"""Custom Gradio UI for showing the trained model's predictions.

Mounts as a second tab next to the OpenEnv playground when ``ENABLE_WEB_INTERFACE``
is on. Lets a viewer:

* pick a subject / condition / run / seed,
* run one full 20-step rollout under the trained policy (or the static
  fallback when the Space has no GPU),
* see what the model predicted -- which parcels, in what order, and how the
  cumulative R^2 climbs as a function of selection step,
* optionally see those parcels rendered on a glass brain (via nilearn's
  Schaefer-2018 atlas, lazy-loaded so a CPU-only Space still serves the
  numerical prediction view).

This module is purely a visualization layer over :func:`server.app.run_brain_rollout`
and the existing ``/rollout`` HTTP endpoint, so anything the UI shows is
reproducible by an external client.
"""

from __future__ import annotations

import io
import json
import os
import threading
from pathlib import Path
from typing import Any, Callable, Iterable

import gradio as gr


# ---------------------------------------------------------------------------
# Lookups (subjects, runs, conditions) -- read once at build_prediction_ui()
# ---------------------------------------------------------------------------

CONDITIONS = ["single_m", "single_f", "mixed_m", "mixed_f"]


def _participant_info_path() -> Path | None:
    """Locate ``participant_run_info.json`` from configured data dirs."""

    config_dir = os.getenv("BRAINRL_CONFIG_DIR")
    if config_dir:
        candidate = Path(config_dir) / "participant_run_info.json"
        if candidate.exists():
            return candidate
    # Fall back to the bundled configs dir shipped with the Space image.
    bundled = Path(__file__).resolve().parent.parent / "configs" / "participant_run_info.json"
    if bundled.exists():
        return bundled
    return None


def _participant_choices() -> tuple[list[str], dict[str, dict[str, str]]]:
    """Return (sorted subject ids, raw subject -> {run: condition} mapping)."""

    info_path = _participant_info_path()
    if info_path is None:
        return ["sub-01"], {}
    try:
        info = json.loads(info_path.read_text())
    except Exception:
        return ["sub-01"], {}
    return sorted(info.keys()), info


# ---------------------------------------------------------------------------
# Schaefer-2018 atlas glass-brain plot -- lazy because nilearn is heavy
# ---------------------------------------------------------------------------

_ATLAS_LOCK = threading.Lock()
_ATLAS_CACHE: dict[str, Any] = {"loaded": False, "labels_img": None, "label_to_index": None, "error": None}


def _load_schaefer_atlas() -> dict[str, Any]:
    """Fetch the Schaefer-2018 atlas once and cache the result.

    The atlas (NIfTI) is ~10MB and nilearn caches it on disk, so this only
    pays the download cost on the very first /web request after a Space
    cold start. Subsequent calls reuse the in-memory ``labels_img``.
    """

    if _ATLAS_CACHE["loaded"]:
        return _ATLAS_CACHE
    with _ATLAS_LOCK:
        if _ATLAS_CACHE["loaded"]:
            return _ATLAS_CACHE
        try:
            from nilearn import datasets as nl_datasets
            from nilearn import image as nl_image
        except ImportError as exc:  # pragma: no cover - graceful degrade
            _ATLAS_CACHE["loaded"] = True
            _ATLAS_CACHE["error"] = (
                "nilearn not installed in this Space; install the [atlas] extra "
                f"to enable the glass-brain view ({exc})."
            )
            return _ATLAS_CACHE
        try:
            atlas = nl_datasets.fetch_atlas_schaefer_2018(
                n_rois=200, yeo_networks=7, resolution_mm=2,
            )
            labels_img = nl_image.load_img(atlas.maps)
            raw_labels: list[str] = []
            for entry in atlas.labels:
                raw_labels.append(entry.decode("utf-8") if isinstance(entry, bytes) else str(entry))
            label_to_index = {lbl: idx + 1 for idx, lbl in enumerate(raw_labels)}
        except Exception as exc:  # pragma: no cover - graceful degrade
            _ATLAS_CACHE["loaded"] = True
            _ATLAS_CACHE["error"] = f"Failed to fetch Schaefer atlas: {exc}"
            return _ATLAS_CACHE
        _ATLAS_CACHE.update(
            loaded=True,
            labels_img=labels_img,
            label_to_index=label_to_index,
            error=None,
        )
        return _ATLAS_CACHE


def _glass_brain_image(steps: Iterable[dict[str, Any]]) -> tuple[Any | None, str | None]:
    """Render a glass-brain overlay where each parcel is colored by selection order.

    The first selected parcel gets the lowest priority value, the last gets the
    highest, and unselected voxels are masked out. Using a divergent colormap
    on a numeric "selection rank" makes the time-ordering of the model's
    predictions readable at a glance.
    """

    atlas = _load_schaefer_atlas()
    if atlas.get("error"):
        return None, atlas["error"]
    labels_img = atlas["labels_img"]
    label_to_index = atlas["label_to_index"] or {}
    if labels_img is None or not label_to_index:
        return None, "Atlas labels not available."

    try:
        import matplotlib

        matplotlib.use("Agg")
        import matplotlib.pyplot as plt
        import numpy as np
        from nilearn import image as nl_image
        from nilearn import plotting as nl_plotting
    except ImportError as exc:  # pragma: no cover - graceful degrade
        return None, f"Plot dependencies missing: {exc}"

    label_data = np.asarray(labels_img.dataobj).astype(int)
    overlay = np.zeros_like(label_data, dtype=np.float32)
    rendered = 0
    for rank, step in enumerate(steps, start=1):
        label = step.get("region_label")
        if not label:
            continue
        idx = label_to_index.get(label)
        if not idx:
            continue
        overlay[label_data == idx] = float(rank)
        rendered += 1
    if rendered == 0:
        return None, "Model picked no parcels that match the Schaefer atlas labels."

    overlay_img = nl_image.new_img_like(labels_img, overlay)
    fig = plt.figure(figsize=(9, 4.0))
    nl_plotting.plot_glass_brain(
        overlay_img,
        figure=fig,
        colorbar=True,
        cmap="viridis",
        plot_abs=False,
        threshold=0.5,
        title=f"Predicted parcels (selection order, n={rendered})",
    )
    return fig, None


# ---------------------------------------------------------------------------
# 2D summary plots -- always available because matplotlib ships in [plots]
# ---------------------------------------------------------------------------

def _r2_curve_figure(steps: list[dict[str, Any]]) -> Any | None:
    if not steps:
        return None
    try:
        import matplotlib

        matplotlib.use("Agg")
        import matplotlib.pyplot as plt
    except ImportError:  # pragma: no cover
        return None

    timesteps = [s["timestep"] for s in steps]
    cumulative = [s["current_r2"] for s in steps]
    rewards = [s["reward"] for s in steps]
    fallback = [bool(s["fallback_used"]) for s in steps]

    fig, axes = plt.subplots(1, 2, figsize=(11, 4.0))
    axes[0].plot([0, *timesteps], [0.0, *cumulative], color="#3b82f6", linewidth=2)
    axes[0].scatter(
        timesteps,
        cumulative,
        c=["#ef4444" if fb else "#3b82f6" for fb in fallback],
        zorder=3,
        s=40,
    )
    axes[0].set_title("Predicted cumulative R\u00b2 over selection budget")
    axes[0].set_xlabel("Selection step")
    axes[0].set_ylabel("Cumulative R\u00b2")
    axes[0].grid(linestyle="--", alpha=0.4)

    bar_colors = ["#ef4444" if fb else "#10b981" for fb in fallback]
    axes[1].bar(timesteps, rewards, color=bar_colors)
    axes[1].set_title("Per-step reward (red = fallback used)")
    axes[1].set_xlabel("Selection step")
    axes[1].set_ylabel("Reward")
    axes[1].grid(axis="y", linestyle="--", alpha=0.4)

    fig.suptitle("Trained policy: predictions on a single episode")
    fig.tight_layout()
    return fig


def _network_distribution_figure(steps: list[dict[str, Any]]) -> Any | None:
    """Bar chart of selected parcels grouped by network x hemisphere.

    Useful sanity check: a sensible policy should bias toward language /
    auditory networks (Default, Cont, SalVentAttn) on auditory conditions
    rather than spreading uniformly across all 7 Yeo networks.
    """

    if not steps:
        return None
    try:
        import matplotlib

        matplotlib.use("Agg")
        import matplotlib.pyplot as plt
    except ImportError:  # pragma: no cover
        return None

    counts: dict[str, dict[str, int]] = {}
    for step in steps:
        network = step.get("network") or "Other"
        hemi = step.get("hemisphere") or "n/a"
        counts.setdefault(network, {"left": 0, "right": 0, "other": 0})
        counts[network][hemi if hemi in ("left", "right") else "other"] += 1
    if not counts:
        return None

    networks = sorted(counts.keys())
    left = [counts[n]["left"] for n in networks]
    right = [counts[n]["right"] for n in networks]
    other = [counts[n]["other"] for n in networks]

    fig, ax = plt.subplots(figsize=(9, 3.5))
    x = list(range(len(networks)))
    ax.bar(x, left, color="#3b82f6", label="left hemisphere")
    ax.bar(x, right, bottom=left, color="#10b981", label="right hemisphere")
    bottoms = [l + r for l, r in zip(left, right)]
    if any(other):
        ax.bar(x, other, bottom=bottoms, color="#94a3b8", label="other")
    ax.set_xticks(x)
    ax.set_xticklabels(networks, rotation=20)
    ax.set_ylabel("Number of selected parcels")
    ax.set_title("Predicted parcels by Yeo-7 network")
    ax.legend(loc="upper right")
    ax.grid(axis="y", linestyle="--", alpha=0.4)
    fig.tight_layout()
    return fig


# ---------------------------------------------------------------------------
# Markdown helpers
# ---------------------------------------------------------------------------

def _stimulus_markdown(rollout: dict[str, Any]) -> str:
    stimulus = rollout.get("stimulus") or {}
    if not stimulus:
        return "_No stimulus context attached to this episode._"
    parts = [
        f"**Condition**: `{rollout.get('condition')}`",
        f"**Subject / run**: `{rollout.get('subject_id')}` / `{rollout.get('run_id')}`",
    ]
    window = stimulus.get("window") if isinstance(stimulus, dict) else None
    if window:
        parts.append(f"**Window**: `{window}`")
    onset = stimulus.get("start_time_s") if isinstance(stimulus, dict) else None
    offset = stimulus.get("end_time_s") if isinstance(stimulus, dict) else None
    if onset is not None and offset is not None:
        parts.append(f"**Time**: `{onset:.1f}s` -> `{offset:.1f}s`")
    pos = stimulus.get("dominant_pos") if isinstance(stimulus, dict) else None
    if pos:
        parts.append(f"**Dominant POS**: `{pos}`")
    text = stimulus.get("text") if isinstance(stimulus, dict) else None
    if text:
        parts.append(f"\n> {text}")
    return "\n\n".join(parts)


def _status_markdown(rollout: dict[str, Any]) -> str:
    policy = rollout.get("policy") or {}
    steps = rollout.get("steps") or []
    fallback_count = sum(1 for s in steps if s.get("fallback_used"))
    final_r2 = float(rollout.get("final_r2") or 0.0)
    budget = int(rollout.get("selection_budget") or 0)
    if policy.get("loaded"):
        model_line = f"**Model**: `{policy.get('model_repo')}` (device=`{policy.get('device')}`)"
    elif policy.get("enabled"):
        err = policy.get("load_error") or "loading"
        model_line = f"**Model**: `{policy.get('model_repo')}` (status=`{err}`)"
    else:
        model_line = "**Model**: static fallback policy (no `BRAINRL_POLICY_MODEL_REPO`)."
    return (
        f"{model_line}\n\n"
        f"**Predicted final R\u00b2**: `{final_r2:.4f}` over `{len(steps)}/{budget}` steps. "
        f"Fallback used on `{fallback_count}/{len(steps)}` steps."
    )


def _steps_table(steps: list[dict[str, Any]]) -> list[list[Any]]:
    rows: list[list[Any]] = []
    for s in steps:
        rows.append(
            [
                s.get("timestep"),
                s.get("region_id"),
                s.get("region_label"),
                s.get("network"),
                s.get("hemisphere"),
                round(float(s.get("current_r2", 0.0)), 4),
                round(float(s.get("delta_r2", 0.0)), 4),
                round(float(s.get("reward", 0.0)), 4),
                "yes" if s.get("fallback_used") else "no",
            ]
        )
    return rows


# ---------------------------------------------------------------------------
# Top-level builder
# ---------------------------------------------------------------------------

def build_prediction_ui(
    run_rollout: Callable[..., dict[str, Any]],
    policy: Any,
) -> Callable[..., gr.Blocks]:
    """Return an OpenEnv-compatible ``gradio_builder``.

    ``run_rollout`` and ``policy`` are bound up front so the Gradio handlers
    can call back into the trained-policy + environment without re-importing
    them at module load time (which would create a circular import with
    ``server.app``).
    """

    subjects, info = _participant_choices()
    default_subject = subjects[0] if subjects else "sub-01"

    def _ui_run_rollout(
        subject: str,
        condition: str,
        run_id: str,
        seed: int,
        stimulus_window: int,
    ):
        try:
            rollout = run_rollout(
                seed=int(seed),
                subject_id=subject or None,
                run_id=run_id or None,
                condition=condition or None,
                stimulus_window=int(stimulus_window) if stimulus_window >= 0 else None,
            )
        except Exception as exc:
            err = f"Rollout failed: {type(exc).__name__}: {exc}"
            return (
                err,
                None,
                None,
                None,
                "_(no rollout)_",
                [],
                "{}",
                "Atlas plot unavailable: rollout failed.",
            )

        steps = rollout.get("steps") or []
        status = _status_markdown(rollout)
        r2_fig = _r2_curve_figure(steps)
        net_fig = _network_distribution_figure(steps)
        glass_fig, glass_err = _glass_brain_image(steps)
        stimulus_md = _stimulus_markdown(rollout)
        table_rows = _steps_table(steps)
        raw_json = json.dumps(rollout, indent=2)
        atlas_status = (
            glass_err if glass_err else f"Glass brain rendered for {len(steps)} predicted parcels."
        )
        return (
            status,
            r2_fig,
            net_fig,
            glass_fig,
            stimulus_md,
            table_rows,
            raw_json,
            atlas_status,
        )

    def _suggest_run_for_condition(subject: str, condition: str) -> str:
        if not subject or not condition:
            return ""
        subject_info = info.get(subject, {})
        for run, cond in subject_info.items():
            if cond == condition:
                # Translate "run1" -> "run-1" because the env uses both forms
                # in different code paths; the dash form is what the notebook
                # demos and the verifier all default to.
                if run.startswith("run") and len(run) > 3 and run[3].isdigit():
                    return f"run-{run[3:]}"
                return run
        return ""

    # Required signature for OpenEnv `gradio_builder`:
    #   (web_manager, action_fields, metadata, is_chat_env, title, quick_start_md) -> gr.Blocks
    # We ignore most of those because the prediction tab does not drive the
    # OpenEnv state machine -- it spins up its own env per request.
    def _builder(
        web_manager: Any,
        action_fields: list[Any],
        metadata: Any,
        is_chat_env: bool,
        title: str,
        quick_start_md: str | None,
    ) -> gr.Blocks:
        with gr.Blocks(title="BrainRL prediction demo") as demo:
            gr.Markdown(
                "## BrainRL prediction demo\n\n"
                "Pick a subject + condition and run a 20-step model rollout. "
                "Each step shows which parcel the trained policy predicted, "
                "its cumulative R\u00b2, and where it sits on the brain. "
                "Same call as `POST /rollout`, just visualised."
            )
            with gr.Row():
                with gr.Column(scale=1):
                    subject_dd = gr.Dropdown(
                        choices=subjects or [default_subject],
                        value=default_subject,
                        label="Subject",
                    )
                    condition_dd = gr.Dropdown(
                        choices=CONDITIONS,
                        value="single_m",
                        label="Condition",
                    )
                    run_tb = gr.Textbox(
                        value=_suggest_run_for_condition(default_subject, "single_m") or "run-1",
                        label="Run ID",
                        info="Override if you want a specific run; otherwise defaults to "
                             "the run that matches the condition for this subject.",
                    )
                    seed_sl = gr.Slider(
                        minimum=0, maximum=1024, step=1, value=42, label="Seed",
                    )
                    stim_sl = gr.Slider(
                        minimum=-1,
                        maximum=64,
                        step=1,
                        value=-1,
                        label="Stimulus window (-1 = auto)",
                    )
                    run_btn = gr.Button("Run model prediction", variant="primary")
                    status_md = gr.Markdown(
                        value=("**Model**: not yet queried. Click "
                               "**Run model prediction** to invoke the policy.")
                    )

                with gr.Column(scale=2):
                    with gr.Tabs():
                        with gr.Tab("R\u00b2 curve & rewards"):
                            r2_plot = gr.Plot(label="Predicted R\u00b2 / step reward")
                        with gr.Tab("Brain map"):
                            atlas_status_md = gr.Markdown(
                                value=("Glass-brain map is rendered after the first "
                                       "rollout; the Schaefer atlas is fetched on demand.")
                            )
                            glass_plot = gr.Plot(label="Predicted parcels (glass brain)")
                        with gr.Tab("Network distribution"):
                            net_plot = gr.Plot(label="Selected parcels by Yeo-7 network")
                        with gr.Tab("Stimulus context"):
                            stimulus_md = gr.Markdown(
                                value="_Run a prediction to see the stimulus window._"
                            )
                        with gr.Tab("Per-step predictions"):
                            steps_table = gr.Dataframe(
                                headers=[
                                    "step",
                                    "region_id",
                                    "label",
                                    "network",
                                    "hemi",
                                    "cum_R\u00b2",
                                    "delta_R\u00b2",
                                    "reward",
                                    "fallback",
                                ],
                                value=[],
                                interactive=False,
                                wrap=True,
                            )
                        with gr.Tab("Raw JSON"):
                            raw_json_box = gr.Code(
                                label="Rollout response", language="json", interactive=False,
                            )

            # Auto-suggest a sensible run-id when subject/condition change.
            def _refresh_run(subject: str, condition: str) -> str:
                return _suggest_run_for_condition(subject, condition) or "run-1"

            subject_dd.change(_refresh_run, inputs=[subject_dd, condition_dd], outputs=[run_tb])
            condition_dd.change(_refresh_run, inputs=[subject_dd, condition_dd], outputs=[run_tb])

            run_btn.click(
                fn=_ui_run_rollout,
                inputs=[subject_dd, condition_dd, run_tb, seed_sl, stim_sl],
                outputs=[
                    status_md,
                    r2_plot,
                    net_plot,
                    glass_plot,
                    stimulus_md,
                    steps_table,
                    raw_json_box,
                    atlas_status_md,
                ],
            )

        return demo

    return _builder