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//! Sink module;

use lib::*;
use super::AbiType;

/// Sink for returning number of arguments
pub struct Sink {
	capacity: usize,
	preamble: Vec<u8>,
	heap: Vec<u8>,
}

impl Sink {
	/// New sink with known capacity
	pub fn new(capacity: usize) -> Self {
		Sink {
			capacity: 32 * capacity,
			preamble: Vec::with_capacity(32 * capacity),
			heap: Vec::new(),
		}
	}

	fn top_ptr(&self) -> usize {
		self.preamble.capacity() + self.heap.len()
	}

	/// Consume `val` to the Sink
	pub fn push<T: AbiType>(&mut self, val: T) {
		if T::IS_FIXED {
			val.encode(self)
		} else {
			let mut nested_sink = Sink::new(1);
			val.encode(&mut nested_sink);
			let top_ptr = self.top_ptr() as u32;
			nested_sink.drain_to(&mut self.heap);
			self.push(top_ptr);
		}
	}

	/// Drain current Sink to the target vector
	pub fn drain_to(self, target: &mut Vec<u8>) {
		let preamble = self.preamble;
		let heap = self.heap;
		target.reserve(preamble.len() + heap.len());
		target.extend_from_slice(&preamble);
		target.extend_from_slice(&heap);
	}

	/// Consume current Sink to produce a vector with content.
	/// May panic if declared number of arguments does not match the resulting number of bytes should be produced.
	pub fn finalize_panicking(self) -> Vec<u8> {
		if self.preamble.len() != self.capacity { panic!("Underflow of pushed parameters {}/{}!", self.preamble.len(), self.capacity); }
		let mut result = self.preamble;
		let heap = self.heap;

		result.extend_from_slice(&heap);
		result
	}

	/// Mutable reference to the Sink preamble
	pub fn preamble_mut(&mut self) -> &mut Vec<u8> {
		&mut self.preamble
	}

	/// Mutable reference to the Sink heap
	pub fn heap_mut(&mut self) -> &mut Vec<u8> {
		&mut self.heap
	}
}