidDocsCategory(category) {
		http.NotFound(w, r)
		return
	}
	filename := filepath.Base(chi.URLParam(r, "filename"))
	if !strings.HasSuffix(filename, ".md") {
		http.NotFound(w, r)
		return
	}

	raw, err := os.ReadFile(filepath.Join(h.config.DocsDir, category, filename))
	if err != nil {
		http.NotFound(w, r)
		return
	}

	var body strings.Builder
	if err := goldmark.Convert(raw, &body); err != nil {
		http.Error(w, "Failed to render markdown", http.StatusInternalServerError)
		return
	}

	if err := h.renderer.Render(w, "docs-view.html", struct {
		Title string
		Body  template.HTML
	}{filename, template.HTML(body.String())}); err != nil {
		http.Error(w, "Failed to render template", http.StatusInternalServerError)
	}
}

func isValidDocsCategory(category string) bool {
	for _, c := range docsCategories {
		if c == category {
			return true
		}
	}
	return false
}