import pandas as pd


def load_data(file):
    """
    Load a CSV or Excel file into a pandas DataFrame.

    This function should work both with:
    - a file path string
    - a Gradio UploadedFile object (has .name)
    """
    try:
        # If "file" is a Gradio upload, it has a .name attribute.
        if hasattr(file, "name"):
            path = file.name
        else:
            path = file

        if path.endswith(".csv"):
            df = pd.read_csv(path)
        elif path.endswith(".xlsx") or path.endswith(".xls"):
            df = pd.read_excel(path)
        else:
            raise ValueError("Only .csv, .xlsx, or .xls files are supported.")

        # Try to parse any column that already looks like a date.
        # For your Tesla data, "Date" will be parsed correctly.
        for col in df.columns:
            if "date" in col.lower():
                try:
                    df[col] = pd.to_datetime(df[col])
                except Exception:
                    # If parsing fails, just keep it as is.
                    pass

        return df, None

    except Exception as e:
        # Return None and an error message so Gradio can display it.
        return None, f"Error loading data: {e}"


def get_basic_info(df):
    """
    Return basic information about the dataset:
    - number of rows and columns
    - column names
    - data types as strings
    """
    shape = df.shape
    columns = list(df.columns)
    dtypes = df.dtypes.astype(str).to_dict()

    info = {
        "n_rows": shape[0],
        "n_cols": shape[1],
        "columns": columns,
        "dtypes": dtypes,
    }
    return info


def detect_column_types(df):
    """
    Split columns into:
    - numeric_cols
    - categorical_cols
    - date_cols

    This will be used for:
    - summary statistics
    - filters
    - visualizations
    """
    numeric_cols = df.select_dtypes(include=["number"]).columns.tolist()
    date_cols = df.select_dtypes(include=["datetime64[ns]", "datetime64[ns, UTC]"]).columns.tolist()

    # Everything else is treated as categorical for this project.
    categorical_cols = [col for col in df.columns if col not in numeric_cols + date_cols]

    col_types = {
        "numeric": numeric_cols,
        "categorical": categorical_cols,
        "date": date_cols,
    }
    return col_types


def numeric_summary(df, numeric_cols):
    """
    Calculate summary statistics for numeric columns.

    Returns a DataFrame where each row is a column and
    columns include: count, mean, std, min, 25%, 50%, 75%, max
    """
    if not numeric_cols:
        return pd.DataFrame()

    summary = df[numeric_cols].describe().T  # transpose so each row is a column
    summary = summary.reset_index().rename(columns={"index": "column"})
    return summary


def categorical_summary(df, categorical_cols, max_unique_to_show=20):
    """
    Create a summary for categorical columns.

    For each categorical column we will show:
    - number of unique values
    - the most frequent value (mode)
    - frequency of the mode
    - up to 'max_unique_to_show' value counts (for display if needed)
    """
    rows = []

    for col in categorical_cols:
        series = df[col].astype("object")

        n_unique = series.nunique(dropna=False)

        # Mode (most common value)
        if not series.mode(dropna=False).empty:
            mode_value = series.mode(dropna=False).iloc[0]
        else:
            mode_value = None

        value_counts = series.value_counts(dropna=False)
        mode_freq = int(value_counts.iloc[0]) if len(value_counts) > 0 else 0

        # We keep the top value counts as a JSON-like string to show in a table if needed.
        top_values = value_counts.head(max_unique_to_show).to_dict()

        rows.append(
            {
                "column": col,
                "unique_values": int(n_unique),
                "mode": mode_value,
                "mode_freq": mode_freq,
                "top_values": str(top_values),
            }
        )

    if not rows:
        return pd.DataFrame()

    summary_df = pd.DataFrame(rows)
    return summary_df


def missing_values_report(df):
    """
    Return a DataFrame with:
    - column name
    - number of missing values
    - percentage of missing values
    """
    total_rows = len(df)
    missing_counts = df.isna().sum()

    rows = []
    for col, count in missing_counts.items():
        if total_rows > 0:
            pct = (count / total_rows) * 100
        else:
            pct = 0.0
        rows.append(
            {
                "column": col,
                "missing_count": int(count),
                "missing_pct": round(pct, 2),
            }
        )

    report_df = pd.DataFrame(rows)
    return report_df


def correlation_matrix(df, numeric_cols):
    """
    Compute the correlation matrix for numeric columns.
    """
    if len(numeric_cols) < 2:
        return pd.DataFrame()
    corr = df[numeric_cols].corr()
    return corr


def build_filter_metadata(df, col_types):
    """
    Prepare simple metadata that the Gradio UI can use to build filters.

    For numeric columns:
        min and max value

    For categorical columns:
        sorted list of unique values

    For date columns:
        min and max date
    """
    meta = {
        "numeric": {},
        "categorical": {},
        "date": {},
    }

    # Numeric ranges
    for col in col_types["numeric"]:
        col_series = df[col].dropna()
        if col_series.empty:
            continue
        meta["numeric"][col] = {
            "min": float(col_series.min()),
            "max": float(col_series.max()),
        }

    # Categorical unique values
    for col in col_types["categorical"]:
        unique_vals = df[col].dropna().unique().tolist()
        # Convert numpy types to plain Python for safety
        unique_vals = [str(v) for v in unique_vals]
        meta["categorical"][col] = sorted(unique_vals)

    # Date min/max
    for col in col_types["date"]:
        col_series = df[col].dropna()
        if col_series.empty:
            continue
        meta["date"][col] = {
            "min": col_series.min(),
            "max": col_series.max(),
        }

    return meta


def apply_filters(df, numeric_filters=None, categorical_filters=None, date_filters=None):
    """
    Apply simple filters to the DataFrame.

    numeric_filters: dict like
        {
            "Estimated_Deliveries": [min_val, max_val],
            "Production_Units": [min_val, max_val],
        }

    categorical_filters: dict like
        {
            "Region": ["Europe", "Asia"],
            "Model": ["Model 3", "Model Y"],
        }

    date_filters: dict like
        {
            "Date": ["2018-01-01", "2023-12-31"]
        }

    All arguments are optional. If a filter dict is None, it is ignored.
    """
    filtered = df.copy()

    # Numeric ranges
    if numeric_filters:
        for col, bounds in numeric_filters.items():
            if col not in filtered.columns:
                continue
            try:
                min_val, max_val = bounds
                filtered = filtered[
                    (filtered[col] >= min_val) & (filtered[col] <= max_val)
                ]
            except Exception:
                # If something goes wrong, just skip this column filter.
                continue

    # Categorical selections (multi-select)
    if categorical_filters:
        for col, allowed_values in categorical_filters.items():
            if col not in filtered.columns:
                continue
            if not allowed_values:
                # If list is empty, skip this filter.
                continue
            filtered = filtered[filtered[col].astype(str).isin(allowed_values)]

    # Date range filters
    if date_filters:
        for col, bounds in date_filters.items():
            if col not in filtered.columns:
                continue
            try:
                start, end = bounds
                # Convert to datetime just in case inputs are strings.
                start = pd.to_datetime(start)
                end = pd.to_datetime(end)
                filtered = filtered[
                    (filtered[col] >= start) & (filtered[col] <= end)
                ]
            except Exception:
                continue

    return filtered