"""Section photo policy: enable uploads only where the tenant's own RAG library shows a trend.

1. **Explicit overrides** — ``SECTION_PHOTO_POLICY_OVERRIDES_JSON``.
2. **Tenant indexed uploads** — completed ``.pdf`` / ``.docx`` for this tenant (same files used for
   tenant RAG) are scanned for embedded images under each RICS section heading. A section only gets
   ``OPTIONAL_IMAGE`` / ``REQUIRES_IMAGE`` when enough uploads contain that heading **and** the
   configured fraction of those uploads include at least one image in that section (default: 100%).

No letter-based heuristics. Knowledge-base exemplar folders are not used for product photo policy.
"""

from __future__ import annotations

import json
import logging
from dataclasses import dataclass
from enum import StrEnum

from sqlalchemy.ext.asyncio import AsyncSession

from app.config import settings
from app.services.photo_policy_corpus import (
    CorpusPhotoStats,
    SectionPhotoStats,
    corpus_ratio_for_section,
    get_or_compute_tenant_photo_stats,
)
from app.templates.registry import get_survey_pack

logger = logging.getLogger(__name__)


class PhotoPolicy(StrEnum):
    requires_image = "REQUIRES_IMAGE"
    optional_image = "OPTIONAL_IMAGE"
    no_image_needed = "NO_IMAGE_NEEDED"


POLICY_SOURCE_OVERRIDE = "override"
POLICY_SOURCE_TENANT_LIBRARY = "tenant_library"
POLICY_SOURCE_TENANT_INSUFFICIENT = "tenant_insufficient"
POLICY_SOURCE_TENANT_NO_DOCUMENTS = "tenant_no_documents"
POLICY_SOURCE_DATA_DRIVEN_DISABLED = "data_driven_disabled"


def _parse_photo_policy_overrides() -> dict[str, PhotoPolicy]:
    raw = (settings.section_photo_policy_overrides_json or "").strip()
    if not raw:
        return {}
    try:
        obj = json.loads(raw)
    except json.JSONDecodeError as exc:
        logger.warning("section_photo_policy_overrides_json is not valid JSON: %s", exc)
        return {}
    if not isinstance(obj, dict):
        return {}
    out: dict[str, PhotoPolicy] = {}
    for k, v in obj.items():
        code = str(k).strip().upper()
        if not code:
            continue
        if isinstance(v, str):
            s = v.strip().upper().replace(" ", "_").replace("-", "_")
            matched: PhotoPolicy | None = None
            for p in PhotoPolicy:
                if s == p.value or s == p.name.upper():
                    matched = p
                    break
            if matched is not None:
                out[code] = matched
    return out


@dataclass(frozen=True, slots=True)
class SectionPhotoPolicy:
    code: str
    policy: PhotoPolicy
    reason: str
    source: str


def _tenant_row_to_policy(
    row: SectionPhotoStats | None, *, min_examples: int, consensus: float
) -> tuple[PhotoPolicy, str]:
    """Map aggregated counts to a policy using ``SECTION_PHOTO_POLICY_TENANT_CONSENSUS_RATIO``."""
    if row is None or row.files_seen < min_examples:
        return (
            PhotoPolicy.no_image_needed,
            (
                f"This RICS section was not detected in at least {min_examples} of your indexed PDF/DOCX "
                "uploads (or appears without enough matching evidence), so photo upload stays disabled."
            ),
        )

    ratio = float(row.files_with_photos) / float(row.files_seen) if row.files_seen else 0.0
    if ratio + 1e-12 < consensus:
        return (
            PhotoPolicy.no_image_needed,
            (
                f"Your indexed uploads show images in this section in {row.files_with_photos}/{row.files_seen} "
                f"cases ({round(ratio * 100)}%). Photo upload is enabled only when at least "
                f"{round(consensus * 100)}% of uploads that include this section also contain an image there."
            ),
        )

    if ratio >= 1.0 - 1e-12:
        return (
            PhotoPolicy.requires_image,
            (
                f"All {row.files_seen} indexed upload(s) that include this section contain at least one image "
                "in that section — matching your library trend."
            ),
        )
    return (
        PhotoPolicy.optional_image,
        (
            f"Photos appear in this section in {row.files_with_photos}/{row.files_seen} indexed uploads "
            f"({round(ratio * 100)}%), meeting the ≥{round(consensus * 100)}% threshold."
        ),
    )


def _source_for_tenant_policy(policy: PhotoPolicy, stats: CorpusPhotoStats) -> str:
    if stats.files_total <= 0:
        return POLICY_SOURCE_TENANT_NO_DOCUMENTS
    if policy == PhotoPolicy.no_image_needed:
        return POLICY_SOURCE_TENANT_INSUFFICIENT
    return POLICY_SOURCE_TENANT_LIBRARY


async def classify_section_photo_policy_async(
    db: AsyncSession | None,
    tenant_id: str,
    code: str,
    *,
    survey_level: int | None = None,
) -> tuple[PhotoPolicy, str]:
    """Resolve policy for one section using overrides, then tenant RAG library scan."""
    c = (code or "").strip()
    if not c:
        return PhotoPolicy.no_image_needed, "No section code."
    if db is None:
        return PhotoPolicy.no_image_needed, "Photo policy skipped (no database session)."

    overrides = _parse_photo_policy_overrides()
    key = c.upper()
    if key in overrides:
        pol = overrides[key]
        return pol, f"Explicit SECTION_PHOTO_POLICY_OVERRIDES_JSON entry for {key!r} → {pol.value}."

    if not settings.section_photo_policy_data_driven:
        return (
            PhotoPolicy.no_image_needed,
            "Tenant photo scan is disabled (SECTION_PHOTO_POLICY_DATA_DRIVEN=false) and this section "
            "has no JSON override.",
        )

    try:
        stats = await get_or_compute_tenant_photo_stats(db, tenant_id, survey_level)
    except Exception as exc:  # noqa: BLE001
        logger.debug("Tenant photo stats failed: %s", exc)
        return (
            PhotoPolicy.no_image_needed,
            "Could not scan indexed uploads for photo placement; no override is set for this section.",
        )

    min_ex = int(settings.section_photo_policy_min_examples)
    consensus = float(settings.section_photo_policy_tenant_consensus_ratio)
    row = corpus_ratio_for_section(stats, c)
    pol, reason = _tenant_row_to_policy(row, min_examples=min_ex, consensus=consensus)
    return pol, reason


async def get_photo_policy_for_tenant_async(
    db: AsyncSession,
    tenant_id: str,
    survey_level: int | None,
) -> tuple[list[SectionPhotoPolicy], CorpusPhotoStats]:
    """Per-section policies plus raw tenant stats (for API metadata)."""
    pack = get_survey_pack(survey_level)
    overrides = _parse_photo_policy_overrides()
    min_ex = int(settings.section_photo_policy_min_examples)
    consensus = float(settings.section_photo_policy_tenant_consensus_ratio)

    if not settings.section_photo_policy_data_driven:
        items = [
            SectionPhotoPolicy(
                code=code,
                policy=PhotoPolicy.no_image_needed,
                reason=(
                    "SECTION_PHOTO_POLICY_DATA_DRIVEN is false. Enable tenant scanning or set "
                    "SECTION_PHOTO_POLICY_OVERRIDES_JSON."
                ),
                source=POLICY_SOURCE_DATA_DRIVEN_DISABLED,
            )
            for code in pack.section_order
        ]
        return items, CorpusPhotoStats(created_at_unix=0, files_total=0, by_code={})

    try:
        stats = await get_or_compute_tenant_photo_stats(db, tenant_id, survey_level)
    except Exception as exc:  # noqa: BLE001
        logger.exception("Tenant photo policy scan failed: %s", exc)
        stats = CorpusPhotoStats(created_at_unix=0, files_total=0, by_code={})

    out: list[SectionPhotoPolicy] = []
    for code in pack.section_order:
        key = (code or "").strip().upper()
        if key in overrides:
            pol = overrides[key]
            out.append(
                SectionPhotoPolicy(
                    code=code,
                    policy=pol,
                    reason=f"Explicit SECTION_PHOTO_POLICY_OVERRIDES_JSON for {key!r} → {pol.value}.",
                    source=POLICY_SOURCE_OVERRIDE,
                )
            )
            continue

        if stats.files_total <= 0:
            out.append(
                SectionPhotoPolicy(
                    code=code,
                    policy=PhotoPolicy.no_image_needed,
                    reason=(
                        "No completed PDF/DOCX uploads were found for this tenant (or files are missing on disk). "
                        "Upload and ingest reference surveys first; photo rules are derived only from those files."
                    ),
                    source=POLICY_SOURCE_TENANT_NO_DOCUMENTS,
                )
            )
            continue

        row = corpus_ratio_for_section(stats, code)
        pol, reason = _tenant_row_to_policy(row, min_examples=min_ex, consensus=consensus)
        src = _source_for_tenant_policy(pol, stats)
        out.append(SectionPhotoPolicy(code=code, policy=pol, reason=reason, source=src))

    return out, stats


def photo_policy_configuration_incomplete(
    stats: CorpusPhotoStats,
    items: list[SectionPhotoPolicy],
) -> bool:
    """True when the tenant library is too small to establish cross-document trends, or scanning is off."""
    if not settings.section_photo_policy_data_driven:
        return any(x.source == POLICY_SOURCE_DATA_DRIVEN_DISABLED for x in items)
    min_ex = int(settings.section_photo_policy_min_examples)
    if stats.files_total < min_ex:
        return True
    return False