package web

import (
	_ "embed"
	"fmt"
	"html/template"
	"io/fs"
	"mime"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"slices"
	"strings"

	"github.com/gomarkdown/markdown"
	"github.com/gomarkdown/markdown/html"
	"github.com/gomarkdown/markdown/parser"
)

type (
	AppState struct {
		Root			string
		FilesDir		string
		IgnoredFiles	[]string
	}

	Directory struct {
		Name string
		Root bool
		Files []*File
		Readme template.HTML
		CSS template.CSS
	}

	File struct {
		Name string
		URI string
		IsDir bool
		Size string
		ModifiedDate string
	}
)

//go:embed dir.html
var dirTemplateSrc string
var dirTemplate = template.Must(template.New("dir").Parse(dirTemplateSrc))

func Handler(app *AppState) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !strings.HasPrefix(r.URL.Path, app.Root) {
			http.NotFound(w, r)
			return
		}
		isRoot := r.URL.Path == app.Root

		fpath := path.Join(app.FilesDir, strings.TrimPrefix(r.URL.Path, app.Root))
		info, err := os.Stat(fpath)
		if err != nil {
			http.NotFound(w, r)
			return
		}

		// downloading file
		if !info.IsDir() {
			if strings.HasSuffix(r.URL.Path, "/") {
				http.Redirect(w, r, strings.TrimSuffix(r.URL.Path, "/"), http.StatusFound)
				return
			}

			file, err := os.Open(fpath)
			if err != nil {
				http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
				return
			}

			defer func() {
				err := file.Close()
				if err != nil {
					fmt.Fprintf(os.Stderr, "failed to close file %s: %v\n", fpath, err)
				}
			}()

			mimeType := "application/octet-stream"
			extPos := strings.LastIndex(info.Name(), ".")
			if extPos != -1 {
				if m := mime.TypeByExtension(info.Name()[extPos:]); m != "" {
					mimeType = m
				}
			}

			w.Header().Set("Content-Type", mimeType)
			w.WriteHeader(http.StatusOK)

			_, err = file.WriteTo(w)
			if err != nil {
				fmt.Fprintf(os.Stderr, "failed to send file %s: %v\n", fpath, err)
			}
			return
		}

		if !strings.HasSuffix(r.URL.Path, "/") {
			http.Redirect(w, r, r.URL.Path + "/", http.StatusFound)
			return
		}

		// serve index.html if present (case-sensitive)
		indexPath := filepath.Join(fpath, "index.html")
		if indexInfo, err := os.Stat(indexPath); err == nil && !indexInfo.IsDir() {
			http.ServeFile(w, r, indexPath)
			return
		}

		// load index.css if present
		var customCSS template.CSS
		cssPath := filepath.Join(fpath, "index.css")
		if cssInfo, err := os.Stat(cssPath); err == nil && !cssInfo.IsDir() {
			if src, err := os.ReadFile(cssPath); err == nil {
				customCSS = template.CSS(src)
			}
		}

		// embeded readme
		var readmeHTML template.HTML
		entries, err := os.ReadDir(fpath)
		if err == nil {
			for _, entry := range entries {
				if strings.EqualFold(entry.Name(), "readme.md") {
					src, err := os.ReadFile(filepath.Join(fpath, entry.Name()))
					if err == nil {
						mdFlags := html.CommonFlags | html.HrefTargetBlank
						mdRenderer := html.NewRenderer(html.RendererOptions{Flags: mdFlags})
						mdParser := parser.NewWithExtensions(parser.CommonExtensions | parser.AutoHeadingIDs)
						md := mdParser.Parse(src)
						readmeHTML = template.HTML(markdown.Render(md, mdRenderer))
					}
					break
				}
			}
		}

		data := Directory{
			Root: isRoot,
			Name: r.URL.Path,
			Files: []*File{},
			Readme: readmeHTML,
			CSS: customCSS,
		}

		fsDir := os.DirFS(fpath)
		directories, err := fs.ReadDir(fsDir, ".")
		for _, dir := range directories {
			name := dir.Name()
			if slices.Contains(app.IgnoredFiles, name) { continue }

			info, err := dir.Info()
			if err != nil { continue }

			var uri string
			if isRoot {
				uri = app.Root + name
			} else {
				uri = r.URL.Path + name
			}

			sizeStr := "—"
			if !info.IsDir() {
				size := info.Size()
				sizeDenom := "B"
				if size > 1000 {
					size /= 1000
					sizeDenom = "KB"
				}
				if size > 1000 {
					size /= 1000
					sizeDenom = "MB"
				}
				if size > 1000 {
					size /= 1000
					sizeDenom = "GB"
				}
				sizeStr = fmt.Sprintf("%d%s", size, sizeDenom)
			}

			dateStr := info.ModTime().Format("02-Jan-2006 15:04")

			data.Files = append(data.Files, &File{
				Name: name,
				URI: uri,
				IsDir: info.IsDir(),
				Size: sizeStr,
				ModifiedDate: dateStr,
			})
		}
		if err != nil {
			fmt.Fprintf(os.Stderr, "failed to open directory: %v\n", err)
		}

		w.Header().Set("Content-Type", "text/html")
		w.Header().Set("Server", "indir")
		w.WriteHeader(http.StatusOK)
		dirTemplate.Execute(w, data)
	}
}