"""Owon PSU SCPI control over raw serial (pyserial).

This module provides a small, programmatic API suitable for tests:

- OwonPSU: context-manageable controller class
- scan_ports(): find devices responding to *IDN?
- auto_detect(): select the first matching device by IDN substring

Behavior follows the working quick demo example (serial):
- Both commands and queries are terminated with a newline ("\n" by default).
- Queries use readline() to fetch a single-line response.
- Command set uses: 'output 0/1', 'output?', 'SOUR:VOLT <V>', 'SOUR:CURR <A>', 'MEAS:VOLT?', 'MEAS:CURR?', '*IDN?'
"""
from __future__ import annotations

from dataclasses import dataclass
from time import sleep
from typing import Iterable, Optional

import serial
from serial import Serial
from serial.tools import list_ports


@dataclass
class SerialParams:
    baudrate: int = 115200
    timeout: float = 1.0  # seconds
    bytesize: int = serial.EIGHTBITS
    parity: str = serial.PARITY_NONE
    stopbits: float = serial.STOPBITS_ONE
    xonxoff: bool = False
    rtscts: bool = False
    dsrdtr: bool = False
    write_timeout: float = 1.0  # seconds


class OwonPSU:
    def __init__(self, port: str, params: SerialParams | None = None, eol: str = "\n") -> None:
        self.port = port
        self.params = params or SerialParams()
        self.eol = eol
        self._ser: Optional[Serial] = None

    def open(self) -> None:
        if self._ser and self._ser.is_open:
            return
        ser = Serial()
        ser.port = self.port
        ser.baudrate = self.params.baudrate
        ser.bytesize = self.params.bytesize
        ser.parity = self.params.parity
        ser.stopbits = self.params.stopbits
        ser.xonxoff = self.params.xonxoff
        ser.rtscts = self.params.rtscts
        ser.dsrdtr = self.params.dsrdtr
        ser.timeout = self.params.timeout
        ser.write_timeout = self.params.write_timeout
        ser.open()
        self._ser = ser

    def close(self) -> None:
        if self._ser and self._ser.is_open:
            try:
                self._ser.close()
            finally:
                self._ser = None

    def __enter__(self) -> "OwonPSU":
        self.open()
        return self

    def __exit__(self, exc_type, exc, tb) -> None:
        self.close()

    @property
    def is_open(self) -> bool:
        return bool(self._ser and self._ser.is_open)

    # ---- low-level ops ----
    def write(self, cmd: str) -> None:
        """Write a SCPI command (append eol)."""
        if not self._ser:
            raise RuntimeError("Port is not open")
        data = (cmd + self.eol).encode("ascii", errors="ignore")
        self._ser.write(data)
        self._ser.flush()

    def query(self, q: str) -> str:
        """Send a query with terminator and return a single-line response using readline()."""
        if not self._ser:
            raise RuntimeError("Port is not open")
        # clear buffers to avoid stale data
        try:
            self._ser.reset_input_buffer()
            self._ser.reset_output_buffer()
        except Exception:
            pass
        self._ser.write((q + self.eol).encode("ascii", errors="ignore"))
        self._ser.flush()
        line = self._ser.readline().strip()
        return line.decode("ascii", errors="ignore")

    # ---- high-level ops ----
    def idn(self) -> str:
        return self.query("*IDN?")

    def set_voltage(self, channel: int, volts: float) -> None:
        # Using SOUR:VOLT <V> per working example
        self.write(f"SOUR:VOLT {volts:.3f}")

    def set_current(self, channel: int, amps: float) -> None:
        # Using SOUR:CURR <A> per working example
        self.write(f"SOUR:CURR {amps:.3f}")

    def set_output(self, on: bool) -> None:
        # Using 'output 1/0' per working example
        self.write("output 1" if on else "output 0")

    def output_status(self) -> str:
        return self.query("output?")

    def measure_voltage(self) -> str:
        return self.query("MEAS:VOLT?")

    def measure_current(self) -> str:
        return self.query("MEAS:CURR?")


# ------- discovery helpers -------

def try_idn_on_port(port: str, params: SerialParams) -> str:
    dev: Optional[Serial] = None
    try:
        dev = Serial()
        dev.port = port
        dev.baudrate = params.baudrate
        dev.bytesize = params.bytesize
        dev.parity = params.parity
        dev.stopbits = params.stopbits
        dev.xonxoff = params.xonxoff
        dev.rtscts = params.rtscts
        dev.dsrdtr = params.dsrdtr
        dev.timeout = params.timeout
        dev.write_timeout = params.write_timeout
        dev.open()
        # Query with newline terminator and read a single line
        dev.reset_input_buffer(); dev.reset_output_buffer()
        dev.write(b"*IDN?\n"); dev.flush()
        line = dev.readline().strip()
        return line.decode("ascii", errors="ignore")
    except Exception:
        return ""
    finally:
        if dev and dev.is_open:
            try:
                dev.close()
            except Exception:
                pass


def scan_ports(params: SerialParams | None = None) -> list[tuple[str, str]]:
    """Return [(port, idn_response), ...] for ports that responded."""
    params = params or SerialParams()
    results: list[tuple[str, str]] = []
    for p in list_ports.comports():
        dev = p.device
        resp = try_idn_on_port(dev, params)
        if resp:
            results.append((dev, resp))
    return results


def auto_detect(params: SerialParams | None = None, idn_substr: str | None = None) -> Optional[str]:
    """Return the first port whose *IDN? contains idn_substr (case-insensitive), else first responder."""
    params = params or SerialParams()
    matches = scan_ports(params)
    if not matches:
        return None
    if idn_substr:
        isub = idn_substr.lower()
        for port, idn in matches:
            if isub in idn.lower():
                return port
    return matches[0][0]


__all__ = [
    "SerialParams",
    "OwonPSU",
    "scan_ports",
    "auto_detect",
]