From 92301fb1d464929a0986a57877a905fe0a3a4f68 Mon Sep 17 00:00:00 2001
From: jeff <jeff@agnos.is>
Date: Tue, 8 Dec 2020 21:47:01 +0000
Subject: [PATCH] Dynamically deserialize character data.

---
 Cargo.lock               | 10 ++++++++++
 Cargo.toml               |  1 +
 src/models/characters.rs | 35 +++++++++++++++++++++++++++++++++++
 src/routes/characters.rs | 21 +++++++++------------
 4 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index bdac6bc..7994578 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -380,6 +380,15 @@ version = "1.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
 
+[[package]]
+name = "erased-serde"
+version = "0.3.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ca8b296792113e1500fd935ae487be6e00ce318952a6880555554824d6ebf38"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "error-chain"
 version = "0.12.4"
@@ -1449,6 +1458,7 @@ version = "0.1.0"
 dependencies = [
  "diesel",
  "diesel-derive-enum",
+ "erased-serde",
  "log 0.4.11",
  "prost",
  "prost-build",
diff --git a/Cargo.toml b/Cargo.toml
index 999d3ff..14bb83c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ prost = "0.6"
 serde = "1.0"
 serde_derive = "1.0"
 serde_json = "1.0"
+erased-serde = "0.3"
 diesel = "1.4"
 diesel-derive-enum = { version = "1", features = ["sqlite"] }
 thiserror = "1.0"
diff --git a/src/models/characters.rs b/src/models/characters.rs
index 89285fc..f0c2ae0 100644
--- a/src/models/characters.rs
+++ b/src/models/characters.rs
@@ -1,8 +1,17 @@
+use crate::errors::Error;
+use crate::models::proto::cofd::*;
 use crate::models::users::User;
 use crate::schema::characters;
 use diesel_derive_enum::DbEnum;
 use serde_derive::Serialize;
 
+/// Dynamic character data is an opaque container type that holds
+/// successfully deserialized character data protobuf object of any
+/// type. It does not know what kind of type it has. This is a
+/// semantically more appropriate name for what is returned from the
+/// dyn_deserialize function.
+pub(crate) type DynCharacterData = dyn erased_serde::Serialize;
+
 /// Control system visibility of a character for a particular user.
 /// Implemented as a trait because there are multiple character
 /// structs that need this.
@@ -59,6 +68,32 @@ impl Visibility for Character {
     }
 }
 
+impl Character {
+    /// Attempt to deserialize the character's data into the given
+    /// type, which must be one of the protobuf types.
+    pub fn try_deserialize<T>(&self) -> Result<T, Error>
+    where
+        T: prost::Message + std::default::Default,
+    {
+        let decoded = T::decode(self.data.as_ref())?;
+        Ok(decoded)
+    }
+
+    /// Attempt to deserialize the character's data based on its
+    /// stored type, but return the deserialized protobuf type as a
+    /// trait object. Primarily used for passing character sheets to
+    /// templates or other places (like a REST API).
+    pub fn dyn_deserialize(&self) -> Result<Box<DynCharacterData>, Error> {
+        use CharacterDataType::*;
+        let decoded: Box<dyn erased_serde::Serialize> = match self.data_type {
+            ChroniclesOfDarknessV1 => Box::new(self.try_deserialize::<CofdSheet>()?),
+            ChangelingV1 => Box::new(self.try_deserialize::<ChangelingSheet>()?),
+        };
+
+        Ok(decoded)
+    }
+}
+
 #[derive(Serialize, Debug, Queryable)]
 pub struct StrippedCharacter {
     pub id: i32,
diff --git a/src/routes/characters.rs b/src/routes/characters.rs
index 10aa2de..5e2644d 100644
--- a/src/routes/characters.rs
+++ b/src/routes/characters.rs
@@ -1,10 +1,11 @@
 use crate::db::{Dao, TenebrousDbConn};
 use crate::errors::Error;
-use crate::models::characters::Visibility;
+use crate::models::characters::{CharacterDataType, DynCharacterData, Visibility};
 use crate::models::users::User;
 use rocket::request::Form;
 use rocket::response::Redirect;
 use rocket_contrib::templates::Template;
+use serde::Serialize;
 use std::collections::HashMap;
 
 pub(crate) fn routes() -> Vec<rocket::Route> {
@@ -23,10 +24,10 @@ struct NewCharacterForm {
 }
 
 #[derive(Serialize)]
-struct ViewCharacterTemlate<'a, T> {
+struct ViewCharacterTemplate<'a> {
     pub name: &'a str,
     pub username: &'a str,
-    pub sheet: T,
+    pub sheet: Box<DynCharacterData>,
 }
 
 #[get("/<username>/<character_id>")]
@@ -43,15 +44,10 @@ fn view_character(
         .and_then(|c| c.as_visible_for(logged_in_user))
         .ok_or(Error::NotFound)?;
 
-    //TODO determine sheet type and deserialize based on that.
-    use crate::models::proto::cofd::CofdSheet;
-    use prost::Message;
-    let sheet = CofdSheet::decode(character.data.as_ref())?;
-
-    let context = ViewCharacterTemlate {
+    let context = ViewCharacterTemplate {
         name: &character.character_name,
         username: &user.username,
-        sheet: sheet,
+        sheet: character.dyn_deserialize()?,
     };
 
     Ok(Template::render("view_character", context))
@@ -77,7 +73,8 @@ fn create_new_character(
     use prost::bytes::BytesMut;
     use prost::Message;
 
-    let new_character = CofdSheet::default();
+    let mut new_character = CofdSheet::default();
+    new_character.strength = 100;
     let mut buf = BytesMut::with_capacity(std::mem::size_of_val(&new_character));
     new_character.encode(&mut buf)?;
 
@@ -85,7 +82,7 @@ fn create_new_character(
         user_id: logged_in_user.id,
         viewable: true,
         character_name: &form.name,
-        data_type: std::any::type_name::<CofdSheet>(),
+        data_type: CharacterDataType::ChroniclesOfDarknessV1,
         data_version: 1,
         data: &buf,
     };