"""
Generic Field Data Extractor
=============================

Reusable extractor for parsing NX exported field data (.fld files).
Works for any result type: displacement, stress, strain, temperature, etc.

Supports TWO formats:
1. NX native .fld format (exported from ResultProbe)
2. CSV format with headers

Usage:
    extractor = FieldDataExtractor(field_file="export_field_dz.fld")
    results = extractor.extract()
    max_value = results['max_abs_value']
"""

import csv
from pathlib import Path
from typing import Dict, Any, Optional, List
import numpy as np


class FieldDataExtractor:
    """
    Generic extractor for NX exported field data files (.fld or .csv format).

    Supports:
    - Displacement (X, Y, Z components)
    - Stress (von Mises, principals, components)
    - Strain
    - Temperature
    - Any other scalar field data
    """

    def __init__(
        self,
        field_file: str,
        result_column: str = "x(mm)",  # Column name to extract (for CSV format)
        aggregation: str = "max_abs",   # max_abs, max, min, mean, std
    ):
        """
        Args:
            field_file: Path to .fld or .csv file
            result_column: Column name containing the result values (for CSV format, ignored for .fld)
            aggregation: How to aggregate values (max_abs, max, min, mean, std)
        """
        self.field_file = Path(field_file)
        self.result_column = result_column
        self.aggregation = aggregation

    def _is_nx_field_format(self) -> bool:
        """Check if file is NX field format or CSV"""
        with open(self.field_file, 'r') as f:
            first_line = f.readline()
            return first_line.startswith('FIELD:')

    def _parse_nx_field_file(self) -> List[float]:
        """
        Parse NX native field export format (.fld).

        Format:
            FIELD: [ResultProbe] : [TABLE]
            ...metadata...
            START DATA
            step, node_id, value
            0, 396, -0.086716040968895
            ...
            END DATA
        """
        values = []
        in_data_section = False

        with open(self.field_file, 'r') as f:
            for line in f:
                line = line.strip()

                if line.startswith('START DATA'):
                    in_data_section = True
                    continue

                if line.startswith('END DATA'):
                    break

                if in_data_section and line:
                    # Data format: step, node_id, value
                    parts = [p.strip() for p in line.split(',')]
                    if len(parts) >= 3:
                        try:
                            value = float(parts[2])  # Third column is the value
                            values.append(value)
                        except ValueError:
                            continue

        return values

    def _parse_csv_file(self) -> List[float]:
        """
        Parse CSV file with column headers.

        Expected format:
            node_id,x(mm),y(mm),z(mm)
            1,0.0,0.0,0.5
            2,0.1,0.0,0.6
            ...
        """
        values = []
        with open(self.field_file, 'r') as f:
            reader = csv.DictReader(f)
            for row in reader:
                try:
                    value = float(row[self.result_column])
                    values.append(value)
                except (KeyError, ValueError) as e:
                    continue  # Skip invalid rows

        return values

    def extract(self) -> Dict[str, Any]:
        """
        Extract and aggregate field data.

        Returns:
            dict: {
                'value': aggregated value,
                'all_values': list of all values,
                'node_count': number of nodes,
                'stats': {min, max, mean, std, max_abs}
            }
        """
        if not self.field_file.exists():
            raise FileNotFoundError(f"Field file not found: {self.field_file}")

        # Detect format and parse
        if self._is_nx_field_format():
            values = self._parse_nx_field_file()
        else:
            values = self._parse_csv_file()

        if not values:
            raise ValueError(f"No valid data found in field file: {self.field_file}")

        values_array = np.array(values)

        # Calculate statistics
        stats = {
            'min': float(np.min(values_array)),
            'max': float(np.max(values_array)),
            'mean': float(np.mean(values_array)),
            'std': float(np.std(values_array)),
            'max_abs': float(np.max(np.abs(values_array))),
        }

        # Get aggregated value based on method
        aggregation_map = {
            'max': stats['max'],
            'min': stats['min'],
            'mean': stats['mean'],
            'std': stats['std'],
            'max_abs': stats['max_abs'],
        }

        aggregated_value = aggregation_map.get(self.aggregation, stats['max_abs'])

        return {
            'value': aggregated_value,
            'all_values': values,
            'node_count': len(values),
            'stats': stats,
            'aggregation_method': self.aggregation,
        }


def extract_displacement_field(
    field_file: str,
    component: str = "z",  # x, y, or z
    aggregation: str = "max_abs"
) -> Dict[str, Any]:
    """
    Convenience function for extracting displacement data.

    Args:
        field_file: Path to displacement field file
        component: Displacement component (x, y, or z)
        aggregation: Aggregation method

    Returns:
        Extracted displacement data
    """
    column_map = {
        'x': 'x(mm)',
        'y': 'y(mm)',
        'z': 'z(mm)',
    }

    column = column_map.get(component.lower(), 'x(mm)')
    extractor = FieldDataExtractor(field_file, result_column=column, aggregation=aggregation)
    return extractor.extract()


if __name__ == "__main__":
    # Example usage
    import sys
    if len(sys.argv) > 1:
        field_file = sys.argv[1]
        results = extract_displacement_field(field_file, component="z")
        print(f"Max absolute Z-displacement: {results['value']:.6f} mm")
        print(f"Statistics: {results['stats']}")