use std::{io, fmt};
use super::{
	Deserialize, Serialize, Error, VarUint7, VarInt7, VarUint1, CountedList,
	CountedListWriter
};

/// Type definition in types section. Currently can be only of the function type.
#[derive(Debug, PartialEq, Clone)]
pub enum Type {
	/// Function type.
	Function(FunctionType),
}

impl Deserialize for Type {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		Ok(Type::Function(FunctionType::deserialize(reader)?))
	}
}

impl Serialize for Type {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		match self {
			Type::Function(fn_type) => fn_type.serialize(writer)
		}
	}
}

/// Value type.
#[derive(Clone, Copy, PartialEq, Debug)]
pub enum ValueType {
	/// 32-bit signed integer
	I32,
	/// 64-bit signed integer
	I64,
	/// 32-bit float
	F32,
	/// 64-bit float
	F64,
}

impl Deserialize for ValueType {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let val = VarInt7::deserialize(reader)?;

		match val.into() {
			-0x01 => Ok(ValueType::I32),
			-0x02 => Ok(ValueType::I64),
			-0x03 => Ok(ValueType::F32),
			-0x04 => Ok(ValueType::F64),
			_ => Err(Error::UnknownValueType(val.into())),
		}
	}
}

impl Serialize for ValueType {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		let val: VarInt7 = match self {
			ValueType::I32 => -0x01,
			ValueType::I64 => -0x02,
			ValueType::F32 => -0x03,
			ValueType::F64 => -0x04,
		}.into();
		val.serialize(writer)?;
		Ok(())
	}
}

impl fmt::Display for ValueType {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		match *self {
			ValueType::I32 => write!(f, "i32"),
			ValueType::I64 => write!(f, "i64"),
			ValueType::F32 => write!(f, "f32"),
			ValueType::F64 => write!(f, "f64"),
		}
	}
}

/// Block type which is basically `ValueType` + NoResult (to define blocks that have no return type)
#[derive(Clone, Copy, PartialEq, Debug)]
pub enum BlockType {
	/// Value-type specified block type
	Value(ValueType),
	/// No specified block type
	NoResult,
}

impl Deserialize for BlockType {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let val = VarInt7::deserialize(reader)?;

		match val.into() {
			-0x01 => Ok(BlockType::Value(ValueType::I32)),
			-0x02 => Ok(BlockType::Value(ValueType::I64)),
			-0x03 => Ok(BlockType::Value(ValueType::F32)),
			-0x04 => Ok(BlockType::Value(ValueType::F64)),
			-0x40 => Ok(BlockType::NoResult),
			_ => Err(Error::UnknownValueType(val.into())),
		}
	}
}

impl Serialize for BlockType {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		let val: VarInt7 = match self {
			BlockType::NoResult => -0x40i8,
			BlockType::Value(ValueType::I32) => -0x01,
			BlockType::Value(ValueType::I64) => -0x02,
			BlockType::Value(ValueType::F32) => -0x03,
			BlockType::Value(ValueType::F64) => -0x04,
		}.into();
		val.serialize(writer)?;
		Ok(())
	}
}

/// Function signature type.
#[derive(Debug, Clone, PartialEq)]
pub struct FunctionType {
	form: u8,
	params: Vec<ValueType>,
	return_type: Option<ValueType>,
}

impl Default for FunctionType {
	fn default() -> Self {
		FunctionType {
			form: 0x60,
			params: Vec::new(),
			return_type: None,
		}
	}
}

impl FunctionType {
	/// New function type given the signature in-params(`params`) and return type (`return_type`)
	pub fn new(params: Vec<ValueType>, return_type: Option<ValueType>) -> Self {
		FunctionType {
			params: params,
			return_type: return_type,
			..Default::default()
		}
	}
	/// Function form (currently only valid value is `0x60`)
	pub fn form(&self) -> u8 { self.form }
	/// Parameters in the function signature.
	pub fn params(&self) -> &[ValueType] { &self.params }
	/// Mutable parameters in the function signature.
	pub fn params_mut(&mut self) -> &mut Vec<ValueType> { &mut self.params }
	/// Return type in the function signature, if any.
	pub fn return_type(&self) -> Option<ValueType> { self.return_type }
	/// Mutable type in the function signature, if any.
	pub fn return_type_mut(&mut self) -> &mut Option<ValueType> { &mut self.return_type }
}

impl Deserialize for FunctionType {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let form: u8 = VarUint7::deserialize(reader)?.into();

		if form != 0x60 {
			return Err(Error::UnknownFunctionForm(form));
		}

		let params: Vec<ValueType> = CountedList::deserialize(reader)?.into_inner();

		let has_return_type = VarUint1::deserialize(reader)?;
		let return_type = if has_return_type.into() {
			Some(ValueType::deserialize(reader)?)
		} else {
			None
		};

		Ok(FunctionType {
			form: form,
			params: params,
			return_type: return_type,
		})
	}
}

impl Serialize for FunctionType {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		VarUint7::from(self.form).serialize(writer)?;

		let data = self.params;
		let counted_list = CountedListWriter::<ValueType, _>(
			data.len(),
			data.into_iter().map(Into::into),
		);
		counted_list.serialize(writer)?;

		if let Some(return_type) = self.return_type {
			VarUint1::from(true).serialize(writer)?;
			return_type.serialize(writer)?;
		} else {
			VarUint1::from(false).serialize(writer)?;
		}

		Ok(())
	}
}

/// Table element type.
#[derive(Clone, Copy, PartialEq, Debug)]
pub enum TableElementType {
	/// A reference to a function with any signature.
	AnyFunc,
}

impl Deserialize for TableElementType {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let val = VarInt7::deserialize(reader)?;

		match val.into() {
			-0x10 => Ok(TableElementType::AnyFunc),
			_ => Err(Error::UnknownTableElementType(val.into())),
		}
	}
}

impl Serialize for TableElementType {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		let val: VarInt7 = match self {
			TableElementType::AnyFunc => -0x10,
		}.into();
		val.serialize(writer)?;
		Ok(())
	}
}
