#!/usr/bin/env python3
# Copyright lowRISC contributors.
# Licensed under the Apache License, Version 2.0, see LICENSE for details.
# SPDX-License-Identifier: Apache-2.0

'''A simulator that runs one instruction at a time, reading from a REPL

The input language is simple (and intended to be generated by another program).
Input should appear with one command per line.

The valid commands are as follows. All arguments are shown here as <argname>.
The integer arguments are read with Python's int() function, so should be
prefixed with "0x" if they are hexadecimal.

    start                Set the PC to zero and start OTBN

    configure            Enable or disable the secure wipe machinery (this is a
                         temporary feature until everything works together)

    step                 Run one instruction. Print trace information to
                         stdout.

    load_elf <path>      Load the ELF file at <path>, replacing current
                         contents of DMEM and IMEM.

    add_loop_warp <addr> <from> <to>

                         Add a loop warp to the simulation. This will trigger
                         at address <addr> and will jump from iteration <from>
                         to iteration <to>.

    clear_loop_warps     Clear any loop warp rules

    load_d <path>        Replace the current contents of DMEM with <path>
                         (read as an array of 32-bit little-endian words)

    load_i <path>        Replace the current contents of IMEM with <path>
                         (read as an array of 32-bit little-endian words)

    dump_d <path>        Write the current contents of DMEM to <path> (same
                         format as for load).

    print_regs           Write the contents of all registers to stdout (in hex)

    edn_rnd_step         Send 32b RND Data to the model.

    edn_rnd_cdc_done     Finish the RND data write process by signalling RTL
                         is also finished processing 32b packages from EDN.

    edn_urnd_step        Send 32b URND seed data to the model.

    edn_urnd_cdc_done    Finish the URND resseding process by signalling RTL
                         is also finished processing 32b packages from EDN and
                         set the seed.

    edn_flush            Flush EDN data from model because of reset signal in
                         EDN clock domain

    otp_key_cdc_done     Lowers the request flag for any external secure wipe
                         operation. Gets called when we acknowledge incoming
                         scrambling key in RTL.

    invalidate_imem      Mark all of IMEM as having invalid ECC checksums

    invalidate_dmem      Mark all of DMEM as having invalid ECC checksums

    set_keymgr_value     Send keymgr data to the model.

    step_crc             Step CRC function with 48 bits of data. No actual
                         change of state (this is pure, but handled in Python
                         to simplify verification).

    send_err_escalation  React to an injected error

'''

import binascii
import sys
from typing import List, Optional

from sim.decode import decode_file
from sim.load_elf import load_elf
from sim.sim import OTBNSim


def read_word(arg_name: str, word_data: str, bits: int) -> int:
    '''Try to read an unsigned word of the specified bit length'''
    try:
        value = int(word_data, 0)
    except ValueError:
        raise ValueError('Failed to read {!r} as an integer for <{}> argument.'
                         .format(word_data, arg_name)) from None

    if value < 0 or value >> bits:
        raise ValueError('<{}> argument is {!r}: '
                         'not representable in {!r} bits.'
                         .format(arg_name, word_data, bits))

    return value


def end_command() -> None:
    '''Print a single '.' to stdout and flush, ending the output for command'''
    print('.')
    sys.stdout.flush()


def check_arg_count(cmd: str, cnt: int, args: List[str]) -> None:
    if len(args) != cnt:
        if cnt == 0:
            txt_cnt = 'no arguments'
        elif cnt == 1:
            txt_cnt = 'exactly one argument'
        else:
            txt_cnt = f'exactly {cnt} arguments'

        raise ValueError(f'{cmd} expects {txt_cnt} arguments. Got {args}.')


def on_start(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Jump to an address given as the (only) argument and start running'''
    check_arg_count('start', 0, args)

    print('START')
    sim.state.ext_regs.commit()
    sim.start(collect_stats=False)

    return None


def on_dmem_wipe(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Sets Status register as SecWipeDmem '''
    check_arg_count('dmem_wipe', 0, args)

    sim.on_dmem_wipe()
    return None


def on_imem_wipe(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Sets Status register as SecWipeImem'''
    check_arg_count('imem_wipe', 0, args)

    sim.on_imem_wipe()
    return None


def on_configure(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('configure', 1, args)

    enable = read_word('secure_wipe_en', args[0], 1) != 0
    sim.configure(enable)

    return None


def on_step(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Step one instruction'''
    check_arg_count('step', 0, args)

    pc = sim.state.pc
    assert 0 == pc & 3

    was_wiping = sim.state.wiping() and sim.state.secure_wipe_enabled

    insn, changes = sim.step(verbose=False)
    if insn is not None:
        hdr = insn.rtl_trace(pc)  # type: Optional[str]
    elif was_wiping:
        # The trailing space is a bit naff but matches the behaviour in the RTL
        # tracer, where it's rather difficult to change.
        hdr = 'U ' if sim.state.wiping() else 'V '
    elif (sim.state.executing() or
          (changes and not sim.state.secure_wipe_enabled)):
        hdr = 'STALL'
    else:
        hdr = None

    rtl_changes = []
    for c in changes:
        rt = c.rtl_trace()
        if rt is not None:
            rtl_changes.append(rt)

    # This is a bit of a hack. Very occasionally, we'll see traced changes when
    # there's not actually an instruction in flight. For example, this happens
    # if there's a RND request still pending when an operation stops. In this
    # case, we might see a change where we drop the REQ signal after the secure
    # wipe has finished. Rather than define a special "do-nothing" trace entry
    # format for this situation, we cheat and use STALL.
    if hdr is None and rtl_changes:
        hdr = 'STALL'

    if hdr is not None:
        print(hdr)
        for rt in rtl_changes:
            print(rt)

    return None


def on_load_elf(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Load contents of ELF at path given by only argument'''
    check_arg_count('load_elf', 1, args)

    path = args[0]

    print('LOAD_ELF {!r}'.format(path))
    load_elf(sim, path)

    return None


def on_add_loop_warp(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Add a loop warp to the simulation'''
    check_arg_count('add_loop_warp', 3, args)

    try:
        addr = int(args[0], 0)
        if addr < 0:
            raise ValueError('addr is negative')
        from_cnt = int(args[1], 0)
        if from_cnt < 0:
            raise ValueError('from_cnt is negative')
        to_cnt = int(args[2], 0)
        if to_cnt < 0:
            raise ValueError('to_cnt is negative')
    except ValueError as err:
        raise ValueError('Bad argument to add_loop_warp: {}'
                         .format(err)) from None

    print('ADD_LOOP_WARP {:#x} {} {}'.format(addr, from_cnt, to_cnt))
    sim.add_loop_warp(addr, from_cnt, to_cnt)

    return None


def on_clear_loop_warps(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Run until ecall or error'''
    check_arg_count('clear_loop_warps', 0, args)

    sim.loop_warps = {}

    return None


def on_load_d(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Load contents of data memory from file at path given by only argument'''
    check_arg_count('load_d', 1, args)

    path = args[0]

    print('LOAD_D {!r}'.format(path))
    with open(path, 'rb') as handle:
        sim.load_data(handle.read(), has_validity=True)

    return None


def on_load_i(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Load contents of insn memory from file at path given by only argument'''
    check_arg_count('load_i', 1, args)

    path = args[0]

    print('LOAD_I {!r}'.format(path))
    sim.load_program(decode_file(0, path))

    return None


def on_dump_d(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Dump contents of data memory to file at path given by only argument'''
    check_arg_count('dump_d', 1, args)

    path = args[0]

    print('DUMP_D {!r}'.format(path))

    with open(path, 'wb') as handle:
        handle.write(sim.state.dmem.dump_le_words())

    return None


def on_print_regs(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Print registers to stdout'''
    check_arg_count('print_regs', 0, args)

    print('PRINT_REGS')
    for idx, value in enumerate(sim.state.gprs.peek_unsigned_values()):
        print(' x{:<2} = 0x{:08x}'.format(idx, value))
    for idx, value in enumerate(sim.state.wdrs.peek_unsigned_values()):
        print(' w{:<2} = 0x{:064x}'.format(idx, value))

    return None


def on_print_call_stack(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    '''Print call stack to stdout. First element is the bottom of the stack'''
    check_arg_count('print_call_stack', 0, args)

    print('PRINT_CALL_STACK')
    for value in sim.state.peek_call_stack():
        print('0x{:08x}'.format(value))

    return None


def on_reset(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if args:
        raise ValueError('reset expects zero arguments. Got {}.'
                         .format(args))

    return OTBNSim()


def on_edn_rnd_step(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if len(args) != 1:
        raise ValueError('edn_rnd_step expects exactly 1 argument. Got {}.'
                         .format(args))

    edn_rnd_data = read_word('edn_rnd_step', args[0], 32)

    sim.state.edn_rnd_step(edn_rnd_data)

    return None


def on_edn_urnd_step(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if len(args) != 1:
        raise ValueError('edn_urnd_step expects exactly 1 argument. Got {}.'
                         .format(args))

    edn_urnd_data = read_word('edn_urnd_step', args[0], 32)

    sim.state.edn_urnd_step(edn_urnd_data)

    return None


def on_edn_flush(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if len(args) != 0:
        raise ValueError('edn_flush expects zero arguments. Got {}.'
                         .format(args))

    sim.state.edn_flush()

    return None


def on_edn_urnd_cdc_done(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if len(args) != 0:
        raise ValueError('edn_urnd_cdc_done expects zero arguments. Got {}.'
                         .format(args))

    sim.state.urnd_completed()

    return None


def on_edn_rnd_cdc_done(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('edn_rnd_cdc_done', 0, args)

    sim.state.rnd_completed()

    return None


def on_invalidate_imem(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('invalidate_imem', 0, args)

    sim.state.invalidate_imem()
    return None


def on_invalidate_dmem(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('invalidate_dmem', 0, args)

    sim.state.dmem.empty_dmem()
    return None


def on_set_keymgr_value(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    if len(args) != 3:
        raise ValueError('set_keymgr_value expects exactly 1 argument. Got {}.'
                         .format(args))
    key0 = read_word('key0', args[0], 384)
    key1 = read_word('key1', args[1], 384)
    valid = read_word('valid', args[2], 1) == 1
    sim.state.wsrs.set_sideload_keys(key0 if valid else None,
                                     key1 if valid else None)

    return None


def on_step_crc(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('step_crc', 2, args)

    item = read_word('item', args[0], 48)
    state = read_word('state', args[1], 32)

    new_state = binascii.crc32(item.to_bytes(6, 'little'), state)
    print(f'! otbn.LOAD_CHECKSUM: 0x{new_state:08x}')

    return None


def on_send_err_escalation(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('send_err_escalation', 1, args)
    err_val = read_word('err_val', args[0], 32)
    sim.send_err_escalation(err_val)
    return None


def on_otp_cdc_done(sim: OTBNSim, args: List[str]) -> Optional[OTBNSim]:
    check_arg_count('otp_key_cdc_done', 0, args)

    sim.on_otp_cdc_done()
    return None


_HANDLERS = {
    'start': on_start,
    'dmem_wipe': on_dmem_wipe,
    'imem_wipe': on_imem_wipe,
    'otp_key_cdc_done': on_otp_cdc_done,
    'configure': on_configure,
    'step': on_step,
    'load_elf': on_load_elf,
    'add_loop_warp': on_add_loop_warp,
    'clear_loop_warps': on_clear_loop_warps,
    'load_d': on_load_d,
    'load_i': on_load_i,
    'dump_d': on_dump_d,
    'print_regs': on_print_regs,
    'print_call_stack': on_print_call_stack,
    'reset': on_reset,
    'edn_rnd_step': on_edn_rnd_step,
    'edn_urnd_step': on_edn_urnd_step,
    'edn_rnd_cdc_done': on_edn_rnd_cdc_done,
    'edn_urnd_cdc_done': on_edn_urnd_cdc_done,
    'edn_flush': on_edn_flush,
    'invalidate_imem': on_invalidate_imem,
    'invalidate_dmem': on_invalidate_dmem,
    'set_keymgr_value': on_set_keymgr_value,
    'step_crc': on_step_crc,
    'send_err_escalation': on_send_err_escalation
}


def on_input(sim: OTBNSim, line: str) -> Optional[OTBNSim]:
    '''Process an input command'''
    words = line.split()

    # Just ignore empty lines
    if not words:
        return None

    verb = words[0]
    handler = _HANDLERS.get(verb)
    if handler is None:
        raise RuntimeError('Unknown command: {!r}'.format(verb))

    ret = handler(sim, words[1:])
    print('.')
    sys.stdout.flush()

    return ret


def main() -> int:
    sim = OTBNSim()
    try:
        for line in sys.stdin:
            ret = on_input(sim, line)
            if ret is not None:
                sim = ret

    except KeyboardInterrupt:
        print("Received shutdown request, ending OTBN simulation.")
        return 0
    return 0


if __name__ == '__main__':
    sys.exit(main())