module SiegeBoard

# File lib/siege_game.rb, line 16
def coord_to_index(coord)
  match = coord.to_s.strip.match(/\A([A-E])([1-5])\z/i)
  return nil unless match

  col = match[1].upcase.ord - "A".ord
  row = match[2].to_i - 1
  return nil unless row.between?(0, SIZE - 1) && col.between?(0, SIZE - 1)

  row * SIZE + col
end

# File lib/siege_game.rb, line 33
def fresh_grid
  Array.new(SIZE * SIZE, EMPTY)
end

# File lib/siege_game.rb, line 27
def index_to_coord(index)
  row = index / SIZE
  col = index % SIZE
  "#{%w[A B C D E][col]}#{row + 1}"
end

# File lib/siege_game.rb, line 69
def move_unit(grid:, unit:, dest_index:)
  return { error: "Invalid coordinate." } if dest_index.nil?
  return { error: "Destination blocked." } unless grid[dest_index] == EMPTY

  from = unit_position(grid, unit)
  return { error: "Unit not on board." } unless from
  return { error: "Not adjacent." } unless neighbors(from).include?(dest_index)

  g = grid.dup
  g[from] = EMPTY
  g[dest_index] = unit
  { grid: g }
end

# File lib/siege_game.rb, line 44
def neighbors(index)
  row = index / SIZE
  col = index % SIZE
  deltas = [[-1, 0], [1, 0], [0, -1], [0, 1]]
  deltas.filter_map do |dr, dc|
    nr = row + dr
    nc = col + dc
    next unless nr.between?(0, SIZE - 1) && nc.between?(0, SIZE - 1)

    nr * SIZE + nc
  end
end

# File lib/siege_game.rb, line 37
def place_units(grid, player_a:, player_b:)
  g = grid.dup
  g[coord_to_index("A1")] = PLAYER_A
  g[coord_to_index("E5")] = PLAYER_B
  g
end

# File lib/siege_game.rb, line 83
def place_wall(grid:, index:)
  return { error: "Invalid coordinate." } if index.nil?
  return { error: "Cell occupied." } unless grid[index] == EMPTY

  g = grid.dup
  g[index] = WALL
  { grid: g }
end

# File lib/siege_game.rb, line 104
def render(grid)
  lines = ["  A B C D E"]
  SIZE.times do |row|
    row_cells = (0...SIZE).map { |col| grid[row * SIZE + col] }
    lines << "#{row + 1} #{row_cells.join(' ')}"
  end
  lines.join("\n")
end

# File lib/siege_game.rb, line 57
def unit_for(game, user)
  if GameStore.same_nick?(user, game["challenger"])
    PLAYER_A
  else
    PLAYER_B
  end
end

# File lib/siege_game.rb, line 65
def unit_position(grid, unit)
  grid.index(unit)
end

# File lib/siege_game.rb, line 92
def winner?(grid, unit)
  pos = unit_position(grid, unit)
  return nil unless pos

  case unit
  when PLAYER_A
    pos == coord_to_index("E5") ? PLAYER_A : nil
  when PLAYER_B
    pos == coord_to_index("A1") ? PLAYER_B : nil
  end
end