#!/usr/bin/env python3
"""
Counter-demonstration for shakespeare-enquiry.org (cipher-arguments, Entry 5):
an equidistant-letter-sequence (ELS) search on the 1609 Sonnets dedication.
Shows that a single-skip ELS rule pulls hundreds of words out of the 146
letters, so "a name drops out" (VERE, HENRY) is the null expectation.

Word list: /usr/share/dict/american-english (Debian `wamerican`, SCOWL-derived;
includes common proper names). Words length 4-7. Single fixed skip, read
forwards or backwards. Transcription is the printed dedication, letters only,
V as printed. Edit DED to change the transcription and watch the numbers move.
"""
import re, os, random

DED = ("TO.THE.ONLIE.BEGETTER.OF.THESE.INSVING.SONNETS.MR.W.H.ALL.HAPPINESSE."
       "AND.THAT.ETERNITIE.PROMISED.BY.OVR.EVER-LIVING.POET.WISHETH.THE."
       "WELL-WISHING.ADVENTVRER.IN.SETTING.FORTH.T.T.")
L = re.sub(r'[^A-Z]', '', DED.upper())
n = len(L)

def find_els(target):
    m = len(target)
    if m < 2: return None
    for skip in range(1, (n - 1) // (m - 1) + 1):
        for start in range(n):
            fwd = [start + skip * k for k in range(m)]
            if fwd[-1] < n and ''.join(L[i] for i in fwd) == target:
                return (start, skip, 'fwd')
            bwd = [start - skip * k for k in range(m)]
            if bwd[-1] >= 0 and ''.join(L[i] for i in bwd) == target:
                return (start, skip, 'bwd')
    return None

def all_els_substrings(lo=4, hi=7):
    S = set()
    for skip in range(1, n):
        for r in range(skip):
            seq = L[r::skip]
            for a in range(len(seq)):
                for m in range(lo, hi + 1):
                    if a + m <= len(seq):
                        sub = seq[a:a + m]; S.add(sub); S.add(sub[::-1])
    return S

if __name__ == "__main__":
    print(f"letters: {n}\n{L}\n")
    print("Named targets (single clean skip, either direction):")
    for t in ["VERE", "EVER", "HENRY", "OXFORD", "WRIOTHESLEY", "DEVERE"]:
        print(f"  {t:12} {find_els(t)}")
    wl = "/usr/share/dict/american-english"
    if os.path.exists(wl):
        words = {w.strip().upper() for w in open(wl, encoding='latin-1')
                 if w.strip().isalpha() and 4 <= len(w.strip()) <= 7}
        hits = sorted(all_els_substrings() & words)
        print(f"\nWord-list words (len 4-7) that drop out as a clean ELS: {len(hits)}")
        print(f"  length >= 5: {len([w for w in hits if len(w) >= 5])}")
        random.seed(3)
        print("  random sample:", ", ".join(random.sample(hits, min(30, len(hits)))))
    else:
        print(f"\n(no word list at {wl}; skipping the dictionary sweep)")