package api

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"log/slog"
	"net/http"
	"strings"
)

type MediaHandler struct {
	uploadDir string
}

func NewMediaHandler(uploadDir string) *MediaHandler {
	return &MediaHandler{uploadDir: uploadDir}
}

// HandleUpload handles POST /media — uploads a single file and returns its markdown reference.
func (h *MediaHandler) HandleUpload(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseMultipartForm(maxUploadSize); err != nil {
		http.Error(w, "too large", http.StatusRequestEntityTooLarge)
		return
	}
	fh, _, err := r.FormFile("file")
	if err != nil {
		http.Error(w, "missing file", http.StatusBadRequest)
		return
	}
	defer fh.Close()

	buf := make([]byte, 512)
	n, _ := fh.Read(buf)
	mime := http.DetectContentType(buf[:n])
	if _, ok := allowedMIME[mime]; !ok {
		http.Error(w, "unsupported type", http.StatusUnsupportedMediaType)
		return
	}

	filename, err := saveUpload(h.uploadDir, randomID(), mime, buf[:n], fh)
	if err != nil {
		http.Error(w, "storage error", http.StatusInternalServerError)
		return
	}

	ref := markdownRef(mime, filename)
	slog.Info("media uploaded", "filename", filename, "mime", mime)

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]string{
		"filename": filename,
		"mime":     mime,
		"ref":      ref,
	})
}

func markdownRef(mime, filename string) string {
	url := "/uploads/" + filename
	switch {
	case strings.HasPrefix(mime, "image/"):
		return "![" + filename + "](" + url + ")"
	case strings.HasPrefix(mime, "video/"):
		return "![" + filename + "](" + url + ")"
	case strings.HasPrefix(mime, "audio/"):
		return "[" + filename + "](" + url + ")"
	default:
		return "[" + filename + "](" + url + ")"
	}
}

func randomID() string {
	b := make([]byte, 12)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)
}