import unittest
from pathlib import Path

from h8536.emulator import (
    HEARTBEAT_FRAME,
    ON_CHIP_RAM_START,
    REGISTER_FIELD_START,
    SCI1_SCR,
    SCI1_SSR,
    SCI1_TDR,
    SCI_SCR_TE,
    SCI_SSR_TDRE,
    H8536Emulator,
    MemoryMap,
    SCI1,
    discover_rom_path,
    load_rom,
)


class EmulatorHarnessTest(unittest.TestCase):
    def test_memory_map_routes_rom_ram_register_and_external(self):
        memory = MemoryMap(bytes([0x12, 0x34, 0x56, 0x78]))

        self.assertEqual(memory.read8(0x0001), 0x34)
        memory.write8(ON_CHIP_RAM_START, 0xA5)
        self.assertEqual(memory.read8(ON_CHIP_RAM_START), 0xA5)
        memory.write8(REGISTER_FIELD_START, 0x5A)
        self.assertEqual(memory.read8(REGISTER_FIELD_START), 0x5A)
        memory.write8(0xF000, 0x11)
        self.assertEqual(memory.read8(0xF000), 0x11)

    def test_sci_transmit_capture_requires_enabled_transmitter(self):
        sci = SCI1()
        sci.write(SCI1_TDR, 0x33)
        self.assertEqual(sci.tx_bytes, [])
        self.assertFalse(sci.tx_events[-1].emitted)

        sci.write(SCI1_SCR, sci.scr | SCI_SCR_TE)
        for byte in HEARTBEAT_FRAME:
            sci.write(SCI1_TDR, byte)

        self.assertEqual(bytes(sci.tx_bytes), HEARTBEAT_FRAME)
        self.assertEqual(sci.tx_frames, [HEARTBEAT_FRAME])
        self.assertTrue(sci.saw_heartbeat())
        self.assertTrue(sci.read(SCI1_SSR) & SCI_SSR_TDRE)

    def test_vector_decoding_uses_minimum_mode_reset_word(self):
        rom = bytearray(0x1004)
        rom[0:2] = b"\x10\x00"
        rom[0x1000] = 0x00

        emulator = H8536Emulator(bytes(rom))

        self.assertEqual(emulator.reset_vector(), 0x1000)
        self.assertEqual(emulator.cpu.pc, 0x1000)
        self.assertEqual(emulator.vectors[0x0000][1], 0x1000)

    def test_harness_instantiates_on_repo_artifacts(self):
        root = Path(__file__).resolve().parents[1]
        rom_path = discover_rom_path(root)
        self.assertIsNotNone(rom_path)
        rom_bytes, loaded_path = load_rom(root=root)

        emulator = H8536Emulator(rom_bytes)
        report = emulator.run(max_steps=4)

        self.assertEqual(loaded_path, rom_path)
        self.assertEqual(emulator.reset_vector(), 0x1000)
        self.assertGreaterEqual(len(rom_bytes), 0x1002)
        self.assertEqual(report.steps, 4)
        self.assertFalse(report.heartbeat_seen)


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