"""Offline cache accounting calculator. USD; no dependencies or network calls."""
from dataclasses import dataclass
from decimal import Decimal
import unittest

D = Decimal
MILLION = D(1_000_000)

@dataclass(frozen=True)
class Rates:
    ordinary: Decimal
    write: Decimal
    read: Decimal
    output: Decimal

def cost(ordinary, written, read, output, rates, storage_usd="0"):
    counts = (ordinary, written, read, output)
    if any(type(n) is not int or n < 0 for n in counts):
        raise ValueError("Counts must be nonnegative integers")
    if any(not p.is_finite() or p < 0 for p in (rates.ordinary, rates.write, rates.read, rates.output)):
        raise ValueError("Rates must be finite and nonnegative")
    storage = D(storage_usd)
    if not storage.is_finite() or storage < 0:
        raise ValueError("Storage must be finite and nonnegative")
    return sum((D(n) * p for n, p in zip(counts, (rates.ordinary, rates.write, rates.read, rates.output))), D(0)) / MILLION + storage

def campaign(requests, prefix, suffix, output, writes, hits, rates):
    if any(type(n) is not int or n < 0 for n in (requests, prefix, suffix, output, writes, hits)):
        raise ValueError("Campaign counts must be nonnegative integers")
    if writes + hits > requests:
        raise ValueError("Writes and hits exceed requests")
    misses = requests - writes - hits
    return cost(requests * suffix + misses * prefix, writes * prefix,
                hits * prefix, requests * output, rates)

SOL = Rates(D("2"), D("2.50"), D("0.10"), D("10"))

class Tests(unittest.TestCase):
    def test_baseline(self):
        self.assertEqual(campaign(100, 20000, 2000, 1000, 0, 0, SOL), D("5.4"))
    def test_warm(self):
        self.assertEqual(campaign(100, 20000, 2000, 1000, 1, 99, SOL), D("1.648"))
    def test_five_epochs(self):
        self.assertEqual(campaign(100, 20000, 2000, 1000, 5, 95, SOL), D("1.84"))
    def test_every_request_writes(self):
        self.assertEqual(campaign(100, 20000, 2000, 1000, 100, 0, SOL), D("6.4"))
    def test_storage(self):
        self.assertEqual(cost(0, 0, 0, 0, SOL, "0.01"), D("0.01"))
    def test_invalid(self):
        for args in ((1, 1, 1, 1, 1, 1), (1, -1, 1, 1, 0, 0), (1.0, 1, 1, 1, 0, 0)):
            with self.assertRaises(ValueError):
                campaign(*args, SOL)
        with self.assertRaises(ValueError):
            cost(0, 0, 0, 0, SOL, "-1")
    def test_nonfinite_money(self):
        for invalid in ("NaN", "Infinity", "-Infinity"):
            with self.assertRaises(ValueError):
                cost(0, 0, 0, 0, SOL, invalid)
            with self.assertRaises(ValueError):
                cost(1, 0, 0, 0, Rates(D(invalid), SOL.write, SOL.read, SOL.output))

if __name__ == "__main__":
    result = unittest.main(exit=False)
    if not result.result.wasSuccessful():
        raise SystemExit(1)
    for label, writes, hits in (("No cache", 0, 0), ("Warm", 1, 99), ("Five epochs", 5, 95), ("Write churn", 100, 0)):
        print(f"{label}: ${campaign(100, 20000, 2000, 1000, writes, hits, SOL):.3f}")