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package forge.define
import forge.util.Args
import scala.annotation.compileTimeOnly
import scala.collection.mutable
import scala.reflect.macros.blackbox.Context
/**
* A generic Applicative-functor macro: translates calls to
*
* Applier.apply{ ... applyable1.apply() ... applyable2.apply() ... }
*
* into
*
* Applier.zipMap(applyable1, applyable2){ (a1, a2, ctx) => ... a1 ... a2 ... }
*/
object Applicative {
trait Applyable[+T]{
@compileTimeOnly("Target#apply() can only be used with a T{...} block")
def apply(): T = ???
}
trait Applyer[W[_], T[_], Ctx]{
@compileTimeOnly("Target.ctx() can only be used with a T{...} block")
def ctx(): Ctx = ???
def underlying[A](v: W[A]): T[_]
def mapCtx[A, B](a: T[A])(f: (A, Ctx) => B): T[B]
def zipMap[R]()(cb: Ctx => R) = mapCtx(zip()){ (_, ctx) => cb(ctx)}
def zipMap[A, R](a: T[A])(f: (A, Ctx) => R) = mapCtx(a)(f)
def zipMap[A, B, R](a: T[A], b: T[B])(cb: (A, B, Ctx) => R) = mapCtx(zip(a, b)){case ((a, b), x) => cb(a, b, x)}
def zipMap[A, B, C, R](a: T[A], b: T[B], c: T[C])
(cb: (A, B, C, Ctx) => R) = mapCtx(zip(a, b, c)){case ((a, b, c), x) => cb(a, b, c, x)}
def zipMap[A, B, C, D, R](a: T[A], b: T[B], c: T[C], d: T[D])
(cb: (A, B, C, D, Ctx) => R) = mapCtx(zip(a, b, c, d)){case ((a, b, c, d), x) => cb(a, b, c, d, x)}
def zipMap[A, B, C, D, E, R](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E])
(cb: (A, B, C, D, E, Ctx) => R) = mapCtx(zip(a, b, c, d, e)){case ((a, b, c, d, e), x) => cb(a, b, c, d, e, x)}
def zipMap[A, B, C, D, E, F, R](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E], f: T[F])
(cb: (A, B, C, D, E, F, Ctx) => R) = mapCtx(zip(a, b, c, d, e, f)){case ((a, b, c, d, e, f), x) => cb(a, b, c, d, e, f, x)}
def zipMap[A, B, C, D, E, F, G, R](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E], f: T[F], g: T[G])
(cb: (A, B, C, D, E, F, G, Ctx) => R) = mapCtx(zip(a, b, c, d, e, f, g)){case ((a, b, c, d, e, f, g), x) => cb(a, b, c, d, e, f, g, x)}
def zip(): T[Unit]
def zip[A](a: T[A]): T[Tuple1[A]]
def zip[A, B](a: T[A], b: T[B]): T[(A, B)]
def zip[A, B, C](a: T[A], b: T[B], c: T[C]): T[(A, B, C)]
def zip[A, B, C, D](a: T[A], b: T[B], c: T[C], d: T[D]): T[(A, B, C, D)]
def zip[A, B, C, D, E](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E]): T[(A, B, C, D, E)]
def zip[A, B, C, D, E, F](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E], f: T[F]): T[(A, B, C, D, E, F)]
def zip[A, B, C, D, E, F, G](a: T[A], b: T[B], c: T[C], d: T[D], e: T[E], f: T[F], g: T[G]): T[(A, B, C, D, E, F, G)]
}
def impl[M[_], T: c.WeakTypeTag, Ctx: c.WeakTypeTag](c: Context)
(t: c.Expr[T]): c.Expr[M[T]] = {
import c.universe._
def rec(t: Tree): Iterator[c.Tree] = Iterator(t) ++ t.children.flatMap(rec(_))
val bound = collection.mutable.Buffer.empty[(c.Tree, ValDef)]
val targetApplySym = typeOf[Applyable[_]].member(TermName("apply"))
// Derived from @olafurpg's
// https://gist.github.com/olafurpg/596d62f87bf3360a29488b725fbc7608
val defs = rec(t.tree).filter(_.isDef).map(_.symbol).toSet
val ctxName = TermName(c.freshName("ctx"))
val ctxSym = c.internal.newTermSymbol(c.internal.enclosingOwner, ctxName)
c.internal.setInfo(ctxSym, weakTypeOf[Ctx])
val transformed = c.internal.typingTransform(t.tree) {
case (t @ q"$fun.apply()", api) if t.symbol == targetApplySym =>
val localDefs = rec(fun).filter(_.isDef).map(_.symbol).toSet
val banned = rec(t).filter(x => defs(x.symbol) && !localDefs(x.symbol))
if (banned.hasNext){
val banned0 = banned.next()
c.abort(
banned0.pos,
"Target#apply() call cannot use `" + banned0.symbol + "` defined within the T{...} block"
)
}
val tempName = c.freshName(TermName("tmp"))
val tempSym = c.internal.newTermSymbol(c.internal.enclosingOwner, tempName)
c.internal.setInfo(tempSym, t.tpe)
val tempIdent = Ident(tempSym)
c.internal.setType(tempIdent, t.tpe)
c.internal.setFlag(tempSym, (1L << 44).asInstanceOf[c.universe.FlagSet])
bound.append((q"${c.prefix}.underlying($fun)", c.internal.valDef(tempSym)))
tempIdent
case (t @ q"$prefix.ctx()", api)
if prefix.tpe.baseClasses.exists(_.fullName == "forge.define.Applicative.Applyer") =>
val tempIdent = Ident(ctxSym)
c.internal.setType(tempIdent, t.tpe)
c.internal.setFlag(ctxSym, (1L << 44).asInstanceOf[c.universe.FlagSet])
tempIdent
case (t, api) => api.default(t)
}
val (exprs, bindings) = bound.unzip
val ctxBinding = c.internal.valDef(ctxSym)
val callback = c.typecheck(q"(..$bindings, $ctxBinding) => $transformed ")
val res = q"${c.prefix}.zipMap(..$exprs){ $callback }"
c.internal.changeOwner(transformed, c.internal.enclosingOwner, callback.symbol)
c.Expr[M[T]](res)
}
}
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