"""schema.org Product data embedded in a page as JSON-LD.

This is the preferred source on any page: it is what the site publishes for
search engines, so it is stable and states price, currency and availability
explicitly.
"""
from __future__ import annotations

import json
import re
from decimal import Decimal, InvalidOperation
from typing import Any, Dict, Iterable, List, Optional

from bs4 import BeautifulSoup

_PRODUCT_TYPES = {"product", "productgroup", "productmodel", "individualproduct"}


def _types(node: dict) -> set:
    t = node.get("@type")
    if isinstance(t, list):
        return {str(x).lower() for x in t}
    return {str(t).lower()} if t else set()


def _walk(node: Any) -> Iterable[dict]:
    if isinstance(node, dict):
        yield node
        for v in node.values():
            yield from _walk(v)
    elif isinstance(node, list):
        for item in node:
            yield from _walk(item)


def json_ld_blocks(html: str) -> List[Any]:
    soup = BeautifulSoup(html, "lxml")
    blocks = []
    for tag in soup.find_all("script", attrs={"type": re.compile(r"ld\+json", re.I)}):
        raw = (tag.string or tag.get_text() or "").strip()
        if not raw:
            continue
        try:
            blocks.append(json.loads(raw))
        except json.JSONDecodeError:
            # Some sites put several objects or trailing commas in one tag.
            try:
                blocks.append(json.loads(re.sub(r",\s*([}\]])", r"\1", raw)))
            except json.JSONDecodeError:
                continue
    return blocks


def _dec(value: Any) -> Optional[Decimal]:
    if value is None or value == "":
        return None
    try:
        return Decimal(str(value).replace(",", "").strip())
    except InvalidOperation:
        return None


def _text(value: Any) -> Optional[str]:
    if isinstance(value, dict):
        value = value.get("name") or value.get("@value")
    if isinstance(value, list):
        value = value[0] if value else None
    return str(value).strip() if value not in (None, "") else None


def _images(value: Any) -> List[str]:
    out: List[str] = []
    for v in value if isinstance(value, list) else [value]:
        if isinstance(v, dict):
            v = v.get("url") or v.get("contentUrl")
        if isinstance(v, str) and v.startswith(("http://", "https://")):
            out.append(v)
    return out


def _availability(value: Any) -> tuple:
    text = (_text(value) or "").lower()
    if not text:
        return None, None
    if "instock" in text or "limitedavailability" in text or "onlineonly" in text:
        return "InStock", True
    if any(k in text for k in ("outofstock", "soldout", "discontinued", "preorder", "presale")):
        return text.rsplit("/", 1)[-1], False
    return text.rsplit("/", 1)[-1], None


def _offer(offers: Any) -> Dict[str, Any]:
    """The price/availability of the product's (lowest) offer."""
    candidates = offers if isinstance(offers, list) else [offers]
    best: Dict[str, Any] = {}
    for o in candidates:
        if not isinstance(o, dict):
            continue
        price = _dec(o.get("price"))
        if price is None:
            price = _dec(o.get("lowPrice"))
        if price is None and isinstance(o.get("priceSpecification"), dict):
            price = _dec(o["priceSpecification"].get("price"))
        currency = _text(o.get("priceCurrency")) or (
            _text(o["priceSpecification"].get("priceCurrency")) if isinstance(o.get("priceSpecification"), dict) else None
        )
        availability, in_stock = _availability(o.get("availability"))
        entry = {"price": price, "currency": currency, "availability": availability, "in_stock": in_stock,
                 "raw": {k: o.get(k) for k in ("price", "lowPrice", "priceCurrency", "availability") if k in o}}
        if price is not None and (not best or best.get("price") is None or price < best["price"]):
            best = entry
        elif not best:
            best = entry
    return best


MAX_REVIEWS_PER_PAGE = 30


def _review_rating(value: Any) -> Optional[Decimal]:
    """A reviewer's star rating, rescaled to 0-5 when the page uses another scale."""
    if not isinstance(value, dict):
        return None
    rating = _dec(value.get("ratingValue"))
    if rating is None:
        return None
    best = _dec(value.get("bestRating")) or Decimal(5)
    if best <= 0:
        return None
    if best != 5:
        rating = rating * Decimal(5) / best
    if not (Decimal(0) <= rating <= Decimal(5)):
        return None
    return rating.quantize(Decimal("0.1"))


def _reviews(node: dict) -> List[Dict[str, Any]]:
    """Customer reviews published on the Product node (schema.org Review).

    Only reviews with text are kept - a bare star with no words is not
    something a reader can weigh. Nothing is paraphrased or summarised: body,
    title and author are the page's own strings.
    """
    raw = node.get("review") or node.get("reviews") or []
    out: List[Dict[str, Any]] = []
    for r in raw if isinstance(raw, list) else [raw]:
        if not isinstance(r, dict):
            continue
        body = _text(r.get("reviewBody")) or _text(r.get("description"))
        if not body:
            continue
        out.append({
            "author": _text(r.get("author")),
            "rating": _review_rating(r.get("reviewRating")),
            "title": _text(r.get("name")) or _text(r.get("headline")),
            "body": body[:4000],
            "review_date": _text(r.get("datePublished")) or _text(r.get("dateCreated")),
        })
        if len(out) >= MAX_REVIEWS_PER_PAGE:
            break
    return out


def _rating_only_nodes(nodes: List[dict]) -> Dict[Optional[str], dict]:
    """Nameless Product nodes that only carry ratings/reviews, keyed by @id.

    Review widgets (Bazaarvoice on samsung.com/in, for one) publish the
    product's aggregateRating and reviews as a SEPARATE Product node with no
    name, linked to the real product by the same @id. Without merging, those
    real reviews would be skipped for lack of a name.
    """
    out: Dict[Optional[str], dict] = {}
    for node in nodes:
        if _text(node.get("name")):
            continue
        if not (isinstance(node.get("aggregateRating"), dict) or node.get("review") or node.get("reviews")):
            continue
        out.setdefault(_text(node.get("@id")), node)
    return out


def extract_products(html: str) -> List[Dict[str, Any]]:
    """All schema.org Product nodes on the page, flattened to plain fields."""
    products: List[Dict[str, Any]] = []
    nodes = [n for block in json_ld_blocks(html) for n in _walk(block) if _types(n) & _PRODUCT_TYPES]
    rating_nodes = _rating_only_nodes(nodes)
    named = [n for n in nodes if _text(n.get("name"))]
    for node in named:
        # Attach a ratings-only node: same @id, or - when it has no @id - the
        # page's only named product (there is then no doubt which it is about).
        extra = rating_nodes.get(_text(node.get("@id"))) if node.get("@id") else None
        if extra is None and len(named) == 1:
            extra = rating_nodes.get(None)
        if extra is not None:
            node = {**node,
                    "aggregateRating": node.get("aggregateRating") or extra.get("aggregateRating"),
                    "review": node.get("review") or extra.get("review") or extra.get("reviews")}
        name = _text(node.get("name"))
        offer = _offer(node.get("offers")) if node.get("offers") else {}
        if not offer and isinstance(node.get("hasVariant"), list):
            offer = _offer([v.get("offers") for v in node["hasVariant"] if isinstance(v, dict) and v.get("offers")])
        props = {}
        for p in node.get("additionalProperty") or []:
            if isinstance(p, dict) and p.get("name") and p.get("value") not in (None, ""):
                props[str(p["name"])] = str(p["value"])
        rating = node.get("aggregateRating") if isinstance(node.get("aggregateRating"), dict) else {}
        products.append({
            "name": name,
            "brand": _text(node.get("brand")),
            "sku": _text(node.get("sku")) or _text(node.get("productID")),
            "mpn": _text(node.get("mpn")),
            "gtin": next((_text(node.get(k)) for k in ("gtin13", "gtin", "gtin12", "gtin14", "gtin8") if node.get(k)), None),
            "color": _text(node.get("color")),
            "images": _images(node.get("image")),
            "description": _text(node.get("description")),
            "price": offer.get("price"),
            "currency": offer.get("currency"),
            "availability": offer.get("availability"),
            "in_stock": offer.get("in_stock"),
            # Sites publish 0 for "no ratings yet"; that is not a rating.
            "rating": (_dec(rating.get("ratingValue")) or None),
            "review_count": int(_dec(rating.get("reviewCount") or rating.get("ratingCount")) or 0) or None,
            "reviews": _reviews(node),
            "properties": props,
            "evidence": json.dumps({"name": name, "offers": offer.get("raw")}, default=str)[:1500],
        })
    return products