"""Synthetic carbon accounting and dilute water-vapor transfer. Python >= 3.10.

Not a fitted crop model. Carbon uses gC/h and hours. Water uses total
conductance per consistently defined leaf area; both pressures use kPa.
No dependencies or file writes. See the accompanying README and article.
"""
import argparse
import json
import math
from pathlib import Path
import unittest


def nonnegative(*values):
    if any(isinstance(v, bool) or not isinstance(v, (int, float))
           or not math.isfinite(v) or v < 0 for v in values):
        raise ValueError("Inputs must be finite nonnegative numbers")


def carbon(uptake_gc_h, release_gc_h, hours):
    nonnegative(uptake_gc_h, release_gc_h, hours)
    return (uptake_gc_h - release_gc_h) * hours


def water(total_conductance, leaf_air_kpa, pressure_kpa=100.0):
    nonnegative(total_conductance, leaf_air_kpa, pressure_kpa)
    if pressure_kpa <= 0 or leaf_air_kpa >= pressure_kpa:
        raise ValueError("Require 0 <= vapor difference < positive total pressure")
    # Positive outward transfer only; condensation is outside this example.
    return total_conductance * (leaf_air_kpa / pressure_kpa) * 0.018 * 3600


def verify(actual, expected):
    if type(actual) is not type(expected):
        raise ValueError("Result type mismatch")
    if isinstance(actual, dict):
        if actual.keys() != expected.keys():
            raise ValueError("Result keys differ")
        for key in actual:
            verify(actual[key], expected[key])
    elif isinstance(actual, (float, int)):
        if not (math.isfinite(actual) and math.isfinite(expected)
                and math.isclose(actual, expected, rel_tol=1e-10, abs_tol=1e-10)):
            raise ValueError("Numerical result differs")
    elif actual != expected:
        raise ValueError("Result differs")


class Checks(unittest.TestCase):
    def test_dark_carbon_loss(self):
        self.assertAlmostEqual(carbon(0, 0.15, 8), -1.2)

    def test_period_partition(self):
        self.assertAlmostEqual(carbon(0.8, 0.15, 16),
                               sum(carbon(0.8, 0.15, 1) for _ in range(16)))

    def test_release_sensitivity(self):
        baseline = carbon(0.8, 0.15, 16) + carbon(0, 0.15, 8)
        changed = carbon(0.8, 0.25, 16) + carbon(0, 0.25, 8)
        self.assertAlmostEqual(baseline - changed, 2.4)

    def test_water_units(self):
        # 2 mmol/(m2 s) * 18 mg/mmol * 3600 s/h = 129600 mg/(m2 h)
        self.assertAlmostEqual(water(0.2, 1), 129600 / 1e6)

    def test_zero_transfer(self):
        self.assertEqual(water(0, 1), 0)
        self.assertEqual(water(0.2, 0), 0)

    def test_same_flux_different_inputs(self):
        self.assertAlmostEqual(water(0.2, 1), water(0.1, 2))

    def test_invalid_inputs(self):
        for bad in (-1, float('nan'), float('inf'), True, '1'):
            with self.subTest(bad=bad):
                with self.assertRaises(ValueError): carbon(bad, 0.15, 16)
                with self.assertRaises(ValueError): water(0.2, bad)
        for pressure in (0, 0.5):
            with self.assertRaises(ValueError): water(0.2, 1, pressure)

    def test_verification_rejects_bad_results(self):
        for bad in ({'x': float('nan')}, {'x': 2.0}, {}, {'x': 1.0, 'y': 2}):
            with self.assertRaises(ValueError): verify({'x': 1.0}, bad)


def examples():
    return {
        'scope': 'synthetic; carbon change is not yield; prescribed conductance',
        'carbon_gc': {
            'light': carbon(0.8, 0.15, 16),
            'dark': carbon(0, 0.15, 8),
            'daily': carbon(0.8, 0.15, 16) + carbon(0, 0.15, 8),
            'higher_release_daily': carbon(0.8, 0.25, 16) + carbon(0, 0.25, 8),
        },
        'water_kg_per_m2_leaf_per_h': {
            'A': water(0.2, 1), 'B': water(0.1, 1), 'C': water(0.1, 2),
        },
    }


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description=__doc__)
    group = parser.add_mutually_exclusive_group()
    group.add_argument('--self-test', action='store_true')
    group.add_argument('--verify', type=Path)
    args = parser.parse_args()
    if args.self_test:
        suite = unittest.defaultTestLoader.loadTestsFromTestCase(Checks)
        result = unittest.TextTestRunner(verbosity=2).run(suite)
        raise SystemExit(0 if result.wasSuccessful() else 1)
    if args.verify:
        verify(examples(), json.loads(args.verify.read_text()))
        print('All expected results verified')
    else:
        print(json.dumps(examples(), indent=2, allow_nan=False))