requires: {#ReadStream. #WriteStream}.
provides: {#Listener}.

"A program providing an interactive read-eval-print loop on some Stream pair.
This does not require being in a terminal medium or emulation."

"See CLIM Spec ch. 24"

Graphics addPrototype: #InputEditingStream derivedFrom: {ReadWriteStream}.
"Overrides a target stream's operations in order to provide input-editing
semantics, but otherwise delegates primarily to that target."
InputEditingStream addDelegate: #target valued: Stream clone.
"The target Stream."
InputEditingStream addSlot: #buffer valued: ExtensibleArray newEmpty.
"The editable contents for the target's input."
InputEditingStream addSlot: #position valued: 0.
"The index into the buffer Sequence where the `cursor' is."
InputEditingStream addSlot: #scanPosition valued: 0.
"The index into the buffer Sequence where the next input is."
InputEditingStream addSlot: #performRescan valued: False.
"Whether the buffer should be rescanned before the next input."
"TODO: include a semaphore or lock/mutex or something for rescan periods."

"NOTE: Invariant: `scanPosition <= position' at all times."
"NOTE: Optional slots: an accumulator or a most-recently-used presentation
history, or others."

s@(InputEditingStream traits) newOn: s
[
  e clone on: s
].

s@(InputEditingStream traits) on: s
[
  e target: s.
  e
].

s@(InputEditingStream traits) rescanBuffer
"Resets the scanPosition to its original state and reparses the buffer's
contents before reading any more input."
[
  s scanPosition: 0.
  "TODO: Perform re-parsing."
  s
].

s@(InputEditingStream traits) next
[| gesture |
  s rescanIfNecessary.
  [s scanPosition < s buffer size
     ifTrue: [gesture: s next. s scanPosition: s scanPosition + 1]
     ifFalse: [s buffer at: s scanPosition insert: (gesture: s target next)].
   s process: gesture.
   gesture is: InputEditingCommand] whileTrue
].

s@(InputEditingStream traits) x
[
  
].

"TODO: CLIM Spec 24.2-5"