from __future__ import annotations

from typing import AsyncIterator

from .audio_frame import AudioFrame


__all__ = ["combine_audio_frames", "sine_wave_generator"]


def combine_audio_frames(buffer: AudioFrame | list[AudioFrame]) -> AudioFrame:
    """
    Combines one or more `rtc.AudioFrame` objects into a single `rtc.AudioFrame`.

    This function concatenates the audio data from multiple frames, ensuring that
    all frames have the same sample rate and number of channels. It efficiently
    merges the data by preallocating the necessary memory and copying the frame
    data without unnecessary reallocations.

    Args:
        buffer: A single `rtc.AudioFrame` or a list of `rtc.AudioFrame`
            objects to be combined.

    Returns:
        rtc.AudioFrame: A new `rtc.AudioFrame` containing the combined audio data.

    Raises:
        ValueError: If the buffer is empty.
        ValueError: If frames have differing sample rates.
        ValueError: If frames have differing numbers of channels.

    Example:
        >>> frame1 = rtc.AudioFrame(
        ...     data=b"\x01\x02", sample_rate=48000, num_channels=2, samples_per_channel=1
        ... )
        >>> frame2 = rtc.AudioFrame(
        ...     data=b"\x03\x04", sample_rate=48000, num_channels=2, samples_per_channel=1
        ... )
        >>> combined_frame = combine_audio_frames([frame1, frame2])
        >>> combined_frame.data
        b'\x01\x02\x03\x04'
        >>> combined_frame.sample_rate
        48000
        >>> combined_frame.num_channels
        2
        >>> combined_frame.samples_per_channel
        2
    """
    if not isinstance(buffer, list):
        return buffer

    if not buffer:
        raise ValueError("buffer is empty")

    sample_rate = buffer[0].sample_rate
    num_channels = buffer[0].num_channels

    total_data_length = 0
    total_samples_per_channel = 0

    for frame in buffer:
        if frame.sample_rate != sample_rate:
            raise ValueError(
                f"Sample rate mismatch: expected {sample_rate}, got {frame.sample_rate}"
            )

        if frame.num_channels != num_channels:
            raise ValueError(
                f"Channel count mismatch: expected {num_channels}, got {frame.num_channels}"
            )

        total_data_length += len(frame.data)
        total_samples_per_channel += frame.samples_per_channel

    data = bytearray(total_data_length)
    offset = 0
    for frame in buffer:
        frame_data = frame.data.cast("b")
        data[offset : offset + len(frame_data)] = frame_data
        offset += len(frame_data)

    return AudioFrame(
        data=data,
        sample_rate=sample_rate,
        num_channels=num_channels,
        samples_per_channel=total_samples_per_channel,
    )


async def sine_wave_generator(
    freq: float,
    duration: float,
    sample_rate: int = 48000,
    amplitude: float = 0.3,
) -> AsyncIterator[AudioFrame]:
    """
    Generate sine wave audio frames.

    Useful for testing audio pipelines and generating test signals.

    Args:
        freq: Frequency of the sine wave in Hz.
        duration: Duration of the audio in seconds.
        sample_rate: Sample rate in Hz (default: 48000).
        amplitude: Amplitude of the sine wave, range [0.0, 1.0] (default: 0.3).

    Yields:
        AudioFrame: Audio frames containing sine wave data.

    Example:
        >>> import asyncio
        >>> async def generate_audio():
        ...     async for frame in sine_wave_generator(440, 1.0):
        ...         print(f"Generated frame with {frame.samples_per_channel} samples")
        >>> asyncio.run(generate_audio())
    """
    try:
        import numpy as np
    except ImportError:
        raise ImportError(
            "numpy is required for sine_wave_generator. Install it with: pip install numpy"
        )

    blocksize = sample_rate // 10
    total_frames = int((duration * sample_rate) // blocksize)
    t_frame = np.arange(blocksize) / sample_rate

    for i in range(total_frames):
        t = t_frame + i * blocksize / sample_rate
        signal = amplitude * np.sin(2 * np.pi * freq * t)
        signal_int16 = np.int16(signal * 32767)
        frame = AudioFrame(
            signal_int16.tobytes(),
            sample_rate,
            1,
            blocksize,
        )
        yield frame