#!/usr/bin/env python3
"""Derive articles.jsonl from the Constitution 2.0 Core. Standard library only.

    python3 build_articles.py            # verify the committed articles.jsonl
    python3 build_articles.py --write    # regenerate it

The dataset rows are DERIVED. The canonical artifact is the Core markdown, byte for
byte, at ./constitution-v2.0-core.md. This script exists so that the
derivation is reproducible by a stranger rather than trusted: regenerate, and the
bytes must be identical to what is committed.

Three refusals, each of which has bitten this corpus before:

  1. The Core is hash-checked BEFORE parsing. Parsing an unverified source and then
     reporting the result would attest to whatever happened to be on disk.
  2. Exactly 47 articles or the build fails. A silently short corpus is worse than no
     corpus, because it looks complete.
  3. Every emitted `text` must be a byte-exact substring of the Core. A `####`
     sub-heading is NOT an article boundary -- treating it as one truncated Article 36
     to nothing in an earlier build of a different tool, and the check below is what
     would have caught it.
"""
import argparse
import hashlib
import json
import os
import re
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
CORE = os.path.join(HERE, "constitution-v2.0-core.md")
OUT = os.path.join(HERE, "data", "articles.jsonl")

CORE_SHA256 = "7e6d12e1025a46cc3a860d6147d79e2362c4d88cb727ce9423854b5008be4c82"
EXPECTED_ARTICLES = 47

# An article opens at a level-3 heading. A boundary is any heading of level 1 to 3 --
# and specifically NOT level 4, which is a sub-heading inside an article's own body.
ARTICLE_OPEN = re.compile(r"^### +Article +([0-9]+[A-Z]?) *: *(.*)$")
BOUNDARY = re.compile(r"^#{1,3}(?!#)\s+\S")
PART = re.compile(r"^## +(PART [IVX]+: .*)$")


def parse(core_text):
    lines = core_text.split("\n")
    part = None
    articles = []
    i = 0
    while i < len(lines):
        part_match = PART.match(lines[i])
        if part_match:
            part = part_match.group(1).strip()
        open_match = ARTICLE_OPEN.match(lines[i])
        if not open_match:
            i += 1
            continue
        start = i
        j = i + 1
        while j < len(lines) and not BOUNDARY.match(lines[j]):
            j += 1
        block = "\n".join(lines[start:j]).rstrip("\n")
        heading = lines[start]
        body = "\n".join(lines[start + 1:j]).strip("\n")
        title = open_match.group(2).strip()
        spine = "[SPINE" in heading
        articles.append({
            "article_id": open_match.group(1),
            "title": re.sub(r"\s*\[SPINE.*?\]\s*$", "", title).strip(),
            "heading": heading,
            "part": part,
            "spine": spine,
            "text": block,
            "body": body,
        })
        i = j
    return articles


def build():
    with open(CORE, "rb") as handle:
        raw = handle.read()
    actual = hashlib.sha256(raw).hexdigest()
    if actual != CORE_SHA256:
        raise SystemExit(
            "REFUSED: the Core does not match its pinned digest.\n"
            "  expected %s\n  actual   %s\n"
            "Parsing an unverified source would attest to whatever is on disk."
            % (CORE_SHA256, actual))
    core_text = raw.decode("utf-8")

    articles = parse(core_text)
    if len(articles) != EXPECTED_ARTICLES:
        raise SystemExit("REFUSED: found %d articles, expected %d. A short corpus that "
                         "looks complete is worse than no corpus."
                         % (len(articles), EXPECTED_ARTICLES))

    ids = [a["article_id"] for a in articles]
    if len(set(ids)) != len(ids):
        raise SystemExit("REFUSED: duplicate article ids: %s" % ids)

    for a in articles:
        for field in ("heading", "text", "body"):
            if a[field] and a[field] not in core_text:
                raise SystemExit(
                    "REFUSED: article %s field %r is not a byte-exact substring of the "
                    "Core. The dataset must quote, never paraphrase."
                    % (a["article_id"], field))

    for a in articles:
        a["source_url"] = "https://article11.ai/constitution-v2.0-core.md"
        a["source_sha256"] = CORE_SHA256
        a["license"] = "CC0-1.0"

    lines = [json.dumps(a, ensure_ascii=False, sort_keys=True) for a in articles]
    return ("\n".join(lines) + "\n").encode("utf-8"), articles


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--write", action="store_true",
                        help="regenerate data/articles.jsonl")
    args = parser.parse_args()

    payload, articles = build()
    digest = hashlib.sha256(payload).hexdigest()
    spine = sum(1 for a in articles if a["spine"])

    if args.write:
        os.makedirs(os.path.dirname(OUT), exist_ok=True)
        with open(OUT, "wb") as handle:
            handle.write(payload)
        print("wrote %s" % OUT)
    else:
        if not os.path.exists(OUT):
            print("data/articles.jsonl is absent; run with --write")
            return 1
        with open(OUT, "rb") as handle:
            committed = handle.read()
        if committed != payload:
            print("MISMATCH: the committed articles.jsonl is not what this script "
                  "derives from the Core.")
            print("  committed %s" % hashlib.sha256(committed).hexdigest())
            print("  derived   %s" % digest)
            return 1
        print("committed articles.jsonl matches a fresh derivation")

    print("  articles      : %d" % len(articles))
    print("  spine articles: %d" % spine)
    print("  bytes         : %d" % len(payload))
    print("  sha256        : %s" % digest)
    print("  every field verified as a byte-exact substring of the Core")
    return 0


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