import unittest

from byteb4rb1e_utils.collections import CircularBuffer

class test_init(unittest.TestCase):
    """CircularBuffer.__init__()"""

    def test_default(self):
        """Test buffer initializes correctly."""
        buffer = CircularBuffer(10)
        self.assertEqual(len(buffer.buf), 10)
        self.assertEqual(buffer.size, 10)
        self.assertEqual(buffer.start, 0)
        self.assertEqual(buffer.end, 0)
        self.assertFalse(buffer.filled)


class test_append(unittest.TestCase):
    """CircularBuffer.append()"""

    def test_without_overflow(self):
        """Test appending bytes without overwriting."""
        buffer = CircularBuffer(5)
        buffer.append(b"abc")
        self.assertEqual(buffer.buf[:3], bytearray(b"abc"))
        self.assertEqual(buffer.start, 0)
        self.assertEqual(buffer.end, 3)
        self.assertFalse(buffer.filled)

    def test_with_overflow(self):
        """appending bytes with overwriting"""
        buffer = CircularBuffer(5)
        buffer.append(b"abcde")  # Fill buffer completely
        buffer.append(b"fg")  # Overwrite some elements

        self.assertEqual(buffer.buf, bytearray(b"fgcde"))  # Last five elements should remain
        self.assertEqual(buffer.start, 3)  # Should have moved forward due to overwrite
        self.assertEqual(buffer.end, 2)  # Wrapped around
        self.assertTrue(buffer.filled)  # Buffer should indicate overwrite occurred

    def test_wraparound_behavior(self):
        """correct handling of buffer wraparound"""
        buffer = CircularBuffer(4)
        buffer.append(b"abcd")  # Fill buffer completely
        buffer.append(b"e")  # Overwrite first element

        self.assertEqual(buffer.buf, bytearray(b"ebcd"))  # Should have wrapped around
        self.assertEqual(buffer.start, 2)
        self.assertEqual(buffer.end, 1)
        self.assertTrue(buffer.filled)

    def test_consecutive_overwrites(self):
        """repeated buffer overwrites across multiple cycles

        verifies that the circular buffer correctly handles multiple overwrite cycles.

        - Initially, the buffer is filled completely (`abcde`).
        - New data (`fghij`) is appended, causing the oldest elements to be replaced.
        - The buffer does not physically shift; only the `start` index moves forward as data is overwritten.
        - When wrapping around, the `start` advances while `end` cycles back to zero.

        Expected:
           - Buffer contents should be `bytearray(b"fghij")`, containing only
             the most recent data
           - `start` moves forward due to full overwriting.
           - `end` correctly wraps around.
           - `filled` flag indicates that overwrites have occurred.

        **Why `start = 1` instead of `0`?**
        Well it took some brain juice for me to fully comprehend it, but in a
        circular buffer, `start` always marks the oldest remaining element.
        When a full overwrite occurs, `start` moves forward to indicate the next
        oldest position, ensuring sequential ordering is preserved.
        """
        buffer = CircularBuffer(5)
        buffer.append(b"abcde")  # Fill buffer
        buffer.append(b"fghij")  # Overwrite completely

        self.assertEqual(buffer.buf, bytearray(b"fghij"))  # Only the latest data remains
        self.assertEqual(buffer.start, 1)
        self.assertEqual(buffer.end, 0)
        self.assertTrue(buffer.filled)