use alloc::string::String;
use super::{Deserialize, Serialize, Error, VarUint7, VarUint32};
use crate::io;

/// Internal reference of the exported entry.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Internal {
	/// Function reference.
	Function(u32),
	/// Table reference.
	Table(u32),
	/// Memory reference.
	Memory(u32),
	/// Global reference.
	Global(u32),
}

impl Deserialize for Internal {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let kind = VarUint7::deserialize(reader)?;
		match kind.into() {
			0x00 => Ok(Internal::Function(VarUint32::deserialize(reader)?.into())),
			0x01 => Ok(Internal::Table(VarUint32::deserialize(reader)?.into())),
			0x02 => Ok(Internal::Memory(VarUint32::deserialize(reader)?.into())),
			0x03 => Ok(Internal::Global(VarUint32::deserialize(reader)?.into())),
			_ => Err(Error::UnknownInternalKind(kind.into())),
		}
	}
}

impl Serialize for Internal {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		let (bt, arg) = match self {
			Internal::Function(arg) => (0x00, arg),
			Internal::Table(arg) => (0x01, arg),
			Internal::Memory(arg) => (0x02, arg),
			Internal::Global(arg) => (0x03, arg),
		};

		VarUint7::from(bt).serialize(writer)?;
		VarUint32::from(arg).serialize(writer)?;

		Ok(())
	}
}

/// Export entry.
#[derive(Debug, Clone, PartialEq)]
pub struct ExportEntry {
	field_str: String,
	internal: Internal,
}

impl ExportEntry {
	/// New export entry.
	pub fn new(field: String, internal: Internal) -> Self {
		ExportEntry {
			field_str: field,
			internal: internal
		}
	}

	/// Public name.
	pub fn field(&self) -> &str { &self.field_str }

	/// Public name (mutable).
	pub fn field_mut(&mut self) -> &mut String { &mut self.field_str }

	/// Internal reference of the export entry.
	pub fn internal(&self) -> &Internal { &self.internal }

	/// Internal reference of the export entry (mutable).
	pub fn internal_mut(&mut self) -> &mut Internal { &mut self.internal }
}

impl Deserialize for ExportEntry {
	type Error = Error;

	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
		let field_str = String::deserialize(reader)?;
		let internal = Internal::deserialize(reader)?;

		Ok(ExportEntry {
			field_str: field_str,
			internal: internal,
		})
	}
}

impl Serialize for ExportEntry {
	type Error = Error;

	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
		self.field_str.serialize(writer)?;
		self.internal.serialize(writer)?;
		Ok(())
	}
}