# Copyright (C) 2026 Hector van der Aa <hector@h3cx.dev>
# Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
# SPDX-License-Identifier: GPL-3.0-or-later

from __future__ import annotations

import csv
import queue
import struct
import sys
import threading
from dataclasses import dataclass
from datetime import datetime
from pathlib import Path

import serial
from serial.tools import list_ports


BAUD_RATE = 115_200
VALID_CHANNELS = frozenset((b"R", b"S"))


@dataclass(frozen=True)
class Sample:
    channel: str
    value: int


class SerialReader(threading.Thread):
    def __init__(
        self,
        port: str,
        recorder: RecorderState,
        errors: queue.Queue[str],
        stop_event: threading.Event,
    ) -> None:
        super().__init__(daemon=True)
        self.port = port
        self.recorder = recorder
        self.errors = errors
        self.stop_event = stop_event

    def run(self) -> None:
        try:
            with serial.Serial(self.port, BAUD_RATE, timeout=0.1) as ser:
                ser.reset_input_buffer()
                while not self.stop_event.is_set():
                    channel = ser.read(1)
                    if not channel:
                        continue

                    if channel not in VALID_CHANNELS:
                        continue

                    payload = ser.read(4)
                    if len(payload) != 4:
                        continue

                    value = struct.unpack("<I", payload)[0]
                    self.recorder.write(Sample(channel.decode("ascii"), value))
        except serial.SerialException as exc:
            self.errors.put(f"Serial error: {exc}")


class Recording:
    def __init__(self, output_dir: Path) -> None:
        started_at = datetime.now().strftime("%Y%m%d_%H%M%S")
        output_dir.mkdir(parents=True, exist_ok=True)

        self.files = {
            "R": (output_dir / f"{started_at}_R.csv").open(
                "w", newline="", buffering=1024 * 1024
            ),
            "S": (output_dir / f"{started_at}_S.csv").open(
                "w", newline="", buffering=1024 * 1024
            ),
        }
        self.writers = {
            channel: csv.writer(file) for channel, file in self.files.items()
        }
        self.counts = {"R": 0, "S": 0}

    @property
    def paths(self) -> list[Path]:
        return [Path(file.name) for file in self.files.values()]

    def write(self, sample: Sample) -> None:
        self.writers[sample.channel].writerow((sample.value,))
        self.counts[sample.channel] += 1

    def close(self) -> None:
        for file in self.files.values():
            file.close()


class RecorderState:
    def __init__(self, output_dir: Path) -> None:
        self.output_dir = output_dir
        self.recording: Recording | None = None
        self.lock = threading.Lock()

    def start(self) -> Recording | None:
        with self.lock:
            if self.recording is not None:
                return None

            self.recording = Recording(self.output_dir)
            return self.recording

    def stop(self) -> Recording | None:
        with self.lock:
            if self.recording is None:
                return None

            recording = self.recording
            self.recording = None
            recording.close()
            return recording

    def write(self, sample: Sample) -> None:
        with self.lock:
            if self.recording is not None:
                self.recording.write(sample)


def choose_port() -> str | None:
    ports = list(list_ports.comports())
    if not ports:
        print("No serial ports found.")
        return None

    print("Available serial ports:")
    for index, port in enumerate(ports, start=1):
        description = port.description or "serial port"
        print(f"  {index}. {port.device} - {description}")

    while True:
        choice = input("Choose a port number, or q to quit: ").strip().lower()
        if choice == "q":
            return None

        try:
            index = int(choice)
        except ValueError:
            print("Please enter a port number.")
            continue

        if 1 <= index <= len(ports):
            return ports[index - 1].device

        print(f"Please choose a number between 1 and {len(ports)}.")


def show_recording_summary(recording: Recording) -> None:
    print(
        "Stopped recording: "
        f"{recording.counts['R']} R samples, {recording.counts['S']} S samples"
    )
    for path in recording.paths:
        print(f"  {path}")


def main() -> int:
    port = choose_port()
    if port is None:
        return 0

    errors: queue.Queue[str] = queue.Queue()
    stop_event = threading.Event()
    recorder = RecorderState(Path("recordings"))
    reader = SerialReader(port, recorder, errors, stop_event)
    reader.start()

    print(f"Reading {port} at {BAUD_RATE} baud.")
    print("Commands: r = record, s = stop recording, q = quit")

    try:
        while True:
            try:
                error = errors.get_nowait()
            except queue.Empty:
                error = None

            if error is not None:
                print(error)
                return 1

            command = input("> ").strip().lower()

            if command == "r":
                recording = recorder.start()
                if recording is None:
                    print("Already recording.")
                    continue

                print("Recording to:")
                for path in recording.paths:
                    print(f"  {path}")
            elif command == "s":
                recording = recorder.stop()
                if recording is None:
                    print("Not recording.")
                    continue

                show_recording_summary(recording)
            elif command == "q":
                recording = recorder.stop()
                if recording is not None:
                    show_recording_summary(recording)
                return 0
            elif command:
                print("Unknown command. Use r, s, or q.")
    except KeyboardInterrupt:
        print()
        recording = recorder.stop()
        if recording is not None:
            show_recording_summary(recording)
        return 130
    finally:
        stop_event.set()
        reader.join(timeout=1.0)


if __name__ == "__main__":
    sys.exit(main())