import colorsys
from datetime import datetime, date, timedelta
import numpy as np
import pandas as pd
import plotly.express as px
import plotly.io as pio

def convert_str_to_date(date_str, format='%Y-%m-%d'):
    try:
        return datetime.strptime(date_str, format).date()
    except ValueError:
        return None
    except TypeError:
        return None

def get_exercise_graph_model(title, estimated_1rm, repetitions, weight, start_dates, messages, epoch, person_id, exercise_id, min_date=None, max_date=None):
    # Precompute ranges
    min_date, max_date = min(start_dates), max(start_dates)
    total_span = (max_date - min_date).days or 1

    min_e1rm, max_e1rm = min(estimated_1rm), max(estimated_1rm)
    min_reps, max_reps = min(repetitions), max(repetitions)
    min_weight, max_weight = min(weight), max(weight)

    e1rm_range = max_e1rm - min_e1rm or 1
    reps_range = max_reps - min_reps or 1
    weight_range = max_weight - min_weight or 1

    # Calculate viewBox dimensions
    vb_width, vb_height = total_span, e1rm_range
    vb_width *= 200 / vb_width  # Scale to 200px width
    vb_height *= 75 / vb_height  # Scale to 75px height

    # Use NumPy arrays for efficient scaling
    relative_positions = np.array([(date - min_date).days / total_span for date in start_dates])
    estimated_1rm_scaled = ((np.array(estimated_1rm) - min_e1rm) / e1rm_range) * vb_height
    repetitions_scaled = ((np.array(repetitions) - min_reps) / reps_range) * vb_height
    weight_scaled = ((np.array(weight) - min_weight) / weight_range) * vb_height

    # Calculate slope and line of best fit
    slope_kg_per_day = e1rm_range / total_span
    best_fit_formula = {
        'kg_per_week': round(slope_kg_per_day * 7, 1),
        'kg_per_month': round(slope_kg_per_day * 30, 1)
    }

    best_fit_points = []
    try:
        if len(relative_positions) > 1:  # Ensure there are enough points for polyfit
            # Calculate line of best fit using NumPy
            m, b = np.polyfit(relative_positions, estimated_1rm_scaled, 1)
            y_best_fit = m * relative_positions + b
            best_fit_points = list(zip(y_best_fit.tolist(), relative_positions.tolist()))
        else:
            raise ValueError("Not enough data points for polyfit")
    except (np.linalg.LinAlgError, ValueError) as e:
        # Handle cases where polyfit fails
        best_fit_points = []
        m, b = 0, 0

    # Prepare data for plots
    repetitions_data = {
        'label': 'Reps',
        'color': '#388fed',
        'points': list(zip(repetitions_scaled.tolist(), relative_positions.tolist()))
    }
    weight_data = {
        'label': 'Weight',
        'color': '#bd3178',
        'points': list(zip(weight_scaled.tolist(), relative_positions.tolist()))
    }
    estimated_1rm_data = {
        'label': 'E1RM',
        'color': '#2ca02c',
        'points': list(zip(estimated_1rm_scaled.tolist(), relative_positions.tolist()))
    }

    # Prepare plot labels
    plot_labels = list(zip(relative_positions.tolist(), messages))

    # Return exercise data with SVG dimensions and data points
    return {
        'title': title,
        'vb_width': vb_width,
        'vb_height': vb_height,
        'plots': [repetitions_data, weight_data, estimated_1rm_data],
        'best_fit_points': best_fit_points,
        'best_fit_formula': best_fit_formula,
        'plot_labels': plot_labels,
        'epochs': ['Custom', '1M', '3M', '6M', 'All'],
        'selected_epoch': epoch,
        'person_id': person_id,
        'exercise_id': exercise_id,
        'min_date': min_date,
        'max_date': max_date
    }

def get_distinct_colors(n):
    colors = []
    for i in range(n):
        # Divide the color wheel into n parts
        hue = i / n
        # Convert HSL (Hue, Saturation, Lightness) to RGB and then to a Hex string
        rgb = colorsys.hls_to_rgb(hue, 0.6, 0.4)  # Fixed lightness and saturation
        hex_color = '#{:02x}{:02x}{:02x}'.format(int(rgb[0]*255), int(rgb[1]*255), int(rgb[2]*255))
        colors.append(hex_color)
    return colors

def generate_plot(df: pd.DataFrame, title: str) -> str:
    """
    Analyzes the DataFrame and generates an appropriate Plotly visualization.
    Returns the Plotly figure as a div string.
    Optimized for speed.
    """
    if df.empty:
        return "<p>No data available to plot.</p>"

    num_columns = len(df.columns)

    # Dictionary-based lookup for faster decision-making
    plot_funcs = {
        1: lambda: px.histogram(df, x=df.columns[0], title=title) 
        if pd.api.types.is_numeric_dtype(df.iloc[:, 0]) else px.bar(df, x=df.columns[0], title=title),

        2: lambda: px.scatter(df, x=df.columns[0], y=df.columns[1], title=title)
        if pd.api.types.is_numeric_dtype(df.iloc[:, 0]) and pd.api.types.is_numeric_dtype(df.iloc[:, 1])
        else px.bar(df, x=df.columns[0], y=df.columns[1], title=title)
    }

    # Select plot function based on column count
    fig = plot_funcs.get(num_columns, lambda: px.imshow(df.corr(numeric_only=True), text_auto=True, title=title))()

    # Use static rendering for speed
    return pio.to_html(fig, full_html=False, include_plotlyjs='cdn', config={'staticPlot': True})


def calculate_estimated_1rm(weight, repetitions):
    # Ensure the inputs are numeric
    if repetitions == 0:  # Avoid division by zero
        return 0
    estimated_1rm = round((100 * int(weight)) / (101.3 - 2.67123 * repetitions), 0)
    return int(estimated_1rm)