"""Page fingerprints, scienting-page/1, and download-stamp rules, scienting-stamps/1.

Non-normative; see spec/07-geometry.md.
"""

import math
import re
import unicodedata

from . import jcs
from .notation import fold_plain_text
from .text import is_ws, norm, sha256_hex


def round_point(x):
    """Round half up to a whole point."""
    return int(math.floor(x + 0.5))


def _in_margin(box, size, margin):
    x0, y0, x1, y1 = box
    w, h = size
    return x1 <= margin or x0 >= w - margin or y1 <= margin or y0 >= h - margin


def is_stamp(line, size, rules):
    text = norm(line["text"])
    for r in rules:
        if r.get("where", "any") == "margin":
            if "box" not in line or not _in_margin(line["box"], size, r.get("margin", 36)):
                continue
        if re.search(r["pattern"], text, re.IGNORECASE | re.ASCII):
            return r["id"]
    return None


def _strip(s):
    return "".join(c for c in s if not is_ws(c) and unicodedata.category(c) not in ("Cc", "Cf"))


def fp_text(text):
    """Steps 3 and 4 of spec/07 §7.1: whitespace and control characters go first, so that "10 -20" and "10-20"
    fold alike; then scripts and dashes fold as in the strict projection, then NFKC."""
    return _strip(unicodedata.normalize("NFKC", fold_plain_text(_strip(text))))


def fingerprint(page, rules):
    """`page`: {"size": [w, h], "lines": [{"text", "box"?}], "images": [sha256...]}.

    Returns (fingerprint, removed stamp rule IDs in line order).
    """
    size = page["size"]
    kept, removed = [], []
    for line in page.get("lines", []):
        rid = is_stamp(line, size, rules)
        if rid:
            removed.append(rid)
        else:
            kept.append(line["text"])
    payload = {
        "format": "scienting-page/1",
        "size": [round_point(size[0]), round_point(size[1])],
        "text": fp_text(" ".join(kept)),
        "images": sorted(page.get("images", [])),
    }
    return sha256_hex(jcs.dumpb(payload)), removed