#!/usr/bin/env python3
"""Parse Perf lines from a log file and plot sample mean, write mean, and loop mean over time."""

import sys
import re
import os
from datetime import datetime

import matplotlib.pyplot as plt


PERF_RE = re.compile(
    r"^(\w+ \d+ \d+:\d+:\d+) .* Perf\(.*?\):"
    r".*?sample mean=([\d.]+)ms"
    r".*?write mean=([\d.]+)ms"
    r".*?loop mean=([\d.]+)ms"
)


def parse_log(log_path):
    timestamps = []
    sample_means = []
    write_means = []
    loop_means = []

    with open(log_path, "r") as f:
        for line in f:
            m = PERF_RE.search(line)
            if m:
                ts_str, sample, write, loop = m.groups()
                ts = datetime.strptime(ts_str, "%b %d %H:%M:%S")
                timestamps.append(ts)
                sample_means.append(float(sample))
                write_means.append(float(write))
                loop_means.append(float(loop))

    if not timestamps:
        print("No Perf lines found in the log file.", file=sys.stderr)
        sys.exit(1)

    t0 = timestamps[0]
    seconds = [(t - t0).total_seconds() for t in timestamps]
    return seconds, sample_means, write_means, loop_means


def plot(seconds, sample_means, write_means, loop_means, out_path):
    plt.figure(figsize=(12, 6))
    plt.plot(seconds, sample_means, label="sample mean (ms)")
    plt.plot(seconds, write_means, label="write mean (ms)")
    plt.plot(seconds, loop_means, label="loop mean (ms)")
    plt.xlabel("Time (s)")
    plt.ylabel("Duration (ms)")
    plt.title("Perf Metrics Over Time")
    plt.legend()
    plt.grid(True)
    plt.tight_layout()
    plt.savefig(out_path, dpi=150)
    print(f"Plot saved to {out_path}")


def main():
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} <path_to_log_file>", file=sys.stderr)
        sys.exit(1)

    log_path = sys.argv[1]
    if not os.path.isfile(log_path):
        print(f"File not found: {log_path}", file=sys.stderr)
        sys.exit(1)

    seconds, sample_means, write_means, loop_means = parse_log(log_path)

    log_dir = os.path.dirname(os.path.abspath(log_path))
    log_base = os.path.splitext(os.path.basename(log_path))[0]
    out_path = os.path.join(log_dir, f"{log_base}_perf_plot.png")

    plot(seconds, sample_means, write_means, loop_means, out_path)


if __name__ == "__main__":
    main()