"""Check an .exe's CodeView debug info to see what PDB GUID + age it
expects. Used to verify whether a candidate acclient.exe matches our
acclient.pdb without running the binary.

Usage:
    py tools/pdb-extract/check_exe_pdb.py <path-to-exe>
"""

import struct
import sys
import uuid


def main():
    if len(sys.argv) < 2:
        print("usage: check_exe_pdb.py <path-to-exe>")
        sys.exit(1)

    with open(sys.argv[1], "rb") as f:
        data = f.read()

    # DOS header -> e_lfanew @ offset 0x3C points to PE header
    pe_off = struct.unpack_from("<I", data, 0x3C)[0]
    assert data[pe_off:pe_off + 4] == b"PE\x00\x00", "not a PE file"

    # COFF header
    machine = struct.unpack_from("<H", data, pe_off + 4)[0]
    n_sections = struct.unpack_from("<H", data, pe_off + 6)[0]
    timestamp = struct.unpack_from("<I", data, pe_off + 8)[0]
    opt_size = struct.unpack_from("<H", data, pe_off + 20)[0]

    print(f"machine        = 0x{machine:04x}")
    print(f"timestamp      = 0x{timestamp:08x} ({timestamp})")

    import datetime
    ts = datetime.datetime.fromtimestamp(timestamp, tz=datetime.timezone.utc)
    print(f"  -> linker UTC: {ts.isoformat()}")

    # Optional header — magic indicates 32 vs 64 bit
    opt_off = pe_off + 24
    magic = struct.unpack_from("<H", data, opt_off)[0]
    is_pe32_plus = (magic == 0x20B)
    print(f"opt magic      = 0x{magic:04x} ({'PE32+' if is_pe32_plus else 'PE32'})")

    # Data directories: PE32 has them at opt_off + 96; PE32+ at opt_off + 112
    dd_off = opt_off + (112 if is_pe32_plus else 96)
    # Debug directory is data dir [6]
    debug_va = struct.unpack_from("<I", data, dd_off + 6 * 8)[0]
    debug_size = struct.unpack_from("<I", data, dd_off + 6 * 8 + 4)[0]
    print(f"debug dir      = VA=0x{debug_va:08x}  size={debug_size}")

    # We need to map the VA back to a file offset via section headers
    sec_off = opt_off + opt_size
    sections = []
    for i in range(n_sections):
        s = sec_off + i * 40
        name = data[s:s + 8].rstrip(b"\x00").decode("ascii", errors="replace")
        vsize = struct.unpack_from("<I", data, s + 8)[0]
        vaddr = struct.unpack_from("<I", data, s + 12)[0]
        rsize = struct.unpack_from("<I", data, s + 16)[0]
        roff = struct.unpack_from("<I", data, s + 20)[0]
        sections.append((name, vaddr, vsize, roff, rsize))

    def va_to_file(va):
        for (name, vaddr, vsize, roff, rsize) in sections:
            if vaddr <= va < vaddr + vsize:
                return roff + (va - vaddr)
        return None

    debug_off = va_to_file(debug_va)
    if debug_off is None:
        print("debug directory VA does not map into any section")
        return

    # Each debug directory entry is 28 bytes
    n_entries = debug_size // 28
    print(f"# debug entries = {n_entries}")

    for i in range(n_entries):
        e = debug_off + i * 28
        characteristics = struct.unpack_from("<I", data, e)[0]
        ts_e = struct.unpack_from("<I", data, e + 4)[0]
        major = struct.unpack_from("<H", data, e + 8)[0]
        minor = struct.unpack_from("<H", data, e + 10)[0]
        type_e = struct.unpack_from("<I", data, e + 12)[0]
        sz = struct.unpack_from("<I", data, e + 16)[0]
        rva = struct.unpack_from("<I", data, e + 20)[0]
        ptr = struct.unpack_from("<I", data, e + 24)[0]

        type_name = {2: "CODEVIEW", 4: "MISC", 12: "VC_FEATURE", 13: "POGO", 16: "REPRO"}.get(type_e, f"type_{type_e}")
        print(f"  entry {i}: type={type_name} sz={sz} fileOff=0x{ptr:08x}")

        if type_e == 2 and sz >= 24:
            cv = data[ptr:ptr + sz]
            sig = cv[:4]
            print(f"    cv signature = {sig!r}")
            if sig == b"RSDS":
                guid_bytes = cv[4:20]
                age = struct.unpack_from("<I", cv, 20)[0]
                pdb_name = cv[24:].rstrip(b"\x00").decode("utf-8", errors="replace")
                pdb_guid = uuid.UUID(bytes_le=guid_bytes)
                print(f"    GUID         = {{{pdb_guid}}}")
                print(f"    age          = {age}")
                print(f"    PDB filename = {pdb_name}")

                expected_guid = uuid.UUID("9e847e2f-777c-4bd9-886c-22256bb87f32")
                expected_age = 1
                if pdb_guid == expected_guid and age == expected_age:
                    print()
                    print("=== MATCH: this exe pairs with our acclient.pdb ===")
                else:
                    print()
                    print("=== MISMATCH ===")
                    print(f"  expected GUID = {{{expected_guid}}}")
                    print(f"  expected age  = {expected_age}")


if __name__ == "__main__":
    main()