"""Visualise system identification results — real vs simulated trajectories.

Loads a recording and runs simulation with both the original and tuned
parameters, then plots a 4-panel comparison (motor angle, motor vel,
pendulum angle, pendulum vel) over time.

Usage:
    python -m src.sysid.visualize \
        --robot-path assets/rotary_cartpole \
        --recording assets/rotary_cartpole/recordings/capture_20260311_120000.npz

    # Also compare with tuned parameters:
    python -m src.sysid.visualize \
        --robot-path assets/rotary_cartpole \
        --recording <file>.npz \
        --result assets/rotary_cartpole/sysid_result.json
"""

from __future__ import annotations

import argparse
import json
from pathlib import Path

import numpy as np
import structlog

log = structlog.get_logger()


def _run_sim(
    robot_path: Path,
    params: dict[str, float],
    recording: dict[str, np.ndarray],
    window_duration: float,
    sim_dt: float,
    substeps: int,
) -> dict[str, np.ndarray]:
    """Run windowed or open-loop rollout depending on window_duration."""
    from src.sysid.rollout import rollout, windowed_rollout

    if window_duration > 0:
        return windowed_rollout(
            robot_path=robot_path, params=params, recording=recording,
            window_duration=window_duration, sim_dt=sim_dt,
            substeps=substeps,
        )
    return rollout(
        robot_path=robot_path, params=params, actions=recording["action"],
        substeps=substeps,
    )


def visualize(
    robot_path: str | Path,
    recording_path: str | Path,
    result_path: str | Path | None = None,
    sim_dt: float = 0.002,
    substeps: int = 10,
    window_duration: float = 0.5,
    save_path: str | Path | None = None,
    show: bool = True,
) -> None:
    """Generate comparison plot."""
    import matplotlib.pyplot as plt

    from src.sysid.rollout import (
        ROTARY_CARTPOLE_PARAMS,
        defaults_vector,
        params_to_dict,
    )

    robot_path = Path(robot_path).resolve()
    recording = dict(np.load(recording_path))

    sim_kwargs = dict(
        robot_path=robot_path, recording=recording,
        window_duration=window_duration, sim_dt=sim_dt,
        substeps=substeps,
    )

    t = recording["time"]
    actions = recording["action"]

    # ── Simulate with default parameters ─────────────────────────
    default_params = params_to_dict(
        defaults_vector(ROTARY_CARTPOLE_PARAMS), ROTARY_CARTPOLE_PARAMS
    )
    log.info("simulating_default_params", windowed=window_duration > 0)
    sim_default = _run_sim(params=default_params, **sim_kwargs)

    # ── Simulate with tuned parameters (if available) ────────────
    # Resolve result path (explicit or auto-detect).
    if result_path is None:
        auto = robot_path / "sysid_result.json"
        if auto.exists():
            result_path = auto

    sim_tuned = None
    tuned_cost = None
    if result_path is not None:
        result_path = Path(result_path)
        if result_path.exists():
            result = json.loads(result_path.read_text())
            tuned_params = result.get("best_params", {})
            tuned_cost = result.get("best_cost")
            log.info("simulating_tuned_params", cost=tuned_cost)
            sim_tuned = _run_sim(params=tuned_params, **sim_kwargs)
        else:
            log.warning("result_file_not_found", path=str(result_path))

    # ── Plot ─────────────────────────────────────────────────────
    fig, axes = plt.subplots(5, 1, figsize=(14, 12), sharex=True)

    channels = [
        ("motor_angle", "Motor Angle (rad)"),
        ("motor_vel", "Motor Velocity (rad/s)"),
        ("pendulum_angle", "Pendulum Angle (rad)"),
        ("pendulum_vel", "Pendulum Velocity (rad/s)"),
    ]

    for ax, (key, ylabel) in zip(axes[:4], channels):
        real = recording[key]

        ax.plot(t, real, "k-", linewidth=1.2, alpha=0.8, label="Real")
        ax.plot(
            t,
            sim_default[key],
            "--",
            color="#d62728",
            linewidth=1.0,
            alpha=0.7,
            label="Sim (original)",
        )
        if sim_tuned is not None:
            ax.plot(
                t,
                sim_tuned[key],
                "--",
                color="#2ca02c",
                linewidth=1.0,
                alpha=0.7,
                label="Sim (tuned)",
            )

        ax.set_ylabel(ylabel)
        ax.legend(loc="upper right", fontsize=8)
        ax.grid(True, alpha=0.3)

    # Action plot (bottom panel).
    axes[4].plot(t, actions, "b-", linewidth=0.8, alpha=0.6)
    axes[4].set_ylabel("Action (norm)")
    axes[4].set_xlabel("Time (s)")
    axes[4].grid(True, alpha=0.3)
    axes[4].set_ylim(-1.1, 1.1)

    # Title with cost info.
    title = "System Identification — Real vs Simulated Trajectories"
    if tuned_cost is not None:
        # Compute original cost for comparison.
        from src.sysid.optimize import cost_function

        orig_cost = cost_function(
            defaults_vector(ROTARY_CARTPOLE_PARAMS),
            recording,
            robot_path,
            ROTARY_CARTPOLE_PARAMS,
            sim_dt=sim_dt,
            substeps=substeps,
            window_duration=window_duration,
        )
        title += f"\nOriginal cost: {orig_cost:.4f}  →  Tuned cost: {tuned_cost:.4f}"
        improvement = (1.0 - tuned_cost / orig_cost) * 100 if orig_cost > 0 else 0
        title += f"  ({improvement:+.1f}%)"

    fig.suptitle(title, fontsize=12)
    plt.tight_layout()

    if save_path:
        save_path = Path(save_path)
        fig.savefig(str(save_path), dpi=150, bbox_inches="tight")
        log.info("figure_saved", path=str(save_path))

    if show:
        plt.show()
    else:
        plt.close(fig)


# ── CLI entry point ──────────────────────────────────────────────────


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Visualise system identification results."
    )
    parser.add_argument(
        "--robot-path",
        type=str,
        default="assets/rotary_cartpole",
    )
    parser.add_argument(
        "--recording",
        type=str,
        required=True,
        help="Path to .npz recording file",
    )
    parser.add_argument(
        "--result",
        type=str,
        default=None,
        help="Path to sysid_result.json (auto-detected if omitted)",
    )
    parser.add_argument("--sim-dt", type=float, default=0.002)
    parser.add_argument("--substeps", type=int, default=10)
    parser.add_argument(
        "--window-duration",
        type=float,
        default=0.5,
        help="Shooting window length in seconds (0 = open-loop)",
    )
    parser.add_argument(
        "--save",
        type=str,
        default=None,
        help="Save figure to this path (PNG, PDF, …)",
    )
    parser.add_argument(
        "--no-show",
        action="store_true",
        help="Don't show interactive window (useful for CI)",
    )
    args = parser.parse_args()

    visualize(
        robot_path=args.robot_path,
        recording_path=args.recording,
        result_path=args.result,
        sim_dt=args.sim_dt,
        substeps=args.substeps,
        window_duration=args.window_duration,
        save_path=args.save,
        show=not args.no_show,
    )


if __name__ == "__main__":
    main()