Refactor plugin to not rely on caching for writing anymore

Also test if the buffer is backed by a file, and fail if not

README.md

@@ -10,8 +10,6 @@ Add `sudo-write.kak` to your autoload dir: `~/.config/kak/autoload/`, or source
 
 Call the `sudo-write` command. If your password has not been cached by `sudo`, you will be prompted to input it. Upon success, the buffer is written to the file.
 
-Note that the plugin will not work if you do not use any cache for `sudo`.
-
 **Warning**: while the input is hidden, the password is still passed through stdin to `sudo`. Do not use this plugin if you are not comfortable with this idea.
 
 ## License

sudo-write.kak

@@ -1,9 +1,9 @@
-# save the current buffer to its file as root
+# save the current buffer to its file as root using `sudo`
 # (optionally pass the user password to sudo if not cached)
 
-define-command -hidden sudo-write-impl %{
+define-command -hidden sudo-write-cached-password %{
+    # easy case: the password was already cached, so we don't need any tricky handling
     eval -save-regs f %{
-        # TOOD this could take the content of the buffer from stdin instead
         reg f %sh{ mktemp --tmpdir XXXXX }
         write %reg{f}
         eval %sh{
@@ -11,49 +11,60 @@ define-command -hidden sudo-write-impl %{
             if [ $? -eq 0 ]; then
                 echo "edit!"
             else
-                echo "echo -markup '{Error}Something went wrong'"
+                echo 'fail "Unknown failure"'
             fi
             rm -f "$kak_main_reg_f"
         }
     }
 }
 
-define-command -hidden -params 1 sudo-cache-password %{
+define-command -hidden sudo-write-prompt-password %{
-    eval -no-hooks -save-regs '"c' %{
-        eval -draft %{
-            edit -scratch *sudo-write-pass*
-            reg '"' %arg{1}
-            exec "<a-p>|sudo -S echo ok<ret>"
-            try %{
-                exec '%H<a-k>ok<ret>'
-                reg c nop
-            } catch %{
-                reg c fail
-            }
-        }
-        delete-buffer *sudo-write-pass*
-        eval %reg{c}
-    }
-}
-
-define-command -hidden sudo-prompt-password %{
     prompt -password 'Password:' %{
-        try %{
+        eval -save-regs r %{
-            sudo-cache-password %val{text}
+            eval -draft -save-regs 'tf|"' %{
-            sudo-write-impl
+                reg t %val{buffile}
-        } catch %{
+                reg f %sh{ mktemp --tmpdir XXXXX }
-            echo -markup '{Error}Incorrect password'
+                write %reg{f}
+
+                # write the password in a buffer in order to pass it through STDIN to sudo
+                # somewhat dangerous, but better than passing the password
+                # through the shell scope's environment or interpolating it inside the shell string
+                # 'exec |' is pretty much the only way to pass data over STDIN
+                edit -scratch '*sudo-password-tmp*'
+                reg '"' "%val{text}"
+                exec <a-P>
+                reg | %{
+                    sudo -S -- dd if="$kak_main_reg_f" of="$kak_main_reg_t" > /dev/null 2>&1
+                    if [ $? -eq 0 ]; then
+                        printf 'edit!'
+                    else
+                        printf 'fail "Incorrect password?"'
+                    fi
+                    rm -f "$kak_main_reg_f"
+                }
+                exec '|<ret>'
+                exec -save-regs '' '%"ry'
+                delete-buffer! '*sudo-password-tmp*'
+            }
+            eval %reg{r}
         }
     }
 }
 
 define-command sudo-write -docstring "Write the content of the buffer using sudo" %{
-    %sh{
+    eval %sh{
+        # tricky posix-way of getting the first character of a variable
+        # no subprocess!
+        if [ "${kak_buffile%"${kak_buffile#?}"}" != "/" ]; then
+            # not entirely foolproof as a scratch buffer may start with '/', but good enough
+            printf 'fail "Not a file"'
+            exit
+        fi
         # check if the password is cached
         if sudo -n true > /dev/null 2>&1; then
-            echo sudo-write-impl
+            printf sudo-write-cached-password
         else
-            echo sudo-prompt-password
+            printf sudo-write-prompt-password
         fi
     }
 }