#!/usr/bin/env python3
#
# src_back.py --- Backward versus Forward Dispersion
#                      See HYSPLIT Tutorial Sec. 13.2
#
# Change history:
# 18 Oct 2025 (BB) - standard-aligned, cross-platform version
# 12 Feb 2026 (SZ) - minor edits for style consistency
# 18 Jun 2026 (SZ) - standardize code for run_cmd(), convert_html_to_img(),
#                    etc. across Python scripts
#                  - ensure encoding is specified when opening files

import os
import sys
import platform
from pathlib import Path
import subprocess

if sys.version_info < (3, 8):
    print("Please use Python 3.8 or higher.")
    sys.exit(1)

system = platform.system().lower()
if system == "windows":
    PGM = Path(sys.argv[1]) if len(sys.argv) > 1 else Path("C:\\hysplit")
    OUT = Path(sys.argv[2]) if len(sys.argv) > 2 else PGM / "working"
    DSP = sys.argv[3] if len(sys.argv) > 3 else "YES"
    TTR = Path(os.environ.get("TTR", "C:\\Tutorial"))
    exe_suffix = ".exe"
else:
    PGM = Path(sys.argv[1]) if len(sys.argv) > 1 else Path.home() / "hysplit"
    OUT = Path(sys.argv[2]) if len(sys.argv) > 2 else PGM / "working"
    DSP = sys.argv[3] if len(sys.argv) > 3 else "YES"
    TTR = Path(os.environ.get("TTR", Path.home() / "tutorial"))
    exe_suffix = ""

if not PGM.exists():
    script = Path(__file__).name if "__file__" in globals() else "src_back.py"
    print(f"ERROR: HYSPLIT not found at {PGM}")
    print(f"""
Please specify the path to your HYSPLIT installation using a command-line argument:

python {script} YOUR_HYSPLIT_DIRECTORY [OUT] [DSP (YES|NO)]

Example:
    python {script} C:\\hysplit C:\\hysplit\\working YES
""")
    sys.exit(1)

if not TTR.exists():
    print(f"ERROR: HYSPLIT tutorial not found at {TTR}")
    print("""
Please set the TTR environment variable to point to your HYSPLIT tutorial directory.

For Windows users (Command Prompt):
   SET TTR=YOUR_HYSPLIT_TUTORIAL_DIRECTORY

For Linux users (bash shell):
   export TTR='YOUR_HYSPLIT_TUTORIAL_DIRECTORY'

For Linux users (csh or tcsh shell):
   setenv TTR 'YOUR_HYSPLIT_TUTORIAL_DIRECTORY'""")
    sys.exit(1)

os.chdir(OUT)

# ------------------------------------------------------------------
# Helper function
# ------------------------------------------------------------------

def run_cmd(cmd, desc="", allow_fail=False, stdout_file=None, append=False):
    if desc:
        print(f"{desc}...")

    exitcode = 0
    with subprocess.Popen(cmd,
                         stdout=subprocess.PIPE,
                         stderr=subprocess.STDOUT,
                         text=True) as p:
        if stdout_file:
            mode="a" if append else "w"
            with open(stdout_file, mode, encoding="utf-8") as f_out:
                for ln in p.stdout:
                    print(ln, end="")
                    f_out.write(ln)
        else:
            with p.stdout as f:
                for ln in iter(f.readline, b'\n'):
                    if len(ln) == 0:
                        break
                    print(ln.rstrip())

        done = False
        while not done:
            try:
                exitcode = p.wait(timeout=1)
                done = True
            except subprocess.TimeoutExpired:
                print("WARN: subprocess timed out.")

    if exitcode != 0:
        if allow_fail:
            print(f"WARN: command failed with exit code {exitcode} -> {' '.join(cmd)}")
        else:
            print(f"ERROR: command failed with exit code {exitcode} -> {' '.join(cmd)}")
            sys.exit(1)


# -------------------------------------------------------------------
# static inputs
# -------------------------------------------------------------------
wrk = TTR
met_dir = wrk / "captex"
met_file = "captex2_wrf27uw.bin"

top = 10000.0
lvl = 10.0

# -------------------------------------------------------------------
# ASCDATA.CFG
# -------------------------------------------------------------------
with open("ASCDATA.CFG", "w", encoding="ascii") as f:
    f.write(
        "-90.0   -180.0\n"
        "1.0     1.0\n"
        "180     360\n"
        "2\n"
        "0.2\n"
        f"'{PGM / 'bdyfiles'}{os.sep}'  directory of files\n"
    )


def write_setup():
    with open("SETUP.CFG", "w", encoding="ascii") as f:
        f.write("&SETUP\n")
        f.write(" numpar = 50000,\n")
        f.write(" maxpar = 100000,\n")
        f.write("/\n")


def write_control(
    syr, smo, sda, shr,
    lat, lon, run_hours,
    inp,
    start_time, end_time
):
    with open("CONTROL", "w", encoding="ascii") as f:
        f.write(f"{syr} {smo} {sda} {shr}\n")
        f.write("1\n")
        f.write(f"{lat} {lon} {lvl}\n")
        f.write(f"{run_hours}\n")
        f.write("0\n")
        f.write(f"{top}\n")
        f.write("1\n")
        f.write(f"{met_dir}{os.sep}\n")
        f.write(f"{met_file}\n")
        f.write("1\n")
        f.write("PMCH\n")
        f.write("1.0\n")
        f.write("1.0\n")
        f.write("00 00 00 00 00\n")
        f.write("1\n")
        f.write("42.0 -78.0\n")
        f.write("0.25 0.25\n")
        f.write("15.0 25.0\n")
        f.write(f".{os.sep}\n")
        f.write(f"{inp}\n")
        f.write("1\n")
        f.write("100\n")
        f.write(f"{start_time}\n")
        f.write(f"{end_time}\n")
        f.write("00 01 00\n")
        f.write("1\n")
        f.write("0.0 0.0 0.0\n")
        f.write("0.0 0.0 0.0 0.0 0.0\n")
        f.write("0.0 0.0 0.0\n")
        f.write("0.0\n")
        f.write("0.0\n")


def run_hycs(inp):
    if Path(inp).exists():
        Path(inp).unlink()

    write_setup()
    run_cmd(
        [str(PGM / "exec" / f"hycs_std{exe_suffix}")],
        "Running hycs_std"
    )


def run_con2stn(inp, station_lat, station_lon, outfile):
    with open("samplers.txt", "w", encoding="ascii") as f:
        f.write(f"S316 {station_lat} {station_lon}\n")

    run_cmd([
        str(PGM / "exec" / f"con2stn{exe_suffix}"),
        "-xn",
        f"-i{inp}",
        f"-o{outfile}",
        "-r1",
        "-c1.0E+15",
        "-ssamplers.txt"
    ], "Running con2stn")

    with open(outfile, "r", encoding="ascii", errors="ignore") as f:
        print(f.read())
    Path("samplers.txt").unlink()


# -------------------------------------------------------------------
# FORWARD RUN
# -------------------------------------------------------------------
inp = "hysp_fwrd.bin"

write_control(
    syr=83, smo=9, sda=25, shr=17,
    lat=39.90, lon=-84.22,
    run_hours=19,
    inp=inp,
    start_time="83 09 25 17 00",
    end_time="83 09 28 15 00"
)

run_hycs(inp)
run_con2stn(inp, 41.30, -82.22, "con2stn_bak1.txt")

if DSP.upper() == "YES":
    input("Press Enter to continue...")

# -------------------------------------------------------------------
# BACKWARD RUN
# -------------------------------------------------------------------
inp = "hysp_back.bin"

write_control(
    syr=83, smo=9, sda=26, shr=8,
    lat=41.30, lon=-82.22,
    run_hours=-15,
    inp=inp,
    start_time="83 09 26 08 00",
    end_time="83 09 25 17 00"
)

run_hycs(inp)
run_con2stn(inp, 39.90, -84.22, "con2stn_bak2.txt")