"""
Pandas transform functions for User Activity report.
"""

from typing import Any

import pandas as pd

from fs_report.models import Config


def user_activity_pandas_transform(
    data: list[dict[str, Any]] | pd.DataFrame, config: Config | None = None
) -> dict[str, Any]:
    """
    Transform audit data for the User Activity report.

    Args:
        data: Raw audit events from API (list of dicts or DataFrame)
        config: Configuration object

    Returns:
        Dictionary with DataFrames and metrics for the report:
        - 'main': Main activity table (recent activity)
        - 'summary': Summary statistics dict
        - 'daily_logins': Daily active user metrics DataFrame
        - 'activity_by_type': Activity breakdown DataFrame
        - 'top_users': Top active users DataFrame
    """
    import logging

    logger = logging.getLogger(__name__)

    _empty = {
        "main": pd.DataFrame(),
        "summary": {
            "total_events": 0,
            "unique_users": 0,
            "active_days": 0,
            "event_types": 0,
        },
        "daily_logins": [],
        "activity_by_type": [],
        "top_users": [],
    }

    if isinstance(data, pd.DataFrame):
        if data.empty:
            logger.warning("User activity transform: No data provided")
            return _empty
        df = data.copy()
    elif not data:
        logger.warning("User activity transform: No data provided")
        return _empty
    else:
        # Convert to DataFrame
        df = pd.DataFrame(data)
    logger.debug(f"User activity transform: DataFrame created with shape {df.shape}")

    # Normalize fields that may be strings or {value: ...} objects
    df = normalize_audit_fields(df)

    # Parse timestamps
    df["timestamp"] = pd.to_datetime(
        df["time"], format="ISO8601", errors="coerce", utc=True
    )
    df["date"] = df["timestamp"].dt.date

    # Filter out rows with invalid timestamps
    df = df.dropna(subset=["timestamp"])

    if df.empty:
        logger.warning("User activity transform: No valid events after parsing")
        return {
            "main": pd.DataFrame(),
            "summary": {
                "total_events": 0,
                "unique_users": 0,
                "active_days": 0,
                "event_types": 0,
            },
            "daily_logins": [],
            "activity_by_type": [],
            "top_users": [],
        }

    # Calculate all metrics
    daily_metrics = calculate_daily_activity_metrics(df)
    activity_metrics = calculate_activity_metrics(df)
    user_metrics = calculate_user_metrics(df)

    # Create the main activity table for display
    activity_df = create_activity_table(df)

    # Calculate average daily users
    daily_user_counts = df.groupby("date")["user"].nunique()
    avg_daily_users = daily_user_counts.mean() if len(daily_user_counts) > 0 else 0

    # Build summary
    summary = {
        "total_events": len(df),
        "unique_users": df["user"].nunique(),
        "active_days": df["date"].nunique(),
        "avg_daily_users": round(avg_daily_users, 1),
    }

    # Convert DataFrames to list of dicts for template rendering
    daily_activity_list = (
        daily_metrics["daily_activity"].to_dict("records")
        if not daily_metrics["daily_activity"].empty
        else []
    )
    activity_by_type_list = activity_metrics["activity_by_type"].to_dict("records")
    top_users_list = user_metrics["top_users"].to_dict("records")

    return {
        "main": activity_df,
        "summary": summary,
        "daily_logins": daily_activity_list,  # Keep key name for template compatibility
        "activity_by_type": activity_by_type_list,
        "top_users": top_users_list,
    }


def normalize_audit_fields(df: pd.DataFrame) -> pd.DataFrame:
    """
    Normalize audit fields that may be strings or {value: ...} objects.

    Args:
        df: Raw audit DataFrame

    Returns:
        DataFrame with normalized fields
    """

    def extract_value(field: Any) -> Any:
        """Extract value from field that may be string or dict with 'value' key."""
        if isinstance(field, dict):
            return field.get("value", str(field))
        return field

    # Normalize user, time, and type fields
    if "user" in df.columns:
        df["user"] = df["user"].apply(extract_value)
    else:
        df["user"] = "Unknown"

    if "time" in df.columns:
        df["time"] = df["time"].apply(extract_value)
    else:
        df["time"] = None

    if "type" in df.columns:
        df["type"] = df["type"].apply(extract_value)
    else:
        df["type"] = "Unknown"

    return df


def create_activity_table(df: pd.DataFrame) -> pd.DataFrame:
    """
    Create the main activity table for display.

    Args:
        df: Normalized audit DataFrame

    Returns:
        Activity table DataFrame
    """
    # Select and format columns for the activity table
    activity_df = df[["timestamp", "user", "type"]].copy()

    # Extract application name if present
    if "application" in df.columns:
        activity_df["project"] = df["application"].apply(
            lambda x: x.get("name", "") if isinstance(x, dict) else ""
        )
    else:
        activity_df["project"] = ""

    # Format for display
    activity_df = activity_df.rename(
        columns={
            "timestamp": "Time",
            "user": "User",
            "type": "Event Type",
            "project": "Project",
        }
    )

    # Sort by time descending (most recent first)
    activity_df = activity_df.sort_values("Time", ascending=False)

    # Format time for display
    activity_df["Time"] = activity_df["Time"].dt.strftime("%Y-%m-%d %H:%M:%S")

    return activity_df


def calculate_daily_activity_metrics(df: pd.DataFrame) -> dict[str, Any]:
    """
    Calculate daily activity metrics (unique active users per day).

    Args:
        df: Normalized audit DataFrame

    Returns:
        Dictionary with daily activity metrics
    """
    if df.empty:
        return {
            "daily_activity": pd.DataFrame(
                columns=["Date", "Unique Users", "Total Logins"]
            ),
        }

    # Daily unique active users and total events
    daily_activity = (
        df.groupby("date")
        .agg(unique_users=("user", "nunique"), total_events=("user", "count"))
        .reset_index()
    )
    daily_activity.columns = [
        "Date",
        "Unique Users",
        "Total Logins",
    ]  # Keep column names for template compatibility
    daily_activity = daily_activity.sort_values("Date")

    # Convert date to string for JSON serialization
    daily_activity["Date"] = daily_activity["Date"].astype(str)

    return {
        "daily_activity": daily_activity,
    }


def calculate_activity_metrics(df: pd.DataFrame) -> dict[str, Any]:
    """
    Calculate activity breakdown metrics.

    Args:
        df: Normalized audit DataFrame

    Returns:
        Dictionary with activity metrics
    """
    # Activity by type
    activity_by_type = df["type"].value_counts().reset_index()
    activity_by_type.columns = ["Event Type", "Count"]
    activity_by_type["Percentage"] = (
        activity_by_type["Count"] / activity_by_type["Count"].sum() * 100
    ).round(1)

    return {
        "total_events": len(df),
        "event_types": df["type"].nunique(),
        "activity_by_type": activity_by_type,
    }


def calculate_user_metrics(df: pd.DataFrame) -> dict[str, Any]:
    """
    Calculate user-specific metrics.

    Args:
        df: Normalized audit DataFrame

    Returns:
        Dictionary with user metrics
    """
    # Top users by activity
    user_activity = (
        df.groupby("user")
        .agg(
            total_actions=("type", "count"),
            first_active=("timestamp", "min"),
            last_active=("timestamp", "max"),
            event_types=("type", "nunique"),
            active_days=("date", "nunique"),
        )
        .reset_index()
    )

    user_activity = user_activity.sort_values("total_actions", ascending=False)
    user_activity.columns = [
        "User",
        "Total Actions",
        "First Active",
        "Last Active",
        "Event Types",
        "Active Days",
    ]

    # Calculate "Logins" as active days for template compatibility
    user_activity["Logins"] = user_activity["Active Days"]

    # Format dates
    user_activity["First Active"] = user_activity["First Active"].dt.strftime(
        "%Y-%m-%d"
    )
    user_activity["Last Active"] = user_activity["Last Active"].dt.strftime(
        "%Y-%m-%d %H:%M"
    )

    # Reorder columns for display
    user_activity = user_activity[
        ["User", "Total Actions", "Logins", "Last Active", "Event Types"]
    ]

    return {
        "total_users": df["user"].nunique(),
        "top_users": user_activity.head(20),
    }
