"""
Cloud analysis user settings helpers — Phase 14.

Provides get_or_create_user_analysis_settings and update_user_analysis_settings:
the single authority for reading and mutating per-user analysis preferences.

Rules:
  - Service raises ValueError only — never HTTPException (CLAUDE.md).
  - Default values are defined here; the router layer never hard-codes them.
  - Tier/admin cache limit maximums are enforced as a seam: pass the admin
    maximum via max_cache_limit_bytes to update_user_analysis_settings.
  - Invalid enum values are rejected before touching the database.
"""
from __future__ import annotations

import uuid
from typing import Optional

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from db.models import UserAnalysisSettings


# ── Valid enum values ─────────────────────────────────────────────────────────

VALID_PROGRESS_DETAIL = {"simple", "detailed"}
VALID_FAILURE_BEHAVIOR = {"pause_batch", "continue_item"}

# Absolute floor for cache limit — prevents pathologically small values
MIN_CACHE_LIMIT_BYTES = 1 * 1024 * 1024  # 1 MB

# Default tier maximum — overridable by caller (admin/tier seam)
DEFAULT_MAX_CACHE_LIMIT_BYTES = 5 * 1024 * 1024 * 1024  # 5 GB

# Default per-user cache limit when row is created
DEFAULT_CACHE_LIMIT_BYTES = 512 * 1024 * 1024  # 512 MB

# Default enum values (mirrors migration server_defaults)
DEFAULT_PROGRESS_DETAIL = "simple"
DEFAULT_FAILURE_BEHAVIOR = "pause_batch"


# ── Public API ─────────────────────────────────────────────────────────────────

async def get_or_create_user_analysis_settings(
    session: AsyncSession,
    *,
    user_id: uuid.UUID,
) -> UserAnalysisSettings:
    """Return the user's analysis settings row, creating defaults if absent.

    Never raises — creates the row on first access so callers always receive
    a valid settings object.

    Args:
        session: Active async SQLAlchemy session.
        user_id: Authenticated user UUID.

    Returns:
        UserAnalysisSettings with current preferences or newly created defaults.
    """
    uid = user_id if isinstance(user_id, uuid.UUID) else uuid.UUID(str(user_id))

    result = await session.execute(
        select(UserAnalysisSettings).where(UserAnalysisSettings.user_id == uid)
    )
    existing = result.scalars().first()
    if existing is not None:
        return existing

    # Create defaults on first access
    settings_row = UserAnalysisSettings(
        user_id=uid,
        analysis_progress_detail=DEFAULT_PROGRESS_DETAIL,
        analysis_failure_behavior=DEFAULT_FAILURE_BEHAVIOR,
        cloud_cache_limit_bytes=DEFAULT_CACHE_LIMIT_BYTES,
    )
    session.add(settings_row)
    await session.flush()
    return settings_row


async def update_user_analysis_settings(
    session: AsyncSession,
    *,
    user_id: uuid.UUID,
    analysis_progress_detail: Optional[str] = None,
    analysis_failure_behavior: Optional[str] = None,
    cloud_cache_limit_bytes: Optional[int] = None,
    max_cache_limit_bytes: int = DEFAULT_MAX_CACHE_LIMIT_BYTES,
) -> UserAnalysisSettings:
    """Update analysis preferences for the user.

    Only provided (non-None) fields are updated.  Enum values and cache limit
    bounds are validated before the database is touched.

    Args:
        session:                   Active async SQLAlchemy session.
        user_id:                   Authenticated user UUID.
        analysis_progress_detail:  "simple" | "detailed" (or None to leave unchanged).
        analysis_failure_behavior: "pause_batch" | "continue_item" (or None).
        cloud_cache_limit_bytes:   User-preferred cache byte limit (or None).
        max_cache_limit_bytes:     Tier/admin maximum (default 5 GB).  Caller
                                   supplies this so the seam is explicit.

    Returns:
        Updated UserAnalysisSettings row.

    Raises:
        ValueError: Invalid enum value or cache limit out of bounds.
    """
    if analysis_progress_detail is not None:
        if analysis_progress_detail not in VALID_PROGRESS_DETAIL:
            raise ValueError(
                f"Invalid analysis_progress_detail {analysis_progress_detail!r}. "
                f"Valid values: {VALID_PROGRESS_DETAIL}"
            )

    if analysis_failure_behavior is not None:
        if analysis_failure_behavior not in VALID_FAILURE_BEHAVIOR:
            raise ValueError(
                f"Invalid analysis_failure_behavior {analysis_failure_behavior!r}. "
                f"Valid values: {VALID_FAILURE_BEHAVIOR}"
            )

    if cloud_cache_limit_bytes is not None:
        if cloud_cache_limit_bytes < MIN_CACHE_LIMIT_BYTES:
            raise ValueError(
                f"cloud_cache_limit_bytes must be at least {MIN_CACHE_LIMIT_BYTES} bytes, "
                f"got {cloud_cache_limit_bytes}"
            )
        if cloud_cache_limit_bytes > max_cache_limit_bytes:
            raise ValueError(
                f"cloud_cache_limit_bytes {cloud_cache_limit_bytes} exceeds tier maximum "
                f"{max_cache_limit_bytes}"
            )

    # Fetch or create the row (never fails)
    row = await get_or_create_user_analysis_settings(session, user_id=user_id)

    if analysis_progress_detail is not None:
        row.analysis_progress_detail = analysis_progress_detail
    if analysis_failure_behavior is not None:
        row.analysis_failure_behavior = analysis_failure_behavior
    if cloud_cache_limit_bytes is not None:
        row.cloud_cache_limit_bytes = cloud_cache_limit_bytes

    await session.flush()
    return row


def build_default_settings() -> dict:
    """Return a dict of default settings values for use in API responses.

    Used when no row exists yet and the caller needs a response without
    committing a new row (e.g. GET /cache before any settings are saved).
    """
    return {
        "analysis_progress_detail": DEFAULT_PROGRESS_DETAIL,
        "analysis_failure_behavior": DEFAULT_FAILURE_BEHAVIOR,
        "cloud_cache_limit_bytes": DEFAULT_CACHE_LIMIT_BYTES,
    }