"""Target-region preparation and preservation QC for core language ROIs."""

from __future__ import annotations

from dataclasses import asdict, dataclass
from pathlib import Path
from typing import Any

import nibabel as nib
from nibabel.processing import resample_from_to
import numpy as np
import pandas as pd

CORE_ROI_NAMES: tuple[str, ...] = (
    "TP",
    "aSTS",
    "pSTS",
    "BA44",
    "BA45",
    "BA47",
    "AG_TPJ",
)


@dataclass(frozen=True)
class CoreROICoverageRow:
    """Coverage diagnostics for one subject-run and one core ROI."""

    subject: str
    run: int
    roi_name: str
    pre_mask_voxels: int
    post_mask_voxels: int
    retention_ratio: float
    centroid_shift_mm: float | None
    min_voxels_required: int
    passed: bool


def _resample_binary_roi_to_reference(
    roi_img: nib.Nifti1Image,
    reference_img: nib.Nifti1Image,
) -> np.ndarray:
    resampled = resample_from_to(
        roi_img,
        (reference_img.shape, reference_img.affine),
        order=0,
    )
    return resampled.get_fdata() > 0.5


def _compute_centroid_mm(mask_bool: np.ndarray, affine: np.ndarray) -> np.ndarray | None:
    indices = np.argwhere(mask_bool)
    if indices.size == 0:
        return None
    points_mm = nib.affines.apply_affine(affine, indices)
    return np.mean(points_mm, axis=0)


def load_core_roi_masks(
    roi_mask_dir: Path,
    reference_img: nib.Nifti1Image,
) -> tuple[dict[str, np.ndarray], dict[str, int]]:
    """Load and resample all core ROI masks into reference analysis grid."""
    roi_masks: dict[str, np.ndarray] = {}
    roi_voxel_counts: dict[str, int] = {}

    for roi_name in CORE_ROI_NAMES:
        roi_path = roi_mask_dir / f"{roi_name}.nii.gz"
        if not roi_path.exists():
            raise FileNotFoundError(f"Missing core ROI mask: {roi_path}")

        roi_img = nib.load(str(roi_path))
        roi_bool = _resample_binary_roi_to_reference(roi_img=roi_img, reference_img=reference_img)

        roi_masks[roi_name] = roi_bool
        roi_voxel_counts[roi_name] = int(roi_bool.sum())

    return roi_masks, roi_voxel_counts


def evaluate_core_roi_preservation(
    manifest_df: pd.DataFrame,
    run_mask_map: dict[tuple[str, int], np.ndarray],
    core_roi_masks: dict[str, np.ndarray],
    reference_affine: np.ndarray,
    min_voxels_required: int,
) -> tuple[pd.DataFrame, pd.DataFrame, dict[str, Any]]:
    """Evaluate whether each core ROI is preserved for every subject-run."""
    rows: list[CoreROICoverageRow] = []

    roi_centroids_pre: dict[str, np.ndarray | None] = {
        roi_name: _compute_centroid_mm(mask_bool=mask_bool, affine=reference_affine)
        for roi_name, mask_bool in core_roi_masks.items()
    }

    for row in manifest_df.itertuples(index=False):
        subject = str(getattr(row, "subject"))
        run = int(getattr(row, "run"))
        run_key = (subject, run)

        run_mask = run_mask_map.get(run_key)
        if run_mask is None:
            for roi_name, roi_mask in core_roi_masks.items():
                rows.append(
                    CoreROICoverageRow(
                        subject=subject,
                        run=run,
                        roi_name=roi_name,
                        pre_mask_voxels=int(roi_mask.sum()),
                        post_mask_voxels=0,
                        retention_ratio=0.0,
                        centroid_shift_mm=None,
                        min_voxels_required=min_voxels_required,
                        passed=False,
                    )
                )
            continue

        for roi_name, roi_mask in core_roi_masks.items():
            pre_count = int(roi_mask.sum())
            post_mask = roi_mask & run_mask
            post_count = int(post_mask.sum())

            retention_ratio = float(post_count / pre_count) if pre_count > 0 else 0.0

            centroid_pre = roi_centroids_pre.get(roi_name)
            centroid_post = _compute_centroid_mm(mask_bool=post_mask, affine=reference_affine)
            if centroid_pre is not None and centroid_post is not None:
                centroid_shift = float(np.linalg.norm(centroid_post - centroid_pre))
            else:
                centroid_shift = None

            passed = bool(pre_count > 0 and post_count >= min_voxels_required)

            rows.append(
                CoreROICoverageRow(
                    subject=subject,
                    run=run,
                    roi_name=roi_name,
                    pre_mask_voxels=pre_count,
                    post_mask_voxels=post_count,
                    retention_ratio=retention_ratio,
                    centroid_shift_mm=centroid_shift,
                    min_voxels_required=min_voxels_required,
                    passed=passed,
                )
            )

    coverage_df = pd.DataFrame([asdict(row) for row in rows])
    if not coverage_df.empty:
        coverage_df = coverage_df.sort_values(["subject", "run", "roi_name"]).reset_index(drop=True)

    failures_df = coverage_df[coverage_df["passed"] == False].copy() if not coverage_df.empty else pd.DataFrame()
    if not failures_df.empty:
        failures_df = failures_df.sort_values(["subject", "run", "roi_name"]).reset_index(drop=True)

    per_run_failures = 0
    if not failures_df.empty:
        per_run_failures = int(failures_df[["subject", "run"]].drop_duplicates().shape[0])

    qc_summary: dict[str, Any] = {
        "n_coverage_rows": int(len(coverage_df)),
        "n_fail_rows": int(len(failures_df)),
        "n_subject_run_failures": per_run_failures,
        "min_voxels_required": int(min_voxels_required),
    }

    if not coverage_df.empty:
        qc_summary["retention_ratio_min"] = float(coverage_df["retention_ratio"].min())
        qc_summary["retention_ratio_max"] = float(coverage_df["retention_ratio"].max())

    return coverage_df, failures_df, qc_summary