from __future__ import annotations

from pathlib import Path

import matplotlib
import numpy as np

matplotlib.use("Agg")
import matplotlib.pyplot as plt

FIG_SIZE_IN = 4.2
MAX_ENERGY_SUBPLOTS = 6
AXIS_LABEL_FONT_SIZE = 8
TICK_LABEL_FONT_SIZE = 8
INPLOT_LABEL_FONT_SIZE = 10


def _to_hourly_zone(values: np.ndarray) -> np.ndarray:
    arr = np.asarray(values)
    if arr.ndim != 2:
        raise ValueError(f"Expected 2D energy matrix, got shape={arr.shape}")

    if arr.shape[0] == 8760:
        return np.asarray(arr, dtype=float)
    if arr.shape[1] == 8760:
        return np.asarray(arr.T, dtype=float)

    raise ValueError(f"Neither axis is 8760 for energy matrix: shape={arr.shape}")


def _decode_zone_names(columns_arr: np.ndarray | None, zone_count: int) -> list[str]:
    if columns_arr is None:
        return [f"zone_{i}" for i in range(zone_count)]

    cols = np.asarray(columns_arr).reshape(-1)
    names = [str(c, "utf-8") if isinstance(c, (bytes, np.bytes_)) else str(c) for c in cols]
    if len(names) < zone_count:
        names.extend([f"zone_{i}" for i in range(len(names), zone_count)])
    return names[:zone_count]


def _time_window(hourly_zone: np.ndarray, start_hour: int, window_hours: int) -> tuple[np.ndarray, int, int]:
    total = int(hourly_zone.shape[0])
    if total < 1:
        raise ValueError("No hourly energy records found")

    start_idx = max(0, min(total - 1, int(start_hour) - 1))
    window = max(1, int(window_hours))
    end_idx = min(total, start_idx + window)
    if end_idx <= start_idx:
        raise ValueError(f"Invalid energy window: start={start_hour}, hours={window_hours}")

    return hourly_zone[start_idx:end_idx, :], start_idx + 1, end_idx


def _major_ticks(length: int) -> list[int]:
    if length <= 8:
        return list(range(1, length + 1))

    tick_count = 6
    ticks = np.linspace(1, length, num=tick_count, dtype=int)
    uniq = sorted(set(int(t) for t in ticks))
    if uniq[-1] != length:
        uniq.append(length)
    return uniq


def visualize_energy(
    energy_npz: str | Path,
    output_png: str | Path,
    *,
    max_zones: int | None = None,
    zone_index: int | None = None,
    start_hour: int = 1,
    window_hours: int = 24,
    dpi: int = 220,
) -> Path:
    """Plot energy curves in compressed square layout with shared x-axis for a selected time window."""
    energy_npz = Path(energy_npz)
    output_png = Path(output_png)

    with np.load(energy_npz, allow_pickle=True) as data:
        if "values" not in data:
            keys = ", ".join(sorted(data.files))
            raise KeyError(f"Missing key 'values' in {energy_npz}; keys=[{keys}]")
        values = np.asarray(data["values"], dtype=float)
        columns = np.asarray(data["columns"], dtype=object) if "columns" in data else None

    hourly_zone = _to_hourly_zone(values)
    window, window_start, window_end = _time_window(hourly_zone, start_hour=start_hour, window_hours=window_hours)
    zone_count = window.shape[1]
    if zone_count < 1:
        raise ValueError(f"No zones found in {energy_npz}")

    names = _decode_zone_names(columns, zone_count)

    zone_indices = list(range(zone_count))
    if zone_index is not None:
        zi = int(zone_index)
        if zi < 0 or zi >= zone_count:
            raise ValueError(f"zone_index out of range: {zi}, valid=[0, {zone_count - 1}]")
        zone_indices = [zi]
    elif max_zones is not None and max_zones > 0:
        zone_indices = zone_indices[: max_zones]

    if len(zone_indices) < 1:
        raise ValueError("No zones selected for plotting")

    plotted_zone_indices = zone_indices[:MAX_ENERGY_SUBPLOTS]
    omitted_count = len(zone_indices) - len(plotted_zone_indices)

    cmap = plt.get_cmap("tab20")
    x = np.arange(1, window.shape[0] + 1, dtype=int)
    major_ticks = _major_ticks(window.shape[0])

    row_count = len(plotted_zone_indices)
    fig, axes = plt.subplots(
        row_count,
        1,
        figsize=(FIG_SIZE_IN, FIG_SIZE_IN),
        sharex=True,
        gridspec_kw={"hspace": 0.0},
    )
    if row_count == 1:
        axes = [axes]

    for row_idx, zone_idx in enumerate(plotted_zone_indices):
        ax = axes[row_idx]
        color = cmap(row_idx % 20)
        ax.plot(x, window[:, zone_idx], color=color, linewidth=0.9, alpha=0.9)
        ax.set_ylabel("")
        ax.text(
            0.02,
            0.86,
            names[zone_idx],
            transform=ax.transAxes,
            ha="left",
            va="top",
            rotation=0,
            fontsize=INPLOT_LABEL_FONT_SIZE,
            bbox={"facecolor": "white", "alpha": 0.65, "edgecolor": "none", "pad": 1.5},
        )
        ax.set_xticks(major_ticks)
        ax.grid(axis="y", alpha=0.25, linewidth=0.5)
        ax.grid(axis="x", alpha=0.22, linewidth=0.45)
        ax.tick_params(axis="both", which="both", labelsize=TICK_LABEL_FONT_SIZE)
        if row_idx < row_count - 1:
            ax.tick_params(axis="x", which="both", labelbottom=False)

    if omitted_count > 0:
        axes[-1].text(
            0.98,
            0.86,
            f"... (+{omitted_count})",
            transform=axes[-1].transAxes,
            ha="right",
            va="top",
            fontsize=INPLOT_LABEL_FONT_SIZE,
            bbox={"facecolor": "white", "alpha": 0.65, "edgecolor": "none", "pad": 1.5},
        )

    axes[-1].set_xlabel(f"hour index in window ({window_start}-{window_end})", fontsize=AXIS_LABEL_FONT_SIZE)
    axes[-1].set_xlim(1, window.shape[0] + 0.5)
    axes[-1].set_xticks(major_ticks)
    axes[-1].set_xticklabels([str(t) for t in major_ticks], fontsize=TICK_LABEL_FONT_SIZE)
    fig.subplots_adjust(left=0.18, right=0.94, bottom=0.14, top=0.98, hspace=0.0)

    output_png.parent.mkdir(parents=True, exist_ok=True)
    fig.savefig(output_png, dpi=dpi)
    plt.close(fig)
    return output_png