agenda/tests/test_fx.py

"""Tests for foreign exchange functionality."""

import json
import os
import tempfile
from decimal import Decimal
from unittest.mock import Mock, patch

import pytest

from agenda.fx import read_cached_rates


class TestReadCachedRates:
    """Test the read_cached_rates function."""

    def test_read_cached_rates_none_filename(self) -> None:
        """Test with None filename returns empty dict."""
        result = read_cached_rates(None, ["USD", "EUR"])
        assert result == {}

    def test_read_cached_rates_valid_file(self) -> None:
        """Test reading valid cached rates file."""
        currencies = ["USD", "EUR", "JPY"]
        data = {
            "quotes": {
                "GBPUSD": 1.25,
                "GBPEUR": 1.15,
                "GBPJPY": 150.0,
                "GBPCAD": 1.70  # Not requested
            }
        }
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            result = read_cached_rates(filepath, currencies)
            
            assert len(result) == 3
            assert result["USD"] == Decimal("1.25")
            assert result["EUR"] == Decimal("1.15")
            assert result["JPY"] == Decimal("150.0")
            assert "CAD" not in result  # Not requested
            
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_missing_currencies(self) -> None:
        """Test with some currencies missing from data."""
        currencies = ["USD", "EUR", "CHF"]  # CHF not in data
        data = {
            "quotes": {
                "GBPUSD": 1.25,
                "GBPEUR": 1.15
                # GBPCHF missing
            }
        }
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            result = read_cached_rates(filepath, currencies)
            
            assert len(result) == 2
            assert result["USD"] == Decimal("1.25")
            assert result["EUR"] == Decimal("1.15")
            assert "CHF" not in result  # Missing from data
            
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_empty_currencies_list(self) -> None:
        """Test with empty currencies list."""
        data = {
            "quotes": {
                "GBPUSD": 1.25,
                "GBPEUR": 1.15
            }
        }
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            result = read_cached_rates(filepath, [])
            assert result == {}
            
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_no_quotes_key(self) -> None:
        """Test with data missing quotes key."""
        currencies = ["USD", "EUR"]
        data = {"other_key": "value"}  # No quotes key
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            with pytest.raises(KeyError):
                read_cached_rates(filepath, currencies)
                
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_file_not_found(self) -> None:
        """Test error handling when file doesn't exist."""
        with pytest.raises(FileNotFoundError):
            read_cached_rates("/nonexistent/file.json", ["USD"])

    def test_read_cached_rates_invalid_json(self) -> None:
        """Test error handling with invalid JSON."""
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            f.write("invalid json content")
            filepath = f.name
        
        try:
            with pytest.raises(json.JSONDecodeError):
                read_cached_rates(filepath, ["USD"])
                
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_decimal_precision(self) -> None:
        """Test that rates are returned as Decimal with proper precision."""
        currencies = ["USD"]
        data = {
            "quotes": {
                "GBPUSD": 1.234567890123456789  # High precision
            }
        }
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            result = read_cached_rates(filepath, currencies)
            
            assert isinstance(result["USD"], Decimal)
            # Should preserve reasonable precision from the JSON  
            # Python's JSON precision may be limited to float precision
            expected = Decimal("1.234567890123456789")
            assert abs(result["USD"] - expected) < Decimal("0.0000000000000001")
            
        finally:
            os.unlink(filepath)

    def test_read_cached_rates_various_currency_codes(self) -> None:
        """Test with various currency codes."""
        currencies = ["USD", "EUR", "JPY", "CHF", "CAD", "AUD"]
        data = {
            "quotes": {
                "GBPUSD": 1.25,
                "GBPEUR": 1.15,
                "GBPJPY": 150.0,
                "GBPCHF": 1.12,
                "GBPCAD": 1.70,
                "GBPAUD": 1.85
            }
        }
        
        with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f:
            json.dump(data, f)
            filepath = f.name
        
        try:
            result = read_cached_rates(filepath, currencies)
            
            assert len(result) == 6
            for currency in currencies:
                assert currency in result
                assert isinstance(result[currency], Decimal)
                
        finally:
            os.unlink(filepath)