"""
    stream_fn.jl - Stream function utilities

This module provides the default stream function configuration for AgentCore.
"""

module StreamFn

using ..Types: StreamFn

let default_stream_fn::Union{StreamFn, Nothing} = nothing

"""
    setDefaultStreamFn(stream_fn)

Configure the fallback used by Agent and low-level loops when callers omit stream_fn.

# Arguments
- `stream_fn`: The stream function to set as default
"""
function setDefaultStreamFn(stream_fn::Union{StreamFn, Nothing})
    global default_stream_fn = stream_fn
end

"""
    getDefaultStreamFn()

Get the configured default stream function, or throw an error if none is configured.

# Returns
- The configured stream function

# Throws
- ErrorException if no default stream function is configured
"""
function getDefaultStreamFn()::StreamFn
    if isnothing(default_stream_fn)
        throw(ErrorException(
            "No default stream function configured. Pass stream_fn explicitly or call setDefaultStreamFn()."
        ))
    end
    return default_stream_fn
end

end