"""Tests for reconstruct.py — the VT1200 EPROM de-interleaver.

The firmware's addresses are now known (see MEMORY_MAP.md): the ROM is
top-aligned at physical byte 0x07E40000 and the EPROM *bank* order is the
reverse of part-number order.  `reconstruct(..., linear=True)` must therefore
emit an image where file offset == physical byte - 0x07E40000.
"""
import os
import struct
import unittest

import reconstruct

ROM_SIZE = 0x1C0000
ROM_BASE = 0x07E40000
RESET_VECTOR = 0x3F200040                 # bit address the reset entry holds
POST_BYTES = bytes.fromhex("6003500540070056")
# In part-number order bank0 (210/211) is first, so its reset vector -- the last
# entry of the vector page -- lands at file offset 0x3FFFC.
RESET_VECTOR_OFFSET_PART_ORDER = 0x3FFFC


def _load(dirname, linear):
    return reconstruct.reconstruct(dirname, linear=linear)[1]


class LinearImageTest(unittest.TestCase):
    """linear=True yields an image whose offsets are CPU-address ordered."""

    def test_size(self):
        self.assertEqual(len(_load("v2.1", linear=True)), ROM_SIZE)

    def test_reset_vector_is_at_top_of_rom(self):
        img = _load("v2.1", linear=True)
        self.assertEqual(struct.unpack_from("<I", img, len(img) - 4)[0], RESET_VECTOR)

    def test_reset_target_holds_post_code(self):
        # 0x3F200040 >> 3 == 0x07E40008 == ROM_BASE + 8
        img = _load("v2.1", linear=True)
        self.assertEqual(img[8:8 + len(POST_BYTES)], POST_BYTES)

    def test_vector_page_is_at_top(self):
        linear = _load("v2.1", linear=True)
        part = _load("v2.1", linear=False)
        self.assertEqual(linear[-0x80:], part[0x3FF80:0x40000])

    def test_known_string_pointer_resolves(self):
        # Stored pointer 0x3F816ED8 >> 3 == ROM_BASE + 0xC2DDB
        img = _load("v2.1", linear=True)
        self.assertEqual(img[0xC2DDB:0xC2DDB + 15], b"Messages re-xmt")


class PartOrderImageTest(unittest.TestCase):
    """linear=False preserves the legacy part-number-ordered layout."""

    def test_reset_vector_location(self):
        img = _load("v2.1", linear=False)
        self.assertEqual(
            struct.unpack_from("<I", img, RESET_VECTOR_OFFSET_PART_ORDER)[0],
            RESET_VECTOR,
        )


if __name__ == "__main__":
    unittest.main()