Add an `EditMessage` builder

When editing messages, not all fields are applicable. Attachments, TTS,
and reactions are not applicable. To help with this distinction,
separate message editing into a different builder.

2 files changed, 47 insertions, 0 deletions

diff --git a/src/builder/edit_message.rs b/src/builder/edit_message.rs
new file mode 100644
index 0000000..29da46a
--- /dev/null
+++ b/src/builder/edit_message.rs
@@ -0,0 +1,45 @@
+use internal::prelude::*;
+use std::fmt::Display;
+use super::CreateEmbed;
+use utils::{self, VecMap};
+
+/// A builder to specify the fields to edit in an existing message.
+///
+/// # Examples
+///
+/// Editing the content of a [`Message`] to `"hello"`:
+///
+/// ```rust,no_run
+/// # use serenity::model::id::{ChannelId, MessageId};
+/// #
+/// # let mut message = ChannelId(7).message(MessageId(8)).unwrap();
+/// #
+///
+/// let _ = message.edit(|m| m.content("hello"));
+/// ```
+///
+/// [`Message`]: ../model/channel/struct.Message.html
+#[derive(Clone, Debug, Default)]
+pub struct EditMessage(pub VecMap<&'static str, Value>);
+
+impl EditMessage {
+    /// Set the content of the message.
+    ///
+    /// **Note**: Message contents must be under 2000 unicode code points.
+    pub fn content<D: Display>(mut self, content: D) -> Self {
+        self.0.insert("content", Value::String(content.to_string()));
+
+        self
+    }
+
+    /// Set an embed for the message.
+    pub fn embed<F>(mut self, f: F) -> Self
+        where F: FnOnce(CreateEmbed) -> CreateEmbed {
+        let map = utils::vecmap_to_json_map(f(CreateEmbed::default()).0);
+        let embed = Value::Object(map);
+
+        self.0.insert("embed", embed);
+
+        self
+    }
+}
diff --git a/src/builder/mod.rs b/src/builder/mod.rs
index 3c59c0d..c372e70 100644
--- a/src/builder/mod.rs
+++ b/src/builder/mod.rs
@@ -11,6 +11,7 @@ mod create_message;
 mod edit_channel;
 mod edit_guild;
 mod edit_member;
+mod edit_message;
 mod edit_profile;
 mod edit_role;
 mod execute_webhook;
@@ -22,6 +23,7 @@ pub use self::create_message::CreateMessage;
 pub use self::edit_channel::EditChannel;
 pub use self::edit_guild::EditGuild;
 pub use self::edit_member::EditMember;
+pub use self::edit_message::EditMessage;
 pub use self::edit_profile::EditProfile;
 pub use self::edit_role::EditRole;
 pub use self::execute_webhook::ExecuteWebhook;