"""
Chart generation for forecast visualization
"""

import plotly.graph_objs as go
from plotly.subplots import make_subplots
import pandas as pd
from typing import List
from config.constants import COLORS, CHART_CONFIG


def create_forecast_chart(
    historical_data: pd.DataFrame,
    forecast_data: pd.DataFrame,
    confidence_levels: List[int],
    title: str = "Time Series Forecast",
    y_axis_label: str = "Value",
    backtest_data: pd.DataFrame = None
) -> go.Figure:
    """
    Create an interactive forecast chart with confidence intervals

    Args:
        historical_data: DataFrame with columns ['ds', 'y']
        forecast_data: DataFrame with forecast and confidence intervals
        confidence_levels: List of confidence levels to plot
        title: Chart title
        y_axis_label: Label for y-axis (variable name being forecasted)
        backtest_data: Optional DataFrame with backtest results

    Returns:
        Plotly figure
    """
    fig = go.Figure()

    # Add historical data
    fig.add_trace(go.Scatter(
        x=historical_data['ds'],
        y=historical_data['y'],
        mode='lines',
        name='Historical',
        line=dict(color=COLORS['historical'], width=2),
        hovertemplate=f'<b>Date:</b> %{{x}}<br><b>{y_axis_label}:</b> %{{y:.2f}}<extra></extra>'
    ))

    # Add backtest data if provided (shows model performance on historical data)
    if backtest_data is not None and len(backtest_data) > 0:
        # Add actual values from backtest period
        fig.add_trace(go.Scatter(
            x=backtest_data['timestamp'],
            y=backtest_data['actual'],
            mode='lines',
            name='Backtest Actual',
            line=dict(color='rgba(100, 100, 100, 0.6)', width=2, dash='dot'),
            hovertemplate=f'<b>Date:</b> %{{x}}<br><b>{y_axis_label} (Actual):</b> %{{y:.2f}}<extra></extra>'
        ))

        # Add predicted values from backtest period
        fig.add_trace(go.Scatter(
            x=backtest_data['timestamp'],
            y=backtest_data['predicted'],
            mode='lines',
            name='Backtest Predicted',
            line=dict(color='rgba(255, 100, 100, 0.8)', width=2),
            hovertemplate=f'<b>Date:</b> %{{x}}<br><b>{y_axis_label} (Predicted):</b> %{{y:.2f}}<extra></extra>'
        ))

    # Add confidence bands (from widest to narrowest)
    for cl in sorted(confidence_levels, reverse=True):
        lower_col = f'lower_{cl}'
        upper_col = f'upper_{cl}'

        if lower_col in forecast_data.columns and upper_col in forecast_data.columns:
            # Add filled area for confidence interval
            fig.add_trace(go.Scatter(
                x=forecast_data['ds'].tolist() + forecast_data['ds'].tolist()[::-1],
                y=forecast_data[upper_col].tolist() + forecast_data[lower_col].tolist()[::-1],
                fill='toself',
                fillcolor=COLORS['confidence'][cl],
                line=dict(width=0),
                name=f'{cl}% Confidence',
                showlegend=True,
                hoverinfo='skip'
            ))

    # Add forecast line
    fig.add_trace(go.Scatter(
        x=forecast_data['ds'],
        y=forecast_data['forecast'],
        mode='lines',
        name='Forecast',
        line=dict(color=COLORS['forecast'], width=2),
        hovertemplate=f'<b>Date:</b> %{{x}}<br><b>{y_axis_label} (Forecast):</b> %{{y:.2f}}<extra></extra>'
    ))

    # Add vertical separator line
    if len(historical_data) > 0:
        last_historical_date = historical_data['ds'].iloc[-1]
        # Use add_shape instead of add_vline to avoid Timestamp arithmetic issues
        fig.add_shape(
            type="line",
            x0=last_historical_date,
            x1=last_historical_date,
            y0=0,
            y1=1,
            yref="paper",
            line=dict(color=COLORS['separator'], dash="dash", width=1)
        )
        # Add annotation
        fig.add_annotation(
            x=last_historical_date,
            y=1.0,
            yref="paper",
            text="Forecast Start",
            showarrow=False,
            yanchor="bottom"
        )

    # Update layout
    fig.update_layout(
        title=dict(text=title, x=0.5, xanchor='center'),
        xaxis_title="Date",
        yaxis_title=y_axis_label,
        hovermode='x unified',
        template='plotly_white',
        height=700,  # Increased height to accommodate rangeslider
        showlegend=True,
        legend=dict(
            orientation="h",
            yanchor="bottom",
            y=1.02,
            xanchor="right",
            x=1
        ),
        margin=dict(l=50, r=50, t=80, b=150),  # Increased bottom margin for larger rangeslider
        xaxis=dict(
            rangeslider=dict(
                visible=True,
                thickness=0.12  # Wider slider (12% of chart height)
            ),
            type='date'
        )
    )

    # Update config
    fig.update_layout(
        modebar_add=['v1hovermode', 'toggleSpikelines']
    )

    return fig


def create_empty_chart(message: str = "No data available") -> go.Figure:
    """
    Create an empty placeholder chart

    Args:
        message: Message to display

    Returns:
        Plotly figure
    """
    fig = go.Figure()

    fig.add_annotation(
        text=message,
        xref="paper",
        yref="paper",
        x=0.5,
        y=0.5,
        showarrow=False,
        font=dict(size=20, color='gray')
    )

    fig.update_layout(
        template='plotly_white',
        height=600,
        xaxis=dict(visible=False),
        yaxis=dict(visible=False)
    )

    return fig


def create_metrics_display(metrics: dict, inference_time: float = None) -> list:
    """
    Create metrics display components

    Args:
        metrics: Dictionary of metric values
        inference_time: Time taken for inference in seconds

    Returns:
        List of Dash components
    """
    import dash_bootstrap_components as dbc
    from dash import html

    metric_cards = []

    # Add inference time if available
    if inference_time is not None:
        metric_cards.append(
            dbc.Col([
                dbc.Card([
                    dbc.CardBody([
                        html.H6("Inference Time", className="text-muted mb-2"),
                        html.H4(f"{inference_time:.2f}s")
                    ])
                ], className="text-center")
            ], md=2)
        )

    # Add other metrics
    metric_names = {
        'MAE': 'Mean Absolute Error',
        'RMSE': 'Root Mean Squared Error',
        'MAPE': 'Mean Absolute % Error',
        'R2': 'R-Squared'
    }

    for key, name in metric_names.items():
        if key in metrics and metrics[key] is not None:
            value = metrics[key]
            if key in ['MAPE']:
                formatted_value = f"{value:.2f}%"
            elif key == 'R2':
                formatted_value = f"{value:.4f}"
            else:
                formatted_value = f"{value:.2f}"

            metric_cards.append(
                dbc.Col([
                    dbc.Card([
                        dbc.CardBody([
                            html.H6(name, className="text-muted mb-2"),
                            html.H4(formatted_value)
                        ])
                    ], className="text-center")
                ], md=2)
            )

    return metric_cards


def create_backtest_metrics_display(metrics: dict) -> list:
    """
    Create backtest metrics display components

    Args:
        metrics: Dictionary of backtest metric values (MAE, RMSE, MAPE, R2)

    Returns:
        Dash component card
    """
    import dash_bootstrap_components as dbc
    from dash import html

    return dbc.Card([
        dbc.CardHeader([
            html.I(className="fas fa-chart-bar me-2"),
            html.Span("Backtest Performance Metrics", className="fw-bold")
        ]),
        dbc.CardBody([
            html.P("Model performance on historical data validation:", className="text-muted small mb-3"),
            dbc.Row([
                dbc.Col([
                    html.Small("MAE", className="text-muted"),
                    html.H5(f"{metrics.get('MAE', 0):.2f}", className="mb-0")
                ], md=3),
                dbc.Col([
                    html.Small("RMSE", className="text-muted"),
                    html.H5(f"{metrics.get('RMSE', 0):.2f}", className="mb-0")
                ], md=3),
                dbc.Col([
                    html.Small("MAPE", className="text-muted"),
                    html.H5(f"{metrics.get('MAPE', 0):.2f}%", className="mb-0")
                ], md=3),
                dbc.Col([
                    html.Small("R²", className="text-muted"),
                    html.H5(f"{metrics.get('R2', 0):.4f}", className="mb-0")
                ], md=3),
            ]),
            html.Hr(),
            html.Small([
                html.I(className="fas fa-info-circle me-1"),
                "Lower MAE/RMSE/MAPE and higher R² (closer to 1.0) indicate better model performance"
            ], className="text-muted")
        ])
    ], className="mt-3")


def decimate_data(df: pd.DataFrame, max_points: int = 10000) -> pd.DataFrame:
    """
    Reduce number of data points for visualization

    Args:
        df: Input DataFrame
        max_points: Maximum number of points to keep

    Returns:
        Decimated DataFrame
    """
    if len(df) <= max_points:
        return df

    # Use systematic sampling
    step = len(df) // max_points
    return df.iloc[::step].reset_index(drop=True)