#include "tak.h"

// Be sure not to set higher bits in colour than LSB
void set_stone(board_t board, bit_board_t *capstand,
               const uint8_t location,
               const uint8_t colour,
               const enum STONE_VARIANT stone) {

  board[location] = (STONE_IS_CAPSTAND(stone) ? CELL_MASK_CAPSTAND : 0x0000)
    | CELL_COUNT_INC | colour;
  if (stone == STONE_CAPSTONE) BITBOARD_SET(*capstand, location);
}

// This can overflow, checks are elsewhere
void push_cells_stack(board_t board, bit_board_t *capstand,
                      const uint8_t location, const uint8_t count,
                      const uint8_t colours,
                      const enum STONE_VARIANT top_stone) {

  if (top_stone == STONE_CAPSTONE) BITBOARD_RST(*capstand, location);

  const cell_t cell = board[location];
  const uint8_t new_count = CELL_GET_COUNT(cell) + count;
  const uint8_t new_stack = (CELL_GET_STACK(cell) << count) | colours;

  board[location] = (STONE_IS_CAPSTAND(top_stone) ? CELL_MASK_CAPSTAND : 0x0000)
    | ((new_count > 0xA) ? 0xA : new_count)
    | (new_stack & CELL_MASK_STACK);
}

// Calling this with count = 0 is destructive
void drop_cells_stack(board_t board, bit_board_t *capstand,
                     const uint8_t location, const uint8_t count) {

  // NOTE: We always clear the bitboard and capstand flags as it's not
  // possible that those stones are underneath anything.

  BITBOARD_RST(*capstand, location);
  const uint8_t cur_count = CELL_GET_COUNT(board[location]);
  if (count >= cur_count) {
    board[location] = CELL_EMPTY_VALUE;
  } else {
    board[location] = ((cur_count - count) << CELL_COUNT_SHIFT)
      | (CELL_GET_STACK(board[location]) >> count);
  }
}

enum ACTION_RESULT try_place_stone(board_t board, bit_board_t *capstand,
                                   const uint8_t location, const uint8_t colour,
                                   const enum STONE_VARIANT stone)
{
  // Can't place on an occupied square
  if (CELL_IS_EMPTY(board[location])) {
    set_stone(board, capstand, location, colour, stone);
    return A_OK;
  } else {
    return A_ILLEGAL;
  }
}