# SPDX-FileCopyrightText: ☭ 2021 Emery Hemingway
# SPDX-License-Identifier: Unlicense

import std/macros
import preserves
import syndicate/[actors, patterns]
export patterns

proc wrapPublishHandler(handler: NimNode): NimNode =
  handler.expectKind nnkDo
  var innerProc = newNimNode(nnkProcDef)
  handler.copyChildrenTo innerProc
  innerProc[0] = genSym(nskProc, "message")
  var
    formalArgs = handler[3]
    valuesSym = genSym(nskVar, "values")
    valuesTuple = newNimNode(nnkTupleTy, handler)
    innerTuple = newNimNode(nnkVarTuple, handler)
    varSectionInner = newNimNode(nnkVarSection, handler).add(innerTuple)
  for i, arg in formalArgs:
    if i > 0:
      arg.expectKind nnkIdentDefs
      if arg[1].kind == nnkEmpty:
        error("type required for capture", arg)
      var def = newNimNode(nnkIdentDefs, arg)
      arg.copyChildrenTo def
      valuesTuple.add(def)
      innerTuple.add(arg[0])
  innerTuple.add(newEmptyNode(), valuesSym)
  var
    varSectionOuter = newNimNode(nnkVarSection, handler).add(
      newIdentDefs(valuesSym, valuesTuple))
    body = newStmtList(varSectionInner, handler[6])
    turnSym = ident"turn"
    handleSym = ident"handle"
    handlerSym = genSym(nskProc, "publish")
  quote do:
    proc `handlerSym`(_: Entity; `turnSym`: var Turn; bindings: Assertion; `handleSym`: Handle) =
      `varSectionOuter`
      if fromPreserve(`valuesSym`, bindings):
        `body`

proc wrapMessageHandler(handler: NimNode): NimNode =
  handler.expectKind nnkDo
  var innerProc = newNimNode(nnkProcDef)
  handler.copyChildrenTo innerProc
  innerProc[0] = genSym(nskProc, "message")
  var
    formalArgs = handler[3]
    valuesSym = genSym(nskVar, "values")
    valuesTuple = newNimNode(nnkTupleTy, handler)
    innerTuple = newNimNode(nnkVarTuple, handler)
    varSectionInner = newNimNode(nnkVarSection, handler).add(innerTuple)
  for i, arg in formalArgs:
    if i > 0:
      arg.expectKind nnkIdentDefs
      if arg[1].kind == nnkEmpty:
        error("type required for capture", arg)
      var def = newNimNode(nnkIdentDefs, arg)
      arg.copyChildrenTo def
      valuesTuple.add(def)
      innerTuple.add(arg[0])
  innerTuple.add(newEmptyNode(), valuesSym)
  var
    varSectionOuter = newNimNode(nnkVarSection, handler).add(
      newIdentDefs(valuesSym, valuesTuple))
    body = newStmtList(varSectionInner, handler[6])
    turnSym = ident"turn"
    handlerSym = genSym(nskProc, "message")
  quote do:
    proc `handlerSym`(_: Entity; `turnSym`: var Turn; bindings: Assertion) =
      `varSectionOuter`
      if fromPreserve(`valuesSym`, bindings):
        `body`

macro onPublish*(turn: Turn; ds: Ref; pattern: Pattern; doHandler: untyped) =
  let
    handlerProc = wrapPublishHandler(doHandler)
    handlerSym = handlerProc[0]
  result = quote do:
    `handlerProc`
    discard observe(`turn`, `ds`, `pattern`, newEntity(publish = `handlerSym`))

macro onMessage*(turn: Turn; ds: Ref; pattern: Pattern; doHandler: untyped) =
  let
    handlerProc = wrapMessageHandler(doHandler)
    handlerSym = handlerProc[0]
  result = quote do:
    `handlerProc`
    discard observe(`turn`, `ds`, `pattern`, newEntity(message = `handlerSym`))