"""Load Power C runtime-helper objects into the 6502 emulator and compare implementations.

usage (library):  h = Helper(obj, base=0x6000, ext={'C$HIGHMEM': 0xC000, ...})
                  h.addr('C$105')
"""
import sys, os, random
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from objfmt import Obj
from cpu6502 import CPU


class Helper:
    def __init__(self, obj, base, ext):
        self.o = obj
        self.base = base
        self.code = bytearray(obj.code)
        for off in obj.reloc:                      # local absolute operands
            v = self.code[off + 1] | self.code[off + 2] << 8
            v = (v + base) & 0xFFFF
            self.code[off + 1] = v & 255; self.code[off + 2] = v >> 8
        syms = {nm: base + off for nm, k, off in obj.defs}
        syms.update({k.encode() if isinstance(k, str) else k: v for k, v in ext.items()})
        for nm, kind, off in obj.refs:
            a = syms[bytes(nm)]
            if kind == 0:
                self.code[off + 1] = a & 255; self.code[off + 2] = a >> 8
            elif kind == 4:
                a += 1; self.code[off + 1] = a & 255; self.code[off + 2] = a >> 8
            elif kind == 2:
                self.code[off + 1] = a & 255
            elif kind == 1:
                self.code[off + 1] = a >> 8
            else:
                raise ValueError('kind %d' % kind)
        self.syms = syms

    def addr(self, name):
        return self.syms[name.encode() if isinstance(name, str) else name]

    def install(self, cpu):
        cpu.m[self.base:self.base + len(self.code)] = self.code


def snapshot(cpu, skip=()):
    m = bytes(cpu.m)
    return m


def diff_mem(a, b, skip):
    out = []
    for i in range(65536):
        if a[i] != b[i] and not any(lo <= i < hi for lo, hi in skip):
            out.append((i, a[i], b[i]))
            if len(out) > 8: break
    return out