//! Co-processor instructions

// Imports
use crate::exe::inst::{
	basic::{Decodable, Encodable},
	InstFmt, Register,
};
use int_conv::{Signed, Truncated, ZeroExtended};

/// Co-processor register kind
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
pub enum RegisterKind {
	/// Data
	Data,

	/// Control
	Control,
}

/// Co-processor instruction kind
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
pub enum Kind {
	/// Execute
	CopN {
		/// Command to execute
		imm: u32,
	},

	/// Move register from co-processor
	MoveFrom {
		/// Destination
		dst: Register,

		/// Source
		src: u8,

		/// Register kind
		kind: RegisterKind,
	},

	/// Move register to co-processor
	MoveTo {
		/// Destination
		dst: u8,

		/// Source
		src: Register,

		/// Register kind
		kind: RegisterKind,
	},

	/// Branch if
	Branch {
		/// Offset
		offset: i16,

		/// Value to branch on
		on: bool,
	},

	/// Load co-processor
	Load {
		/// Destination
		dst: u8,

		/// Source
		src: Register,

		/// offset
		offset: i16,
	},

	/// Store co-processor
	Store {
		/// Destination
		dst: u8,

		/// Source
		src: Register,

		/// offset
		offset: i16,
	},
}

/// Store instructions
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
pub struct Inst {
	/// Co-processor number
	pub n: u32,

	/// Kind
	pub kind: Kind,
}

impl Decodable for Inst {
	type Raw = u32;

	#[bitmatch::bitmatch]
	fn decode(raw: Self::Raw) -> Option<Self> {
		// Get `n`
		#[bitmatch]
		let "????nn_?????_?????_?????_?????_??????" = raw;

		#[rustfmt::skip]
		let kind = #[bitmatch] match raw {
			"0100??_1iiii_iiiii_iiiii_iiiii_iiiiii" => Kind::CopN     { imm: i },
			"0100??_00000_ttttt_ddddd_?????_000000" => Kind::MoveFrom { dst: Register::new(t)?, src: d.truncated(), kind: RegisterKind::Data    },
			"0100??_00010_ttttt_ddddd_?????_000000" => Kind::MoveFrom { dst: Register::new(t)?, src: d.truncated(), kind: RegisterKind::Control },
			"0100??_00100_ttttt_ddddd_?????_000000" => Kind::MoveTo   { dst: d.truncated(), src: Register::new(t)?, kind: RegisterKind::Data    },
			"0100??_00110_ttttt_ddddd_?????_000000" => Kind::MoveTo   { dst: d.truncated(), src: Register::new(t)?, kind: RegisterKind::Control },
			"0100??_01000_00000_iiiii_iiiii_iiiiii" => Kind::Branch   { offset: i.truncated::<u16>().as_signed(), on: false },
			"0100??_01000_00001_iiiii_iiiii_iiiiii" => Kind::Branch   { offset: i.truncated::<u16>().as_signed(), on: true  },
			"1100??_sssss_ttttt_iiiii_iiiii_iiiiii" => Kind::Load     { dst: t.truncated(), src: Register::new(s)?, offset: i.truncated::<u16>().as_signed() },
			"1110??_sssss_ttttt_iiiii_iiiii_iiiiii" => Kind::Store    { dst: t.truncated(), src: Register::new(s)?, offset: i.truncated::<u16>().as_signed() },
			_ => return None,
		};

		Some(Self { n, kind })
	}
}
impl Encodable for Inst {
	#[bitmatch::bitmatch]
	fn encode(&self) -> Self::Raw {
		let n = self.n;

		match self.kind {
			Kind::CopN { imm: i } => bitpack!("0100nn_1iiii_iiiii_iiiii_iiiii_iiiiii"),
			Kind::MoveFrom { dst, src, kind } => {
				let t = dst.idx();
				let d = src.zero_extended::<u32>();
				match kind {
					RegisterKind::Data => bitpack!("0100nn_00000_ttttt_ddddd_?????_000000"),
					RegisterKind::Control => bitpack!("0100nn_00010_ttttt_ddddd_?????_000000"),
				}
			},
			Kind::MoveTo { dst, src, kind } => {
				let d = dst.zero_extended::<u32>();
				let t = src.idx();
				match kind {
					RegisterKind::Data => bitpack!("0100nn_00100_ttttt_ddddd_?????_000000"),
					RegisterKind::Control => bitpack!("0100nn_00110_ttttt_ddddd_?????_000000"),
				}
			},
			Kind::Branch { offset, on } => {
				let i = offset.as_unsigned().zero_extended::<u32>();
				match on {
					true => bitpack!("0100nn_01000_00001_iiiii_iiiii_iiiiii"),
					false => bitpack!("0100nn_01000_00000_iiiii_iiiii_iiiiii"),
				}
			},
			Kind::Load { dst, src, offset } => {
				let t = dst.zero_extended::<u32>();
				let s = src.idx();
				let i = offset.as_unsigned().zero_extended::<u32>();
				bitpack!("1100nn_sssss_ttttt_iiiii_iiiii_iiiiii")
			},
			Kind::Store { dst, src, offset } => {
				let t = dst.zero_extended::<u32>();
				let s = src.idx();
				let i = offset.as_unsigned().zero_extended::<u32>();
				bitpack!("1110nn_sssss_ttttt_iiiii_iiiii_iiiiii")
			},
		}
	}
}

impl InstFmt for Inst {
	#[rustfmt::skip]
	fn fmt(&self, _pos: crate::Pos, f: &mut std::fmt::Formatter) -> std::fmt::Result {
		let Self { n, kind } = self;
		match kind {
			Kind::CopN     { imm } => write!(f, "cop{n} {imm:#x}"),
			Kind::MoveFrom { dst, src, kind } => match kind {
				RegisterKind::Control => write!(f, "cfc{n} {dst}, ${src:#x}"),
				RegisterKind::Data    => write!(f, "mfc{n} {dst}, ${src:#x}"),
			}
			Kind::MoveTo   { dst, src, kind } => match kind {
				RegisterKind::Data    => write!(f, "mtc{n} {src}, ${dst:#x}"),
				RegisterKind::Control => write!(f, "ctc{n} {src}, ${dst:#x}"),
			}
			Kind::Branch   { offset, on } => match on {
				true  => write!(f, "bc{n}f {offset:#x}"),
				false => write!(f, "bc{n}t {offset:#x}"),
			}
			Kind::Load     { dst, src, offset } => write!(f, "lwc{n} ${dst:#x}, {offset:#x}({src})"),
			Kind::Store    { dst, src, offset } => write!(f, "swc{n} ${dst:#x}, {offset:#x}({src})"),
		}
	}
}