Implement conditional nested tag

This commit is contained in:
Paul-Henri Froidmont 2025-08-06 00:27:55 +02:00
parent 0aa10b3114
commit f0986c1664
Signed by: phfroidmont
GPG key ID: BE948AFD7E7873BE
5 changed files with 185 additions and 149 deletions

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@ -1,149 +0,0 @@
import scala.collection.immutable.ArraySeq
import zio.json.*
import zio.json.ast.*
import scala.collection.mutable.ListBuffer
@main
def main =
val r = TestLiveView.render(MyModel("Initial title"))
println(JsonWriter.toJson(r.buildClientStateInit))
r.update(MyModel("Updated title"))
println(JsonWriter.toJson(r.buildClientStateDiff))
r.update(MyModel("Updated title"))
println(JsonWriter.toJson(r.buildClientStateDiff))
trait LiveView[Model]:
val model: Dyn[Model, Model] = Dyn.id
def view: HtmlTag[Model]
final case class MyModel(title: String)
object TestLiveView extends LiveView[MyModel]:
val view: HtmlTag[MyModel] =
div(
div("before"),
model(_.title),
div("after")
)
object JsonWriter:
def toJson(init: ClientState.Init): String =
Json
.Obj("s" -> Json.Arr(init.static.map(Json.Str(_))*))
.merge(
Json.Obj(
init.dynamic.zipWithIndex.map((v, i) => i.toString -> Json.Str(v))*
)
)
.toJsonPretty
def toJson(diff: ClientState.Diff): String =
Json
.Obj(
"diff" ->
Json.Obj(
diff.dynamic.map((i, v) => i.toString -> Json.Str(v))*
)
)
.toJsonPretty
class RenderedDyn[I, O](d: Dyn[I, O], init: I):
private var value: O = d.run(init)
private var updated: Boolean = false
def wasUpdated: Boolean = updated
def currentValue: O = value
def update(v: I): Unit =
val newValue = d.run(v)
if value == newValue then updated = false
else
value = newValue
updated = true
opaque type Dyn[I, O] = I => O
extension [I, O](d: Dyn[I, O])
def apply[O2](f: O => O2): Dyn[I, O2] = d.andThen(f)
def run(v: I): O = d(v)
object Dyn:
def id[T]: Dyn[T, T] = identity
enum Mod[T]:
case Tag(v: HtmlTag[T])
case Text(v: String)
case DynText(v: Dyn[T, String])
given [T]: Conversion[HtmlTag[T], Mod[T]] = Mod.Tag(_)
given [T]: Conversion[String, Mod[T]] = Mod.Text(_)
given [T]: Conversion[Dyn[T, String], Mod[T]] = Mod.DynText(_)
object ClientState:
final case class Init(static: Seq[String], dynamic: Seq[String])
final case class Diff(dynamic: Seq[(Int, String)])
extension [Model](lv: LiveView[Model])
def render(model: Model): RenderedLiveView[Model] =
RenderedLiveView(lv.view, model)
class RenderedLiveView[Model] private (
private val static: ArraySeq[String],
private val dynamic: ArraySeq[
RenderedDyn[Model, String] // | RenderedLiveView[Model]
]
):
def update(model: Model): Unit =
dynamic.foreach(_.update(model))
def buildClientStateInit: ClientState.Init =
ClientState.Init(
static,
dynamic.map(_.currentValue)
)
def buildClientStateDiff: ClientState.Diff =
ClientState.Diff(
dynamic.zipWithIndex.collect {
case (dyn, i) if dyn.wasUpdated => i -> dyn.currentValue
}
)
object RenderedLiveView:
def apply[Model](tag: HtmlTag[Model], model: Model) =
val static = ListBuffer.empty[String]
val dynamic = ListBuffer.empty[RenderedDyn[Model, String]]
var staticFragment = ""
for elem <- buildTag(tag, model) do
elem match
case s: String =>
staticFragment += s
case d: Dyn[Model, String] =>
static.append(staticFragment)
staticFragment = ""
dynamic.append(RenderedDyn(d, model))
if staticFragment.nonEmpty then static.append(staticFragment)
new RenderedLiveView(static.to(ArraySeq), dynamic.to(ArraySeq))
private def buildTag[Model](
tag: HtmlTag[Model],
model: Model
): List[String | Dyn[Model, String]] =
(s"<${tag.name}>"
:: tag.mods.flatMap(buildMod(_, model))) :+
(s"</${tag.name}>")
private def buildMod[Model](
mod: Mod[Model],
model: Model
): List[String | Dyn[Model, String]] =
mod match
case Mod.Tag(v) => buildTag(v, model)
case Mod.Text(v) => List(v)
case Mod.DynText[Model](v) => List(v)
trait HtmlTag[Model]:
def name: String
def mods: List[Mod[Model]]
class Div[Model](val mods: List[Mod[Model]]) extends HtmlTag[Model]:
val name = "div"
def div[Model](mods: Mod[Model]*): Div[Model] = Div(mods.toList)

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package scalive
import zio.json.ast.*
object JsonAstBuilder:
def buildInit(static: Seq[String], dynamic: Seq[RenderedMod[?]]): Json =
Json
.Obj("s" -> Json.Arr(static.map(Json.Str(_))*))
.merge(buildDiffValue(dynamic, includeUnchanged = true))
def buildDiff(dynamic: Seq[RenderedMod[?]]): Json =
Json.Obj("diff" -> buildDiffValue(dynamic))
private def buildDiffValue(
dynamic: Seq[RenderedMod[?]],
includeUnchanged: Boolean = false
): Json =
Json.Obj(
dynamic.zipWithIndex.filter(includeUnchanged || _._1.wasUpdated).map {
case (v: RenderedMod.Dynamic[?, ?], i) =>
i.toString -> Json.Str(v.currentValue.toString)
case (v: RenderedMod.When[?], i) =>
if v.displayed then
if includeUnchanged || v.dynCond.wasUpdated then
i.toString -> v.nested.buildInitJson
else i.toString -> buildDiffValue(v.nested.dynamic)
else i.toString -> Json.Bool(false)
}*
)

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package scalive
trait LiveView[Model]:
val model: Dyn[Model, Model] = Dyn.id
def view: HtmlTag[Model]
opaque type Dyn[I, O] = I => O
extension [I, O](d: Dyn[I, O])
def apply[O2](f: O => O2): Dyn[I, O2] = d.andThen(f)
def when(f: O => Boolean)(tag: HtmlTag[I]) = Mod.When(d.andThen(f), tag)
def run(v: I): O = d(v)
object Dyn:
def id[T]: Dyn[T, T] = identity
enum Mod[T]:
case Tag(tag: HtmlTag[T])
case Text(text: String)
case DynText(dynText: Dyn[T, String])
case When(dynCond: Dyn[T, Boolean], tag: HtmlTag[T])
given [T]: Conversion[HtmlTag[T], Mod[T]] = Mod.Tag(_)
given [T]: Conversion[String, Mod[T]] = Mod.Text(_)
given [T]: Conversion[Dyn[T, String], Mod[T]] = Mod.DynText(_)
trait HtmlTag[Model]:
def name: String
def mods: List[Mod[Model]]
class Div[Model](val mods: List[Mod[Model]]) extends HtmlTag[Model]:
val name = "div"
def div[Model](mods: Mod[Model]*): Div[Model] = Div(mods.toList)

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package scalive
import scala.collection.mutable.ListBuffer
import scala.collection.immutable.ArraySeq
import zio.json.ast.Json
sealed trait RenderedMod[Model]:
def update(model: Model): Unit
def wasUpdated: Boolean
object RenderedMod:
class Tag[Model] private[scalive] (
val static: ArraySeq[String],
val dynamic: ArraySeq[RenderedMod[Model]]
) extends RenderedMod[Model]:
def update(model: Model): Unit =
dynamic.foreach(_.update(model))
def wasUpdated: Boolean = dynamic.exists(_.wasUpdated)
def buildInitJson: Json = JsonAstBuilder.buildInit(static, dynamic)
def buildDiffJson: Json = JsonAstBuilder.buildDiff(dynamic)
class Dynamic[I, O](d: Dyn[I, O], init: I) extends RenderedMod[I]:
private var value: O = d.run(init)
private var updated: Boolean = false
def wasUpdated: Boolean = updated
def currentValue: O = value
def update(v: I): Unit =
val newValue = d.run(v)
if value == newValue then updated = false
else
value = newValue
updated = true
class When[Model](
val dynCond: Dynamic[Model, Boolean],
val nested: Tag[Model]
) extends RenderedMod[Model]:
def displayed: Boolean = dynCond.currentValue
def wasUpdated: Boolean = dynCond.wasUpdated || nested.wasUpdated
def update(model: Model): Unit =
dynCond.update(model)
nested.update(model)
object LiveViewRenderer:
def render[Model](lv: LiveView[Model], model: Model): RenderedMod.Tag[Model] =
render(lv.view, model)
private def render[Model](
tag: HtmlTag[Model],
model: Model
): RenderedMod.Tag[Model] =
val static = ListBuffer.empty[String]
val dynamic = ListBuffer.empty[RenderedMod[Model]]
var staticFragment = ""
for elem <- renderTag(tag, model) do
elem match
case s: String =>
staticFragment += s
case d: RenderedMod[Model] =>
static.append(staticFragment)
staticFragment = ""
dynamic.append(d)
if staticFragment.nonEmpty then static.append(staticFragment)
new RenderedMod.Tag(static.to(ArraySeq), dynamic.to(ArraySeq))
private def renderTag[Model](
tag: HtmlTag[Model],
model: Model
): List[String | RenderedMod[Model]] =
(s"<${tag.name}>"
:: tag.mods.flatMap(renderMod(_, model))) :+
(s"</${tag.name}>")
private def renderMod[Model](
mod: Mod[Model],
model: Model
): List[String | RenderedMod[Model]] =
mod match
case Mod.Tag(tag) => renderTag(tag, model)
case Mod.Text(text) => List(text)
case Mod.DynText[Model](dynText) =>
List(RenderedMod.Dynamic(dynText, model))
case Mod.When[Model](dynCond, tag) =>
List(
RenderedMod.When(
RenderedMod.Dynamic(dynCond, model),
LiveViewRenderer.render(tag, model)
)
)

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package scalive
import zio.json.*
@main
def main =
val r =
LiveViewRenderer.render(
TestLiveView,
MyModel("Initial string", true, "nested init")
)
println(r.buildInitJson.toJsonPretty)
r.update(MyModel("Updated string", true, "nested updated"))
println(r.buildDiffJson.toJsonPretty)
r.update(MyModel("Updated string", false, "nested updated"))
println(r.buildDiffJson.toJsonPretty)
r.update(MyModel("Updated string", true, "nested displayed again"))
println(r.buildDiffJson.toJsonPretty)
r.update(MyModel("Updated string", true, "nested updated"))
println(r.buildDiffJson.toJsonPretty)
final case class MyModel(title: String, bool: Boolean, nestedTitle: String)
object TestLiveView extends LiveView[MyModel]:
val view: HtmlTag[MyModel] =
div(
div("Static string 1"),
model(_.title),
div("Static string 2"),
model.when(_.bool)(
div("maybe rendered", model(_.nestedTitle))
)
)