#!/usr/bin/env python
# -*- coding: utf-8 -*-
# vim: fenc=utf-8:et:ts=4:sts=4:sw=4:fdm=marker
import os
from shutil import which
import subprocess
from typing import List, Optional

VALIDATION_CONSTANTS = [3, 2, 7, 6, 5, 4, 3, 2]


def validation_digit(first_eight: str) -> int:
    dot_product = 0
    for i, char in enumerate(first_eight):
        dot_product += VALIDATION_CONSTANTS[i] * int(char)
    mod = dot_product % 11
    if mod == 0:
        return 0
    if mod == 1:
        # If the modulus returns 1 then the random number is not usable
        return None
    else:
        return 11 - mod


def generate_kennitala(first_six: str, randoms: str, century: str) -> Optional[str]:
    first_eight = str(first_six) + str(randoms)
    validation = validation_digit(first_eight)
    kt = None
    if validation is not None:
        kt = first_eight + str(validation) + str(century)
    return kt


def generate_kennitalas(
    first_six: str, century: str, random_from: int = 20, random_to: int = 99
) -> List[str]:
    kennitalas = []
    for n in range(random_from, random_to + 1):
        kt = generate_kennitala(first_six, n, century)
        if kt is not None:
            kennitalas.append(kt)
    return kennitalas


def rust_from_kennitalas(kennitalas: List[str]) -> str:
    num = len(kennitalas)
    test = f"const KENNITALAS: [&'static str; {num}] = [\n"
    for kt in kennitalas:
        test += f'    "{kt}",\n'
    test += "];\n"
    return test


def test_from_kennitalas(test_name: str, kennitalas: List[str], bad=True) -> str:
    assert len(test_name) > 0
    assert all(ord(c) < 128 for c in test_name)
    test = "#[test]\n"
    test += f"fn {test_name}()" + "{\n"
    test += rust_from_kennitalas(kennitalas)
    test += "    for kt_str in KENNITALAS.iter()" + "{\n"
    test += "        let kt_result = Kennitala::new(kt_str);\n"
    if bad:
        test += "        assert!(kt_result.is_err());\n"
    else:
        test += "let kt = kt_result.unwrap();\n"
    if not bad:
        test += "        assert_eq!(kt.to_string(), kt_str.to_owned());"
    test += "    }\n"
    test += "}\n"
    return test


def run_rustfmt(rust_code):
    """
    Run `rustfmt` on the given Rust code if it is available on the current
    system.
    """
    if which("rustfmt"):
        rustfmt = subprocess.Popen(
            ["rustfmt"], stdin=subprocess.PIPE, stdout=subprocess.PIPE
        )
        rust_code = rustfmt.communicate(rust_code.encode("utf-8"))[0].decode("utf-8")
    return rust_code


def dump_to_file(string: str, file_path: str):
    with open(file_path, "w", encoding="utf-8") as f:
        f.write(string)


def main():
    BAD_PARAMS = [
        ["month_is_zero_1", "220001", "0"],
        ["month_is_zero_2", "030012", "9"],
        ["day_is_zero_1", "000300", "9"],
        ["day_is_zero_2", "001175", "0"],
        ["leap_day_in_2001", "290201", "0"],
    ]

    GOOD_PARAMS = [
        ["new_years_1999", "311299", "9"],
        ["new_years_2000", "311200", "0"],
        ["first_january_2001", "010101", "0"],
        ["leap_day_in_2000", "290200", "0"],
    ]

    file_contents = "// DO NOT EDIT! This file was automatically generated by"
    file_contents += " the\n// `autogenerate_tests.py` Python script.\n"
    file_contents += "use kennitolur::Kennitala;\n"
    file_contents += "use std::string::ToString;\n\n"
    for (test_name, first_six, century) in BAD_PARAMS:
        kennitalas = generate_kennitalas(first_six, century)
        file_contents += test_from_kennitalas(test_name, kennitalas, bad=True)
    for (test_name, first_six, century) in GOOD_PARAMS:
        kennitalas = generate_kennitalas(first_six, century)
        file_contents += test_from_kennitalas(test_name, kennitalas, bad=False)

    # Run rustfmt on the generated code
    file_contents = run_rustfmt(file_contents)

    # Generate the tests/ directory
    this_dir = os.path.abspath(os.path.dirname(__file__))
    target_dir = os.path.join(this_dir, "tests")
    os.makedirs(target_dir, exist_ok=True)

    # Dump the generated tests to tests/autogenerated_tests.rs
    file_path = os.path.join(target_dir, "autogenerated_tests.rs")
    dump_to_file(file_contents, file_path)


if __name__ == "__main__":
    main()