//! Arithmetic operations: add, subtract, etc.

use crate::prelude::*;
use crate::tile::prelude::*;

use veccell::VecRef;

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct Store {
    signal: Option<Signal>,
}

impl Store {
    pub fn signal(&self) -> Option<&Signal> {
        self.signal.as_ref()
    }
}

impl Tile for Store {
    fn update<'b>(&'b mut self, mut context: UpdateContext<'b>) {
        if let Some(signal) = context.take_signal() {
            let position = context.position();

            // NOTE: we *could* write the signal immediately,
            // but by delaying the write we can read from a `Store` without being order-dependent
            context.callback(move |pane| {
                if let Some(mut this) = pane.borrow_mut_as::<Self>(position) {
                    this.signal = Some(signal);
                }
            });
        }

        if context.state() != State::Idle {
            context.next_state();
        }
    }

    fn draw_simple(&self, ctx: DrawContext) -> TextChar {
        if self.signal.is_some() {
            TextChar::from_state('\u{25c9}', ctx.state) // FISHEYE
        } else {
            TextChar::from_state('\u{25cb}', ctx.state) // WHITE CIRCLE
        }
    }
}

/// When a signal is received, reads a signal from a [`Store`] (at the reader's tail),
/// then outputs that signal (at the reader's head).
///
/// # Example
///
/// The following circuit can receive a value in `B`, then store it indefinitely.
/// Sending a signal in `A` will output the stored signal from `B` in `OUT`.
///
/// ```text
/// o = Store
/// ▸ = Reader(Right)
///
/// (A) ---+
///        |
/// (B) --o▸-- (OUT)
/// ```
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct Reader(Direction);

impl Reader {
    pub fn new(direction: Direction) -> Self {
        Self(direction)
    }
}

impl Tile for Reader {
    fn update<'b>(&'b mut self, mut context: UpdateContext<'b>) {
        if let Some(_signal) = context.take_signal() {
            let _: Option<()> = try {
                let store_position = context.offset(self.0.opposite().into_offset())?;
                let store = context.get(store_position).and_then(get_store)?;
                let signal = store.signal.clone()?;
                drop(store);

                let target_position = context.offset(self.0.into_offset())?;

                let _ = context.send(target_position, self.0, signal);
            };
        }

        if context.state() != State::Idle {
            context.next_state();
        }
    }

    fn draw_simple(&self, ctx: DrawContext) -> TextChar {
        match self.0 {
            Direction::Down => TextChar::from_state('\u{25bd}', ctx.state), // WHITE DOWN-POINTING TRIANGLE
            Direction::Left => TextChar::from_state('\u{25c1}', ctx.state), // WHITE LEFT-POINTING TRIANGLE
            Direction::Right => TextChar::from_state('\u{25b7}', ctx.state), // WHITE RIGHT-POINTING TRIANGLE
            Direction::Up => TextChar::from_state('\u{25b3}', ctx.state), // WHITE UP-POINTING TRIANGLE
        }
    }
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct StorageCount;

impl Tile for StorageCount {
    fn update<'b>(&'b mut self, mut context: UpdateContext<'b>) {
        if let Some(mut signal) = context.take_signal() {
            let mut count = 0;
            for dir in Orientation::Any.into_directions() {
                if let Some(store_position) = context.offset(dir.into_offset()) {
                    if let Some(store) = context.get(store_position).and_then(get_store) {
                        count += store.signal.is_some() as u8;
                    }
                }
            }

            signal.push(Value::Number(count.into()));

            if let Some(target_position) = context.offset(signal.direction().into_offset()) {
                let _ = context.send(target_position, signal.direction(), signal);
            }

            if context.state() != State::Idle {
                context.next_state();
            }
        }
    }

    fn draw_simple(&self, ctx: DrawContext) -> TextChar {
        TextChar::from_state('\u{2058}', ctx.state) // FOUR DOT PUNCTUATION
    }
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct Stacker {
    signal: Option<Signal>,
    /// May only be Horizontal or Vertical
    orientation: Orientation,
}

impl Stacker {
    pub fn new(orientation: Orientation) -> Self {
        Self {
            signal: None,
            orientation,
        }
    }

    pub fn signal(&self) -> Option<&Signal> {
        self.signal.as_ref()
    }
}

impl Tile for Stacker {
    fn update<'b>(&'b mut self, mut context: UpdateContext<'b>) {
        if let Some(mut signal) = context.take_signal() {
            if self.orientation.contains(signal.direction()) {
                // Stack the stored signal on top of the incomming signal
                if let Some(ref stored) = self.signal {
                    signal.append(stored);
                }

                if let Some(target_position) = context.offset(signal.direction().into_offset()) {
                    let _ = context.send(target_position, signal.direction(), signal);
                }

                if context.state() != State::Idle {
                    context.next_state();
                }
            } else {
                // Store the signal inside of ourselves
                self.signal = Some(signal);

                context.set_state(State::Idle);
            }
        } else {
            if context.state() != State::Idle {
                context.next_state();
            }
        }
    }

    fn draw_simple(&self, ctx: DrawContext) -> TextChar {
        match self.orientation {
            Orientation::Vertical => TextChar::from_state('\u{03a6}', ctx.state), // GREEK CAPITAL LETTER PHI
            Orientation::Horizontal => TextChar::from_state('\u{a74a}', ctx.state), // LATIN CAPITAL LETTER O WITH LONG STROKE
            _ => TextChar::from_state('+', ctx.state),
        }
    }
}

/// Tries to convert a [`FullTile`] to a [`Store`]
fn get_store<'a>(full: VecRef<'a, FullTile>) -> Option<VecRef<'a, Store>> {
    VecRef::try_map(full, |tile| {
        let tile = tile.get().ok_or(())?;
        let store = tile.try_into().map_err(|_| ())?;
        Ok::<&Store, ()>(store)
    }).ok()
}