// Copyright (c) 2025 taitep
// SPDX-License-Identifier: MIT
//
// This file is part of TRVE (https://gitea.taitep.se/taitep/trve)
// See LICENSE file in the project root for full license text.

mod rvi;

use crate::{
    core::Core,
    decode::Instruction,
    exceptions::ExceptionType::{self, IllegalInstruction},
};

pub(crate) fn find_and_exec(instr: Instruction, core: &mut Core) -> Result<(), ExceptionType> {
    match instr.opcode_noncompressed() {
        0b01100 => match (instr.funct7(), instr.funct3()) {
            // OP
            (0b0000000, 0b000) => rvi::add(core, instr),
            (0b0100000, 0b000) => rvi::sub(core, instr),
            (0b0000000, 0b111) => rvi::and(core, instr),
            (0b0000000, 0b110) => rvi::or(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b00100 => match instr.funct3() {
            // OP_IMM
            0b000 => rvi::addi(core, instr),
            0b001 => {
                if instr.funct6() == 0 {
                    rvi::slli(core, instr)
                } else {
                    Err(IllegalInstruction)
                }
            }
            0b101 => match instr.funct6() {
                // immediate right-shift
                0b000000 => rvi::srli(core, instr),
                _ => Err(IllegalInstruction),
            },
            0b111 => rvi::andi(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b00110 => match instr.funct3() {
            // OP_IMM_32
            0b000 => rvi::addiw(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b01000 => match instr.funct3() {
            // STORE
            0b000 => rvi::sb(core, instr),
            0b001 => rvi::sh(core, instr),
            0b010 => rvi::sw(core, instr),
            0b011 => rvi::sd(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b00000 => match instr.funct3() {
            // LOAD
            0b000 => rvi::lb(core, instr),
            0b100 => rvi::lbu(core, instr),
            0b001 => rvi::lh(core, instr),
            0b010 => rvi::lw(core, instr),
            0b011 => rvi::ld(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b11000 => match instr.funct3() {
            // BRANCH
            0b000 => rvi::beq(core, instr),
            0b001 => rvi::bne(core, instr),
            0b100 => rvi::blt(core, instr),
            0b110 => rvi::bltu(core, instr),
            0b111 => rvi::bgeu(core, instr),
            _ => Err(IllegalInstruction),
        },
        0b01101 => rvi::lui(core, instr),
        0b00101 => rvi::auipc(core, instr),
        0b11011 => rvi::jal(core, instr),
        // 0b11001 => (instr.funct3() == 0).then(|| rvi::jalr(core, instr)),
        0b11001 => {
            if instr.funct3() == 0 {
                rvi::jalr(core, instr)
            } else {
                Err(IllegalInstruction)
            }
        }
        _ => Err(IllegalInstruction),
    }
}