"""Check an existing U-Boot prompt or configure its volatile environment."""
import argparse
import fcntl
import re
import sys
import time

import serial

# Match the complete final line, never a prompt embedded in command output.
PROMPT = re.compile(r"(?:^|\n)([^\r\n]*=>) ?$")
ERROR = re.compile(
    r"Unknown command|## Error|^Error:|^Usage:|^.*(?:not defined|not found|failed|failure).*$",
    re.IGNORECASE | re.MULTILINE
)


class UBoot:
    def __init__(self, port):
        self.port = port
        self.prompt = None

    def read_prompt(self, timeout):
        output = ""
        deadline = time.monotonic() + timeout
        while time.monotonic() < deadline:
            data = self.port.read(self.port.in_waiting or 1)
            if data:
                chunk = data.decode("utf-8", errors="replace").replace("\r", "")
                print(chunk, end="", flush=True)
                output += chunk
            match = PROMPT.search(output)
            if match and (self.prompt is None or match[1] == self.prompt):
                # Wait for a quiet prompt rather than a partial output line.
                time.sleep(0.15)
                if self.port.in_waiting:
                    continue
                return output, match[1]
        raise RuntimeError("Timed out waiting for the CLI prompt")

    def detect(self):
        # Observe before requesting a fresh prompt.
        try:
            _, candidate = self.read_prompt(3)
        except RuntimeError:
            candidate = None
        if candidate is None:
            # An idle prompt may have been printed before the port was opened.
            # A newline only requests a fresh prompt; no U-Boot command is sent.
            self.port.write(b"\r")
            self.port.flush()
            _, candidate = self.read_prompt(5)
        if not candidate.endswith("=>"):
            raise RuntimeError("Response is not a recognized U-Boot CLI prompt")
        self.prompt = candidate
        print("\nU-Boot-style CLI prompt detected: " + candidate, flush=True)

    def command(self, command, expected=None, timeout=10):
        print("\n>>> " + command, flush=True)
        self.port.write((command + "\r").encode())
        self.port.flush()
        output, _ = self.read_prompt(timeout)
        # Query immediately, before another command changes the return status.
        self.port.write(b"echo __UBOOT_STATUS_ $?\r")
        self.port.flush()
        status, _ = self.read_prompt(5)
        codes = re.findall(r"(?m)^__UBOOT_STATUS_ (\d+) *$", status)
        if codes != ["0"]:
            raise RuntimeError("Command failed or its exit status could not be verified: " + command)
        if ERROR.search(output):
            raise RuntimeError("Error in command response: " + command)
        if expected and not re.search(expected, output, re.MULTILINE):
            raise RuntimeError("Expected response missing: " + command)
        print("\nVerified: " + command, flush=True)
        return output


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("mode", choices=("check", "configure"), default="check", nargs="?")
    parser.add_argument("--port", default="/dev/ttyUSB0")
    args = parser.parse_args()
    # Shared by both workflows: fail rather than interleave serial commands.
    with open("/tmp/uboot-serial.lock", "w") as lock:
        fcntl.flock(lock, fcntl.LOCK_EX | fcntl.LOCK_NB)
        with serial.Serial(args.port, 115200, timeout=0.1, write_timeout=2, exclusive=True) as port:
            cli = UBoot(port)
            cli.detect()
            if args.mode == "check":
                return
            cli.command("version", r"^U-Boot \d")
            cli.command("printenv ipaddr serverip ethaddr bootcmd bootargs")
            cli.command("setenv ipaddr 192.168.75.100")
            cli.command("printenv ipaddr", r"^ipaddr=192\.168\.75\.100$")
            cli.command("setenv serverip 192.168.75.247")
            cli.command("printenv serverip", r"^serverip=192\.168\.75\.247$")
            cli.command("ping 192.168.75.247", r"^host 192\.168\.75\.247 is alive$", timeout=30)
            cli.command("sf probe 0:0", r"^SF: Detected .+", timeout=20)
            print("\nAll commands verified; environment changes were not saved to flash.")


if __name__ == "__main__":
    try:
        main()
    except (RuntimeError, OSError, serial.SerialException) as exc:
        print("\nERROR: " + str(exc), file=sys.stderr)
        sys.exit(1)