tenebrous-dicebot/src/commands/parser.rs

66 lines
2.6 KiB
Rust
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use nom::{alt, complete, named, tag, take_while, tuple, IResult};
use crate::cofd::parser::{create_chance_die, parse_dice_pool};
use crate::commands::{Command, HelpCommand, PoolRollCommand, RollCommand};
use crate::dice::parser::parse_element_expression;
use crate::help::parse_help_topic;
use crate::parser::{eat_whitespace, trim};
// Parse a roll expression.
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fn parse_roll(input: &str) -> IResult<&str, Box<dyn Command>> {
let (input, _) = eat_whitespace(input)?;
let (input, expression) = parse_element_expression(input)?;
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Ok((input, Box::new(RollCommand(expression))))
}
fn parse_pool_roll(input: &str) -> IResult<&str, Box<dyn Command>> {
let (input, _) = eat_whitespace(input)?;
let (input, pool) = parse_dice_pool(input)?;
Ok((input, Box::new(PoolRollCommand(pool))))
}
fn chance_die() -> IResult<&'static str, Box<dyn Command>> {
let (input, pool) = create_chance_die()?;
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))))
}
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/// 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
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pub fn parse_command(original_input: &str) -> IResult<&str, Option<Box<dyn Command>>> {
let (input, _) = eat_whitespace(original_input)?;
//Parser understands either specific !commands with no input, or any !command with extra input.
named!(command(&str) -> (&str, &str), tuple!(
complete!(tag!("!")),
alt!(
//TODO figure out how to gracefully handle arbitrary single commands.
complete!(tag!("chance")) |
complete!(tag!("help")) |
complete!(take_while!(char::is_alphabetic))
)
));
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let (input, command) = match command(input) {
// Strip the exclamation mark
Ok((input, (_, result))) => (input, result),
Err(_e) => {
return Ok((original_input, None));
}
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};
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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))),
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// No recognized command, ignore this.
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_ => Ok((original_input, None)),
}
}