from __future__ import annotations

import json
from pathlib import Path
from typing import Any, Mapping
from urllib.parse import urlparse


HOME_COMMERCE_FIXTURE = "home-commerce-complete-2026-07-25.json"
HOME_COMMERCE_EVIDENCE_CLASSES = frozenset(
    {
        "direct-home-commerce",
        "regional-converted-home-commerce",
        "local-simulation-home-commerce",
    }
)


class HomeCommerceError(ValueError):
    pass


def load_home_commerce_offers(
    fixture_root: Path,
    home_catalog: Mapping[str, Mapping[str, Any]],
) -> tuple[dict[str, Any], ...]:
    """Load dated default offers without widening their evidence boundary."""

    fixture_root = fixture_root.resolve()
    candidate = (fixture_root / HOME_COMMERCE_FIXTURE).resolve()
    if fixture_root not in candidate.parents or not candidate.is_file():
        raise HomeCommerceError("home commerce fixture does not exist")
    try:
        payload = json.loads(candidate.read_text(encoding="utf-8"))
    except (OSError, json.JSONDecodeError) as exc:
        raise HomeCommerceError("home commerce fixture is invalid") from exc
    if payload.get("schema") != "amazon-clone.home-commerce-offers.v2":
        raise HomeCommerceError("unsupported home commerce fixture schema")
    offers = payload.get("offers")
    if not isinstance(offers, list) or not offers:
        raise HomeCommerceError("home commerce offers must be a non-empty array")
    if payload.get("sourceHomepageProducts") != 157:
        raise HomeCommerceError("home commerce fixture has an invalid source denominator")
    if payload.get("sourceOfferCount") != len(offers):
        raise HomeCommerceError("home commerce fixture offer count is inconsistent")
    if len(offers) != 157:
        raise HomeCommerceError("home commerce fixture must cover all homepage products")
    expected_counts = payload.get("evidenceClassCounts")
    if not isinstance(expected_counts, dict):
        raise HomeCommerceError("home commerce evidence counts are missing")

    normalized: list[dict[str, Any]] = []
    seen: set[str] = set()
    for offer in offers:
        if not isinstance(offer, dict):
            raise HomeCommerceError("home commerce offers must be objects")
        asin = offer.get("asin")
        home_product = home_catalog.get(str(asin))
        title = offer.get("title")
        price_minor = offer.get("price_minor")
        currency = offer.get("currency")
        source_url = offer.get("source_url")
        evidence_class = offer.get("evidence_class")
        if (
            not isinstance(asin, str)
            or len(asin) != 10
            or asin in seen
            or home_product is None
        ):
            raise HomeCommerceError("home commerce offer has an invalid ASIN")
        if not isinstance(title, str) or not title.strip():
            raise HomeCommerceError(f"home commerce offer {asin} has no title")
        if (
            isinstance(price_minor, bool)
            or not isinstance(price_minor, int)
            or price_minor <= 0
            or currency != "USD"
        ):
            raise HomeCommerceError(f"home commerce offer {asin} has an invalid price")
        if evidence_class not in HOME_COMMERCE_EVIDENCE_CLASSES:
            raise HomeCommerceError(
                f"home commerce offer {asin} has an invalid evidence class"
            )
        if not isinstance(source_url, str):
            raise HomeCommerceError(f"home commerce offer {asin} has an invalid source URL")
        parsed_source = urlparse(source_url)
        if (
            parsed_source.scheme != "https"
            or parsed_source.hostname not in {"www.amazon.com", "www.amazon.sg"}
            or asin not in parsed_source.path
        ):
            raise HomeCommerceError(f"home commerce offer {asin} has an invalid source URL")
        if evidence_class == "regional-converted-home-commerce":
            source_price_minor = offer.get("source_price_minor")
            if (
                parsed_source.hostname != "www.amazon.sg"
                or isinstance(source_price_minor, bool)
                or not isinstance(source_price_minor, int)
                or source_price_minor <= 0
                or offer.get("source_currency") != "SGD"
                or not offer.get("conversion_rate_source")
            ):
                raise HomeCommerceError(
                    f"regional home commerce offer {asin} is incomplete"
                )
        if evidence_class == "local-simulation-home-commerce" and not offer.get(
            "simulation_disclosure"
        ):
            raise HomeCommerceError(
                f"local simulation home commerce offer {asin} is undisclosed"
            )
        if not (
            offer.get("local_add_to_cart_enabled")
            and offer.get("local_buy_now_enabled")
        ):
            raise HomeCommerceError(
                f"home commerce offer {asin} has incomplete local purchase controls"
            )
        image_path = home_product.get("image_path")
        if not isinstance(image_path, str) or not image_path.startswith("/static/"):
            raise HomeCommerceError(f"home commerce offer {asin} has no local image")
        seen.add(asin)
        normalized.append(
            {
                "asin": asin,
                "slug": "home-offer",
                "canonical_path": f"/dp/{asin}",
                "title": title,
                "brand": "",
                "capacity": "",
                "color": "",
                "price_minor": price_minor,
                "list_price_minor": None,
                "currency": "USD",
                "rating": "",
                "reviews": 0,
                "image_path": image_path,
                "badge": "",
                "evidence_class": evidence_class,
                "offer_observation_source": str(
                    offer.get("price_observation_source") or ""
                ),
                "purchase_state": str(offer.get("purchase_state") or ""),
                "source_capture": str(offer.get("source_capture") or ""),
                "source_url": source_url,
                "offer_disclosure": (
                    "Direct USD offer captured from the product's Amazon purchase surface."
                    if evidence_class == "direct-home-commerce"
                    else "USD quote converted from a dated Amazon regional offer."
                    if evidence_class == "regional-converted-home-commerce"
                    else "Offline-only local simulation quote."
                ),
            }
        )
    observed_counts = {
        evidence_class: sum(
            offer["evidence_class"] == evidence_class for offer in normalized
        )
        for evidence_class in HOME_COMMERCE_EVIDENCE_CLASSES
    }
    if observed_counts != expected_counts:
        raise HomeCommerceError("home commerce evidence counts are inconsistent")
    return tuple(normalized)