//! The framework is a customizable method of separating commands, used in
//! combination with [`Client::with_framework`].
//!
//! The framework has a number of configurations, and can have any number of
//! commands bound to it. The primary purpose of it is to offer the utility of
//! not needing to manually match message content strings to determine if a
//! message is a command.
//!
//! Additionally, "checks" can be added to commands, to ensure that a certain
//! condition is met prior to calling a command; this could be a check that the
//! user who posted a message owns the bot, for example.
//!
//! Each command has a given named, and an associated function/closure. For
//! example, you might have two commands: `"ping"` and `"weather"`. These each
//! have an associated function that are called if the framework determines
//! that a message is of that command.
//!
//! Assuming a command prefix of `"~"`, then the following would occur with the
//! two previous commands:
//!
//! ```ignore
//! ~ping // calls the ping command's function
//! ~pin // does not
//! ~ ping // _does_ call it _if_ the `allow_whitespace` option is enabled
//! ~~ping // does not
//! ```
//!
//! # Examples
//!
//! Configuring a Client with a framework, which has a prefix of `"~"` and a
//! ping and about command:
//!
//! ```rust,no_run
//! use serenity::client::{Client, Context};
//! use serenity::model::Message;
//! use std::env;
//!
//! let mut client = Client::login_bot(&env::var("DISCORD_BOT_TOKEN").unwrap());
//!
//! client.with_framework(|f| f
//!     .configure(|c| c.prefix("~"))
//!     .on("about", about)
//!     .on("ping", ping));
//!
//! fn about(context: &Context, _message: &Message, _args: Vec<String>) {
//!     let _ = context.say("A simple test bot");
//! }
//!
//! fn ping(context: &Context, _message: &Message, _args: Vec<String>) {
//!     let _ = context.say("Pong!");
//! }
//! ```
//!
//! [`Client::with_framework`]: ../../client/struct.Client.html#method.with_framework

mod command;
mod configuration;

pub use self::command::Command;
pub use self::configuration::Configuration;

use self::command::InternalCommand;
use std::collections::HashMap;
use std::sync::Arc;
use std::thread;
use ::client::Context;
use ::model::Message;

/// A macro to generate "named parameters". This is useful to avoid manually
/// using the "arguments" parameter and manually parsing types.
///
/// This is meant for use with the command [`Framework`].
///
/// # Examples
///
/// Create a regular `ping` command which takes no arguments:
///
/// ```rust,ignore
/// command!(ping(_context, message, _args) {
///     if let Err(why) = message.reply("Pong!") {
///         println!("Error sending pong: {:?}", why);
///     }
/// });
/// ```
///
/// Create a command named `multiply` which accepts 2 floats and multiplies
/// them, sending the product as a reply:
///
/// ```rust,ignore
/// command!(multiply(_context, message, _args, first: f64, second: f64) {
///     let product = first * second;
///
///     if let Err(why) = message.reply(&product.to_string()) {
///         println!("Error sending product: {:?}", why);
///     }
/// });
/// ```
///
/// [`Framework`]: ext/framework/index.html
#[macro_export]
macro_rules! command {
    ($fname:ident($c:ident, $m:ident, $a:ident) $b:block) => {
        pub fn $fname($c: &Context, $m: &Message, $a: Vec<String>) {
            $b
        }
    };
    ($fname:ident($c:ident, $m:ident, $a:ident, $($name:ident: $t:ty),*) $b:block) => {
        pub fn $fname($c: &Context, $m: &Message, $a: Vec<String>) {
            let mut i = $a.iter();

            $(
                let $name = match i.next() {
                    Some(v) => match v.parse::<$t>() {
                        Ok(v) => v,
                        Err(_why) => return,
                    },
                    None => return,
                };
            )*

            drop(i);

            $b
        }
    };
}

/// A utility for easily managing dispatches to commands.
///
/// Refer to the [module-level documentation] for more information.
///
/// [module-level documentation]: index.html
#[allow(type_complexity)]
#[derive(Default)]
pub struct Framework {
    configuration: Configuration,
    commands: HashMap<String, InternalCommand>,
    before: Option<Arc<Fn(&Context, &Message, &String) + Send + Sync + 'static>>,
    after: Option<Arc<Fn(&Context, &Message, &String) + Send + Sync + 'static>>,
    checks: HashMap<String, Arc<Fn(&Context, &Message) -> bool + Send + Sync + 'static>>,
    /// Whether the framework has been "initialized".
    ///
    /// The framework is initialized once one of the following occurs:
    ///
    /// - configuration has been set;
    /// - a command handler has been set;
    /// - a command check has been set.
    ///
    /// This is used internally to determine whether or not - in addition to
    /// dispatching to the [`Client::on_message`] handler - to have the
    /// framework check if a [`Event::MessageCreate`] should be processed by
    /// itself.
    ///
    /// [`Client::on_message`]: ../../client/struct.Client.html#method.on_message
    /// [`Event::MessageCreate`]: ../../model/event/enum.Event.html#variant.MessageCreate
    pub initialized: bool,
}

impl Framework {
    /// Configures the framework, setting non-default values. All fields are
    /// optional. Refer to [`Configuration::default`] for more information on
    /// the default values.
    ///
    /// # Examples
    ///
    /// Configuring the framework for a [`Client`], setting the [`depth`] to 3,
    /// [allowing whitespace], and setting the [`prefix`] to `"~"`:
    ///
    /// ```rust,no_run
    /// use serenity::Client;
    /// use std::env;
    ///
    /// let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
    /// client.with_framework(|f| f
    ///     .configure(|c| c
    ///         .depth(3)
    ///         .allow_whitespace(true)
    ///         .prefix("~")));
    /// ```
    ///
    /// [`Client`]: ../../client/struct.Client.html
    /// [`Configuration::default`]: struct.Configuration.html#method.default
    /// [`depth`]: struct.Configuration.html#method.depth
    /// [`prefix`]: struct.Configuration.html#method.prefix
    /// [allowing whitespace]: struct.Configuration.html#method.allow_whitespace
    pub fn configure<F>(mut self, f: F) -> Self
        where F: FnOnce(Configuration) -> Configuration {
        self.configuration = f(self.configuration);

        self
    }

    #[doc(hidden)]
    pub fn dispatch(&mut self, context: Context, message: Message) {
        let res = command::positions(&message.content, &self.configuration);

        let positions = match res {
            Some(positions) => positions,
            None => return,
        };

        // Ensure that the message length is at least longer than a prefix
        // length. There's no point in checking further ahead if there's nothing
        // _to_ check.
        if positions.iter().all(|p| message.content.len() <= *p) {
            return;
        }

        for position in positions {
            let mut built = String::new();

            for i in 0..self.configuration.depth {
                if i != 0 {
                    built.push(' ');
                }

                built.push_str(match {
                    message.content
                        .split_at(position)
                        .1
                        .trim()
                        .split_whitespace()
                        .collect::<Vec<&str>>()
                        .get(i)
                } {
                    Some(piece) => piece,
                    None => continue,
                });

                if let Some(command) = self.commands.get(&built) {
                    if let Some(check) = self.checks.get(&built) {
                        if !(check)(&context, &message) {
                            continue;
                        }
                    }

                    let before = self.before.clone();
                    let command = command.clone();
                    let after = self.after.clone();

                    thread::spawn(move || {
                        if let Some(before) = before {
                            (before)(&context, &message, &built);
                        }

                        let args = message.content[position + built.len()..]
                            .split_whitespace()
                            .map(|arg| arg.to_owned())
                            .collect::<Vec<String>>();

                        (command)(&context, &message, args);

                        if let Some(after) = after {
                            (after)(&context, &message, &built);
                        }
                    });

                    return;
                }
            }
        }
    }

    /// Adds a function to be associated with a command, which will be called
    /// when a command is used in a message.
    ///
    /// This requires that a check - if one exists - passes, prior to being
    /// called.
    ///
    /// Refer to the [module-level documentation] for more information and
    /// usage.
    ///
    /// [module-level documentation]: index.html
    pub fn on<F, S>(mut self, command_name: S, f: F) -> Self
        where F: Fn(&Context, &Message, Vec<String>) + Send + Sync + 'static,
              S: Into<String> {
        self.commands.insert(command_name.into(), Arc::new(f));
        self.initialized = true;

        self
    }

    /// This will call given closure before every command's execution
    pub fn before<F>(mut self, f: F) -> Self
        where F: Fn(&Context, &Message, &String) + Send + Sync + 'static {
        self.before = Some(Arc::new(f));

        self
    }

    /// This will call given closure after every command's execution
    pub fn after<F>(mut self, f: F) -> Self
        where F: Fn(&Context, &Message, &String) + Send + Sync + 'static {
        self.after = Some(Arc::new(f));

        self
    }

    /// Adds a "check" to a command, which checks whether or not the command's
    /// associated function should be called.
    ///
    /// # Examples
    ///
    /// Ensure that the user who created a message, calling a "ping" command,
    /// is the owner.
    ///
    /// ```rust,no_run
    /// use serenity::client::{Client, Context};
    /// use serenity::model::Message;
    /// use std::env;
    ///
    /// let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
    ///
    /// client.with_framework(|f| f
    ///     .configure(|c| c.prefix("~"))
    ///     .on("ping", ping)
    ///     .set_check("ping", owner_check));
    ///
    /// fn ping(context: &Context, _message: &Message, _args: Vec<String>) {
    ///     context.say("Pong!");
    /// }
    ///
    /// fn owner_check(_context: &Context, message: &Message) -> bool {
    ///     // replace with your user ID
    ///     message.author.id == 7
    /// }
    /// ```
    pub fn set_check<F, S>(mut self, command: S, check: F) -> Self
        where F: Fn(&Context, &Message) -> bool + Send + Sync + 'static,
              S: Into<String> {
        self.checks.insert(command.into(), Arc::new(check));

        self
    }
}