# app/utils/version_migration.py
"""
Version tracking and data migration utilities.

This module handles:
- Application version tracking via AppSettings
- Automatic phash recomputation when version changes
- Settings retrieval/storage from database
"""

import logging
import os
import time
from typing import Optional

from PIL import Image
import imagehash

from app import db
from app.models import AppSettings, ImageRecord

log = logging.getLogger("version-migration")

# =============================================================================
# Version and pHash Configuration
# =============================================================================

APP_VERSION = "26.01.19.1"  # Format: YY.MM.DD.iteration

# pHash configuration - 256-bit (hash_size=16 -> 16x16 grid)
PHASH_HASH_SIZE = 16
PHASH_BITS = PHASH_HASH_SIZE * PHASH_HASH_SIZE  # 256
PHASH_THRESHOLD_DEFAULT = 10  # Scaled from 2 (64-bit) to 10 (256-bit)

# Batch size for phash recomputation
PHASH_RECOMPUTE_BATCH_SIZE = int(os.environ.get("PHASH_RECOMPUTE_BATCH_SIZE", "100"))


# =============================================================================
# Settings Access Functions
# =============================================================================

def get_setting(key: str, default: Optional[str] = None) -> Optional[str]:
    """
    Retrieve a setting value from the database.
    Returns default if the key doesn't exist.
    """
    try:
        setting = AppSettings.query.filter_by(key=key).first()
        if setting is not None:
            return setting.value
        return default
    except Exception as e:
        log.warning(f"Failed to get setting '{key}': {e}")
        return default


def set_setting(key: str, value: str) -> None:
    """
    Store a setting value in the database.
    Creates the key if it doesn't exist, updates if it does.
    """
    try:
        setting = AppSettings.query.filter_by(key=key).first()
        if setting is None:
            setting = AppSettings(key=key, value=value)
            db.session.add(setting)
        else:
            setting.value = value
        db.session.commit()
    except Exception as e:
        log.error(f"Failed to set setting '{key}': {e}")
        db.session.rollback()
        raise


def get_setting_int(key: str, default: int) -> int:
    """Get a setting as an integer."""
    val = get_setting(key)
    if val is None:
        return default
    try:
        return int(val)
    except ValueError:
        return default


def get_setting_float(key: str, default: float) -> float:
    """Get a setting as a float."""
    val = get_setting(key)
    if val is None:
        return default
    try:
        return float(val)
    except ValueError:
        return default


def get_setting_bool(key: str, default: bool) -> bool:
    """Get a setting as a boolean."""
    val = get_setting(key)
    if val is None:
        return default
    return val.lower() in ("true", "1", "yes")


# =============================================================================
# Import Settings (DB-backed)
# =============================================================================

def get_import_settings() -> dict:
    """
    Load import filter settings from database, with environment variable fallbacks.
    This replaces the file-based load_import_settings() function.
    """
    return {
        "min_width": get_setting_int("import_min_width", int(os.environ.get("IMPORT_MIN_WIDTH", "0"))),
        "min_height": get_setting_int("import_min_height", int(os.environ.get("IMPORT_MIN_HEIGHT", "0"))),
        "skip_transparent": get_setting_bool("import_skip_transparent", os.environ.get("IMPORT_SKIP_TRANSPARENT", "false").lower() == "true"),
        "transparency_threshold": get_setting_float("import_transparency_threshold", float(os.environ.get("IMPORT_TRANSPARENCY_THRESHOLD", "0.9"))),
        "phash_threshold": get_setting_int("phash_threshold", PHASH_THRESHOLD_DEFAULT),
    }


# =============================================================================
# pHash Computation (256-bit)
# =============================================================================

def calculate_phash_256(file_path: str) -> Optional[imagehash.ImageHash]:
    """
    Calculate a 256-bit perceptual hash for an image.
    Uses hash_size=16 for a 16x16 grid = 256 bits.
    """
    try:
        with Image.open(file_path) as img:
            return imagehash.phash(img, hash_size=PHASH_HASH_SIZE)
    except Exception as e:
        log.debug(f"Could not compute phash for {file_path}: {e}")
        return None


# =============================================================================
# Version Migration Logic
# =============================================================================

def recompute_all_phashes() -> dict:
    """
    Recompute perceptual hashes for all images using 256-bit hashing.
    Returns statistics about the operation.
    """
    stats = {
        "total": 0,
        "updated": 0,
        "skipped": 0,
        "failed": 0,
    }

    log.info("Starting phash recomputation (256-bit)...")
    t_start = time.time()

    batch_size = PHASH_RECOMPUTE_BATCH_SIZE
    last_id = 0

    while True:
        # Fetch batch of images
        images = (
            ImageRecord.query
            .filter(ImageRecord.id > last_id)
            .order_by(ImageRecord.id.asc())
            .limit(batch_size)
            .all()
        )

        if not images:
            break

        batch_updated = 0
        for img in images:
            stats["total"] += 1

            # Skip videos (no phash)
            ext = (img.format or "").lower()
            if ext in ("mp4", "mov") or (img.filepath and img.filepath.lower().endswith((".mp4", ".mov"))):
                stats["skipped"] += 1
                continue

            # Skip if file doesn't exist
            if not img.filepath or not os.path.exists(img.filepath):
                log.warning(f"File not found for image id={img.id}: {img.filepath}")
                stats["failed"] += 1
                continue

            # Compute new phash
            try:
                phash = calculate_phash_256(img.filepath)
                if phash:
                    img.perceptual_hash = str(phash)
                    batch_updated += 1
                    stats["updated"] += 1
                else:
                    stats["failed"] += 1
            except Exception as e:
                log.warning(f"Failed to compute phash for id={img.id}: {e}")
                stats["failed"] += 1

        # Commit batch
        db.session.commit()
        last_id = images[-1].id
        log.info(f"Processed batch up to id={last_id}, updated={batch_updated}")

    elapsed = time.time() - t_start
    log.info(
        f"pHash recomputation complete in {elapsed:.1f}s: "
        f"total={stats['total']}, updated={stats['updated']}, "
        f"skipped={stats['skipped']}, failed={stats['failed']}"
    )

    return stats


def check_and_run_migrations() -> None:
    """
    Check the stored app version and run data migrations if needed.

    This function:
    1. Reads the stored app_version from the database
    2. Compares it with the current APP_VERSION
    3. If different, triggers necessary data migrations (e.g., phash recomputation)
    4. Updates the stored version
    """
    log.info(f"Checking app version (current: {APP_VERSION})...")

    stored_version = get_setting("app_version")
    phash_version = get_setting("phash_version")

    log.info(f"Stored version: {stored_version}, pHash version: {phash_version}")

    # Initialize settings if this is first run
    if stored_version is None:
        log.info("First run detected, initializing settings...")
        _initialize_default_settings()
        stored_version = "0.0.0.0"  # Force migration on first run

    # Check if phash recomputation is needed
    needs_phash_recompute = (
        phash_version is None or
        phash_version != APP_VERSION or
        get_setting_int("phash_bits", 64) != PHASH_BITS
    )

    if needs_phash_recompute:
        log.info(f"pHash migration needed (stored bits: {get_setting('phash_bits')}, new: {PHASH_BITS})")

        # Update phash configuration
        set_setting("phash_bits", str(PHASH_BITS))
        set_setting("phash_hash_size", str(PHASH_HASH_SIZE))

        # Recompute all hashes
        recompute_all_phashes()

        # Mark phash version as current
        set_setting("phash_version", APP_VERSION)

    # Update app version
    if stored_version != APP_VERSION:
        log.info(f"Updating app version from {stored_version} to {APP_VERSION}")
        set_setting("app_version", APP_VERSION)

    log.info("Version check complete.")


def _initialize_default_settings() -> None:
    """Initialize default settings on first run."""
    defaults = {
        "app_version": APP_VERSION,
        "phash_version": None,  # Will trigger recomputation
        "phash_bits": str(PHASH_BITS),
        "phash_hash_size": str(PHASH_HASH_SIZE),
        "phash_threshold": str(PHASH_THRESHOLD_DEFAULT),
        "import_min_width": "0",
        "import_min_height": "0",
        "import_skip_transparent": "false",
        "import_transparency_threshold": "0.9",
    }

    for key, value in defaults.items():
        if get_setting(key) is None and value is not None:
            set_setting(key, value)