#! /usr/bin/env python
import csv
from datetime import datetime

def calculate_diff(input_file, output_file):
    last_values = {}
    output_rows = []

    with open(input_file, 'r') as infile:
        reader = csv.reader(infile)
        for row in reader:
            timestamp_str, metric, value_str = row
            timestamp = datetime.strptime(timestamp_str, '%Y-%m-%d %H:%M:%S.%f')
            value = float(value_str)

            output_rows.append(row)

            if metric in last_values:
                last_timestamp, last_value = last_values[metric]
                time_diff = (timestamp - last_timestamp).total_seconds()
                
                if time_diff > 0:
                    value_diff = value - last_value
                    if metric in ["Azimuth", "Elev"]:
                        value_diff = (value_diff + 90) % 180 - 90
                    value_diff = value_diff / time_diff
                    output_rows.append([timestamp_str, f"{metric}_diff", f"{value_diff:.6f}"])

            last_values[metric] = (timestamp, value)

    with open(output_file, 'w', newline='') as outfile:
        writer = csv.writer(outfile)
        writer.writerows(output_rows)

if __name__ == "__main__":
    import sys
    if len(sys.argv) != 3 and len(sys.argv) != 2:
        print("Usage: python process_log.py <input_file> <output_file>")
        sys.exit(1)
    
    input_file = sys.argv[1]
    if sys.argv == 3:
        output_file = sys.argv[2]
    else:
        name, extension = input_file.rsplit('.', 1)
        # Add "_diff" to the name and then add the extension back
        output_file = f"{name}_diff.{extension}"

    print("Generate new diff file :"+str(output_file))
    
    calculate_diff(input_file, output_file)