//! evtclib tracker definitions.
//!
//! The idea behind a "tracker" is to have one object taking care of one
//! specific thing. This makes it easier to organize the whole "statistic
//! gathering loop", and it keeps each tracker somewhat small.
//!
//! It's also easy to define your own trackers if there are any statistics that
//! you want to track. Just implement [`Tracker`](trait.Tracker.html). It
//! doesn't matter what you track, it doesn't matter how many trackers you
//! define.
//!
//! You can use [`run_trackers`](../fn.run_trackers.html) to run multiple
//! trackers on the same log.
use std::collections::HashMap;
use std::error::Error;

use super::super::{Event, EventKind, Log};
use super::DamageStats;

// A support macro to introduce a new block.
//
// Doesn't really require a macro, but it's nicer to look at
//   with! { foo = bar }
// rather than
//   { let foo = bar; ... }
macro_rules! with {
    ($name:ident = $expr:expr => $bl:block) => {{
        let $name = $expr;
        $bl
    }};
}

/// A tracker.
///
/// A tracker should be responsible for tracking a single statistic. Each
/// tracker is fed each event. If an error is returned while feeding, the whole
/// calculation will be aborted.
pub trait Tracker {
    /// The resulting statistic that this tracker will return.
    type Stat;
    /// The error that this tracker might return.
    type Error: Error;

    /// Feed a single event into this tracker.
    ///
    /// The tracker will update its internal state.
    fn feed(&mut self, event: &Event) -> Result<(), Self::Error>;

    /// Finalize this tracker and get the statistics out.
    fn finalize(self) -> Result<Self::Stat, Self::Error>;
}

/// A helper trait that erases the types from a tracker.
///
/// This makes it able to use references like `&mut RunnableTracker` without
/// having to specify the generic types, allowing you to e.g. store a bunch of
/// them in a vector, regardless of their output type. Unless you want to do
/// that, you probably don't want to use this trait directly.
///
/// Note that you do not need to implement this yourself. It is automatically
/// implemented for all types that implement `Tracker`.
///
/// RunnableTrackers provide no way to extract their resources, and they wrap
/// all errors in `Box<_>`, so you should always keep a "real" reference around
/// if you plan on getting any data.
pub trait RunnableTracker {
    /// See `Tracker.feed()`. Renamed to avoid conflicts.
    fn run_feed(&mut self, event: &Event) -> Result<(), Box<Error>>;
}

impl<S, E: Error + 'static, T: Tracker<Stat = S, Error = E>> RunnableTracker for T {
    fn run_feed(&mut self, event: &Event) -> Result<(), Box<Error>> {
        self.feed(event).map_err(|e| Box::new(e) as Box<Error>)
    }
}

/// A tracker that tracks per-target damage of all agents.
pub struct DamageTracker<'l> {
    log: &'l Log,
    // Source -> Target -> Damage
    damages: HashMap<u64, HashMap<u64, DamageStats>>,
}

impl<'t> DamageTracker<'t> {
    /// Create a new damage tracker for the given log.
    pub fn new(log: &Log) -> DamageTracker {
        DamageTracker {
            log,
            damages: HashMap::new(),
        }
    }

    fn get_stats(&mut self, source: u64, target: u64) -> &mut DamageStats {
        self.damages
            .entry(source)
            .or_insert_with(Default::default)
            .entry(target)
            .or_insert_with(Default::default)
    }
}

impl<'t> Tracker for DamageTracker<'t> {
    type Stat = HashMap<u64, HashMap<u64, DamageStats>>;
    type Error = !;

    fn feed(&mut self, event: &Event) -> Result<(), Self::Error> {
        match event.kind {
            EventKind::Physical {
                source_agent_addr,
                destination_agent_addr,
                damage,
                ..
            } => {
                with! { stats = self.get_stats(source_agent_addr, destination_agent_addr) => {
                    stats.total_damage += damage as u64;
                    stats.power_damage += damage as u64;
                }}

                if let Some(master) = self.log.master_agent(source_agent_addr) {
                    let master_stats = self.get_stats(master.addr, destination_agent_addr);
                    master_stats.total_damage += damage as u64;
                    master_stats.add_damage += damage as u64;
                }
            }

            EventKind::ConditionTick {
                source_agent_addr,
                destination_agent_addr,
                damage,
                ..
            } => {
                with! { stats = self.get_stats(source_agent_addr, destination_agent_addr) => {
                    stats.total_damage += damage as u64;
                    stats.condition_damage += damage as u64;
                }}

                if let Some(master) = self.log.master_agent(source_agent_addr) {
                    let master_stats = self.get_stats(master.addr, destination_agent_addr);
                    master_stats.total_damage += damage as u64;
                    master_stats.add_damage += damage as u64;
                }
            }

            _ => (),
        }
        Ok(())
    }

    fn finalize(self) -> Result<Self::Stat, Self::Error> {
        Ok(self.damages)
    }
}

/// Tracks when the log has been started.
#[derive(Default)]
pub struct LogStartTracker {
    event_time: u64,
}

impl LogStartTracker {
    /// Create a new log start tracker.
    pub fn new() -> LogStartTracker {
        LogStartTracker { event_time: 0 }
    }
}

impl Tracker for LogStartTracker {
    type Stat = u64;
    type Error = !;

    fn feed(&mut self, event: &Event) -> Result<(), Self::Error> {
        if let EventKind::LogStart { .. } = event.kind {
            self.event_time = event.time;
        }
        Ok(())
    }

    fn finalize(self) -> Result<Self::Stat, Self::Error> {
        Ok(self.event_time)
    }
}

/// A tracker that tracks the combat entry and exit times for each agent.
#[derive(Default)]
pub struct CombatTimeTracker {
    times: HashMap<u64, (u64, u64)>,
}

impl CombatTimeTracker {
    /// Create a new combat time tracker.
    pub fn new() -> CombatTimeTracker {
        CombatTimeTracker {
            times: HashMap::new(),
        }
    }
}

impl Tracker for CombatTimeTracker {
    // Maps from agent addr to (entry time, exit time)
    type Stat = HashMap<u64, (u64, u64)>;
    type Error = !;

    fn feed(&mut self, event: &Event) -> Result<(), Self::Error> {
        match event.kind {
            EventKind::EnterCombat { agent_addr, .. } => {
                self.times.entry(agent_addr).or_insert((0, 0)).0 = event.time;
            }

            EventKind::ExitCombat { agent_addr } => {
                self.times.entry(agent_addr).or_insert((0, 0)).1 = event.time;
            }

            _ => (),
        }
        Ok(())
    }

    fn finalize(self) -> Result<Self::Stat, Self::Error> {
        Ok(self.times)
    }
}