"""
plot_wave.py
============
波形与能量动态图：读取 display.txt，绘制原子位移波形
（纵波 + 2 个横波）和系统能量/输入功率随时间变化的二维动画。

用法：
    python plot_wave.py                          # 使用 dynamics 根目录下 output/
    python plot_wave.py examples/case05/output    # 指定案例输出目录
"""

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import os
import sys
import json

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import compute


def load_disp_data(output_dir):
    """加载 display.npz（优先）或 display.txt。"""
    npz_path = os.path.join(output_dir, "display.npz")
    txt_path = os.path.join(output_dir, "display.txt")
    if os.path.exists(npz_path):
        return compute.load_display_npz(npz_path)
    if os.path.exists(txt_path):
        return compute.load_display_txt(txt_path)
    raise FileNotFoundError(f"找不到 display.npz 或 display.txt in {output_dir}")


def _header_json(header_fields, key, default):
    raw = header_fields.get(key, "")
    if not raw:
        return default
    try:
        return json.loads(raw)
    except json.JSONDecodeError:
        return default


def _load_wave_dataset(output_dir):
    """Load wave/energy plotting data from display metadata or sibling input files."""
    disp_data = load_disp_data(output_dir)
    header = disp_data["header_fields"]

    x = disp_data["frames_x"]
    y = disp_data["frames_y"]
    z = disp_data["frames_z"]
    vx = disp_data["frames_vx"]
    vy = disp_data["frames_vy"]
    vz = disp_data["frames_vz"]
    atom_ids = np.array(disp_data["atom_ids"], dtype=np.int64)
    n_frames = x.shape[0]
    dt = float(header.get("DT", 0.001))
    nstep = int(header.get("NSTEP", 1))
    t = np.arange(n_frames, dtype=np.float64) * dt * nstep

    masses = np.array(_header_json(header, "atom_masses", []), dtype=np.float64)
    pos_0 = np.array(_header_json(header, "atom_positions", []), dtype=np.float64)
    bond_pairs = np.array(_header_json(header, "bond_pairs", []), dtype=np.int64)
    bond_stiffness = np.array(_header_json(header, "bond_stiffness", []), dtype=np.float64)
    bond_rest_lengths = np.array(_header_json(header, "bond_rest_lengths", []), dtype=np.float64)
    gravity_vec = _header_json(header, "G", [0.0, 0.0, 0.0])

    # Backward-compatible fallback for older display.txt outputs.
    if masses.size == 0 or pos_0.size == 0:
        input_dir = os.path.join(os.path.dirname(output_dir), "input")
        coord_path = os.path.join(input_dir, "coord.txt")
        if os.path.exists(coord_path):
            (_, masses_fb, _, positions_fb, _, _) = compute.load_coord_file(coord_path)
            masses = np.array(masses_fb, dtype=np.float64)
            pos_0 = np.array(positions_fb, dtype=np.float64)
        else:
            raise ValueError("display.txt 缺少 atom_masses/atom_positions 元数据，且未找到 input/coord.txt")

    if bond_pairs.size == 0:
        input_dir = os.path.join(os.path.dirname(output_dir), "input")
        connection_path = os.path.join(input_dir, "connection.txt")
        bond_path = os.path.join(input_dir, "bond.txt")
        if os.path.exists(connection_path) and os.path.exists(bond_path):
            bond_map = compute.load_bond_parameters(bond_path)
            pairs_fb, _, stiffness_fb, rest_lengths_fb = compute.load_bond_connections(
                connection_path, atom_ids, pos_0, bond_map)
            bond_pairs = np.array(pairs_fb, dtype=np.int64)
            bond_stiffness = np.array(stiffness_fb, dtype=np.float64)
            bond_rest_lengths = np.array(rest_lengths_fb, dtype=np.float64)

    return {
        "n_frames": n_frames,
        "t": t,
        "x": x,
        "y": y,
        "z": z,
        "vx": vx,
        "vy": vy,
        "vz": vz,
        "pos_0": pos_0,
        "masses": masses,
        "atom_ids": atom_ids,
        "bond_pairs": bond_pairs,
        "bond_stiffness": bond_stiffness,
        "bond_rest_lengths": bond_rest_lengths,
        "gravity_field": int(header.get("gravity_field", 0)),
        "gravity_interaction": int(header.get("gravity_interaction", 0)),
        "gravity_strength": float(header.get("gravity_strength", 1.0)),
        "G": gravity_vec,
        "driving_force": int(header.get("driving_force", 0)),
    }


def compute_energy(x, y, z, vx, vy, vz, masses, mass_arr,
                   bond_pairs, bond_stiffness, bond_rest_lengths,
                   gravity_field, G, gravity_interaction, gravity_strength):
    """计算系统各能量分量。

    Returns:
        ek_sys:  系统动能 (n_frames,)
        us_sys:  系统弹性势能 (n_frames,)
        ug_sys:  系统重力势能 (n_frames,)
        ugr_sys: 系统万有引力势能 (n_frames,)
    """
    n_frames = x.shape[0]
    masses_2d = masses[np.newaxis, :]  # (1, n_atoms)

    # 动能 Ek = ½ m v²
    ek = 0.5 * masses_2d * (vx**2 + vy**2 + vz**2)
    ek_sys = np.sum(ek, axis=1)

    # 弹性势能 Us = ½ k (d - d₀)²
    us_sys = np.zeros(n_frames)
    if bond_pairs is not None and len(bond_pairs) > 0:
        for b_idx in range(len(bond_pairs)):
            i, j = bond_pairs[b_idx]
            dx = x[:, j] - x[:, i]
            dy = y[:, j] - y[:, i]
            dz = z[:, j] - z[:, i]
            dist = np.sqrt(dx**2 + dy**2 + dz**2)
            stretch = dist - bond_rest_lengths[b_idx]
            us_sys += 0.5 * bond_stiffness[b_idx] * stretch**2

    # 均匀重力场势能 Ug = -m G·r
    ug_sys = np.zeros(n_frames)
    if gravity_field:
        G_vec = np.array(G)
        ug_sys = -masses_2d * (G_vec[0] * x + G_vec[1] * y + G_vec[2] * z)
        ug_sys = np.sum(ug_sys, axis=1)

    # 万有引力势能 Ug_grav = -G_grav Σ m_i m_j / r
    ugr_sys = np.zeros(n_frames)
    if gravity_interaction:
        n_atoms = len(masses)
        # 为避免巨大计算量，仅当原子数较少时计算
        if n_atoms <= 200:
            for i in range(n_atoms):
                for j in range(i + 1, n_atoms):
                    dx = x[:, j] - x[:, i]
                    dy = y[:, j] - y[:, i]
                    dz = z[:, j] - z[:, i]
                    dist = np.sqrt(dx**2 + dy**2 + dz**2)
                    dist = np.maximum(dist, 1e-12)
                    pair_pe = -gravity_strength * masses[i] * masses[j] / dist
                    ugr_sys += pair_pe

    return ek_sys, us_sys, ug_sys, ugr_sys


def plot_wave(output_dir, save_gif=False, save_mp4=False):
    """主绘图函数：读取 display.txt 并生成波形+能量动画。

    Args:
        output_dir: 输出目录（含 display.txt）
        save_gif:   是否保存 GIF
        save_mp4:   是否保存 MP4
    """
    data = _load_wave_dataset(output_dir)

    n_frames = int(data["n_frames"])
    t = np.array(data["t"])

    # 位置 / 速度
    x = np.array(data["x"])
    y = np.array(data["y"])
    z = np.array(data["z"])
    vx = np.array(data["vx"])
    vy = np.array(data["vy"])
    vz = np.array(data["vz"])

    # 原子信息
    pos_0 = np.array(data["pos_0"])
    masses = np.array(data["masses"])
    atom_ids = np.array(data["atom_ids"])
    n_atoms = len(atom_ids)

    # 成键
    bond_pairs = np.array(data.get("bond_pairs", []), dtype=np.int64)
    bond_stiffness = np.array(data.get("bond_stiffness", []), dtype=np.float64)
    bond_rest_lengths = np.array(data.get("bond_rest_lengths", []), dtype=np.float64)

    # 物理开关
    gravity_field = int(data.get("gravity_field", 0))
    gravity_interaction = int(data.get("gravity_interaction", 0))
    G = data.get("G", [0, 0, 0])
    gravity_strength = float(data.get("gravity_strength", 1.0))
    driving_force = int(data.get("driving_force", 0))

    # ── 位移（偏离初始平衡位形）──
    dx = x - pos_0[np.newaxis, :, 0]   # 纵波（沿链方向 x）
    dy = y - pos_0[np.newaxis, :, 1]   # 横波 1（y 方向）
    dz = z - pos_0[np.newaxis, :, 2]   # 横波 2（z 方向）

    # ── 能量 ──
    ek, us, ug, ugr = compute_energy(
        x, y, z, vx, vy, vz, masses, masses,
        bond_pairs, bond_stiffness, bond_rest_lengths,
        gravity_field, G, gravity_interaction, gravity_strength)
    e_total = ek + us + ug + ugr
    power = np.gradient(e_total, t)  # 输入功率 = dE/dt

    # ── 波形纵轴范围（全局统一，避免抖动）──
    def get_ylim(disp_data):
        vmax = np.max(np.abs(disp_data))
        if vmax < 1e-10:
            return -1.0, 1.0
        margin = vmax * 0.2
        return -vmax - margin, vmax + margin

    ylims = [get_ylim(dx), get_ylim(dy), get_ylim(dz)]
    e_max = max(np.max(e_total), 0.01) * 1.3
    p_abs = np.max(np.abs(power))
    p_max = max(p_abs * 1.3, 0.01)

    atom_idx = np.arange(n_atoms)

    # ── 图形设置 ──
    plt.rcParams['font.sans-serif'] = ['Microsoft YaHei', 'SimHei', 'DejaVu Sans']
    plt.rcParams['axes.unicode_minus'] = False

    fig, axes = plt.subplots(2, 2, figsize=(14, 10))
    fig.suptitle("波形与能量分析", fontsize=16)

    # ── 3 个波形子图 ──
    titles = [
        "纵波 (x 方向位移)",
        "横波 (y 方向位移)",
        "横波 (z 方向位移)",
    ]
    colors = ["#2563eb", "#ea580c", "#16a34a"]
    wave_configs = list(zip(
        [axes[0, 0], axes[0, 1], axes[1, 0]],
        [dx, dy, dz], titles, colors, ylims
    ))

    wave_lines = []
    time_texts = []
    for ax, disp, title, color, yl in wave_configs:
        ax.set_xlim(0, n_atoms - 1)
        ax.set_ylim(yl)
        ax.set_xlabel("原子序号")
        ax.set_ylabel("位移")
        ax.set_title(title)
        ax.grid(True, alpha=0.3)
        line, = ax.plot([], [], color=color, linewidth=1.5)
        wave_lines.append(line)
        tt = ax.text(0.02, 0.95, "", transform=ax.transAxes,
                     fontsize=11, verticalalignment="top")
        time_texts.append(tt)

    # ── 能量+功率子图 ──
    ax_ep = axes[1, 1]
    ax_ep.set_xlim(t[0], t[-1])
    ep_ylow = min(-0.1 * max(e_max, p_max), -p_max * 0.1)
    ep_yhigh = max(e_max, p_max)
    ax_ep.set_ylim(ep_ylow, ep_yhigh)
    ax_ep.set_xlabel("时间 (s)")
    ax_ep.set_ylabel("能量 / 功率")
    ax_ep.set_title("系统能量与输入功率")
    ax_ep.grid(True, alpha=0.3)

    line_ek, = ax_ep.plot([], [], "b-",  lw=1.5, label="动能")
    line_us, = ax_ep.plot([], [], "orange", lw=1.5, label="弹性势能")
    line_et, = ax_ep.plot([], [], "r--", lw=1.5, label="总能量")
    line_pw, = ax_ep.plot([], [], "g-",  lw=1.5, alpha=0.7, label="输入功率 (dE/dt)")
    if gravity_field:
        line_ug, = ax_ep.plot([], [], "purple", lw=1.0, alpha=0.5, label="重力势能")
    else:
        line_ug = None
    if gravity_interaction and n_atoms <= 200:
        line_ugr, = ax_ep.plot([], [], "brown", lw=1.0, alpha=0.5, label="万有引力势能")
    else:
        line_ugr = None

    ax_ep.legend(loc="upper right", fontsize=9)

    plt.tight_layout(rect=[0, 0, 1, 0.95])

    # ── 动画更新 ──
    def update(frame):
        # 波形
        for i in range(3):
            wave_lines[i].set_data(atom_idx, [dx, dy, dz][i][frame])
            time_texts[i].set_text(f"t = {t[frame]:.2f} s  |  帧 {frame+1}/{n_frames}")

        # 能量（累计到当前帧）
        cur_t = t[:frame + 1]
        line_ek.set_data(cur_t, ek[:frame + 1])
        line_us.set_data(cur_t, us[:frame + 1])
        line_et.set_data(cur_t, e_total[:frame + 1])
        line_pw.set_data(cur_t, power[:frame + 1])
        if line_ug:
            line_ug.set_data(cur_t, ug[:frame + 1])
        if line_ugr:
            line_ugr.set_data(cur_t, ugr[:frame + 1])

        # 能量图 x 轴动态扩展
        ax_ep.set_xlim(t[0], max(t[frame] + max(t[-1] * 0.05, 1), t[-1]))

        artists = wave_lines + time_texts + [line_ek, line_us, line_et, line_pw]
        if line_ug:  artists.append(line_ug)
        if line_ugr: artists.append(line_ugr)
        return artists

    ani = FuncAnimation(fig, update, frames=n_frames, interval=50, blit=True)

    # ── 输出 GIF ──
    if save_gif:
        gif_path = os.path.join(output_dir, "wave_animation.gif")
        ani.save(gif_path, writer="pillow", fps=min(20, max(1, n_frames // 5)))
        print(f"[plot_wave] GIF 已保存: {gif_path}")

    # ── 输出 MP4（需要 ffmpeg）──
    gif_path = None
    if save_gif:
        gif_path = os.path.join(output_dir, "wave_animation.gif")
    if save_mp4:
        try:
            import matplotlib.animation as manim
            import matplotlib.pyplot as _plt

            # 尝试通过 imageio_ffmpeg 定位 ffmpeg
            ffmpeg_path = None
            try:
                import imageio_ffmpeg
                ffmpeg_path = imageio_ffmpeg.get_ffmpeg_exe()
            except Exception:
                pass
            if ffmpeg_path and os.path.exists(ffmpeg_path):
                _plt.rcParams['animation.ffmpeg_path'] = ffmpeg_path

            ffps = min(20, max(1, n_frames // 5))
            writer = manim.FFMpegWriter(fps=ffps, codec="libx264",
                                         extra_args=["-pix_fmt", "yuv420p"])
            mp4_path = os.path.join(output_dir, "wave_animation.mp4")
            ani.save(mp4_path, writer=writer)
            print(f"[plot_wave] MP4 已保存: {mp4_path}")
        except FileNotFoundError:
            print("[plot_wave] 警告: 未找到 ffmpeg，跳过 MP4 输出")
        except Exception as e:
            print(f"[plot_wave] 警告: MP4 输出失败 ({e})，跳过")

    # ── 最后显示动画窗口 ──
    plt.show()
    return gif_path


if __name__ == "__main__":
    script_dir = os.path.dirname(os.path.abspath(__file__))
    if len(sys.argv) > 1:
        output_dir = os.path.abspath(sys.argv[1])
    else:
        output_dir = compute.get_output_dir(script_dir)
    plot_wave(output_dir)