Switch to using serde for deserialization

The current build system is rudimentary, incomplete, and rigid, offering
little in the way of customizing decoding options.

To solve this, switch to using serde-derive with custom Deserialization
implementations. This allows very simple deserialization when special
logic does not need to be applied, yet allows us to implement our own
deserialization logic when required.

The problem with the build system was that it built enums and structs
from YAML files. This is not so good, because it requires creating a
custom build system (which was rudimentary), creating "special struct
configs" when logic needed to be ever so slightly extended (rigid), and
if special logic needed to be applied, a custom deserialization method
would have been needed to be made anyway (incomplete).

To solve this, switch to serde-derive and implementing Deserialize
ourselves where required. This reduces YAML definitions that might
look like:

```yaml
---
name: Group
description: >
  A group channel, potentially including other users, separate from a [`Guild`].
    [`Guild`]: struct.Guild.html
fields:
  - name: channel_id
    description: The Id of the group channel.
    from: id
    type: ChannelId
  - name: icon
    description: The optional icon of the group channel.
    optional: true
    type: string
  - name: last_message_id
    description: The Id of the last message sent.
    optional: true
    type: MessageId
  - name: last_pin_timestamp
    description: Timestamp of the latest pinned message.
    optional: true
    type: string
  - name: name
    description: The name of the group channel.
    optional: true
    type: string
  - name: owner_id
    description: The Id of the group channel creator.
    type: UserId
  - name: recipients
    description: Group channel's members.
    custom: decode_users
    t: UserId, Arc<RwLock<User>>
    type: hashmap
```

to:

```rs
/// A group channel - potentially including other [`User`]s - separate from a
/// [`Guild`].
///
/// [`Guild`]: struct.Guild.html
/// [`User`]: struct.User.html
pub struct Group {
    /// The Id of the group channel.
    #[serde(rename="id")]
    pub channel_id: ChannelId,
    /// The optional icon of the group channel.
    pub icon: Option<String>,
    /// The Id of the last message sent.
    pub last_message_id: Option<MessageId>,
    /// Timestamp of the latest pinned message.
    pub last_pin_timestamp: Option<String>,
    /// The name of the group channel.
    pub name: Option<String>,
    /// The Id of the group owner.
    pub owner_id: UserId,
    /// A map of the group's recipients.
    #[serde(deserialize_with="deserialize_users")]
    pub recipients: HashMap<UserId, Arc<RwLock<User>>>,
}
```

This is much simpler and does not have as much boilerplate.

There should not be any backwards incompatible changes other than the
old, public - yet undocumented (and hidden from documentation) - decode
methods being removed. Due to the nature of this commit, field names may
be incorrect, and will need to be corrected as deserialization errors
are found.

1 files changed, 60 insertions, 45 deletions

diff --git a/src/utils/builder/create_embed.rs b/src/utils/builder/create_embed.rs
index 86d5b11..7c1c606 100644
--- a/src/utils/builder/create_embed.rs
+++ b/src/utils/builder/create_embed.rs
@@ -15,11 +15,10 @@
 //! [`ExecuteWebhook::embeds`]: struct.ExecuteWebhook.html#method.embeds
 //! [here]: https://discordapp.com/developers/docs/resources/channel#embed-object
 
-use serde_json::builder::ObjectBuilder;
 use serde_json::Value;
-use std::collections::BTreeMap;
 use std::default::Default;
 use time::Tm;
+use ::internal::prelude::*;
 use ::model::Embed;
 use ::utils::Colour;
 
@@ -34,7 +33,7 @@ use ::utils::Colour;
 /// [`Context::send_message`]: ../../client/struct.Context.html#method.send_message
 /// [`Embed`]: ../../model/struct.Embed.html
 /// [`ExecuteWebhook::embeds`]: struct.ExecuteWebhook.html#method.embeds
-pub struct CreateEmbed(pub BTreeMap<String, Value>);
+pub struct CreateEmbed(pub Map<String, Value>);
 
 impl CreateEmbed {
     /// Set the author of the embed.
@@ -45,9 +44,9 @@ impl CreateEmbed {
     /// [`CreateEmbedAuthor`]: struct.CreateEmbedAuthor.html
     pub fn author<F>(mut self, f: F) -> Self
         where F: FnOnce(CreateEmbedAuthor) -> CreateEmbedAuthor {
-        let author = f(CreateEmbedAuthor::default()).0.build();
+        let author = f(CreateEmbedAuthor::default()).0;
 
-        self.0.insert("author".to_owned(), author);
+        self.0.insert("author".to_owned(), Value::Object(author));
 
         CreateEmbed(self.0)
     }
@@ -63,7 +62,7 @@ impl CreateEmbed {
 
     /// Set the colour of the left-hand side of the embed.
     pub fn colour<C: Into<Colour>>(mut self, colour: C) -> Self {
-        self.0.insert("color".to_owned(), Value::U64(colour.into().0 as u64));
+        self.0.insert("color".to_owned(), Value::Number(Number::from(colour.into().0 as u64)));
 
         CreateEmbed(self.0)
     }
@@ -89,7 +88,7 @@ impl CreateEmbed {
     /// [`CreateEmbedField`]: struct.CreateEmbedField.html
     pub fn field<F>(mut self, f: F) -> Self
         where F: FnOnce(CreateEmbedField) -> CreateEmbedField {
-        let field = f(CreateEmbedField::default()).0.build();
+        let field = f(CreateEmbedField::default()).0;
 
         {
             let key = "fields".to_owned();
@@ -106,7 +105,7 @@ impl CreateEmbed {
                     return CreateEmbed(self.0);
                 },
             };
-            arr.push(field);
+            arr.push(Value::Object(field));
 
             self.0.insert("fields".to_owned(), Value::Array(arr));
         }
@@ -122,18 +121,18 @@ impl CreateEmbed {
     /// [`CreateEmbedFooter`]: struct.CreateEmbedFooter.html
     pub fn footer<F>(mut self, f: F) -> Self
         where F: FnOnce(CreateEmbedFooter) -> CreateEmbedFooter {
-        let footer = f(CreateEmbedFooter::default()).0.build();
+        let footer = f(CreateEmbedFooter::default()).0;
 
-        self.0.insert("footer".to_owned(), footer);
+        self.0.insert("footer".to_owned(), Value::Object(footer));
 
         CreateEmbed(self.0)
     }
 
     /// Set the image associated with the embed. This only supports HTTP(S).
     pub fn image(mut self, url: &str) -> Self {
-        let image = ObjectBuilder::new()
-            .insert("url".to_owned(), url.to_owned())
-            .build();
+        let image = json!({
+            "url": url.to_owned()
+        });
 
         self.0.insert("image".to_owned(), image);
 
@@ -142,9 +141,9 @@ impl CreateEmbed {
 
     /// Set the thumbnail of the embed. This only supports HTTP(S).
     pub fn thumbnail(mut self, url: &str) -> Self {
-        let thumbnail = ObjectBuilder::new()
-            .insert("url".to_owned(), url.to_owned())
-            .build();
+        let thumbnail = json!({
+            "url": url.to_owned(),
+        });
 
         self.0.insert("thumbnail".to_owned(), thumbnail);
 
@@ -198,7 +197,7 @@ impl CreateEmbed {
 impl Default for CreateEmbed {
     /// Creates a builder with default values, setting the `type` to `rich`.
     fn default() -> CreateEmbed {
-        let mut map = BTreeMap::new();
+        let mut map = Map::new();
         map.insert("type".to_owned(), Value::String("rich".to_owned()));
 
         CreateEmbed(map)
@@ -233,13 +232,11 @@ impl From<Embed> for CreateEmbed {
             b = b.description(&description);
         }
 
-        if let Some(fields) = embed.fields {
-            for field in fields {
-                b = b.field(move |f| f
-                    .inline(field.inline)
-                    .name(&field.name)
-                    .value(&field.value));
-            }
+        for field in embed.fields {
+            b = b.field(move |f| f
+                .inline(field.inline)
+                .name(&field.name)
+                .value(&field.value));
         }
 
         if let Some(image) = embed.image {
@@ -266,7 +263,6 @@ impl From<Embed> for CreateEmbed {
     }
 }
 
-
 /// A builder to create a fake [`Embed`] object's author, for use with the
 /// [`CreateEmbed::author`] method.
 ///
@@ -276,22 +272,28 @@ impl From<Embed> for CreateEmbed {
 /// [`CreateEmbed::author`]: struct.CreateEmbed.html#method.author
 /// [`name`]: #method.name
 #[derive(Default)]
-pub struct CreateEmbedAuthor(pub ObjectBuilder);
+pub struct CreateEmbedAuthor(pub Map<String, Value>);
 
 impl CreateEmbedAuthor {
     /// Set the URL of the author's icon.
-    pub fn icon_url(self, icon_url: &str) -> Self {
-        CreateEmbedAuthor(self.0.insert("icon_url", icon_url))
+    pub fn icon_url(mut self, icon_url: &str) -> Self {
+        self.0.insert("icon_url".to_owned(), Value::String(icon_url.to_owned()));
+
+        self
     }
 
     /// Set the author's name.
-    pub fn name(self, name: &str) -> Self {
-        CreateEmbedAuthor(self.0.insert("name", name))
+    pub fn name(mut self, name: &str) -> Self {
+        self.0.insert("name".to_owned(), Value::String(name.to_owned()));
+
+        self
     }
 
     /// Set the author's URL.
-    pub fn url(self, url: &str) -> Self {
-        CreateEmbedAuthor(self.0.insert("url", url))
+    pub fn url(mut self, url: &str) -> Self {
+        self.0.insert("url".to_owned(), Value::String(url.to_owned()));
+
+        self
     }
 }
 
@@ -303,22 +305,28 @@ impl CreateEmbedAuthor {
 ///
 /// [`Embed`]: ../../model/struct.Embed.html
 /// [`CreateEmbed::field`]: struct.CreateEmbed.html#method.field
-pub struct CreateEmbedField(pub ObjectBuilder);
+pub struct CreateEmbedField(pub Map<String, Value>);
 
 impl CreateEmbedField {
     /// Set whether the field is inlined. Set to true by default.
-    pub fn inline(self, inline: bool) -> Self {
-        CreateEmbedField(self.0.insert("inline", inline))
+    pub fn inline(mut self, inline: bool) -> Self {
+        self.0.insert("inline".to_owned(), Value::Bool(inline));
+
+        self
     }
 
     /// Set the field's name. It can't be longer than 256 characters.
-    pub fn name(self, name: &str) -> Self {
-        CreateEmbedField(self.0.insert("name", name))
+    pub fn name(mut self, name: &str) -> Self {
+        self.0.insert("name".to_owned(), Value::String(name.to_owned()));
+
+        self
     }
 
     /// Set the field's value. It can't be longer than 1024 characters.
-    pub fn value(self, value: &str) -> Self {
-        CreateEmbedField(self.0.insert("value", value))
+    pub fn value(mut self, value: &str) -> Self {
+        self.0.insert("value".to_owned(), Value::String(value.to_owned()));
+
+        self
     }
 }
 
@@ -326,7 +334,10 @@ impl Default for CreateEmbedField {
     /// Creates a builder with default values, setting the value of `inline` to
     /// `true`.
     fn default() -> CreateEmbedField {
-        CreateEmbedField(ObjectBuilder::new().insert("inline", true))
+        let mut map = Map::new();
+        map.insert("inline".to_owned(), Value::Bool(true));
+
+        CreateEmbedField(map)
     }
 }
 
@@ -338,17 +349,21 @@ impl Default for CreateEmbedField {
 /// [`Embed`]: ../../model/struct.Embed.html
 /// [`CreateEmbed::footer`]: struct.CreateEmbed.html#method.footer
 #[derive(Default)]
-pub struct CreateEmbedFooter(pub ObjectBuilder);
+pub struct CreateEmbedFooter(pub Map<String, Value>);
 
 impl CreateEmbedFooter {
     /// Set the icon URL's value. This only supports HTTP(S).
-    pub fn icon_url(self, icon_url: &str) -> Self {
-        CreateEmbedFooter(self.0.insert("icon_url", icon_url))
+    pub fn icon_url(mut self, icon_url: &str) -> Self {
+        self.0.insert("icon_url".to_owned(), Value::String(icon_url.to_owned()));
+
+        self
     }
 
     /// Set the footer's text.
-    pub fn text(self, text: &str) -> Self {
-        CreateEmbedFooter(self.0.insert("text", text))
+    pub fn text(mut self, text: &str) -> Self {
+        self.0.insert("text".to_owned(), Value::String(text.to_owned()));
+
+        self
     }
 }