"""C4 pose-estimator config block (AZ-355).

Registered into the global config registry via
``register_component_block("c4_pose", C4PoseConfig)`` on import of
``gps_denied_onboard.components.c4_pose``. The runtime root reads
``config.components["c4_pose"]`` and dispatches to the
``opencv_gtsam`` strategy (the only one defined; the Protocol exists
for ADR-009).
"""

from __future__ import annotations

from dataclasses import dataclass
from typing import Final

from gps_denied_onboard.config.schema import ConfigError

__all__ = ["KNOWN_POSE_STRATEGIES", "C4PoseConfig"]


KNOWN_POSE_STRATEGIES: Final[frozenset[str]] = frozenset({"opencv_gtsam"})


@dataclass(frozen=True)
class C4PoseConfig:
    """C4 pose-estimator config block.

    Fields per the C4 contract §"Config-load-time validation":

    * ``enabled`` — AZ-776 composition-graph flag. When ``False`` the
      composition root strips ``c4_pose`` from the airborne component
      graph entirely (open-loop ESKF profile per ADR-012). Default
      ``True`` preserves the full GTSAM pipeline that ADR-003 mandates
      as the steady-state airborne path. Forbidden pairings (rejected
      by ``compose_root`` with :class:`CompositionError`):
      ``enabled=False`` + ``c5_state.strategy="gtsam_isam2"`` (iSAM2
      requires a C4 anchor); ``enabled=True`` +
      ``c5_state.strategy="eskf"`` (ESKF has no iSAM2 graph for C4 to
      anchor against).
    * ``strategy`` — selects the concrete estimator. Currently only
      ``"opencv_gtsam"`` is defined.
    * ``ransac_iterations`` — OpenCV ``solvePnPRansac`` iteration
      budget. Default 200 per the contract.
    * ``ransac_reprojection_threshold_px`` — RANSAC inlier-distance
      threshold. Default 4.0 pixels per the contract.
    * ``thermal_throttle_threshold_celsius`` — informational only;
      the actual ``ThermalState.thermal_throttle_active`` decision is owned by C7
      (AZ-302). Default 75.0 °C.
    * ``covariance_degraded_warn_window_ns`` — AZ-361 rate-limit
      window for ``CovarianceDegradedWarning`` emissions AND the
      paired ``c4.pose.covariance_degraded`` WARN log + FDR record.
      Default 60 s. Set to 0 to disable rate-limiting (useful in
      tests that want to see every warning).
    * ``ridge_regularisation_epsilon`` — AZ-361 ridge added to
      ``JᵀJ/σ²`` before inversion to stabilise near-singular
      Jacobians on degenerate inlier sets. Default 1e-9; raise
      to 1e-6 if Jacobian-path SPD failures begin spiking in
      forensics.
    * ``tile_size_px`` — AZ-358 satellite-tile pixel dimensions
      (square). Used to map ``MatchResult`` inlier tile-pixel
      coordinates back to WGS84 lat/lon → local-ENU world points
      consumed by ``solvePnPRansac``. Default 256 matches the OSM /
      C6 tile-cache convention. If the upstream tile source
      provides a different square size, override at composition
      time; the spec assumes a square tile (any non-square tile
      handling would land in a future config extension).
    """

    enabled: bool = True
    strategy: str = "opencv_gtsam"
    ransac_iterations: int = 200
    ransac_reprojection_threshold_px: float = 4.0
    thermal_throttle_threshold_celsius: float = 75.0
    covariance_degraded_warn_window_ns: int = 60_000_000_000
    ridge_regularisation_epsilon: float = 1e-9
    tile_size_px: int = 256

    def __post_init__(self) -> None:
        if self.strategy not in KNOWN_POSE_STRATEGIES:
            raise ConfigError(
                f"C4PoseConfig.strategy={self.strategy!r} not in {sorted(KNOWN_POSE_STRATEGIES)}"
            )
        if self.ransac_iterations <= 0:
            raise ConfigError(
                f"C4PoseConfig.ransac_iterations must be > 0; got {self.ransac_iterations}"
            )
        if self.ransac_reprojection_threshold_px <= 0.0:
            raise ConfigError(
                "C4PoseConfig.ransac_reprojection_threshold_px must be > 0; "
                f"got {self.ransac_reprojection_threshold_px}"
            )
        if self.thermal_throttle_threshold_celsius <= 0.0:
            raise ConfigError(
                "C4PoseConfig.thermal_throttle_threshold_celsius must be > 0; "
                f"got {self.thermal_throttle_threshold_celsius}"
            )
        if self.covariance_degraded_warn_window_ns < 0:
            raise ConfigError(
                "C4PoseConfig.covariance_degraded_warn_window_ns must be >= 0; "
                f"got {self.covariance_degraded_warn_window_ns}"
            )
        if self.ridge_regularisation_epsilon <= 0.0:
            raise ConfigError(
                "C4PoseConfig.ridge_regularisation_epsilon must be > 0; "
                f"got {self.ridge_regularisation_epsilon}"
            )
        if self.tile_size_px <= 0:
            raise ConfigError(
                f"C4PoseConfig.tile_size_px must be > 0; got {self.tile_size_px}"
            )