from typing import List, Optional

import pandas as pd
from PySide6.QtCore import Qt
from PySide6.QtWidgets import QDialog, QVBoxLayout, QLabel, QTableWidget, QTableWidgetItem, QSizePolicy

try:
    from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as FigureCanvas
except Exception:
    # Fallback for older backends
    from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas  # type: ignore
import matplotlib.pyplot as plt


class TablePreviewDialog(QDialog):
    def __init__(self, title: str, df: pd.DataFrame, parent=None) -> None:
        super().__init__(parent)
        self.setWindowTitle(title or "表格预览")
        layout = QVBoxLayout()
        layout.addWidget(QLabel(title or "表格预览"))

        table = QTableWidget()
        if df is not None and not df.empty:
            columns: List[str] = [str(c) for c in df.columns]
            table.setColumnCount(len(columns))
            table.setHorizontalHeaderLabels(columns)
            table.setRowCount(len(df))
            for r in range(len(df)):
                for c, col in enumerate(columns):
                    val = df.iloc[r][col]
                    table.setItem(r, c, QTableWidgetItem(str(val)))
        else:
            table.setColumnCount(0)
            table.setRowCount(0)
        table.resizeColumnsToContents()
        layout.addWidget(table)
        self.setLayout(layout)
        self.resize(900, 600)


class ChartPreviewDialog(QDialog):
    def __init__(self, title: str, df: pd.DataFrame, fields: Optional[List[str]] = None, chart_type: str = "line", parent=None) -> None:
        super().__init__(parent)
        self.setWindowTitle(title or "图表预览")
        layout = QVBoxLayout()
        layout.addWidget(QLabel(title or "图表预览"))

        fig, ax = plt.subplots(figsize=(8, 4))
        canvas = FigureCanvas(fig)
        canvas.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
        layout.addWidget(canvas)

        # Attempt to plot time series by field
        if df is not None and not df.empty and "_time" in df.columns and "_value" in df.columns:
            plot_fields: List[str] = fields or sorted([str(f) for f in df.get("_field", pd.Series(dtype=str)).unique() if pd.notna(f)])
            if not plot_fields:
                plot_fields = ["_value"]
            for field in plot_fields:
                if "_field" in df.columns:
                    sdf = df[df["_field"] == field]
                else:
                    sdf = df
                if not sdf.empty:
                    ax.plot(pd.to_datetime(sdf["_time"]), pd.to_numeric(sdf["_value"], errors="coerce"), label=str(field))
            ax.set_xlabel("Time")
            ax.set_ylabel("Value")
            ax.grid(True, alpha=0.3)
            ax.legend(loc="best")
        else:
            ax.text(0.5, 0.5, "无可绘制的数据", ha="center", va="center", transform=ax.transAxes)

        canvas.draw()
        self.setLayout(layout)
        self.resize(900, 600)