package api

import (
	"io"
	"net/http"
	"path"
	"regexp"
	"strings"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"git.golem15.com/golem15/summercms/modules/wire"
	"gocloud.dev/blob"
	"gocloud.dev/gcerrors"
)

const mediaMaxBytes = 10240 << 10

var mediaFolderPattern = regexp.MustCompile(`^[A-Za-z0-9_\-/]*$`)

// UploadMedia is POST /_journal/api/v1/media/upload (JOURNAL-006).
func UploadMedia(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		r, pr, ok := requireBackendPrincipal(app, w, r)
		if !ok {
			return
		}
		if !requireAccessPosts(w, pr) {
			return
		}
		folder := strings.TrimSpace(r.FormValue("folder"))
		if len(folder) > 100 || !mediaFolderPattern.MatchString(folder) || strings.Contains(folder, "..") {
			writeValidation(w, map[string][]string{"folder": {"The folder format is invalid."}})
			return
		}
		file, header, err := r.FormFile("file")
		if err != nil {
			writeValidation(w, map[string][]string{"file": {"The file field is required."}})
			return
		}
		defer file.Close()
		name := path.Base(strings.ReplaceAll(header.Filename, `\`, "/"))
		ext := strings.ToLower(strings.TrimPrefix(path.Ext(name), "."))
		switch ext {
		case "jpg", "jpeg", "png", "gif", "webp":
		default:
			writeValidation(w, map[string][]string{"file": {"The file must be an image."}})
			return
		}
		bucket, ok := app.Lookup[*blob.Bucket]()
		if !ok || bucket == nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		keyPath := mediaObjectPath(folder, name)
		body, err := io.ReadAll(io.LimitReader(file, mediaMaxBytes+1))
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		if int64(len(body)) > mediaMaxBytes {
			writeValidation(w, map[string][]string{"file": {"The file may not be greater than 10240 kilobytes."}})
			return
		}
		keyPath, err = uniqueMediaKey(r, bucket, keyPath)
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		wtr, err := bucket.NewWriter(r.Context(), strings.TrimPrefix(keyPath, "/"), nil)
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		if _, err := wtr.Write(body); err != nil {
			_ = wtr.Close()
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		if err := wtr.Close(); err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		wire.WriteJSON(w, http.StatusCreated, map[string]any{
			"data": map[string]any{
				"url":  attach.PublicURL(strings.TrimPrefix(keyPath, "/")),
				"path": keyPath,
			},
		})
	}
}

func mediaObjectPath(folder, fileName string) string {
	segments := make([]string, 0, 4)
	for _, part := range strings.Split(strings.Trim(folder, "/"), "/") {
		if part == "" || part == "." || part == ".." {
			continue
		}
		segments = append(segments, part)
	}
	if len(segments) > 0 && strings.EqualFold(segments[0], "journal") {
		segments = segments[1:]
	}
	folder = strings.Join(segments, "/")
	if folder == "" {
		return "/journal/" + fileName
	}
	return "/journal/" + folder + "/" + fileName
}

func uniqueMediaKey(r *http.Request, bucket *blob.Bucket, pathName string) (string, error) {
	key := strings.TrimPrefix(pathName, "/")
	ok, err := bucket.Exists(r.Context(), key)
	if err != nil && gcerrors.Code(err) != gcerrors.NotFound {
		return "", err
	}
	if !ok {
		return pathName, nil
	}
	ext := path.Ext(pathName)
	base := strings.TrimSuffix(pathName, ext)
	for n := 1; n < 1000; n++ {
		candidate := base + "-" + itoa(n) + ext
		exists, err := bucket.Exists(r.Context(), strings.TrimPrefix(candidate, "/"))
		if err != nil && gcerrors.Code(err) != gcerrors.NotFound {
			return "", err
		}
		if !exists {
			return candidate, nil
		}
	}
	return pathName, nil
}

func itoa(n int) string {
	if n == 0 {
		return "0"
	}
	var b [16]byte
	i := len(b)
	for n > 0 {
		i--
		b[i] = byte('0' + n%10)
		n /= 10
	}
	return string(b[i:])
}