Configuration Manipulation

def merge(*configs):
    """
    Merge multiple configs with copying for safety.
    
    Parameters:
    - *configs: Variable number of configs to merge (DictConfig, ListConfig, or dicts/lists)
    
    Returns:
    Merged configuration (DictConfig or ListConfig)
    
    Notes:
    - Later configs override earlier ones
    - Creates copies to avoid modifying originals
    - Supports deep merging of nested structures
    """

def unsafe_merge(*configs):
    """
    Fast merge without copying for performance.
    
    Parameters:
    - *configs: Variable number of configs to merge
    
    Returns:
    Merged configuration
    
    Warning:
    - May modify input configurations
    - Use only when input configs won't be reused
    """

def select(cfg, key, default=None, throw_on_resolution_failure=True, throw_on_missing=False):
    """
    Select value using dot notation key.
    
    Parameters:
    - cfg: Configuration to select from
    - key: Dot notation key (e.g., "database.host" or "servers[0].name")
    - default: Value to return if key not found
    - throw_on_resolution_failure: Whether to raise on interpolation errors
    - throw_on_missing: Whether to raise on missing keys
    
    Returns:
    Selected value or default
    
    Examples:
    - select(cfg, "database.host") -> cfg.database.host
    - select(cfg, "servers[0]") -> cfg.servers[0]
    - select(cfg, "missing.key", "default") -> "default"
    """

def update(cfg, key, value, merge=True, force_add=False):
    """
    Update configuration value using dot notation.
    
    Parameters:
    - cfg: Configuration to update
    - key: Dot notation key for update location
    - value: New value to set
    - merge: Whether to merge if value is a config/dict
    - force_add: Whether to add new keys even in struct mode
    
    Examples:
    - update(cfg, "database.host", "new-host")
    - update(cfg, "new.nested.key", {"a": 1, "b": 2})
    """

def resolve(cfg):
    """
    Resolve all interpolations in configuration.
    
    Parameters:
    - cfg: Configuration to resolve
    
    Returns:
    None (modifies configuration in-place)
    
    Notes:
    - Resolves ${key} interpolations
    - Handles nested interpolations
    - Detects and prevents circular references
    - Uses registered resolvers for custom interpolations
    """

def missing_keys(cfg):
    """
    Get set of keys with missing mandatory values.
    
    Parameters:
    - cfg: Configuration to analyze
    
    Returns:
    Set of dot notation paths to missing keys
    
    Examples:
    - {"key": "???"} -> {"key"}
    - {"nested": {"key": "???"}} -> {"nested.key"}
    """

def masked_copy(conf, keys):
    """
    Create copy with only specified keys included.
    
    Parameters:
    - conf: Configuration to copy
    - keys: List of keys to include in copy
    
    Returns:
    New configuration with only specified keys
    """

from omegaconf import OmegaConf

# Basic merging
base = OmegaConf.create({"a": 1, "b": {"x": 10}})
override = OmegaConf.create({"b": {"y": 20}, "c": 3})
merged = OmegaConf.merge(base, override)
# Result: {"a": 1, "b": {"x": 10, "y": 20}, "c": 3}

# Multiple config merging
config = OmegaConf.merge(base_config, user_config, cli_overrides)

# Performance-focused merging (unsafe)
result = OmegaConf.unsafe_merge(cfg1, cfg2, cfg3)

from omegaconf import OmegaConf

config = OmegaConf.create({
    "database": {
        "connections": [
            {"host": "primary", "port": 5432},
            {"host": "replica", "port": 5432}
        ]
    },
    "features": {"auth": True, "logging": "???"}
})

# Select values
host = OmegaConf.select(config, "database.connections[0].host")  # "primary"
missing = OmegaConf.select(config, "missing.key", default="fallback")  # "fallback"

# Update values
OmegaConf.update(config, "database.connections[1].port", 5433)
OmegaConf.update(config, "new.nested.setting", {"enabled": True})

# Check for missing values
missing_keys = OmegaConf.missing_keys(config)  # {"features.logging"}

from omegaconf import OmegaConf

# Config with interpolations
config = OmegaConf.create({
    "server": {
        "host": "localhost",
        "port": 8080,
        "url": "http://${server.host}:${server.port}",
        "api_url": "${server.url}/api/v1"
    },
    "client": {
        "endpoint": "${server.api_url}/users"
    }
})

# Before resolution
print(config.server.url)  # "http://${server.host}:${server.port}"

# Resolve all interpolations
OmegaConf.resolve(config)

# After resolution
print(config.server.url)      # "http://localhost:8080"
print(config.client.endpoint) # "http://localhost:8080/api/v1/users"

from omegaconf import OmegaConf

config = OmegaConf.create({
    "database": {"host": "localhost", "port": 5432},
    "cache": {"enabled": True, "ttl": 300},
    "logging": {"level": "INFO", "file": "/var/log/app.log"}
})

# Create masked copy with subset of keys
db_config = OmegaConf.masked_copy(config, ["database"])
# Result: {"database": {"host": "localhost", "port": 5432}}

# Bulk updates with merging
updates = {"database": {"pool_size": 10}, "cache": {"ttl": 600}}
for key, value in updates.items():
    OmegaConf.update(config, key, value, merge=True)

# Check configuration completeness
if OmegaConf.missing_keys(config):
    print("Configuration has missing mandatory values")