"""
Generation versions management module.

Each generation can have multiple audio versions: a clean (unprocessed)
version and any number of processed versions with different effects chains.
"""

from __future__ import annotations

import json
import uuid
from pathlib import Path
from typing import List, Optional

from sqlalchemy.orm import Session

from ..database import (
    GenerationVersion as DBGenerationVersion,
    Generation as DBGeneration,
)
from ..models import GenerationVersionResponse, EffectConfig
from .. import config


def _version_response(v: DBGenerationVersion) -> GenerationVersionResponse:
    """Convert a DB version row to a Pydantic response."""
    effects_chain = None
    if v.effects_chain:
        raw = json.loads(v.effects_chain)
        effects_chain = [EffectConfig(**e) for e in raw]
    return GenerationVersionResponse(
        id=v.id,
        generation_id=v.generation_id,
        label=v.label,
        audio_path=v.audio_path,
        effects_chain=effects_chain,
        source_version_id=v.source_version_id,
        is_default=v.is_default,
        created_at=v.created_at,
    )


def list_versions(generation_id: str, db: Session) -> List[GenerationVersionResponse]:
    """List all versions for a generation."""
    versions = (
        db.query(DBGenerationVersion)
        .filter_by(generation_id=generation_id)
        .order_by(DBGenerationVersion.created_at)
        .all()
    )
    return [_version_response(v) for v in versions]


def get_version(version_id: str, db: Session) -> Optional[GenerationVersionResponse]:
    """Get a specific version by ID."""
    v = db.query(DBGenerationVersion).filter_by(id=version_id).first()
    if not v:
        return None
    return _version_response(v)


def get_default_version(generation_id: str, db: Session) -> Optional[GenerationVersionResponse]:
    """Get the default version for a generation."""
    v = (
        db.query(DBGenerationVersion)
        .filter_by(generation_id=generation_id, is_default=True)
        .first()
    )
    if not v:
        # Fallback: return the first version
        v = (
            db.query(DBGenerationVersion)
            .filter_by(generation_id=generation_id)
            .order_by(DBGenerationVersion.created_at)
            .first()
        )
    if not v:
        return None
    return _version_response(v)


def create_version(
    generation_id: str,
    label: str,
    audio_path: str,
    db: Session,
    effects_chain: Optional[List[dict]] = None,
    is_default: bool = False,
    source_version_id: Optional[str] = None,
) -> GenerationVersionResponse:
    """Create a new version for a generation.

    If ``is_default`` is True, all other versions for this generation
    are un-defaulted first.
    """
    if is_default:
        _clear_defaults(generation_id, db)

    version = DBGenerationVersion(
        id=str(uuid.uuid4()),
        generation_id=generation_id,
        label=label,
        audio_path=audio_path,
        effects_chain=json.dumps(effects_chain) if effects_chain else None,
        source_version_id=source_version_id,
        is_default=is_default,
    )
    db.add(version)
    db.commit()
    db.refresh(version)

    # If this version is the default, update the generation's audio_path
    if is_default:
        gen = db.query(DBGeneration).filter_by(id=generation_id).first()
        if gen:
            gen.audio_path = audio_path
            db.commit()

    return _version_response(version)


def set_default_version(version_id: str, db: Session) -> Optional[GenerationVersionResponse]:
    """Set a version as the default for its generation."""
    version = db.query(DBGenerationVersion).filter_by(id=version_id).first()
    if not version:
        return None

    _clear_defaults(version.generation_id, db)
    version.is_default = True
    db.commit()
    db.refresh(version)

    # Update generation's audio_path to point to this version
    gen = db.query(DBGeneration).filter_by(id=version.generation_id).first()
    if gen:
        gen.audio_path = version.audio_path
        db.commit()

    return _version_response(version)


def delete_version(version_id: str, db: Session) -> bool:
    """Delete a version. Cannot delete the last remaining version."""
    version = db.query(DBGenerationVersion).filter_by(id=version_id).first()
    if not version:
        return False

    # Don't allow deleting the last version
    count = (
        db.query(DBGenerationVersion)
        .filter_by(generation_id=version.generation_id)
        .count()
    )
    if count <= 1:
        return False

    was_default = version.is_default
    gen_id = version.generation_id

    # Delete audio file
    audio_path = config.resolve_storage_path(version.audio_path)
    if audio_path is not None and audio_path.exists():
        audio_path.unlink()

    db.delete(version)
    db.commit()

    # If this was the default, promote the first remaining version
    if was_default:
        first = (
            db.query(DBGenerationVersion)
            .filter_by(generation_id=gen_id)
            .order_by(DBGenerationVersion.created_at)
            .first()
        )
        if first:
            first.is_default = True
            db.commit()
            gen = db.query(DBGeneration).filter_by(id=gen_id).first()
            if gen:
                gen.audio_path = first.audio_path
                db.commit()

    return True


def delete_versions_for_generation(generation_id: str, db: Session) -> int:
    """Delete all versions for a generation (used when deleting a generation)."""
    versions = (
        db.query(DBGenerationVersion)
        .filter_by(generation_id=generation_id)
        .all()
    )
    count = 0
    for v in versions:
        audio_path = config.resolve_storage_path(v.audio_path)
        if audio_path is not None and audio_path.exists():
            audio_path.unlink()
        db.delete(v)
        count += 1
    if count > 0:
        db.commit()
    return count


def _clear_defaults(generation_id: str, db: Session) -> None:
    """Clear the is_default flag on all versions for a generation."""
    db.query(DBGenerationVersion).filter_by(
        generation_id=generation_id, is_default=True
    ).update({"is_default": False})
    db.flush()