"""Service layer for cache-aware fetching of FINN ads and Eiendom.no units.

Hash-aware fetch pattern
------------------------
Every ``get_or_fetch_*`` function follows the same contract:

  1. TTL check  -- if cached row is fresh enough, return it directly.
  2. Remote fetch -- if TTL expired (or force_refresh), fetch from network.
  3. Hash check  -- compare incoming payload hash to stored hash.
     If equal the remote data has not changed; skip the DB write so that
     the analysis_cache entry for this finnkode remains valid.
  4. Write + invalidate -- if hash differs, persist the new row and
     delete any cached analysis (it will be recomputed on next call to
     ``analyze_ad``).

This means analysis results survive TTL resets as long as the remote
data has not actually changed.
"""

import logging
from typing import Any

from .ad import fetch_ad_details
from .analysis import analyze_search as run_analysis_search
from .cache import (
    get_eiendom_unit as get_cached_eiendom_unit,
    get_finn_ad,
    get_similar_units as get_cached_similar_units,
    init_db,
    invalidate_analysis,
    save_eiendom_unit,
    save_finn_ad,
    save_similar_units,
)
from .config import EIENDOM_NO_CACHE_TTL_HOURS, FINN_CACHE_PATH, FINN_CACHE_TTL_AD_HOURS
from .eiendom_no import (
    build_unit_vector,
    decode_unit_vector,
    get_similar_units,
    get_unit,
    search_unit_from_finn_url,
)
from .feedback import save_feedback as save_feedback_impl
from .models import EiendomUnit, FinnAd, SimilarUnit

logger = logging.getLogger(__name__)


async def get_or_fetch_ad(finnkode: str, force_refresh: bool = False) -> FinnAd:
    """Get FinnAd from cache or fetch fresh. Never returns None.

    On a TTL expiry or force_refresh the ad is re-fetched from FINN.
    If the remote payload hash matches the stored hash the DB row is
    NOT updated, so analysis_cache entries for this finnkode stay valid.
    If the hash differs the row is updated and any cached analysis is
    invalidated.
    """
    conn = init_db(FINN_CACHE_PATH)
    ad = None if force_refresh else get_finn_ad(conn, finnkode, ttl_hours=FINN_CACHE_TTL_AD_HOURS)
    if ad is not None:
        return ad

    # Cache miss or force_refresh: fetch from remote.
    ad = await fetch_ad_details(finnkode)
    _, changed = save_finn_ad(conn, ad)
    if changed:
        logger.debug("finn_ad %s updated -- invalidating analysis cache", finnkode)
        invalidate_analysis(conn, finnkode)
    return ad


async def ensure_eiendom_unit_code(ad: FinnAd) -> str | None:
    """Backfill ``ad.eiendom_unit_code`` by resolving it from the FINN URL.

    ``fetch_ad_details`` never populates ``eiendom_unit_code`` -- only the
    Eiendom.no resolver (``search_unit_from_finn_url``) can map a FINN listing
    to an Eiendom.no unit. Every enrichment path gates on this field, so
    without an explicit resolve step the gate is always falsy and enrichment
    silently no-ops.

    Resolves once, mutates the ad in place, and persists the backfill to the
    cache so subsequent cache hits skip the network round trip.

    IMPORTANT: callers must run this BEFORE serialising the ad with
    ``model_dump()`` -- otherwise the dumped dict carries a stale
    ``eiendom_unit_code: None`` even though enrichment succeeded.

    Returns the unit_code, or ``None`` if the listing cannot be resolved
    (e.g. new-build project ads, off-market addresses).
    """
    if ad.eiendom_unit_code:
        return ad.eiendom_unit_code

    unit = await search_unit_from_finn_url(ad.url)
    if unit is None or not unit.unit_code:
        logger.info("No Eiendom.no unit resolved for finnkode %s", ad.finnkode)
        return None

    ad.eiendom_unit_code = unit.unit_code
    conn = init_db(FINN_CACHE_PATH)

    # Persist the backfilled unit_code.  If the hash changes (new field),
    # invalidate the analysis cache so it is recomputed with the enriched ad.
    _, changed = save_finn_ad(conn, ad)
    if changed:
        invalidate_analysis(conn, ad.finnkode)

    logger.info("Resolved finnkode %s -> unit %s", ad.finnkode, unit.unit_code)
    return ad.eiendom_unit_code


async def get_or_fetch_eiendom_unit(
    unit_code: str, force_refresh: bool = False
) -> EiendomUnit | None:
    """Get EiendomUnit from cache or fetch fresh.

    Hash-aware: if the remote payload is identical to what is stored,
    the DB row is not updated (analysis_cache stays valid).
    """
    conn = init_db(FINN_CACHE_PATH)
    unit = (
        None
        if force_refresh
        else get_cached_eiendom_unit(conn, unit_code, ttl_hours=24)
    )
    if unit is not None:
        return unit

    unit = await get_unit(unit_code)
    if unit is not None:
        _, changed = save_eiendom_unit(conn, unit)
        if changed:
            logger.debug(
                "eiendom_unit %s updated -- analysis caches for linked finnkodes may be stale",
                unit_code,
            )
            # We don't have a direct finnkode → unit_code reverse map in the
            # DB yet, so we cannot invalidate analysis here.  The deps_hash
            # mismatch in get_analysis() handles this automatically.
    return unit


async def get_or_fetch_similar_units(
    unit_code: str, listing_status: str = "RECENTLY_SOLD", force_refresh: bool = False
) -> list[SimilarUnit]:
    """Get similar units (comps) from cache or fetch fresh.

    Hash-aware: identical remote payloads do not trigger a DB write,
    so the analysis_cache entry for any finnkode that uses these comps
    remains valid.
    """
    conn = init_db(FINN_CACHE_PATH)

    # Ensure we have the unit to build its vector.
    unit = await get_or_fetch_eiendom_unit(unit_code, force_refresh=force_refresh)
    if unit is None:
        return []

    if not force_refresh:
        cached_similar = get_cached_similar_units(
            conn, unit_code, listing_status, ttl_hours=EIENDOM_NO_CACHE_TTL_HOURS
        )
        if cached_similar:
            logger.debug(
                "Using cached similar units for %s (status=%s)", unit_code, listing_status
            )
            return cached_similar

    # Cache miss or force_refresh: fetch from remote.
    vector = build_unit_vector(unit)
    similar = await get_similar_units(vector, listing_status=listing_status)

    if similar:
        _, changed = save_similar_units(conn, unit_code, listing_status, similar)
        if changed:
            logger.debug(
                "similar_units %s/%s updated -- analysis caches may be stale",
                unit_code,
                listing_status,
            )

    return similar


async def get_unit_images(unit_code: str, force_refresh: bool = False) -> dict[str, Any]:
    """Fetch unit images for visual assessment."""
    unit = await get_or_fetch_eiendom_unit(unit_code, force_refresh=force_refresh)
    if unit is None:
        raise ValueError(f"Could not fetch Eiendom.no unit {unit_code}")

    return {
        "unit_code": unit.unit_code,
        "address": unit.address,
        "unit_images": unit.unit_images or [],
        "property_type": unit.property_type,
        "rooms": unit.rooms,
        "usable_area": unit.usable_area,
    }


async def resolve_eiendom_unit_from_finn_url(finn_url: str) -> EiendomUnit | None:
    """Resolve an Eiendom.no unit from a FINN listing URL."""
    return await search_unit_from_finn_url(finn_url)


# ============================================================================
# Orchestration functions -- delegate to analysis.py
# ============================================================================


async def analyze_search(
    search_url: str,
    *,
    max_pages: int = 3,
    detail_limit: int = 20,
    include_details: bool = True,
    include_eiendom_no: bool = True,
    ctx: Any = None,
) -> dict[str, Any]:
    """Analyze a FINN search URL and return a ranked shortlist.

    Individual ad analyses are served from analysis_cache when the
    underlying data has not changed.
    """
    return await run_analysis_search(
        search_url,
        max_pages=max_pages,
        fetch_details=include_details,
        detail_limit=detail_limit,
        include_eiendom_no=include_eiendom_no,
        ctx=ctx,
    )


async def analyze_ad(
    finnkode: str,
    *,
    include_eiendom_no: bool = True,
    include_similar_units: bool = False,
) -> dict[str, Any]:
    """Fetch and enrich a single FINN ad with analysis."""
    ad = await get_or_fetch_ad(finnkode)

    # Resolve BEFORE model_dump() so the serialised ad carries the backfilled
    # eiendom_unit_code instead of a stale None.
    unit_code = await ensure_eiendom_unit_code(ad) if include_eiendom_no else None

    result: dict[str, Any] = {
        "ad": ad.model_dump(mode="json"),
    }
    if unit_code:
        unit = await get_or_fetch_eiendom_unit(unit_code)
        if unit:
            result["eiendom_unit"] = unit.model_dump(mode="json")
            if include_similar_units:
                similar = await get_or_fetch_similar_units(unit_code)
                result["similar_units"] = [s.model_dump(mode="json") for s in similar]
    return result


async def analyze_ad_against_comps(
    finnkode: str, listing_status: str = "RECENTLY_SOLD"
) -> dict[str, Any]:
    """Evaluate one listing against recent comparable sales."""
    ad = await get_or_fetch_ad(finnkode)

    # Resolve before model_dump() -- see analyze_ad.
    unit_code = await ensure_eiendom_unit_code(ad)

    result: dict[str, Any] = {
        "ad": ad.model_dump(mode="json"),
    }
    if unit_code:
        unit = await get_or_fetch_eiendom_unit(unit_code)
        if unit:
            result["eiendom_unit"] = unit.model_dump(mode="json")
            comps = await get_or_fetch_similar_units(unit_code, listing_status=listing_status)
            result["comparable_units"] = [c.model_dump(mode="json") for c in comps]
    return result


async def find_similar_to_liked(
    finnkode: str, *, mode: str = "recommendations", listing_status: str = "FOR_SALE"
) -> dict[str, Any]:
    """Find properties similar to a listing the user has liked."""
    ad = await get_or_fetch_ad(finnkode)

    unit_code = await ensure_eiendom_unit_code(ad)
    if not unit_code:
        raise ValueError(
            f"Finnkode {finnkode} could not be resolved to an Eiendom.no unit; "
            "cannot find similar properties"
        )

    # TODO: verify feedback verdict = "liked" exists
    unit = await get_or_fetch_eiendom_unit(unit_code)
    if not unit:
        raise ValueError(f"Cannot enrich finnkode {finnkode} with Eiendom.no data")

    similar = await get_or_fetch_similar_units(unit_code, listing_status=listing_status)
    return {
        "base_ad": ad.model_dump(mode="json"),
        "similar_listings": [s.model_dump(mode="json") for s in similar],
        "mode": mode,
    }


async def compare_ads(
    finnkoder: list[str], *, include_eiendom_no: bool = True, include_comps: bool = True
) -> dict[str, Any]:
    """Compare multiple FINN listings side by side."""
    ads = []
    for finnkode in finnkoder:
        ad = await get_or_fetch_ad(finnkode)

        # Resolve before model_dump() -- see analyze_ad.
        unit_code = await ensure_eiendom_unit_code(ad) if include_eiendom_no else None

        ad_data = ad.model_dump(mode="json")
        if unit_code:
            unit = await get_or_fetch_eiendom_unit(unit_code)
            if unit:
                ad_data["eiendom_unit"] = unit.model_dump(mode="json")
                if include_comps:
                    comps = await get_or_fetch_similar_units(
                        unit_code, listing_status="RECENTLY_SOLD"
                    )
                    ad_data["comps"] = [c.model_dump(mode="json") for c in comps]

        ads.append(ad_data)

    return {"listings": ads}


# ============================================================================
# Helper functions
# ============================================================================


async def build_unit_vector_for_unit_code(unit_code: str) -> dict[str, Any]:
    """Build a unit_vector for a unit_code by fetching and encoding the unit data."""
    unit = await get_or_fetch_eiendom_unit(unit_code)
    if unit is None:
        raise ValueError(f"Could not fetch Eiendom.no unit {unit_code}")
    vector = build_unit_vector(unit)
    return {"unit_code": unit_code, "unit_vector": vector}


def decode_unit_vector_to_dict(unit_vector: str) -> dict[str, Any]:
    """Decode a unit_vector string to a dict."""
    return decode_unit_vector(unit_vector)


def save_feedback(finnkode: str, verdict: str, notes: str | None = None) -> dict[str, Any]:
    """Store user feedback/verdict for a listing."""
    return save_feedback_impl(finnkode, verdict, notes)


def get_shortlist(run_id: int | None = None, limit: int = 10) -> dict[str, Any]:
    """Fetch stored shortlist from a search run."""
    # TODO: implement via search_runs table in cache.py
    return {"shortlist": [], "run_id": run_id, "limit": limit}


def get_new_ads_since_last_run(search_url: str) -> dict[str, Any]:
    """Detect new/removed/changed listings vs the previous run."""
    # TODO: implement via search_runs table in cache.py
    return {"new_ads": [], "removed_ads": [], "changed_ads": [], "search_url": search_url}