Implement Flags parser and handle choose --everyone

- A generic Flags parser that could handle any `--flag` argument.
- `choose --everyone` overrides the Offline/DnD check.

youmubot-core/src/community/mod.rs

@@ -51,6 +51,7 @@ Note that only online/idle users in the channel are chosen from."]
 #[bucket = "community"]
 #[max_args(2)]
 pub async fn choose(ctx: &Context, m: &Message, mut args: Args) -> CommandResult {
+    let flags = Flags::collect_from(&mut args);
     let role = args.find::<RoleId>().ok();
     let title = if args.is_empty() {
         "the chosen one".to_owned()
@@ -58,6 +59,8 @@ pub async fn choose(ctx: &Context, m: &Message, mut args: Args) -> CommandResult
         args.single::<String>()?
     };
 
+    let online_only = !flags.contains("everyone");
+
     let users: Result<Vec<_>, Error> = {
         let guild = m.guild(&ctx).await.unwrap();
         let presences = &guild.presences;
@@ -69,6 +72,9 @@ pub async fn choose(ctx: &Context, m: &Message, mut args: Args) -> CommandResult
                 .into_iter()
                 .filter(|v| !v.user.bot) // Filter out bots
                 .filter(|v| {
+                    if !online_only {
+                        return true;
+                    }
                     // Filter out only online people
                     presences
                         .get(&v.user.id)

youmubot-prelude/src/flags.rs

@@ -0,0 +1,38 @@
+use serenity::prelude::Args;
+use std::collections::HashSet as Set;
+
+/// Handle flags parsing.
+pub struct Flags(Set<String>);
+
+struct Flag(pub String);
+
+impl std::str::FromStr for Flag {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s.starts_with("--") {
+            Ok(Flag(s.trim_start_matches("--").to_owned()))
+        } else {
+            Err(())
+        }
+    }
+}
+
+impl Flags {
+    /// Parses the set of flags from a given `Args` structure.
+    pub fn collect_from(args: &mut Args) -> Flags {
+        let mut set = Set::new();
+        loop {
+            if let Some(Flag(s)) = args.find().ok() {
+                set.insert(s);
+            } else {
+                break Flags(set);
+            }
+        }
+    }
+
+    /// Checks whether `flag` exists in the flags set.
+    pub fn contains(&self, flag: impl AsRef<str>) -> bool {
+        self.0.contains(flag.as_ref())
+    }
+}

youmubot-prelude/src/lib.rs

@@ -5,6 +5,7 @@ use std::sync::Arc;
 
 pub mod announcer;
 pub mod args;
+pub mod flags;
 pub mod hook;
 pub mod member_cache;
 pub mod pagination;
@@ -13,6 +14,7 @@ pub mod setup;
 
 pub use announcer::{Announcer, AnnouncerHandler};
 pub use args::{Duration, UsernameArg};
+pub use flags::Flags;
 pub use hook::Hook;
 pub use member_cache::MemberCache;
 pub use pagination::{paginate, paginate_fn, paginate_reply, paginate_reply_fn, Paginate};