/************************************************************************/
/* Disassembler for Samsung SAM8 processors                             */
/************************************************************************/

#include "sam8.hpp"


/**
 * Register operand
 */
static void reg_operand(int op, bool indirect, bool workingReg,
                        bool regPair, int regNum) {
  // do it
  if (!indirect) {
    cmd.Operands[op].type = o_reg;
    cmd.Operands[op].reg = regNum;
    cmd.Operands[op].fl_workingReg = workingReg;
    cmd.Operands[op].fl_regPair = regPair;
  } else {
    cmd.Operands[op].type = o_phrase;
    cmd.Operands[op].phrase = fIndReg;
    cmd.Operands[op].v_phrase_reg = regNum;
    cmd.Operands[op].fl_workingReg = workingReg;
    cmd.Operands[op].fl_regPair = regPair;
  }
}


/**
 * Indexed register operand
 */
static void idx_reg_operand(int op, int baseRegNum, int idxRegNum) {
  cmd.Operands[op].type = o_phrase;
  cmd.Operands[op].phrase = fIdxReg;
  cmd.Operands[op].v_phrase_reg = baseRegNum;
  cmd.Operands[op].v_phrase_idxreg = idxRegNum;
}


/**
 * Indexed address operand in code memory
 */
static void idx_cdata_operand(int op, int offset, int baseAddr,
                              int idxRegNum) {
  cmd.Operands[op].type = o_displ;
  cmd.Operands[op].phrase = fIdxCAddr;
  cmd.Operands[op].addr = baseAddr;
  cmd.Operands[op].v_phrase_idxreg = idxRegNum;
  cmd.Operands[op].dtyp = dt_word;
  cmd.Operands[op].offb = offset;
}


/**
 * Indexed address operand in external (data) memory
 */
static void idx_edata_operand(int op, int offset, int baseAddr,
                              int idxRegNum) {
  cmd.Operands[op].type = o_displ;
  cmd.Operands[op].phrase = fIdxEAddr;
  cmd.Operands[op].addr = baseAddr;
  cmd.Operands[op].v_phrase_idxreg = idxRegNum;
  cmd.Operands[op].dtyp = dt_word;
  cmd.Operands[op].offb = offset;
}


/**
 * Register bit operand
 */
static void regbit_operand(int op, bool workingReg, int regNum, int bit) {
  cmd.Operands[op].type = o_reg_bit;
  cmd.Operands[op].reg = regNum;
  cmd.Operands[op].fl_workingReg = workingReg;
  cmd.Operands[op].v_bit = bit;
}


/**
 * Immediate operand
 */
static void imm_operand(int op, int offset, ulong value, char dtyp) {
  cmd.Operands[op].type = o_imm;
  cmd.Operands[op].value = value;
  cmd.Operands[op].dtyp = dtyp;
  cmd.Operands[op].offb = offset;
}


/**
 * Address operand in external (data) memory
 */
static void addr_edata_operand(int op, int offset, ea_t address) {
  cmd.Operands[op].type = o_emem;
  cmd.Operands[op].addr = address;
  cmd.Operands[op].offb = offset;
}


/**
 * Address operand in code memory
 */
static void addr_cdata_operand(int op, int offset, ea_t address) {
  cmd.Operands[op].type = o_cmem;
  cmd.Operands[op].addr = address;
  cmd.Operands[op].offb = offset;
}


/**
 * Code operand (e.g. JP destination)
 */
static void code_operand(int op, int offset, ea_t address) {
  cmd.Operands[op].type = o_near;
  cmd.Operands[op].addr = address;
  cmd.Operands[op].offb = offset;
}


/**
 * Indirect code operand in "zero" page
 */
static void ind_code_operand(int op, int offset, ea_t address) {
  cmd.Operands[op].type = o_cmem_ind;
  cmd.Operands[op].addr = address;
  cmd.Operands[op].offb = offset;
}


/**
 * Finalise cmd data structure
 */
static int finalise_insn(int opcode) {
  // final checks on operands
  for(int i=0; i < 3; i++) {
    // check reg pair operands are even
    if ((cmd.Operands[i].type == o_reg) &&
        (cmd.Operands[i].fl_regPair) &&
        (cmd.Operands[i].reg & 1)) {
      return 0;
    }

    // check idxreg is even
    if ((cmd.Operands[i].type == o_displ) &&
        ((cmd.Operands[i].phrase == fIdxCAddr) ||
         (cmd.Operands[i].phrase == fIdxEAddr)) &&
        (cmd.Operands[i].v_phrase_idxreg & 1)) {
      return 0;
    }

    // check workingReg is valid for register operands
    if ((cmd.Operands[i].type == o_reg) &&
        (cmd.Operands[i].fl_workingReg) &&
        (cmd.Operands[i].reg > 15)) {
      return 0;
    }

    // check workingReg is valid for indreg operands
    if ((cmd.Operands[i].type == o_phrase) &&
        (cmd.Operands[i].phrase == fIndReg) &&
        (cmd.Operands[i].fl_workingReg) &&
        (cmd.Operands[i].v_phrase_reg > 15)) {
      return 0;
    }
  }

  // set opcode & set no condition code
  cmd.itype = opcode;
  cmd.c_condition = ccNone;

  // return size
  return cmd.size;
}


/**
 * Finalise cmd data structure, with condition code
 */
static int finalise_insn(int opcode, int condition) {
  // do initial instruction setup
  if (!finalise_insn(opcode)) return 0;

  // set return code
  cmd.c_condition = condition;

  // return size
  return cmd.size;
}


/**
 * Get the next LITTLE ENDIAN word.
 * For some reason this processor uses LITTLE ENDIAN OCCASIONALLY!!!
 */
static inline ushort next_word_le() {
  return ua_next_byte() | (ua_next_byte() << 8);
}



//----------------------------------------------------------------------
// analyze an basic instruction
static int ana_basic(void) {
  // get the command code byte
  ushort code = ua_next_byte();

  // decode the special case (annoying) instructions
  switch(code) {
  case 0x30:
    reg_operand(0, true, false, true, ua_next_byte());
    return finalise_insn(SAM8_JP);

  case 0x31: {
    // need to decode second byte to determine exact type
    ushort tmp = ua_next_byte();
    switch(tmp & 0x03) {
    case 0:
      imm_operand(0, 1, tmp & 0xF0, dt_byte);
      return finalise_insn(SAM8_SRP);

    case 1:
      imm_operand(0, 1, tmp & 0xF8, dt_byte);
      return finalise_insn(SAM8_SRP1);

    case 2:
      imm_operand(0, 1, tmp & 0xF8, dt_byte);
      return finalise_insn(SAM8_SRP0);

    case 3:
      return 0; // invalid instruction
    }
  }

  case 0x82: case 0x92: case 0x83: case 0x93: {
    // work out correct code
    ushort opcode;
    switch(code) {
    case 0x82: opcode = SAM8_PUSHUD; break;
    case 0x92: opcode = SAM8_POPUD; break;
    case 0x83: opcode = SAM8_PUSHUI; break;
    case 0x93: opcode = SAM8_POPUI; break;
    }

    // setup operands
    if ((opcode == SAM8_POPUD) || (opcode == SAM8_POPUI)) {
      reg_operand(1, true, false, false, ua_next_byte());
      reg_operand(0, false, false, false, ua_next_byte());
    } else {
      reg_operand(0, true, false, false, ua_next_byte());
      reg_operand(1, false, false, false, ua_next_byte());
    }
    return finalise_insn(opcode);
  }

  case 0xC2: case 0xD2: {
    // work out correct code
    ushort opcode;
    switch(code) {
    case 0xC2: opcode = SAM8_CPIJE; break;
    case 0xD2: opcode = SAM8_CPIJNE; break;
    }

    // decode it
    ushort tmp = ua_next_byte();
    reg_operand(0, false, true, false, bottom_nibble(tmp));
    reg_operand(1, true, true, false, top_nibble(tmp));
    code_operand(2, 2, cmd.ea + 3 + (char) ua_next_byte());
    return finalise_insn(opcode);
  }

  case 0xE2: case 0xF2: case 0xC3: case 0xD3: case 0xE3: case 0xF3: {
    // need the next byte to tell whether data or code memory
    ushort opcode;
    ushort tmp = ua_next_byte();
    ushort operandT = top_nibble(tmp);
    ushort operandB = bottom_nibble(tmp);
    if (operandB & 1) {
      switch(code) {
      case 0xE2: opcode = SAM8_LDED; break;
      case 0xF2: opcode = SAM8_LDEPD; break;
      case 0xC3: opcode = SAM8_LDE; break;
      case 0xD3: opcode = SAM8_LDE; break;
      case 0xE3: opcode = SAM8_LDEI; break;
      case 0xF3: opcode = SAM8_LDEPI; break;
      }
      operandB--;
    } else {
      switch(code) {
      case 0xE2: opcode = SAM8_LDCD; break;
      case 0xF2: opcode = SAM8_LDCPD; break;
      case 0xC3: opcode = SAM8_LDC; break;
      case 0xD3: opcode = SAM8_LDC; break;
      case 0xE3: opcode = SAM8_LDCI; break;
      case 0xF3: opcode = SAM8_LDCPI; break;
      }
    }

    // decode it
    if (code & 0x10) {
      reg_operand(0, true, true, true, operandB);
      reg_operand(1, false, true, false, operandT);
    } else {
      reg_operand(0, false, true, false, operandT);
      reg_operand(1, true, true, true, operandB);
    }
    return finalise_insn(opcode);
  }

  case 0xD4: {
    // get indirect address & check it is valid
    ushort tmp = ua_next_byte();
    if (tmp & 1) return 0;

    // generate operation
    ind_code_operand(0, 1, tmp);
    return finalise_insn(SAM8_CALL);
  }

  case 0xF4:
    reg_operand(0, true, false, true, ua_next_byte());
    return finalise_insn(SAM8_CALL);

  case 0xF6:
    code_operand(0, 1, ua_next_word());
    return finalise_insn(SAM8_CALL);

  case 0xE4: {
    reg_operand(1, false, false, false, ua_next_byte());
    reg_operand(0, false, false, false, ua_next_byte());
    return finalise_insn(SAM8_LD);
  }

  case 0xE5: {
    reg_operand(1, true, false, false, ua_next_byte());
    reg_operand(0, false, false, false, ua_next_byte());
    return finalise_insn(SAM8_LD);
  }

  case 0xF5: {
    reg_operand(1, false, false, false, ua_next_byte());
    reg_operand(0, true, false, false, ua_next_byte());
    return finalise_insn(SAM8_LD);
  }

  case 0xD5:
    return 0; // invalid instruction

  case 0x87: case 0x97: {
    // get next byte
    ushort tmp = ua_next_byte();

    // setup operands
    switch(code) {
    case 0x87:
      reg_operand(0, false, true, false, top_nibble(tmp));
      idx_reg_operand(1, ua_next_byte(), bottom_nibble(tmp));
      break;

    case 0x97:
      idx_reg_operand(0, ua_next_byte(), bottom_nibble(tmp));
      reg_operand(1, false, true, false, top_nibble(tmp));
      break;
    }

    // finalise the instruction
    return finalise_insn(SAM8_LD);
  }

  case 0xd6:
    reg_operand(0, true, false, false, ua_next_byte());
    imm_operand(1, 2, ua_next_byte(), dt_byte);
    return finalise_insn(SAM8_LD);

  case 0xe6:
    reg_operand(0, false, false, false, ua_next_byte());
    imm_operand(1, 2, ua_next_byte(), dt_byte);
    return finalise_insn(SAM8_LD);

  case 0xc7: {
    ushort tmp = ua_next_byte();
    reg_operand(0, false, true, false, top_nibble(tmp));
    reg_operand(1, true, true, false, bottom_nibble(tmp));
    return finalise_insn(SAM8_LD);
  }

  case 0xd7: {
    ushort tmp = ua_next_byte();
    reg_operand(0, true, true, false, top_nibble(tmp));
    reg_operand(1, false, true, false, bottom_nibble(tmp));
    return finalise_insn(SAM8_LD);
  }

  case 0xa7: case 0xb7: {
    // extract data
    ushort tmp = ua_next_byte();

    // decode opcode + setup operands
    ushort opcode;
    switch(bottom_nibble(tmp)) {
    case 0:
      opcode = SAM8_LDC;
      switch(code) {
      case 0xa7:
        reg_operand(0, false, true, false, top_nibble(tmp));
        addr_cdata_operand(1, 2, next_word_le());
        break;

      case 0xb7:
        addr_cdata_operand(0, 2, next_word_le());
        reg_operand(1, false, true, false, top_nibble(tmp));
        break;
      }
      break;

    case 1:
      opcode = SAM8_LDE;
      switch(code) {
      case 0xa7:
        reg_operand(0, false, true, false, top_nibble(tmp));
        addr_edata_operand(1, 2, next_word_le());
        break;

      case 0xb7:
        addr_edata_operand(0, 2, next_word_le());
        reg_operand(1, false, true, false, top_nibble(tmp));
        break;
      }
      break;

    default:
      // extract operand nibbles
      ushort operandT = top_nibble(tmp);
      ushort operandB = bottom_nibble(tmp);

      // decode the correct opcode
      if (operandB & 1) {
        opcode = SAM8_LDE;
        operandB--;
      } else {
        opcode = SAM8_LDC;
      }

      // generate operands
      switch(code) {
      case 0xA7:
        reg_operand(0, false, true, false, operandT);
        if (opcode == SAM8_LDC)
          idx_cdata_operand(1, 2, next_word_le(), operandB);
        else idx_edata_operand(1, 2, next_word_le(), operandB);
        break;

      case 0xB7:
        if (opcode == SAM8_LDC)
          idx_cdata_operand(0, 2, next_word_le(), operandB);
        else idx_edata_operand(0, 2, next_word_le(), operandB);
        reg_operand(1, false, true, false, operandT);
        break;
      }
    }

    // finalise instruction
    return finalise_insn(opcode);
  }

  case 0xE7: case 0xF7: {
    // extract data
    ushort tmp = ua_next_byte();
    ushort operandT = top_nibble(tmp);
    ushort operandB = bottom_nibble(tmp);

    // decode the correct opcode
    ushort opcode;
    if (operandB & 1) {
      opcode = SAM8_LDE;
      operandB--;
    } else {
      opcode = SAM8_LDC;
    }

    // generate operands
    switch(code) {
    case 0xE7:
      reg_operand(0, false, true, false, operandT);
      if (opcode == SAM8_LDC)
        idx_cdata_operand(1, 2, (int) (char) ua_next_byte(), operandB);
      else idx_edata_operand(1, 2, (int) (char) ua_next_byte(), operandB);
      break;

    case 0xF7:
      if (opcode == SAM8_LDC)
        idx_cdata_operand(0, 2, (int) (char) ua_next_byte(), operandB);
      else idx_edata_operand(0, 2, (int) (char) ua_next_byte(), operandB);
      reg_operand(1, false, true, false, operandT);
      break;
    }

    // finalise the instruction
    return finalise_insn(opcode);
  }

  case 0x84: case 0x85: case 0x86:
  case 0x94: case 0x95: case 0x96: {
    // decode correct opcode
    ushort opcode;
    switch(top_nibble(code)) {
    case 8: opcode = SAM8_MULT; break;
    case 9: opcode = SAM8_DIV; break;
    }

    // Now, generate instruction
    ushort src = ua_next_byte();
    ushort dst = ua_next_byte();
    reg_operand(0, false, false, true, dst);
    switch(bottom_nibble(code)) {
    case 4: reg_operand(1, false, false, false, src); break;
    case 5: reg_operand(1, true, false, false, src); break;
    case 6: imm_operand(1, 1, src, dt_byte); break;
    }
    return finalise_insn(opcode);
  }

  case 0xC4: case 0xC5: {
    // get data
    ushort src = ua_next_byte();
    ushort dst = ua_next_byte();

    // generate instruction
    reg_operand(0, false, false, true, dst);

    // decode addrmode for opcode 2
    switch(code) {
    case 0xC4: reg_operand(1, false, false, true, src); break;
    case 0xC5: reg_operand(1, true, false, false, src); break;
    }
    return finalise_insn(SAM8_LDW);
  }

  case 0xC6:
    reg_operand(0, false, false, true, ua_next_byte());
    imm_operand(1, 2, ua_next_word(), dt_word);
    return finalise_insn(SAM8_LDW);

  case 0x17: {
    // get data
    ushort operandA = ua_next_byte();
    ushort src = ua_next_byte();

    // ensure operandA bit0 is 0
    if (operandA & 1) return 0;

    // generate instruction
    reg_operand(0, false, true, false, top_nibble(operandA));
    regbit_operand(1, false, src, bottom_nibble(operandA) >> 1);
    return finalise_insn(SAM8_BCP);
  }

  case 0x37: {
    // get data
    ushort operandA = ua_next_byte();
    ushort dst = ua_next_byte();

    // generate operands
    code_operand(0, 2, cmd.ea + 3 + (char) dst);
    regbit_operand(1, true,
                   top_nibble(operandA), bottom_nibble(operandA) >> 1);

    // generate operand
    switch(operandA & 1) {
    case 0: return finalise_insn(SAM8_BTJRF);
    case 1: return finalise_insn(SAM8_BTJRT);
    }
  }

  case 0x57: {
    // get data
    ushort operandA = ua_next_byte();

    // ensure operandA bit0 is 0
    if (operandA & 1) return 0;

    // generate instruction
    regbit_operand(0, true,
                   top_nibble(operandA), bottom_nibble(operandA) >> 1);
    return finalise_insn(SAM8_BITC);
  }

  case 0x77: {
    // get data
    ushort operandA = ua_next_byte();

    // generate instruction
    regbit_operand(0, true,
                   top_nibble(operandA), bottom_nibble(operandA) >> 1);
    switch(operandA & 1) {
    case 0: return finalise_insn(SAM8_BITR);
    case 1: return finalise_insn(SAM8_BITS);
    }
  }
  }


  // Decode bit instructions
  if ((bottom_nibble(code) == 7) && (top_nibble(code) < 8)) {
    int codeTable[] = { SAM8_BOR, SAM8_null,
                        SAM8_BXOR, SAM8_null,
                        SAM8_LDB, SAM8_null,
                        SAM8_BAND, SAM8_null };
    // extract data
    ushort operandA = ua_next_byte();
    ushort operandB = ua_next_byte();

    // generate instruction
    switch(operandA & 1) {
    case 0:
      reg_operand(0, false, true, false, top_nibble(operandA));
      regbit_operand(1, false, operandB, bottom_nibble(operandA) >> 1);
      break;

    case 1:
      regbit_operand(0, false, operandB, bottom_nibble(operandA) >> 1);
      reg_operand(1, false, true, false, top_nibble(operandA));
      break;
    }
    return finalise_insn(codeTable[top_nibble(code)]);
  }


  // Do the instructions with stuff encoded in them
  switch(bottom_nibble(code)) {
  case 0x08:
    reg_operand(0, false, true, false, top_nibble(code));
    reg_operand(1, false, false, false, ua_next_byte());
    return finalise_insn(SAM8_LD);

  case 0x09:
    reg_operand(0, false, false, false, ua_next_byte());
    reg_operand(1, false, true, false, top_nibble(code));
    return finalise_insn(SAM8_LD);

  case 0x0A:
    reg_operand(0, false, true, false, top_nibble(code));
    code_operand(1, 1, cmd.ea + 2 + (char) ua_next_byte());
    return finalise_insn(SAM8_DJNZ);

  case 0x0B:
    code_operand(0, 1, cmd.ea + 2 + (char) ua_next_byte());
    return finalise_insn(SAM8_JR, top_nibble(code));

  case 0x0C:
    reg_operand(0, false, true, false, top_nibble(code));
    imm_operand(1, 1, ua_next_byte(), dt_byte);
    return finalise_insn(SAM8_LD);

  case 0x0D:
    code_operand(0, 1, ua_next_word()); // UNSURE ****
    return finalise_insn(SAM8_JP, top_nibble(code));

  case 0x0E:
    reg_operand(0, false, true, false, top_nibble(code));
    return finalise_insn(SAM8_INC);

  case 0x0F: {
    int codeTable[] = { SAM8_NEXT, SAM8_ENTER,
                        SAM8_EXIT, SAM8_WFI,
                        SAM8_SB0,  SAM8_SB1,
                        SAM8_IDLE, SAM8_STOP,
                        SAM8_DI,   SAM8_EI,
                        SAM8_RET,  SAM8_IRET,
                        SAM8_RCF,  SAM8_SCF,
                        SAM8_CCF,  SAM8_NOP };
    return finalise_insn(codeTable[top_nibble(code)]);
  }
  }

  // Do R/RR/IR-only mode instructions
  if (bottom_nibble(code) < 2) {
    int codeTable[] = { SAM8_DEC, SAM8_RLC,
                        SAM8_INC, SAM8_null,
                        SAM8_DA, SAM8_POP,
                        SAM8_COM, SAM8_PUSH,
                        SAM8_DECW, SAM8_RL,
                        SAM8_INCW, SAM8_CLR,
                        SAM8_RRC, SAM8_SRA,
                        SAM8_RR, SAM8_SWAP };
    // do the operand
    if (code & 1) {
      reg_operand(0, true, false, false, ua_next_byte());
    } else {
      if ((top_nibble(code) == 8) || (top_nibble(code) == 0xA)) {
        reg_operand(0, false, false, true, ua_next_byte());
      } else {
        reg_operand(0, false, false, false, ua_next_byte());
      }
    }

    // finalise it
    return finalise_insn(codeTable[top_nibble(code)]);
  }

  // Decode arithmetic-style instructions
  if ((bottom_nibble(code) > 1) && (bottom_nibble(code) < 7)) {
    int codeTable[] = { SAM8_ADD,  SAM8_ADC,
                        SAM8_SUB,  SAM8_SBC,
                        SAM8_OR,   SAM8_AND,
                        SAM8_TCM,  SAM8_TM,
                        SAM8_null, SAM8_null,
                        SAM8_CP,   SAM8_XOR,
                        SAM8_null, SAM8_null,
                        SAM8_null, SAM8_null };
    ushort operandA = ua_next_byte();
    switch(bottom_nibble(code)) {
    case 2:
      reg_operand(0, false, true, false, top_nibble(operandA));
      reg_operand(1, false, true, false, bottom_nibble(operandA));
      return finalise_insn(codeTable[top_nibble(code)]);

    case 3:
      reg_operand(0, false, true, false, top_nibble(operandA));
      reg_operand(1, true, true, false, bottom_nibble(operandA));
      return finalise_insn(codeTable[top_nibble(code)]);

    case 4:
      reg_operand(0, false, false, false, ua_next_byte());
      reg_operand(1, false, false, false, operandA);
      return finalise_insn(codeTable[top_nibble(code)]);

    case 5:
      reg_operand(0, false, false, false, ua_next_byte());
      reg_operand(1, true, false, false, operandA);
      return finalise_insn(codeTable[top_nibble(code)]);

    case 6:
      reg_operand(0, false, false, false, operandA);
      imm_operand(1, 1, ua_next_byte(), dt_byte);
      return finalise_insn(codeTable[top_nibble(code)]);
    }
  }

  // If we get here, we've got an invalid instruction
  return 0;
}

//----------------------------------------------------------------------
// analyze an instruction
int idaapi ana(void) {
  // analyze it!
  return ana_basic();
}