pf1e-simulator/src/pf1e_simulator/map.py

"""Map YAML loading and validation.

Maps are multi-layer ASCII: a mandatory `terrain` layer plus optional
`elevation` and `zones` layers of identical dimensions, named `markers`, and
a `deployment` section binding sides to zone letters. One char = one square,
row 0 is the top line of the ASCII block.
"""

from __future__ import annotations

from typing import TYPE_CHECKING

import yaml
from pydantic import BaseModel, ConfigDict, Field, ValidationError

if TYPE_CHECKING:
    from pathlib import Path

Pos = tuple[int, int]  # (row, col), 0-indexed

_ELEVATION_CHARS = frozenset("0123456789.")  # digit = height, '.' = ground level


class MapValidationError(Exception):
    """Raised when a map YAML file fails validation; carries path and reason."""

    def __init__(self, path: Path, reason: str) -> None:
        super().__init__(f"{path}: {reason}")
        self.path = path
        self.reason = reason


class TerrainType(BaseModel):
    """What one square means for movement and sight lines."""

    model_config = ConfigDict(frozen=True, extra="forbid")

    type: str
    move_cost: int | None = Field(default=None, ge=1)
    cover: bool = False
    blocks_los: bool = False


class MapSpec(BaseModel):
    """A fully validated map, ready for Grid construction."""

    model_config = ConfigDict(frozen=True, extra="forbid")

    name: str
    square_size_ft: int = Field(default=5, gt=0)
    terrain: tuple[str, ...]
    legend: dict[str, TerrainType]
    elevation: tuple[str, ...] | None = None
    zones: tuple[str, ...] | None = None
    markers: dict[str, Pos] = Field(default_factory=dict)
    deployment: dict[str, str] = Field(default_factory=dict)


class _MapFile(BaseModel):
    """Raw YAML shape; cross-layer checks live in load_map."""

    model_config = ConfigDict(extra="forbid")

    name: str
    square_size_ft: int = Field(default=5, gt=0)
    terrain: str
    legend: dict[str, TerrainType]
    elevation: str | None = None
    zones: str | None = None
    markers: dict[str, Pos] = Field(default_factory=dict)
    deployment: dict[str, str] = Field(default_factory=dict)


def _split_rows(block: str, what: str, path: Path) -> tuple[str, ...]:
    rows = tuple(line.rstrip() for line in block.splitlines() if line.strip())
    if not rows:
        msg = f"{what} layer is empty"
        raise MapValidationError(path, msg)
    if len({len(row) for row in rows}) != 1:
        msg = f"{what} layer has ragged rows"
        raise MapValidationError(path, msg)
    return rows


def _check_layer_dimensions(
    rows: tuple[str, ...], what: str, height: int, width: int, path: Path
) -> None:
    if len(rows) != height or len(rows[0]) != width:
        msg = f"{what} layer dimensions do not match terrain"
        raise MapValidationError(path, msg)


def _optional_layer(block: str | None, what: str, path: Path) -> tuple[str, ...] | None:
    """Split an optional ASCII layer, or None when the layer is absent."""
    return _split_rows(block, what, path) if block else None


def _check_elevation(elevation: tuple[str, ...], height: int, width: int, path: Path) -> None:
    _check_layer_dimensions(elevation, "elevation", height, width, path)
    bad = sorted({ch for row in elevation for ch in row if ch not in _ELEVATION_CHARS})
    if bad:
        msg = f"elevation chars must be digits or '.': {bad}"
        raise MapValidationError(path, msg)


def _check_markers(markers: dict[str, Pos], height: int, width: int, path: Path) -> None:
    for marker_name, (row, col) in markers.items():
        if not (0 <= row < height and 0 <= col < width):
            msg = f"marker {marker_name!r} out of bounds: {(row, col)}"
            raise MapValidationError(path, msg)


def _check_deployment(
    deployment: dict[str, str], zones: tuple[str, ...] | None, path: Path
) -> None:
    if not deployment:
        return
    if zones is None:
        msg = "deployment declared but no zones layer"
        raise MapValidationError(path, msg)
    available = {ch for row in zones for ch in row if ch != "."}
    missing = sorted({letter for letter in deployment.values() if letter not in available})
    if missing:
        msg = f"deployment zones absent from zones layer: {missing}"
        raise MapValidationError(path, msg)


def load_map(path: Path) -> MapSpec:
    try:
        text = path.read_text(encoding="utf-8")
    except OSError as exc:
        msg = f"cannot read file: {exc}"
        raise MapValidationError(path, msg) from exc
    try:
        data: object = yaml.safe_load(text)
    except yaml.YAMLError as exc:
        msg = f"invalid YAML: {exc}"
        raise MapValidationError(path, msg) from exc
    try:
        raw = _MapFile.model_validate(data)
    except ValidationError as exc:
        raise MapValidationError(path, str(exc)) from exc

    terrain = _split_rows(raw.terrain, "terrain", path)
    height, width = len(terrain), len(terrain[0])
    unknown = sorted({ch for row in terrain for ch in row if ch not in raw.legend})
    if unknown:
        msg = f"terrain chars missing from legend: {unknown}"
        raise MapValidationError(path, msg)

    elevation = _optional_layer(raw.elevation, "elevation", path)
    if elevation is not None:
        _check_elevation(elevation, height, width, path)

    zones = _optional_layer(raw.zones, "zones", path)
    if zones is not None:
        _check_layer_dimensions(zones, "zones", height, width, path)

    _check_markers(raw.markers, height, width, path)
    _check_deployment(raw.deployment, zones, path)

    return MapSpec(
        name=raw.name,
        square_size_ft=raw.square_size_ft,
        terrain=terrain,
        legend=raw.legend,
        elevation=elevation,
        zones=zones,
        markers=raw.markers,
        deployment=raw.deployment,
    )


def zone_cells(spec: MapSpec, letter: str) -> list[Pos]:
    """Cells of a deployment zone, sorted by (row, col); empty if no zones layer."""
    if spec.zones is None:
        return []
    return [
        (row, col)
        for row, line in enumerate(spec.zones)
        for col, ch in enumerate(line)
        if ch == letter
    ]