#!/usr/bin/env python3
"""Jar inspection without unzip/java.

  jx.py ls    JAR[!nested.jar...] [regex]       list entries
  jx.py cat   JAR[!nested.jar...] entry         print entry
  jx.py str   JAR[!nested.jar...] classregex strregex   UTF8 constants of classes
"""
import io, re, struct, sys, zipfile


def open_jar(spec):
    parts = spec.split("!")
    z = zipfile.ZipFile(parts[0])
    for p in parts[1:]:
        z = zipfile.ZipFile(io.BytesIO(z.read(p)))
    return z


def utf8_consts(data):
    out = []
    if data[:4] != b"\xca\xfe\xba\xbe":
        return out
    n = struct.unpack(">H", data[8:10])[0]
    i, k = 10, 1
    while k < n:
        tag = data[i]
        if tag == 1:
            ln = struct.unpack(">H", data[i + 1:i + 3])[0]
            out.append(data[i + 3:i + 3 + ln].decode("utf-8", "replace"))
            i += 3 + ln
        elif tag in (3, 4):
            i += 5
        elif tag in (5, 6):
            i += 9; k += 1
        elif tag in (7, 8, 16, 19, 20):
            i += 3
        elif tag in (9, 10, 11, 12, 17, 18):
            i += 5
        elif tag == 15:
            i += 4
        else:
            break
        k += 1
    return out


def main():
    cmd, spec = sys.argv[1], sys.argv[2]
    z = open_jar(spec)
    if cmd == "ls":
        rx = re.compile(sys.argv[3]) if len(sys.argv) > 3 else None
        for n in z.namelist():
            if not rx or rx.search(n):
                print(n)
    elif cmd == "cat":
        sys.stdout.write(z.read(sys.argv[3]).decode("utf-8", "replace"))
    elif cmd == "str":
        crx, srx = re.compile(sys.argv[3]), re.compile(sys.argv[4])
        for n in z.namelist():
            if n.endswith(".class") and crx.search(n):
                hits = [s for s in utf8_consts(z.read(n)) if srx.search(s)]
                if hits:
                    print("==", n)
                    for h in hits:
                        print("  ", repr(h))


main()