// LLM converted. Here be dragons.

#include "disas.h"

#include <string>
#include <vector>
#include <sstream>
#include <iomanip>

static const std::string ZERO      = "#0";
static const std::string DEST_NONE = "_";
static const std::string JUMP_NONE = "";

static const std::vector<std::string> JUMPS_IF_NZERO = {"jgt", "jlt", "jne", "jmp"};
static const std::vector<std::string> JUMPS_IF_ZERO  = {"jge", "jle", "jeq", "jmp"};

struct Decoded {
    std::string mnemonic;
    std::string dest;
    std::string op1;
    std::string op2;
    std::string jumpdest;
};

static bool in_list(const std::string &s, const std::vector<std::string> &v) {
    for (const auto &x : v) {
        if (x == s) return true;
    }
    return false;
}

static std::string decode_jump(uint16_t ins) {
    if ((ins & 0x7) == 0) {
        return JUMP_NONE;
    }

    if ((ins & 0x7) == 0x7) {
        return "jmp";
    }

    bool jl = (ins & (1 << 2)) != 0;
    bool je = (ins & (1 << 1)) != 0;
    bool jg = (ins & (1 << 0)) != 0;

    if (jl && je) {
        return "jle";
    }
    if (jl && jg) {
        return "jne";
    }
    if (je && jg) {
        return "jge";
    }

    if (jl) return "jlt";
    if (je) return "jeq";
    if (jg) return "jgt";

    return "<unknown>";
}

static std::pair<std::string, bool> decode_ins(uint16_t ins) {
    int opcode = (ins >> 8) & 0x03;
    bool ar_n_log = (ins & (1 << 10)) != 0;
    opcode |= (ar_n_log ? 1 : 0) << 2;

    switch (opcode) {
        case 0b000: return {"and", true};
        case 0b001: return {"or",  true};
        case 0b010: return {"xor", true};
        case 0b011: return {"not", false};
        case 0b100: return {"add", true};
        case 0b101: return {"inc", false};
        case 0b110: return {"sub", true};
        case 0b111: return {"dec", false};
        default:    return {"<?>", false};
    }
}

static std::string decode_arg1(uint16_t ins) {
    bool use_mem = (ins & (1 << 12)) != 0;
    bool zx      = (ins & (1 << 7))  != 0;
    bool sw      = (ins & (1 << 6))  != 0;

    if (zx) return ZERO;
    if (!sw) return "D";
    return use_mem ? "M" : "A";
}

static std::string decode_arg2(uint16_t ins) {
    bool use_mem = (ins & (1 << 12)) != 0;
    bool sw      = (ins & (1 << 6))  != 0;

    if (sw) return "D";
    return use_mem ? "M" : "A";
}

static std::string decode_dest(uint16_t ins) {
    bool dA = (ins & (1 << 5)) != 0;
    bool dD = (ins & (1 << 4)) != 0;
    bool dM = (ins & (1 << 3)) != 0;

    std::string dest;
    if (dA) dest += "A";
    if (dD) dest += "D";
    if (dM) dest += "M";

    return dest.empty() ? DEST_NONE : dest;
}

static Decoded decode_instruction(uint16_t ins) {
    if ((ins & 0x8000) == 0) {
        return {"mov", "A", "#" + std::to_string(ins), "", ""};
    } else {
        auto [mnemonic, two_op] = decode_ins(ins);
        std::string dest    = decode_dest(ins);
        std::string op1     = decode_arg1(ins);
        std::string op2     = two_op ? decode_arg2(ins) : "";
        std::string jumpdst = decode_jump(ins);
        return {mnemonic, dest, op1, op2, jumpdst};
    }
}

static Decoded fixup_ins(uint16_t ins) {
    Decoded d = decode_instruction(ins);
    std::string &mnemonic = d.mnemonic;
    std::string &dest     = d.dest;
    std::string &op1      = d.op1;
    std::string &op2      = d.op2;
    std::string &jumpdest = d.jumpdest;

    if (op1 == ZERO) {
        if (mnemonic == "sub") {
            return {"neg", dest, op2, "", jumpdest};
        }

        if (mnemonic == "and") {
            if (dest == DEST_NONE) {
                if (in_list(jumpdest, JUMPS_IF_ZERO)) {
                    return {"jmp", "", "", "", ""};
                } else {
                    return {"nop", "", "", "", ""};
                }
            } else {
                std::string newjmp = in_list(jumpdest, JUMPS_IF_ZERO) ? "jmp" : "";
                return {"mov", dest, ZERO, "", newjmp};
            }
        }

        if (mnemonic == "add" || mnemonic == "or" || mnemonic == "xor") {
            if (dest == DEST_NONE && jumpdest == JUMP_NONE) {
                return {"nop", "", "", "", ""};
            } else {
                return {"mov", dest, op2, "", jumpdest};
            }
        }

        if (mnemonic == "not") {
            if (dest == DEST_NONE) {
                if (jumpdest == "jeq" || jumpdest == "jgt" ||
                    jumpdest == "jge" || jumpdest == JUMP_NONE) {
                    return {"nop", "", "", "", ""};
                } else {
                    return {"jmp", "", "", "", ""};
                }
            }
        }
    }

    return d;
}

std::string print_decoded(uint16_t ins, bool simplify) {
    Decoded d = simplify ? fixup_ins(ins) : decode_instruction(ins);

    std::string jumpdest_str = d.jumpdest.empty() ? "" : "." + d.jumpdest;
    std::string opcode_str   = d.mnemonic + jumpdest_str;
    std::string dest_str     = d.dest.empty() ? std::string(7, ' ')
                                              : d.dest + ", ";
    std::string op2_str      = d.op2.empty() ? "" : ", ";
    std::string op1_str      = d.op1 + op2_str;

    std::ostringstream oss;
    oss << std::left << std::setw(9) << opcode_str
        << std::setw(6) << dest_str
        << std::setw(4) << op1_str
        << d.op2;

    return oss.str();
}