from __future__ import annotations

from engine.character import Character
from engine.world import World


def in_water(character: Character, world: World) -> bool:
    """True if the character is currently standing in a water tile (resources/defs/tiles.json's
    "water" flooring def) - gates the free vertical swim movement (req 6) the same way
    resources/logic/steering.py::at_helm gates ship-steering movement in main.py.
    """
    if character.position is None:
        return False
    map_ = world.maps[character.position.map_id]
    tile = map_.get_tile(character.position.x, character.position.y, character.position.z)
    return tile.layer_id("flooring") == "water"


def try_swim_vertical(character: Character, world: World, dz: int) -> bool:
    """Moves one z-level up/down while submerged - unlike land staircases this needs no placed
    connector tile, since every water column is swimmable end to end (see
    engine/worldgen/terrain.py's underground fill: a water column stays water all the way
    down, rather than turning to solid rock like dry land does). No-op if not currently in
    water, or if the target z isn't itself walkable (e.g. surfacing above the waterline into a
    solid tile, or diving below the seabed).
    """
    if not in_water(character, world):
        return False
    return world.try_move(character, 0, 0, dz)