use crate::cofd::dice::DicePool;
use crate::dice::ElementExpression;
use crate::help::HelpTopic;
use crate::parser::trim;
use crate::roll::Roll;

pub mod parser;

pub struct Execution {
    plain: String,
    html: String,
}

impl Execution {
    pub fn plain(&self) -> &str {
        &self.plain
    }

    pub fn html(&self) -> &str {
        &self.html
    }
}

pub trait Command {
    fn execute(&self) -> Execution;
    fn name(&self) -> &'static str;
}

pub struct RollCommand(ElementExpression);

impl Command for RollCommand {
    fn name(&self) -> &'static str {
        "roll regular dice"
    }

    fn execute(&self) -> Execution {
        let roll = self.0.roll();
        let plain = format!("Dice: {}\nResult: {}", self.0, roll);
        let html = format!(
            "<p><strong>Dice:</strong> {}</p><p><strong>Result</strong>: {}</p>",
            self.0, roll
        );
        Execution { plain, html }
    }
}

pub struct PoolRollCommand(DicePool);

impl Command for PoolRollCommand {
    fn name(&self) -> &'static str {
        "roll dice pool"
    }

    fn execute(&self) -> Execution {
        let roll = self.0.roll();
        let plain = format!("Pool: {}\nResult: {}", self.0, roll);
        let html = format!(
            "<p><strong>Pool:</strong> {}</p><p><strong>Result</strong>: {}</p>",
            self.0, roll
        );
        Execution { plain, html }
    }
}

pub struct HelpCommand(Option<HelpTopic>);

impl Command for HelpCommand {
    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
            //after executing a previous command.
            ("", Some(_)) | (_, None) => Ok(command),

            //Any unconsumed input (except whitespace) is considered a parsing error.
            (extra, _) => match trim(extra).as_str() {
                "" => Ok(command),
                _ => Err(format!("{}: malformed dice expression", s)),
            },
        },
        Err(err) => Err(err.to_string()),
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn chance_die_is_not_malformed() {
        assert!(parse_command("!chance").is_ok());
    }

    #[test]
    fn roll_malformed_expression_test() {
        assert!(parse_command("!roll 1d20asdlfkj").is_err());
        assert!(parse_command("!roll 1d20asdlfkj   ").is_err());
    }

    #[test]
    fn roll_dice_pool_malformed_expression_test() {
        assert!(parse_command("!pool 8abc").is_err());
        assert!(parse_command("!pool 8abc    ").is_err());
    }

    #[test]
    fn pool_whitespace_test() {
        assert!(parse_command("!pool 8ns3   ")
            .map(|p| p.is_some())
            .expect("was error"));
        assert!(parse_command("   !pool 8ns3")
            .map(|p| p.is_some())
            .expect("was error"));
        assert!(parse_command("   !pool 8ns3   ")
            .map(|p| p.is_some())
            .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   ")
            .map(|p| p.is_some())
            .expect("was error"));
        assert!(parse_command("!roll 1d4 + 5d6 -3   ")
            .map(|p| p.is_some())
            .expect("was error"));
        assert!(parse_command("   !roll 1d4 + 5d6 -3   ")
            .map(|p| p.is_some())
            .expect("was error"));
    }
}