Implement basic, not-well-formatted help.

Cargo.lock

@@ -172,6 +172,7 @@ dependencies = [
  "async-trait",
  "dirs",
  "env_logger",
+ "indoc",
  "itertools",
  "log",
  "matrix-sdk",
@@ -680,6 +681,15 @@ dependencies = [
  "hashbrown",
 ]
 
+[[package]]
+name = "indoc"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "644defcefee68d7805653a682e99a2e2a5014a1fc3cc9be7059a215844eeea6f"
+dependencies = [
+ "unindent",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.6"
@@ -2051,6 +2061,12 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
 
+[[package]]
+name = "unindent"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af41d708427f8fd0e915dcebb2cae0f0e6acb2a939b2d399c265c39a38a18942"
+
 [[package]]
 name = "url"
 version = "2.1.1"

Cargo.toml

@@ -21,6 +21,7 @@ itertools = "0.9"
 async-trait = "0.1"
 url = "2.1"
 dirs = "3.0"
+indoc = "1.0"
 
 # The versioning of the matrix SDK follows its Cargo.toml. The SDK and
 # macros are on master, but it imports the common and base from 0.1.0.

src/commands.rs

@@ -1,5 +1,6 @@
 use crate::cofd::dice::DicePool;
 use crate::dice::ElementExpression;
+use crate::help::HelpTopic;
 use crate::parser::trim;
 use crate::roll::Roll;
 
@@ -61,10 +62,29 @@ impl Command for PoolRollCommand {
     }
 }
 
-/// Parse a command string into a dynamic command execution trait object.
+pub struct HelpCommand(Option<HelpTopic>);
-/// Returns an error if a command was recognized but not parsed correctly.  Returns None if no
+
-/// command was recognized.
+impl Command for HelpCommand {
-pub fn parse_command(s: &str) -> Result<Option<Box<dyn Command>>, String> {
+    fn name(&self) -> &'static str {
+        "help information"
+    }
+
+    fn execute(&self) -> Execution {
+        let help = match &self.0 {
+            Some(topic) => topic.message(),
+            _ => "There is no help for this topic",
+        };
+
+        let plain = format!("Help: {}", help);
+        let html = format!("<p><strong>Help:</strong> {}", help.replace("\n", "<br/>"));
+        Execution { plain, html }
+    }
+}
+
+/// Parse a command string into a dynamic command execution trait
+/// object. Returns an error if a command was recognized but not
+/// parsed correctly. Returns None if no command was recognized.
+pub fn parse_command<'a>(s: &'a str) -> Result<Option<Box<dyn Command + 'a>>, String> {
     match parser::parse_command(s) {
         Ok((input, command)) => match (input, &command) {
             //This clause prevents bot from spamming messages to itself
@@ -115,6 +135,19 @@ mod tests {
             .expect("was error"));
     }
 
+    #[test]
+    fn help_whitespace_test() {
+        assert!(parse_command("!help stuff   ")
+            .map(|p| p.is_some())
+            .expect("was error"));
+        assert!(parse_command("   !help stuff")
+            .map(|p| p.is_some())
+            .expect("was error"));
+        assert!(parse_command("   !help stuff   ")
+            .map(|p| p.is_some())
+            .expect("was error"));
+    }
+
     #[test]
     fn roll_whitespace_test() {
         assert!(parse_command("!roll 1d4 + 5d6 -3   ")

src/commands/parser.rs

@@ -1,9 +1,10 @@
 use nom::{alt, complete, named, tag, take_while, tuple, IResult};
 
 use crate::cofd::parser::{create_chance_die, parse_dice_pool};
-use crate::commands::{Command, PoolRollCommand, RollCommand};
+use crate::commands::{Command, HelpCommand, PoolRollCommand, RollCommand};
 use crate::dice::parser::parse_element_expression;
-use crate::parser::eat_whitespace;
+use crate::help::parse_help_topic;
+use crate::parser::{eat_whitespace, trim};
 
 // Parse a roll expression.
 fn parse_roll(input: &str) -> IResult<&str, Box<dyn Command>> {
@@ -23,6 +24,12 @@ fn chance_die() -> IResult<&'static str, Box<dyn Command>> {
     Ok((input, Box::new(PoolRollCommand(pool))))
 }
 
+fn help(topic: &str) -> IResult<&str, Box<dyn Command>> {
+    let (topic, _) = eat_whitespace(topic)?;
+    let topic = parse_help_topic(&trim(topic));
+    Ok(("", Box::new(HelpCommand(topic))))
+}
+
 /// Potentially parse a command expression.  If we recognize the command, an error should be raised
 /// if the command is misparsed.  If we don't recognize the command, ignore it and return none
 pub fn parse_command(original_input: &str) -> IResult<&str, Option<Box<dyn Command>>> {
@@ -32,7 +39,9 @@ pub fn parse_command(original_input: &str) -> IResult<&str, Option<Box<dyn Comma
     named!(command(&str) -> (&str, &str), tuple!(
         complete!(tag!("!")),
         alt!(
-            complete!(tag!("chance")) | //TODO figure out how to just have it read single commands.
+            //TODO figure out how to gracefully handle arbitrary single commands.
+            complete!(tag!("chance")) |
+            complete!(tag!("help")) |
             complete!(take_while!(char::is_alphabetic))
         )
     ));
@@ -40,13 +49,16 @@ pub fn parse_command(original_input: &str) -> IResult<&str, Option<Box<dyn Comma
     let (input, command) = match command(input) {
         // Strip the exclamation mark
         Ok((input, (_, result))) => (input, result),
-        Err(_e) => return Ok((original_input, None)),
+        Err(_e) => {
+            return Ok((original_input, None));
+        }
     };
 
     match command {
         "r" | "roll" => parse_roll(input).map(|(input, command)| (input, Some(command))),
         "rp" | "pool" => parse_pool_roll(input).map(|(input, command)| (input, Some(command))),
         "chance" => chance_die().map(|(input, command)| (input, Some(command))),
+        "help" => help(input).map(|(input, command)| (input, Some(command))),
         // No recognized command, ignore this.
         _ => Ok((original_input, None)),
     }

src/help.rs

@@ -0,0 +1,86 @@
+use indoc::indoc;
+
+pub fn parse_help_topic(input: &str) -> Option<HelpTopic> {
+    match input {
+        "cofd" => Some(HelpTopic::ChroniclesOfDarkness),
+        "dicepool" => Some(HelpTopic::DicePool),
+        "dice" => Some(HelpTopic::RollingDice),
+        "" => Some(HelpTopic::General),
+        _ => None,
+    }
+}
+
+pub enum HelpTopic {
+    ChroniclesOfDarkness,
+    DicePool,
+    RollingDice,
+    General,
+}
+
+const COFD_HELP: &'static str = indoc! {"
+Chronicles of Darkness
+
+Commands available:
+ !pool, !rp: roll a dice pool
+ !chance: roll a chance die
+
+See also:
+ !help dicepool
+"};
+
+const DICE_HELP: &'static str = indoc! {"
+Rolling basic dice
+
+Command: !roll, !r
+
+Syntax !roll <dice-expression>
+
+Dice expression can be a basic die (e.g. 1d4), with a bonus (1d4+3),
+or a more complex series of dice rolls or arbitrary numbers.
+Parentheses are not supported.
+
+Examples:
+ !roll 1d4
+ !roll 1d4+5
+ !roll 2d6+8
+ !roll 2d8 + 4d6 - 3
+"};
+
+const DICEPOOL_HELP: &'static str = indoc! {"
+Rolling dice pools
+
+Command: !pool, !rp
+
+Syntax: !pool <num><modifiers>
+
+Modifiers:
+ n = nine-again
+ e = eight-again
+ r = rote quality
+ x = do not re-roll 10s
+ s<num> = number of successes for exceptional
+
+Examples:
+ !pool 8 (roll a regular pool of 8 dice)
+ !pool 5n (roll dice pool of 5, nine-again)
+ !pool 6rs3 (roll dice pool of 6, rote quality, 3 successes for exceptional)
+"};
+
+const GENERAL_HELP: &'static str = indoc! {"
+General Help
+
+Try these help commands:
+  !help cofd
+  !help dice
+"};
+
+impl HelpTopic {
+    pub fn message(&self) -> &str {
+        match self {
+            HelpTopic::ChroniclesOfDarkness => COFD_HELP,
+            HelpTopic::DicePool => DICEPOOL_HELP,
+            HelpTopic::RollingDice => DICE_HELP,
+            HelpTopic::General => GENERAL_HELP,
+        }
+    }
+}

src/lib.rs

@@ -2,5 +2,6 @@ pub mod bot;
 pub mod cofd;
 pub mod commands;
 pub mod dice;
+mod help;
 mod parser;
 pub mod roll;