use std::ffi::CStr;
use std::str::from_utf8_unchecked;
use std::marker::PhantomData;

use ffi::*;
use super::{Pad, Flags};

pub struct Filter {
	ptr: *mut AVFilter,
}

impl Filter {
	pub unsafe fn wrap(ptr: *mut AVFilter) -> Self {
		Filter { ptr: ptr }
	}

	pub unsafe fn as_ptr(&self) -> *const AVFilter {
		self.ptr as *const _
	}

	pub unsafe fn as_mut_ptr(&mut self) -> *mut AVFilter {
		self.ptr
	}
}

impl Filter {
	pub fn name(&self) -> &str {
		unsafe {
			from_utf8_unchecked(CStr::from_ptr((*self.as_ptr()).name).to_bytes())
		}
	}

	pub fn description(&self) -> Option<&str> {
		unsafe {
			let ptr = (*self.as_ptr()).description;

			if ptr.is_null() {
				None
			}
			else {
				Some(from_utf8_unchecked(CStr::from_ptr(ptr).to_bytes()))
			}
		}
	}

	pub fn inputs(&self) -> Option<PadIter> {
		unsafe {
			let ptr = (*self.as_ptr()).inputs;

			if ptr.is_null() {
				None
			}
			else {
				Some(PadIter::new((*self.as_ptr()).inputs))
			}
		}
	}

	pub fn outputs(&self) -> Option<PadIter> {
		unsafe {
			let ptr = (*self.as_ptr()).outputs;

			if ptr.is_null() {
				None
			}
			else {
				Some(PadIter::new((*self.as_ptr()).outputs))
			}
		}
	}

	pub fn flags(&self) -> Flags {
		unsafe {
			Flags::from_bits_truncate((*self.as_ptr()).flags)
		}
	}
}

pub struct PadIter<'a> {
	ptr: *const AVFilterPad,
	cur: isize,

	_marker: PhantomData<&'a ()>,
}

impl<'a> PadIter<'a> {
	pub fn new(ptr: *const AVFilterPad) -> Self {
		PadIter { ptr: ptr, cur: 0, _marker: PhantomData }
	}
}

impl<'a> Iterator for PadIter<'a> {
	type Item = Pad<'a>;

	fn next(&mut self) -> Option<Self::Item> {
		unsafe {
			if self.cur >= avfilter_pad_count(self.ptr) as isize {
				return None;
			}

			let pad   = Pad::wrap(self.ptr.offset(self.cur));
			self.cur += 1;

			Some(pad)
		}
	}
}