From 13ce66ac5b27c47dce103e487358d2a9db6bd588 Mon Sep 17 00:00:00 2001
From: Myriad-Dreamin <35292584+Myriad-Dreamin@users.noreply.github.com>
Date: Mon, 13 Nov 2023 16:09:34 +0800
Subject: [PATCH] dev(core): add DynPolymorphicExporter (#411)

---
 core/src/exporter.rs | 57 ++++++++++++++++++++++++++++++++++++++++----
 core/src/lib.rs      |  4 +++-
 2 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/core/src/exporter.rs b/core/src/exporter.rs
index 272f5035f..be387d3ae 100644
--- a/core/src/exporter.rs
+++ b/core/src/exporter.rs
@@ -5,8 +5,8 @@ use typst::{diag::SourceResult, World};
 pub type DynExporter<Input, Output = ()> = Box<dyn Exporter<Input, Output> + Send>;
 
 pub trait Transformer<Input, Output = ()> {
-    /// Export the given input with given world.
-    /// the writable world is hiden by trait itself.
+    /// Export the given input with given world. the writable world is hiden by
+    /// trait itself.
     fn export(&self, world: &dyn World, output: Input) -> SourceResult<Output>;
 }
 
@@ -21,8 +21,8 @@ where
 }
 
 pub trait Exporter<Input, Output = ()> {
-    /// Export the given input with given world.
-    /// the writable world is hiden by trait itself.
+    /// Export the given input with given world. the writable world is hiden by
+    /// trait itself.
     fn export(&self, world: &dyn World, output: Arc<Input>) -> SourceResult<Output>;
 }
 
@@ -45,6 +45,55 @@ where
     }
 }
 
+pub type DynGenericExporter<X, Input, Output = ()> =
+    Box<dyn GenericExporter<Input, Output, W = X> + Send>;
+
+pub trait GenericTransformer<Input, Output = ()> {
+    type W;
+
+    /// Export the given input with given world. the writable world is hiden by
+    /// trait itself.
+    fn export(&self, world: &Self::W, output: Input) -> SourceResult<Output>;
+}
+
+pub trait GenericExporter<Input, Output = ()> {
+    type W;
+
+    /// Export the given input with given world. the writable world is hiden by
+    /// trait itself.
+    fn export(&self, world: &Self::W, output: Arc<Input>) -> SourceResult<Output>;
+}
+
+pub enum DynPolymorphicExporter<W, Input, Output> {
+    /// It is just applied to exactly the same world type.
+    Just(DynGenericExporter<W, Input, Output>),
+    /// A dynamic exporter that can be applied to any dyn world.
+    Dyn(DynExporter<Input, Output>),
+}
+
+impl<X, Input, Output> DynPolymorphicExporter<X, Input, Output> {
+    pub fn new(exporter: DynExporter<Input, Output>) -> Self {
+        Self::Dyn(exporter)
+    }
+    pub fn new_dyn(exporter: DynExporter<Input, Output>) -> Self {
+        Self::Dyn(exporter)
+    }
+}
+
+impl<X, Input, Output> GenericExporter<Input, Output> for DynPolymorphicExporter<X, Input, Output>
+where
+    X: World,
+{
+    type W = X;
+
+    fn export(&self, world: &Self::W, output: Arc<Input>) -> SourceResult<Output> {
+        match self {
+            Self::Just(exporter) => exporter.export(world, output),
+            Self::Dyn(exporter) => exporter.export(world, output),
+        }
+    }
+}
+
 pub mod builtins {
     use std::{fs::File, sync::Arc};
 
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 3379f7a8e..5bd30ede5 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -23,7 +23,9 @@ pub mod config;
 // Core mechanism of typst-ts.
 pub(crate) mod exporter;
 pub use exporter::{builtins as exporter_builtins, utils as exporter_utils};
-pub use exporter::{DynExporter, Exporter, Transformer};
+pub use exporter::{
+    DynExporter, DynGenericExporter, DynPolymorphicExporter, Exporter, GenericExporter, Transformer,
+};
 pub mod font;
 pub use font::{FontLoader, FontResolver, FontSlot};
 pub mod package;