#!/usr/bin/env python3
"""check_realconst.py -- the six bytes of TP3's Real, against CALC-PORT.md.

CALC-PORT.md decoded the format from CALCDEMO.MCS, cross-checked against the
cells holding 1, 2, 3, 4 and 5:

    value = (1 + N/2^39) * 2^(E-129)

byte 0 = E biased by 129, bytes 1..5 = N little-endian, the sign is bit 7 of
byte 5, and all-zero is 0.0.  No execution oracle can read a Real back yet, so
this check asserts the OPERAND BYTES in the emitted code instead: integer
constants stored through a symbol (B8 vv 00 A2 addr), through DI (C6 45 off
vv), and the six-byte copy (A0 src / 88 45 off).

The fixture is t80_realconst; its execution still checks the integer fields on
either side of the Real, which is what pins the store's WIDTH.
"""
import os
import re
import subprocess
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
SHELL = os.path.dirname(HERE)
FIX = os.path.join(HERE, "fixtures", "t80_realconst.pas")

# From the measured table (CALC-PORT.md).
MBF = {
    "0": bytes.fromhex("000000000000"),
    "1": bytes.fromhex("810000000000"),
    "2": bytes.fromhex("820000000000"),
    "3": bytes.fromhex("820000000040"),
    "5": bytes.fromhex("830000000020"),
}


def dump():
    r = subprocess.run([os.path.join(SHELL, "compiletest")],
                       input=("@image\n" + FIX + "\n").encode(),
                       capture_output=True, cwd=SHELL)
    text = r.stdout.decode("latin-1")
    if "  OK " not in text:
        sys.exit("the fixture did not compile:\n" + text)
    data = bytearray()
    for line in text.splitlines():
        m = re.match(r"^\s+([0-9A-Fa-f]{4}):\s+((?:[0-9A-Fa-f]{2}\s*)+)$", line)
        if m:
            data.extend(int(t, 16) for t in m.group(2).split())
    return bytes(data)


def symbol_stores(data):
    """The 6-byte runs of B8 vv 00 A2 lo hi with consecutive addresses."""
    runs = []
    i = 0
    while i + 6 <= len(data):
        if data[i] == 0xB8 and data[i + 2] == 0x00 and data[i + 3] == 0xA2:
            runs.append((data[i + 1], data[i + 4] | (data[i + 5] << 8)))
            i += 6
        else:
            i += 1
    found = {}
    for s in range(len(runs) - 5):
        seg = runs[s:s + 6]
        if all(seg[t + 1][1] == seg[t][1] + 1 for t in range(5)):
            found[bytes(v for v, _ in seg)] = seg[0][1]
    return found


def main():
    data = dump()
    problems = []

    found = symbol_stores(data)
    for name, want in MBF.items():
        if want not in found:
            problems.append("no symbol store of %s as %s" % (name, want.hex(" ")))
        else:
            print("  %s -> %s at %04xh" % (name, want.hex(" "), found[want]))

    # The DI form of `V := 1'.
    di1 = bytes.fromhex("C6450081C6450100C6450200C6450300C6450400C6450500")
    if di1 not in data:
        problems.append("the DI store of 1 is not C6 45 00 81 ... 05 00")

    # The six-byte copy through DI.
    for k in range(6):
        if bytes([0x88, 0x45, k]) not in data:
            problems.append("the copy never stores byte %d through DI" % k)

    if problems:
        print("FAIL:")
        for p in problems:
            print("  - " + p)
        return 1
    print("PASS: the measured MBF bytes for 0,1,2,3,5 are emitted, the DI "
          "store holds them,\n      and the six-byte copy stores every byte")
    return 0


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