"""
Test / validation script for src/graph/build_graph.py and
src/graph/node_features.py — runs the full pipeline against real data
under --data-root and checks the result is actually sane (no NaN/Inf,
correct shapes, no accidental cross-basin edges, targets kept separate
from inputs, etc.) rather than just "it didn't crash".

Usage:
    python test_build_graph.py --data-root datasets

Expected layout under DATASETS_DIR (any missing piece is skipped, same
as generate_plots.py):
    station_elevations.csv
    idpr.csv
    ades/groundwater_levels_watershed.csv
    ades/groundwater_stations.csv
    safran/era5_*.nc
    hydrometric/discharge_observations.csv
    hydrometric/waterlevel_observations.csv
    centerlines/eure_centerline.csv
    centerlines/risle_centerline.csv
"""
import argparse
import sys
from pathlib import Path

import numpy as np

try:
    from .graph.node_features import build_node_features
    from .graph.build_graph import build_surface_edges, build_pyg_graph, build_pyg_graphs_per_basin
    from .data.river_centerline import load_centerline, snap_gauges_to_centerline
    from .graph.physics_losses import build_confluence_index, build_braid_index
except ImportError:
    sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
    from src.graph.node_features import build_node_features
    from src.graph.build_graph import build_surface_edges, build_pyg_graph, build_pyg_graphs_per_basin
    from src.data.river_centerline import load_centerline, snap_gauges_to_centerline
    from src.graph.physics_losses import build_confluence_index, build_braid_index

import pandas as pd


def _to_numpy(t):
    """
    Convert a torch tensor (or the plain-numpy stub used when this
    script is tested without torch installed) to a numpy array.

    NOTE: `hasattr(t, "data")` is NOT a safe way to distinguish "real
    torch tensor" from "something else" — every real torch tensor has
    a `.data` attribute (it returns a Tensor, not a numpy array), so
    that check silently does nothing on a real install and lets a live
    Tensor leak through. `.detach()` is a better discriminator here:
    real tensors have it, plain numpy/stub objects don't.
    """
    if hasattr(t, "detach"):
        return t.detach().cpu().numpy()
    if hasattr(t, "numpy"):
        return t.numpy()
    return np.asarray(t)


def _check(label: str, condition, detail: str = "") -> bool:
    """Print PASS/FAIL and return a genuine Python bool. `condition` may be
    a plain bool, numpy bool_, or (if a torch boolean expression leaked
    through) a tensor — bool() forces it to a real Python bool either way,
    so a stray tensor can never contaminate the running `all_ok` total."""
    condition = bool(condition)
    status = "PASS" if condition else "FAIL"
    print(f"  [{status}] {label}" + (f" — {detail}" if detail and not condition else ""))
    return condition


def run_checks(data_root: Path, basin_file_names=None) -> bool:
    basin_file_names = basin_file_names or {0: "eure", 1: "risle"}
    all_ok = True

    print("=" * 60)
    print("STEP 1: build_node_features")
    print("=" * 60)
    enriched, feat_report = build_node_features(
        station_elevations_path=data_root / "station_elevations.csv",
        idpr_path=data_root / "idpr.csv",
        ades_path=data_root / "ades",
        safran_path=data_root / "safran",
        hydrometric_path=data_root / "hydrometric",
    )
    print(feat_report)
    all_ok &= _check("base station table is non-empty", len(enriched) > 0)
    all_ok &= _check("no duplicate station_code", enriched["station_code"].is_unique)

    print()
    print("=" * 60)
    print("STEP 2: build_surface_edges")
    print("=" * 60)
    base_nodes, edges_df, graph_report = build_surface_edges(
        enriched, centerline_dir=data_root / "centerlines", basin_file_names=basin_file_names,
    )
    print(graph_report)
    all_ok &= _check("nodes returned == nodes fed in (no silent drops)",
                      len(base_nodes) == len(enriched),
                      f"{len(base_nodes)} vs {len(enriched)}")
    all_ok &= _check("every edge endpoint exists in nodes",
                      set(edges_df["source"]).union(edges_df["target"]).issubset(set(base_nodes["station_code"])))
    cross_basin = edges_df.merge(
        base_nodes[["station_code", "basin_id"]].rename(columns={"station_code": "source", "basin_id": "src_basin"}),
        on="source",
    ).merge(
        base_nodes[["station_code", "basin_id"]].rename(columns={"station_code": "target", "basin_id": "tgt_basin"}),
        on="target",
    )
    all_ok &= _check("no cross-basin edges (surface connectivity only, as intended)",
                      (cross_basin["src_basin"] == cross_basin["tgt_basin"]).all())

    print()
    print("=" * 60)
    print("STEP 3: merge enriched features back onto graph-ordered nodes")
    print("=" * 60)
    full_nodes = base_nodes.merge(
        enriched.drop(columns=["basin_id", "latitude", "longitude", "elevation_m"]),
        on="station_code", how="left",
    )
    all_ok &= _check("merge preserved row count", len(full_nodes) == len(base_nodes))

    print()
    print("=" * 60)
    print("STEP 4: build_pyg_graph (directed)")
    print("=" * 60)
    data = build_pyg_graph(full_nodes, edges_df)
    print(data)
    print("feature_names:", data.feature_names)
    print("target_names:", getattr(data, "target_names", None))

    x_np = _to_numpy(data.x)
    all_ok &= _check("x has no NaN", not np.isnan(x_np).any())
    all_ok &= _check("x has no Inf", not np.isinf(x_np).any())
    all_ok &= _check("x row count matches node count", x_np.shape[0] == len(full_nodes))
    all_ok &= _check("target_* columns excluded from feature_names",
                      not any(c.startswith("target_") for c in data.feature_names))

    # Confirm standardization actually happened: for any feature that isn't
    # constant (std > 0 in the original data) and isn't a __was_missing flag,
    # its standardized column should have ~0 mean and ~1 std. A feature that
    # silently stayed in raw units (e.g. climate_solar_Wm2 in the hundreds
    # sitting next to a z-scored elevation near 0) would dominate distance-
    # based GNN layers purely by scale, not by actual signal.
    non_flag_idx = [i for i, name in enumerate(data.feature_names) if not name.endswith("__was_missing")]
    means = x_np[:, non_flag_idx].mean(axis=0)
    # ddof=1 (sample std) to match pandas' .std() default, which is what
    # build_pyg_graph actually standardizes with — comparing against numpy's
    # default ddof=0 (population std) would show a spurious mismatch for
    # small station counts (sqrt((n-1)/n) off from 1.0), not a real bug.
    stds = x_np[:, non_flag_idx].std(axis=0, ddof=1)
    non_constant = stds > 1e-6
    all_ok &= _check(
        "standardized features have ~0 mean / ~1 std (feature normalization is active)",
        bool(np.allclose(means[non_constant], 0, atol=1e-3) and np.allclose(stds[non_constant], 1, atol=1e-3)),
        f"mean range [{means[non_constant].min():.3f}, {means[non_constant].max():.3f}], "
        f"std range [{stds[non_constant].min():.3f}, {stds[non_constant].max():.3f}]"
        if non_constant.any() else "no non-constant features to check",
    )

    ei_np = _to_numpy(data.edge_index)
    all_ok &= _check("edge_index shape is (2, n_edges)",
                      ei_np.shape == (2, len(edges_df)), f"got {ei_np.shape}")
    all_ok &= _check("edge_index values are valid node indices",
                      bool((ei_np >= 0).all()) and bool((ei_np < len(full_nodes)).all()))

    if hasattr(data, "y"):
        y_np = _to_numpy(data.y)
        all_ok &= _check("y row count matches node count", y_np.shape[0] == len(full_nodes))
        all_ok &= _check("y column count matches target_names", y_np.shape[1] == len(data.target_names))

    print()
    print("=" * 60)
    print("STEP 5: build_pyg_graph (bidirectional)")
    print("=" * 60)
    data_bidir = build_pyg_graph(full_nodes, edges_df, bidirectional=True)
    ei_bidir = _to_numpy(data_bidir.edge_index)
    all_ok &= _check("bidirectional edge_index is exactly 2x directed",
                      ei_bidir.shape[1] == 2 * len(edges_df), f"got {ei_bidir.shape[1]}")

    print()
    print("=" * 60)
    print("STEP 6: build_pyg_graphs_per_basin (Eure and Risle as SEPARATE graphs)")
    print("=" * 60)
    graphs = build_pyg_graphs_per_basin(full_nodes, edges_df)
    all_ok &= _check("exactly one graph per basin present in nodes_df",
                      set(graphs.keys()) == set(full_nodes["basin_id"].unique()),
                      f"got basins {sorted(graphs.keys())}")
    all_ok &= _check("returned more than one graph (not accidentally merged)", len(graphs) > 1)

    total_nodes_across_graphs = 0
    for basin_id, g in graphs.items():
        print(f"  basin {basin_id}: {g}")
        g_x = _to_numpy(g.x)
        g_ei = _to_numpy(g.edge_index)
        total_nodes_across_graphs += g_x.shape[0]
        all_ok &= _check(f"  basin {basin_id}: basin_id excluded from its own feature set",
                          "basin_id" not in g.feature_names)
        all_ok &= _check(f"  basin {basin_id}: edge_index uses local 0..n-1 indexing",
                          bool((g_ei >= 0).all()) and bool((g_ei < g_x.shape[0]).all()),
                          f"n_nodes={g_x.shape[0]}, edge_index range [{g_ei.min()}, {g_ei.max()}]")
        all_ok &= _check(f"  basin {basin_id}: x has no NaN", not np.isnan(g_x).any())
    all_ok &= _check("node counts across per-basin graphs sum to the combined total",
                      total_nodes_across_graphs == len(full_nodes),
                      f"{total_nodes_across_graphs} vs {len(full_nodes)}")

    print()
    print("=" * 60)
    print("STEP 7: known_losing_reaches flagging (smoke test, using first edge)")
    print("=" * 60)
    if len(edges_df) > 0:
        first_edge = (edges_df.iloc[0]["source"], edges_df.iloc[0]["target"])
        _, flagged_edges, flagged_report = build_surface_edges(
            enriched, centerline_dir=data_root / "centerlines", basin_file_names=basin_file_names,
            known_losing_reaches=[first_edge],
        )
        print(flagged_report)
        flagged_row = flagged_edges[
            (flagged_edges["source"] == first_edge[0]) & (flagged_edges["target"] == first_edge[1])
        ]
        all_ok &= _check("flagged edge has verified_continuous=False",
                          bool((~flagged_row["verified_continuous"]).iloc[0]))
    else:
        print("  (skipped: no edges to test with)")

    print()
    print("=" * 60)
    print("STEP 8: centerline accuracy sanity check (snap_distance_km)")
    print("=" * 60)
    # A real BD TOPO/BD TOPAGE-sourced centerline should put gauges within
    # ~sub-km of the mapped line. A stale/approximate centerline (e.g. one
    # still digitized from a road-map screenshot, ~4km georeferencing
    # error) shows up here as a much larger mean snap distance -- this
    # check exists specifically to catch "one basin got upgraded to real
    # geometry and the other was silently left on the old approximate
    # version" without anyone having to eyeball it.
    MEAN_SNAP_DISTANCE_WARN_KM = 2.0
    centerline_dir = data_root / "centerlines"
    if not centerline_dir.exists():
        print("  (skipped: no centerlines/ directory found)")
    else:
        for basin_id, file_key in basin_file_names.items():
            csv_path = centerline_dir / f"{file_key}_centerline.csv"
            if not csv_path.exists():
                print(f"  basin {basin_id} ({file_key}): no centerline file, skipped")
                continue
            cl = load_centerline(csv_path)
            b_nodes = full_nodes[full_nodes["basin_id"] == basin_id]
            if b_nodes.empty:
                continue
            snapped = snap_gauges_to_centerline(cl, b_nodes)
            mean_dist = snapped["snap_distance_km"].mean()
            max_dist = snapped["snap_distance_km"].max()
            print(f"  basin {basin_id} ({file_key}): {len(cl)} centerline points, "
                  f"mean snap_distance={mean_dist:.3f} km, max={max_dist:.3f} km")
            all_ok &= _check(
                f"  basin {basin_id} ({file_key}): mean snap distance < {MEAN_SNAP_DISTANCE_WARN_KM} km "
                f"(a much larger value usually means this basin is still on an approximate/stale centerline)",
                mean_dist < MEAN_SNAP_DISTANCE_WARN_KM,
                f"mean={mean_dist:.3f} km",
            )

    print()
    print("=" * 60)
    print("RESULT:", "ALL CHECKS PASSED" if all_ok else "SOME CHECKS FAILED — see above")
    print("=" * 60)
    return all_ok


def run_reach_graph_checks(data_root: Path, basin_file_names=None) -> bool:
    """
    Validates the reach graph pipeline (scripts/build_reach_graphs.py ->
    scripts/enrich_reach_graph.py -> build_pyg_graph), separately from
    run_checks' coverage of the original single-chain pipeline -- the
    two build nodes_df/edges_df in genuinely different ways (real
    branching topology + splits/rejoins vs. a single ordered chain), so
    keeping their checks in separate functions keeps each readable
    rather than threading conditionals through one long function.

    Specifically regression-tests the three bugs found and fixed in the
    previous session: structural columns (is_gauged/is_confluence/etc.)
    leaking into model features, targets attaching to non-gauge nodes,
    and edge_attr breaking on the real edges schema's extra string
    columns (toponym, cleabs).

    Gracefully returns True (not a failure) if the reach graph hasn't
    been built/enriched yet -- this is meant to add coverage once that
    pipeline is in use, not force it to exist.
    """
    basin_file_names = basin_file_names or {0: "eure", 1: "risle"}
    all_ok = True
    graph_dir = data_root / "reach_graph"

    print()
    print("=" * 60)
    print("REACH GRAPH CHECKS")
    print("=" * 60)

    if not graph_dir.exists():
        print(f"  No {graph_dir} found -- skipping (run scripts/build_reach_graphs.py "
              f"and scripts/enrich_reach_graph.py first for this coverage). Not a failure.")
        return True

    any_basin_found = False
    for basin_id, file_key in basin_file_names.items():
        enriched_path = graph_dir / f"{file_key}_nodes_enriched.csv"
        edges_path = graph_dir / f"{file_key}_edges.csv"
        if not enriched_path.exists() or not edges_path.exists():
            print(f"  basin {basin_id} ({file_key}): missing enriched nodes/edges CSV, skipped")
            continue
        any_basin_found = True

        nodes_df = pd.read_csv(enriched_path)
        edges_df = pd.read_csv(edges_path)
        print()
        print(f"--- basin {basin_id} ({file_key}): {len(nodes_df)} nodes, {len(edges_df)} edges ---")

        structural_cols = ["is_gauged", "is_confluence", "is_split_point", "is_rejoin_point"]
        for col in structural_cols:
            all_ok &= _check(f"  '{col}' column present on nodes_df", col in nodes_df.columns)

        n_gauged = int(nodes_df["is_gauged"].sum()) if "is_gauged" in nodes_df.columns else 0
        n_confluence = int(nodes_df["is_confluence"].sum()) if "is_confluence" in nodes_df.columns else 0
        n_split = int(nodes_df["is_split_point"].sum()) if "is_split_point" in nodes_df.columns else 0
        n_rejoin = int(nodes_df["is_rejoin_point"].sum()) if "is_rejoin_point" in nodes_df.columns else 0
        print(f"  {n_gauged} gauged, {n_confluence} confluences, {n_split} splits, {n_rejoin} rejoins")

        data = build_pyg_graph(nodes_df, edges_df)
        x_np = _to_numpy(data.x)
        all_ok &= _check("  x has no NaN", not np.isnan(x_np).any())
        all_ok &= _check("  x has no Inf", not np.isinf(x_np).any())
        all_ok &= _check("  x row count matches node count", x_np.shape[0] == len(nodes_df),
                          f"{x_np.shape[0]} vs {len(nodes_df)}")

        # REGRESSION: structural columns must never leak into model features
        leaked = [f for f in data.feature_names
                  if f in ("is_gauged", "is_confluence", "is_split_point", "is_rejoin_point",
                            "snap_distance_km", "braid_id")]
        all_ok &= _check("  no structural columns leaked into feature_names", not leaked,
                          f"leaked: {leaked}")

        # REGRESSION: structural columns still accessible as their own Data attributes
        for col in structural_cols:
            all_ok &= _check(f"  data.{col} attribute present", hasattr(data, col))

        # REGRESSION: targets only ever attach to gauged nodes, never confluences/virtual nodes
        if hasattr(data, "y") and hasattr(data, "is_gauged"):
            y_np = _to_numpy(data.y)
            is_gauged_np = _to_numpy(data.is_gauged).astype(bool)
            has_real_target = ~np.isnan(y_np).all(axis=1)
            mislabeled = has_real_target & ~is_gauged_np
            all_ok &= _check("  no target values on non-gauged nodes", not mislabeled.any(),
                              f"{int(mislabeled.sum())} mislabeled node(s)")
            all_ok &= _check("  target coverage matches gauge count or less",
                              int(has_real_target.sum()) <= n_gauged,
                              f"{int(has_real_target.sum())} with targets vs {n_gauged} gauged")

        # REGRESSION: edge_attr stays 3 columns despite extra edge metadata (toponym, cleabs)
        edge_attr_np = _to_numpy(data.edge_attr)
        all_ok &= _check("  edge_attr has exactly 3 columns despite extra edge metadata",
                          edge_attr_np.shape[1] == 3, f"got {edge_attr_np.shape[1]} columns")

        # Physics loss index builders (physics_losses.py) sanity-checked against this same data
        conf_idx = build_confluence_index(nodes_df, edges_df)
        braid_idx = build_braid_index(nodes_df)
        all_ok &= _check("  confluence_index count matches is_confluence sum",
                          len(conf_idx) == n_confluence, f"{len(conf_idx)} vs {n_confluence}")
        if conf_idx:
            max_idx = max(max(upstream) for _, upstream in conf_idx)
            all_ok &= _check("  confluence_index indices within node bounds",
                              0 <= max_idx < len(nodes_df))
            min_upstream = min(len(upstream) for _, upstream in conf_idx)
            all_ok &= _check("  every confluence has >= 2 upstream branches", min_upstream >= 2)
        if braid_idx:
            max_braid_idx = max(max(pair) for pair in braid_idx)
            all_ok &= _check("  braid_index indices within node bounds",
                              0 <= max_braid_idx < len(nodes_df))
        all_ok &= _check("  braid_index count matches is_rejoin_point sum",
                          len(braid_idx) == n_rejoin, f"{len(braid_idx)} vs {n_rejoin}")

        n_climate = int(nodes_df["climate_precip_mm"].notna().sum()) if "climate_precip_mm" in nodes_df.columns else 0
        n_catchment = int(nodes_df["catchment_area_km2"].notna().sum()) if "catchment_area_km2" in nodes_df.columns else 0
        n_idpr = int(nodes_df["idpr_value"].notna().sum()) if "idpr_value" in nodes_df.columns else 0
        print(f"  coverage: climate {n_climate}/{len(nodes_df)}, idpr {n_idpr}/{len(nodes_df)}, "
              f"catchment_area (Hub'Eau, gauges only) {n_catchment}/{len(nodes_df)}")
        all_ok &= _check("  idpr present on the enriched table (was missing in a real run once -- "
                          "check the idpr_path passed to enrich_reach_graph.py if this fails)",
                          "idpr_value" in nodes_df.columns)

        if "cumulative_catchment_area_km2" in nodes_df.columns:
            n_cumulative = int(nodes_df["cumulative_catchment_area_km2"].notna().sum())
            print(f"  cumulative_catchment_area_km2 (BD TOPO, graph-wide) coverage: "
                  f"{n_cumulative}/{len(nodes_df)}")
            all_ok &= _check("  cumulative_catchment_area_km2 covers meaningfully more than "
                              "the Hub'Eau-only catchment_area_km2",
                              n_cumulative > n_catchment,
                              f"{n_cumulative} vs {n_catchment} -- if this fails, "
                              f"scripts/compute_cumulative_catchment.py likely needs a re-run")
        else:
            print("  cumulative_catchment_area_km2 not present -- run "
                  "scripts/compute_cumulative_catchment.py for graph-wide catchment coverage "
                  "(known gap otherwise: only the ~8 real gauges Hub'Eau publishes it for).")

    if not any_basin_found:
        print("  No enriched reach graph files found for any basin -- run "
              "scripts/build_reach_graphs.py then scripts/enrich_reach_graph.py first.")
        return True

    print()
    print("=" * 60)
    print("REACH GRAPH RESULT:", "ALL CHECKS PASSED" if all_ok else "SOME CHECKS FAILED — see above")
    print("=" * 60)
    return all_ok


def main() -> None:
    parser = argparse.ArgumentParser(description="Test build_graph.py / node_features.py against real data")
    parser.add_argument("--data-root", type=Path, default=Path("datasets"))
    args = parser.parse_args()

    ok_original = run_checks(args.data_root)
    ok_reach_graph = run_reach_graph_checks(args.data_root)
    sys.exit(0 if (ok_original and ok_reach_graph) else 1)


if __name__ == "__main__":
    main()