Autogeneration

from alembic.autogenerate import compare_metadata, produce_migrations, render_python_code
from alembic.autogenerate.api import RevisionContext, AutogenContext, _render_migration_diffs
from alembic.autogenerate.compare import _produce_net_changes, comparators
from alembic.autogenerate.render import render_op_text, renderers

def compare_metadata(context, metadata):
    """
    Compare metadata against database and return differences.
    
    Args:
        context (MigrationContext): Migration context with database connection
        metadata (MetaData): SQLAlchemy metadata to compare
    
    Returns:
        list: List of operation objects representing differences
    """

from alembic.autogenerate import compare_metadata
from alembic.runtime.migration import MigrationContext
from sqlalchemy import create_engine

engine = create_engine('postgresql://user:pass@localhost/db')
with engine.connect() as conn:
    context = MigrationContext.configure(conn)
    diffs = compare_metadata(context, target_metadata)
    for diff in diffs:
        print(diff)

def produce_migrations(context, metadata):
    """
    Produce migration operations from metadata comparison.
    
    Args:
        context (MigrationContext): Migration context
        metadata (MetaData): Target metadata
    
    Returns:
        UpgradeOps: Container of upgrade operations
    """

from alembic.autogenerate import produce_migrations

operations = produce_migrations(context, target_metadata)
for op in operations.ops:
    print(f"Operation: {op}")

def render_python_code(up_or_down_op, sqlalchemy_module_prefix='sa.', alembic_module_prefix='op.', render_as_batch=False, imports=None, render_item=None):
    """
    Render operations as Python code.
    
    Args:
        up_or_down_op (OperationContainer): Operations to render
        sqlalchemy_module_prefix (str): Prefix for SQLAlchemy imports
        alembic_module_prefix (str): Prefix for Alembic operations
        render_as_batch (bool): Render as batch operations
        imports (set): Set to collect required imports
        render_item (callable): Custom rendering function
    
    Returns:
        str: Python code representation
    """

from alembic.autogenerate import render_python_code

# Render upgrade operations
imports = set()
code = render_python_code(
    operations,
    sqlalchemy_module_prefix='sa.',
    alembic_module_prefix='op.',
    imports=imports
)
print("Required imports:", imports)
print("Migration code:")
print(code)

def _render_migration_diffs(autogen_context, template_args):
    """
    Render migration differences for template generation.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        template_args (dict): Template arguments
    
    Returns:
        str: Rendered migration code
    """

def _produce_net_changes(autogen_context, metadata):
    """
    Produce net changes from metadata comparison.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        metadata (MetaData): Target metadata
    
    Returns:
        UpgradeOps: Net change operations
    """

def render_op_text(autogen_context, op):
    """
    Render operation as text representation.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        op (MigrateOperation): Operation to render
    
    Returns:
        str: Text representation of operation
    """

class RevisionContext:
    def __init__(self, config, script_directory, command_args, process_revision_directives=None):
        """
        Context for revision generation.
        
        Args:
            config (Config): Alembic configuration
            script_directory (ScriptDirectory): Script directory
            command_args (dict): Command arguments
            process_revision_directives (callable): Custom directive processing
        """

    def run_autogenerate(self, rev_id, context):
        """
        Run autogeneration process.
        
        Args:
            rev_id (str): Revision identifier
            context (MigrationContext): Migration context
        
        Returns:
            Script: Generated script object
        """

    def run_no_autogenerate(self, rev_id, context):
        """
        Create empty revision without autogeneration.
        
        Args:
            rev_id (str): Revision identifier
            context (MigrationContext): Migration context
        
        Returns:
            Script: Generated script object
        """

class AutogenContext:
    def __init__(self, migration_context, metadata=None, opts=None, autogenerate=True):
        """
        Context for autogeneration operations.
        
        Args:
            migration_context (MigrationContext): Migration context
            metadata (MetaData): Target metadata
            opts (dict): Configuration options
            autogenerate (bool): Enable autogeneration
        """
        
    # Properties and methods available on AutogenContext
    migration_context: MigrationContext
    metadata: MetaData
    connection: Connection
    dialect: Dialect
    imports: Set[str]

from alembic.autogenerate import comparators

@comparators.dispatch_for("schema")
def compare_schema(autogen_context, upgrade_ops, schemas):
    """
    Custom schema comparison.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        upgrade_ops (UpgradeOps): Container for upgrade operations
        schemas (set): Set of schema names
    """

@comparators.dispatch_for("table")  
def compare_table(autogen_context, upgrade_ops, schema, table_name, conn_table, metadata_table):
    """
    Custom table comparison.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        upgrade_ops (UpgradeOps): Container for upgrade operations
        schema (str): Schema name
        table_name (str): Table name
        conn_table (Table): Database table reflection
        metadata_table (Table): Metadata table definition
    """

@comparators.dispatch_for("table")
def ignore_temp_tables(autogen_context, upgrade_ops, schema, table_name, conn_table, metadata_table):
    """Ignore temporary tables during comparison."""
    if table_name.startswith('temp_'):
        return
    # Continue with default comparison
    return comparators.dispatch("table")(autogen_context, upgrade_ops, schema, table_name, conn_table, metadata_table)

def compare_type(context, inspected_column, metadata_column, inspected_type, metadata_type):
    """
    Compare column types for differences.
    
    Args:
        context (MigrationContext): Migration context
        inspected_column (dict): Database column information
        metadata_column (Column): Metadata column
        inspected_type (TypeEngine): Database column type
        metadata_type (TypeEngine): Metadata column type
    
    Returns:
        bool: True if types are different
    """
    # Custom type comparison logic
    if isinstance(metadata_type, sa.String) and isinstance(inspected_type, sa.Text):
        return False  # Consider String and Text as equivalent
    return None  # Use default comparison

# Configure in context.configure()
context.configure(
    connection=connection,
    target_metadata=target_metadata,
    compare_type=compare_type
)

def compare_server_default(context, inspected_column, metadata_column, inspected_default, metadata_default, rendered_metadata_default):
    """
    Compare server defaults for differences.
    
    Args:
        context (MigrationContext): Migration context
        inspected_column (dict): Database column information
        metadata_column (Column): Metadata column
        inspected_default (str): Database default value
        metadata_default: Metadata default value
        rendered_metadata_default (str): Rendered metadata default
    
    Returns:
        bool: True if defaults are different
    """
    # Custom server default comparison
    if inspected_default == "''" and metadata_default is None:
        return False  # Empty string equals NULL
    return None  # Use default comparison

context.configure(
    connection=connection,
    target_metadata=target_metadata,
    compare_server_default=compare_server_default
)

from alembic.autogenerate import renderers

@renderers.dispatch_for(CreateTableOp)
def render_create_table(autogen_context, op):
    """
    Custom rendering for CREATE TABLE operations.
    
    Args:
        autogen_context (AutogenContext): Autogeneration context
        op (CreateTableOp): Create table operation
    
    Returns:
        str: Python code for the operation
    """
    return f"op.create_table({op.table_name!r}, ...)"

def include_object(object, name, type_, reflected, compare_to):
    """
    Determine whether to include an object in autogeneration.
    
    Args:
        object: Database object
        name (str): Object name
        type_ (str): Object type ('table', 'column', 'index', etc.)
        reflected (bool): True if object was reflected from database
        compare_to: Corresponding metadata object
    
    Returns:
        bool: True to include object in comparison
    """
    # Skip temporary tables
    if type_ == "table" and name.startswith("temp_"):
        return False
    
    # Skip certain indexes
    if type_ == "index" and name.startswith("_"):
        return False
        
    return True

def include_name(name, type_, parent_names):
    """
    Filter object names during reflection.
    
    Args:
        name (str): Object name
        type_ (str): Object type
        parent_names (dict): Parent object names
    
    Returns:
        bool: True to include object
    """
    # Skip system schemas
    if type_ == "schema" and name.startswith("information_"):
        return False
    return True

# Configure filtering
context.configure(
    connection=connection,
    target_metadata=target_metadata,
    include_object=include_object,
    include_name=include_name
)

def process_revision_directives(context, revision, directives):
    """
    Process and modify revision directives.
    
    Args:
        context (MigrationContext): Migration context
        revision (tuple): Revision information
        directives (list): List of MigrationScript directives
    """
    # Skip empty migrations
    script = directives[0]
    if script.upgrade_ops.is_empty():
        directives[:] = []
        print("Skipping empty migration")
        return

    # Add custom header comment
    script.upgrade_ops.ops.insert(0, 
        ExecuteSQLOp("-- Auto-generated migration"))

# Use in context configuration
context.configure(
    connection=connection,
    target_metadata=target_metadata,
    process_revision_directives=process_revision_directives
)

def process_revision_directives(context, revision, directives):
    """Add custom template variables."""
    script = directives[0]
    script.template_args = {
        'author': 'AutoGen System',
        'created_at': datetime.now().isoformat()
    }

# In migration template
"""${message}

Revision ID: ${up_revision}
Revises: ${down_revision | comma,n}
Create Date: ${create_date}
Author: ${author}
Created At: ${created_at}
"""

# Configure batch rendering
context.configure(
    connection=connection,
    target_metadata=target_metadata,
    render_as_batch=True  # Use batch operations
)

# Or in rendering
code = render_python_code(
    operations,
    render_as_batch=True
)

from flask import current_app
from alembic import context
from flask_sqlalchemy import SQLAlchemy

def get_metadata():
    """Get metadata from Flask-SQLAlchemy."""
    with current_app.app_context():
        return current_app.extensions['sqlalchemy'].db.metadata

def run_migrations_online():
    """Run migrations with Flask app context."""
    connectable = engine_from_config(
        config.get_section(config.config_ini_section),
        prefix='sqlalchemy.',
        poolclass=pool.NullPool,
    )

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=get_metadata(),
            include_object=include_object,
            compare_type=True,
            compare_server_default=True
        )

        with context.begin_transaction():
            context.run_migrations()

def run_autogenerate_with_django():
    """Run autogeneration with Django models."""
    import django
    from django.conf import settings
    
    django.setup()
    
    # Convert Django models to SQLAlchemy metadata
    metadata = convert_django_models_to_sqlalchemy()
    
    engine = create_engine(get_database_url())
    with engine.connect() as connection:
        context = MigrationContext.configure(
            connection,
            opts={
                'target_metadata': metadata,
                'compare_type': True,
                'include_object': include_object
            }
        )
        
        diffs = compare_metadata(context, metadata)
        return diffs

# Autogeneration context types
class AutogenContext:
    migration_context: MigrationContext
    metadata: Optional[MetaData]
    connection: Connection
    dialect: Dialect
    imports: Set[str]
    
class RevisionContext:
    config: Config
    script_directory: ScriptDirectory
    command_args: Dict[str, Any]
    
# Operation containers
class UpgradeOps:
    ops: List[MigrateOperation]
    
class DowngradeOps:
    ops: List[MigrateOperation]

# Comparison function types
CompareTypeFunc = Callable[[MigrationContext, Column, Column, TypeEngine, TypeEngine], Optional[bool]]
CompareServerDefaultFunc = Callable[[MigrationContext, Column, Column, Any, Any, str], Optional[bool]]
IncludeObjectFunc = Callable[[Any, str, str, bool, Any], bool]
ProcessRevisionDirectivesFunc = Callable[[MigrationContext, Tuple, List], None]