import io
import base64
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import pandas as pd


def render_group_charts(groups: list, y_min: float, y_max: float) -> list:
    padding_fraction = 0.05
    y_range = y_max - y_min
    if y_range == 0:
        y_pad = 1.0
    else:
        y_pad = y_range * padding_fraction

    charts = []
    for i, g in enumerate(groups):
        fig, ax = plt.subplots(figsize=(9, 4))

        x = g["time"]
        y = g["speed"]

        ax.plot(x, y, marker="o", linewidth=1.5, markersize=5, color="#1f77b4")

        ax.set_ylim(y_min - y_pad, y_max + y_pad)

        ax.xaxis.set_major_formatter(mdates.DateFormatter("%H:%M:%S"))
        fig.autofmt_xdate(rotation=30)

        ax.set_title(f"Group {i + 1}  —  {len(g)} shot(s)")
        ax.set_xlabel("Time of Day")
        ax.set_ylabel("Speed")
        ax.grid(True, alpha=0.3)
        fig.tight_layout()

        buf = io.BytesIO()
        fig.savefig(buf, format="png", dpi=100)
        plt.close(fig)
        buf.seek(0)
        charts.append(base64.b64encode(buf.read()).decode("utf-8"))

    return charts


def render_overview_chart(group_stats: list) -> str:
    """Dual-axis line chart: avg speed and avg std dev per group."""
    indices = [s["group_index"] for s in group_stats]
    speeds  = [s["mean_speed"] for s in group_stats]
    stds    = [s["std_speed"] if s["std_speed"] is not None else 0.0 for s in group_stats]

    fig, ax1 = plt.subplots(figsize=(7, 3))

    color_speed = "#1f77b4"
    color_std   = "#d62728"

    ax1.plot(indices, speeds, marker="o", linewidth=1.8, markersize=5,
             color=color_speed, label="Avg speed")
    ax1.set_xlabel("Group")
    ax1.set_ylabel("Avg speed", color=color_speed)
    ax1.tick_params(axis="y", labelcolor=color_speed)
    ax1.set_xticks(indices)

    ax2 = ax1.twinx()
    ax2.plot(indices, stds, marker="s", linewidth=1.8, markersize=5,
             color=color_std, linestyle="--", label="Avg std dev")
    ax2.set_ylabel("Avg std dev", color=color_std)
    ax2.tick_params(axis="y", labelcolor=color_std)

    lines1, labels1 = ax1.get_legend_handles_labels()
    lines2, labels2 = ax2.get_legend_handles_labels()
    ax1.legend(lines1 + lines2, labels1 + labels2, fontsize=8, loc="upper right")

    ax1.grid(True, alpha=0.3)
    fig.tight_layout()

    buf = io.BytesIO()
    fig.savefig(buf, format="png", dpi=100)
    plt.close(fig)
    buf.seek(0)
    return base64.b64encode(buf.read()).decode("utf-8")