//! Audio output and file export module
//!
//! This module provides functionality for real-time audio playback and
//! exporting generated music to audio files.

use crate::SAMPLE_RATE;
use crate::core::Composition;
use crate::sequencer::Sequencer;
use std::fs;
use std::path::Path;
use std::sync::{Arc, Mutex};

/// Audio output configuration
#[derive(Debug, Clone)]
pub struct AudioConfig {
    pub sample_rate: f32,
    pub buffer_size: usize,
    pub channels: usize,
}

impl Default for AudioConfig {
    fn default() -> Self {
        Self {
            sample_rate: SAMPLE_RATE,
            buffer_size: 512,
            channels: 2, // Stereo
        }
    }
}

/// Real-time audio player using cpal
pub struct AudioPlayer {
    sequencer: Arc<Mutex<Sequencer>>,
    is_playing: bool,
}

impl AudioPlayer {
    /// Create a new audio player
    pub fn new(_config: AudioConfig) -> Result<Self, String> {
        let sequencer = Arc::new(Mutex::new(Sequencer::new(120.0)));

        Ok(Self {
            sequencer,
            is_playing: false,
        })
    }

    /// Load a composition into the player
    pub fn load_composition(&mut self, composition: &Composition) -> Result<(), String> {
        let mut sequencer = self
            .sequencer
            .lock()
            .map_err(|e| format!("Lock error: {}", e))?;
        sequencer.load_composition(composition)
    }

    /// Start real-time audio playback
    pub fn start_playback(&mut self) -> Result<(), String> {
        use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};

        let host = cpal::default_host();
        let device = host
            .default_output_device()
            .ok_or("No output device available")?;

        let supported_config = device
            .default_output_config()
            .map_err(|e| format!("Failed to get default config: {}", e))?;

        let sample_format = supported_config.sample_format();
        let config = supported_config.into();

        let sequencer = Arc::clone(&self.sequencer);

        let stream = match sample_format {
            cpal::SampleFormat::F32 => {
                device.build_output_stream(
                    &config,
                    move |data: &mut [f32], _: &cpal::OutputCallbackInfo| {
                        if let Ok(mut seq) = sequencer.lock() {
                            let _ = seq.process_audio(data);
                        } else {
                            // Fill with silence if we can't lock
                            for sample in data.iter_mut() {
                                *sample = 0.0;
                            }
                        }
                    },
                    |err| eprintln!("Audio stream error: {}", err),
                    None,
                )
            }
            cpal::SampleFormat::I16 => {
                device.build_output_stream(
                    &config,
                    move |data: &mut [i16], _: &cpal::OutputCallbackInfo| {
                        let mut float_buffer = vec![0.0f32; data.len()];

                        if let Ok(mut seq) = sequencer.lock() {
                            let _ = seq.process_audio(&mut float_buffer);
                        }

                        // Convert f32 to i16
                        for (i, &sample) in float_buffer.iter().enumerate() {
                            data[i] = (sample * i16::MAX as f32) as i16;
                        }
                    },
                    |err| eprintln!("Audio stream error: {}", err),
                    None,
                )
            }
            cpal::SampleFormat::U16 => {
                device.build_output_stream(
                    &config,
                    move |data: &mut [u16], _: &cpal::OutputCallbackInfo| {
                        let mut float_buffer = vec![0.0f32; data.len()];

                        if let Ok(mut seq) = sequencer.lock() {
                            let _ = seq.process_audio(&mut float_buffer);
                        }

                        // Convert f32 to u16
                        for (i, &sample) in float_buffer.iter().enumerate() {
                            let sample_u16 = ((sample + 1.0) * 0.5 * u16::MAX as f32) as u16;
                            data[i] = sample_u16;
                        }
                    },
                    |err| eprintln!("Audio stream error: {}", err),
                    None,
                )
            }
            _ => {
                return Err("Unsupported sample format".to_string());
            }
        }
        .map_err(|e| format!("Failed to build stream: {}", e))?;

        stream
            .play()
            .map_err(|e| format!("Failed to play stream: {}", e))?;

        // Start the sequencer
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.play();
        }

        self.is_playing = true;

        // Keep the stream alive (in a real application, you'd want better lifecycle management)
        std::mem::forget(stream);

        Ok(())
    }

    /// Stop playback
    pub fn stop_playback(&mut self) -> Result<(), String> {
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.stop();
        }
        self.is_playing = false;
        Ok(())
    }

    /// Pause playback
    pub fn pause_playback(&mut self) -> Result<(), String> {
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.pause();
        }
        Ok(())
    }

    /// Resume playback
    pub fn resume_playback(&mut self) -> Result<(), String> {
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.play();
        }
        Ok(())
    }

    /// Set playback position
    pub fn set_position(&mut self, position: f32) -> Result<(), String> {
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.set_position(position);
        }
        Ok(())
    }

    /// Set tempo
    pub fn set_tempo(&mut self, tempo: f32) -> Result<(), String> {
        if let Ok(mut seq) = self.sequencer.lock() {
            seq.set_tempo(tempo);
        }
        Ok(())
    }

    /// Get sequencer for direct control
    pub fn get_sequencer(&self) -> Arc<Mutex<Sequencer>> {
        Arc::clone(&self.sequencer)
    }
}

/// Audio file exporter
pub struct AudioExporter {
    sample_rate: f32,
}

impl AudioExporter {
    /// Create a new audio exporter
    pub fn new(sample_rate: f32) -> Self {
        Self { sample_rate }
    }

    /// Ensure output directory exists
    fn ensure_output_dir() -> Result<(), String> {
        let output_dir = Path::new("output");
        if !output_dir.exists() {
            fs::create_dir_all(output_dir)
                .map_err(|e| format!("Failed to create output directory: {}", e))?;
        }
        Ok(())
    }

    /// Get full path for output file
    fn get_output_path(filename: &str) -> String {
        format!("output/{}", filename)
    }

    /// Export a composition to a WAV file
    ///
    /// # Arguments
    /// * `composition` - The composition to export
    /// * `filename` - Output filename
    /// * `duration_seconds` - Duration to export in seconds (None for full composition)
    pub fn export_wav(
        &self,
        composition: &Composition,
        filename: &str,
        duration_seconds: Option<f32>,
    ) -> Result<(), String> {
        Self::ensure_output_dir()?;
        let output_path = Self::get_output_path(filename);
        let spec = hound::WavSpec {
            channels: 1, // Mono for simplicity
            sample_rate: self.sample_rate as u32,
            bits_per_sample: 16,
            sample_format: hound::SampleFormat::Int,
        };

        let mut writer = hound::WavWriter::create(&output_path, spec)
            .map_err(|e| format!("Failed to create WAV file: {}", e))?;

        // Create a sequencer for rendering
        let mut sequencer = Sequencer::new(composition.params.tempo);
        sequencer
            .load_composition(composition)
            .map_err(|e| format!("Failed to load composition: {}", e))?;

        sequencer.play();

        // Calculate total samples to render
        let export_duration = duration_seconds
            .unwrap_or(composition.total_duration * 60.0 / composition.params.tempo);
        let total_samples = (export_duration * self.sample_rate) as usize;

        // Render audio in chunks
        let chunk_size = 1024;
        let mut buffer = vec![0.0f32; chunk_size];
        let mut samples_rendered = 0;

        while samples_rendered < total_samples {
            let samples_to_render = (total_samples - samples_rendered).min(chunk_size);
            buffer.resize(samples_to_render, 0.0);

            // Process audio
            if let Err(e) = sequencer.process_audio(&mut buffer) {
                return Err(format!("Audio processing error: {}", e));
            }

            // Convert to i16 and write to file
            for &sample in &buffer {
                let sample_i16 = (sample * i16::MAX as f32) as i16;
                writer
                    .write_sample(sample_i16)
                    .map_err(|e| format!("Failed to write sample: {}", e))?;
            }

            samples_rendered += samples_to_render;

            // Progress indication (optional)
            if samples_rendered % (self.sample_rate as usize) == 0 {
                let progress = samples_rendered as f32 / total_samples as f32 * 100.0;
                println!("Export progress: {:.1}%", progress);
            }
        }

        writer
            .finalize()
            .map_err(|e| format!("Failed to finalize WAV file: {}", e))?;

        println!("Successfully exported to {}", output_path);
        Ok(())
    }

    /// Export a composition to a stereo WAV file with separate channels for different tracks
    pub fn export_stereo_wav(
        &self,
        composition: &Composition,
        filename: &str,
        duration_seconds: Option<f32>,
    ) -> Result<(), String> {
        Self::ensure_output_dir()?;
        let output_path = Self::get_output_path(filename);
        let spec = hound::WavSpec {
            channels: 2, // Stereo
            sample_rate: self.sample_rate as u32,
            bits_per_sample: 16,
            sample_format: hound::SampleFormat::Int,
        };

        let mut writer = hound::WavWriter::create(&output_path, spec)
            .map_err(|e| format!("Failed to create WAV file: {}", e))?;

        // Create a sequencer for rendering
        let mut sequencer = Sequencer::new(composition.params.tempo);
        sequencer
            .load_composition(composition)
            .map_err(|e| format!("Failed to load composition: {}", e))?;

        sequencer.play();

        // Calculate total samples to render
        let export_duration = duration_seconds
            .unwrap_or(composition.total_duration * 60.0 / composition.params.tempo);
        let total_samples = (export_duration * self.sample_rate) as usize;

        // Render audio in chunks
        let chunk_size = 1024;
        let mut buffer = vec![0.0f32; chunk_size];
        let mut samples_rendered = 0;

        while samples_rendered < total_samples {
            let samples_to_render = (total_samples - samples_rendered).min(chunk_size);
            buffer.resize(samples_to_render, 0.0);

            // Process audio
            if let Err(e) = sequencer.process_audio(&mut buffer) {
                return Err(format!("Audio processing error: {}", e));
            }

            // Write stereo samples (duplicate mono to both channels)
            for &sample in &buffer {
                let sample_i16 = (sample * i16::MAX as f32) as i16;
                writer
                    .write_sample(sample_i16) // Left channel
                    .map_err(|e| format!("Failed to write left sample: {}", e))?;
                writer
                    .write_sample(sample_i16) // Right channel
                    .map_err(|e| format!("Failed to write right sample: {}", e))?;
            }

            samples_rendered += samples_to_render;

            // Progress indication
            if samples_rendered % (self.sample_rate as usize) == 0 {
                let progress = samples_rendered as f32 / total_samples as f32 * 100.0;
                println!("Export progress: {:.1}%", progress);
            }
        }

        writer
            .finalize()
            .map_err(|e| format!("Failed to finalize WAV file: {}", e))?;

        println!("Successfully exported stereo to {}", output_path);
        Ok(())
    }

    /// Export multiple takes of a composition with different parameters
    pub fn export_variations(
        &self,
        base_composition: &Composition,
        filename_prefix: &str,
        variations: usize,
        duration_seconds: Option<f32>,
    ) -> Result<(), String> {
        Self::ensure_output_dir()?;

        for i in 0..variations {
            // Create variation by modifying parameters
            let mut params = base_composition.params.clone();
            params.complexity = (i as f32 / variations as f32).clamp(0.1, 1.0);
            params.rhythmic_density = 0.5 + (i as f32 / variations as f32) * 0.4;

            let mut variation = Composition::new(params);
            variation
                .generate()
                .map_err(|e| format!("Failed to generate variation {}: {}", i, e))?;

            let filename = format!("{}_{:02}.wav", filename_prefix, i + 1);
            self.export_wav(&variation, &filename, duration_seconds)?;
        }

        println!("Successfully exported {} variations", variations);
        Ok(())
    }

    /// Export composition as raw audio data (for further processing)
    pub fn export_raw_audio(
        &self,
        composition: &Composition,
        duration_seconds: Option<f32>,
    ) -> Result<Vec<f32>, String> {
        // Create a sequencer for rendering
        let mut sequencer = Sequencer::new(composition.params.tempo);
        sequencer
            .load_composition(composition)
            .map_err(|e| format!("Failed to load composition: {}", e))?;

        sequencer.play();

        // Calculate total samples to render
        let export_duration = duration_seconds
            .unwrap_or(composition.total_duration * 60.0 / composition.params.tempo);
        let total_samples = (export_duration * self.sample_rate) as usize;

        let mut audio_data = Vec::with_capacity(total_samples);

        // Render audio in chunks
        let chunk_size = 1024;
        let mut buffer = vec![0.0f32; chunk_size];
        let mut samples_rendered = 0;

        while samples_rendered < total_samples {
            let samples_to_render = (total_samples - samples_rendered).min(chunk_size);
            buffer.resize(samples_to_render, 0.0);

            // Process audio
            if let Err(e) = sequencer.process_audio(&mut buffer) {
                return Err(format!("Audio processing error: {}", e));
            }

            audio_data.extend_from_slice(&buffer);
            samples_rendered += samples_to_render;
        }

        Ok(audio_data)
    }
}

impl Default for AudioExporter {
    fn default() -> Self {
        Self::new(SAMPLE_RATE)
    }
}

/// Simple audio analysis utilities
pub struct AudioAnalyzer;

impl AudioAnalyzer {
    /// Calculate RMS (Root Mean Square) level of audio data
    pub fn calculate_rms(audio_data: &[f32]) -> f32 {
        if audio_data.is_empty() {
            return 0.0;
        }

        let sum_squares: f32 = audio_data.iter().map(|&x| x * x).sum();
        (sum_squares / audio_data.len() as f32).sqrt()
    }

    /// Find peak amplitude in audio data
    pub fn find_peak(audio_data: &[f32]) -> f32 {
        audio_data.iter().map(|&x| x.abs()).fold(0.0, f32::max)
    }

    /// Calculate dynamic range (ratio of peak to RMS)
    pub fn calculate_dynamic_range(audio_data: &[f32]) -> f32 {
        let peak = Self::find_peak(audio_data);
        let rms = Self::calculate_rms(audio_data);

        if rms > 0.0 {
            20.0 * (peak / rms).log10() // In dB
        } else {
            f32::INFINITY
        }
    }

    /// Simple frequency analysis using zero-crossing rate
    pub fn zero_crossing_rate(audio_data: &[f32]) -> f32 {
        if audio_data.len() < 2 {
            return 0.0;
        }

        let mut crossings = 0;
        for i in 1..audio_data.len() {
            if (audio_data[i] >= 0.0) != (audio_data[i - 1] >= 0.0) {
                crossings += 1;
            }
        }

        crossings as f32 / audio_data.len() as f32
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::core::{CompositionBuilder, CompositionStyle};

    #[test]
    fn test_audio_config() {
        let config = AudioConfig::default();
        assert_eq!(config.sample_rate, SAMPLE_RATE);
        assert_eq!(config.channels, 2);
        assert!(config.buffer_size > 0);
    }

    #[test]
    fn test_audio_exporter_creation() {
        let exporter = AudioExporter::new(44100.0);
        assert_eq!(exporter.sample_rate, 44100.0);
    }

    #[test]
    fn test_raw_audio_export() {
        let mut composition = CompositionBuilder::new()
            .style(CompositionStyle::Electronic)
            .measures(2)
            .tempo(120.0)
            .build();

        let _ = composition.generate();

        let exporter = AudioExporter::new(44100.0);
        let result = exporter.export_raw_audio(&composition, Some(1.0));

        assert!(result.is_ok());
        let audio_data = result.unwrap();
        assert_eq!(audio_data.len(), 44100); // 1 second at 44.1kHz
    }

    #[test]
    fn test_audio_analysis() {
        // Test with a simple sine wave
        let sample_rate = 44100.0;
        let frequency = 440.0;
        let duration = 1.0;
        let samples = (sample_rate * duration) as usize;

        let mut audio_data = Vec::with_capacity(samples);
        for i in 0..samples {
            let t = i as f32 / sample_rate;
            let sample = (2.0 * std::f32::consts::PI * frequency * t).sin() * 0.5;
            audio_data.push(sample);
        }

        let rms = AudioAnalyzer::calculate_rms(&audio_data);
        let peak = AudioAnalyzer::find_peak(&audio_data);
        let zcr = AudioAnalyzer::zero_crossing_rate(&audio_data);

        assert!(rms > 0.0);
        assert!(peak > rms);
        assert!(zcr > 0.0);

        // For a sine wave, RMS should be approximately peak / sqrt(2)
        let expected_rms = 0.5 / (2.0_f32).sqrt();
        assert!((rms - expected_rms).abs() < 0.01);
    }

    #[test]
    fn test_dynamic_range_calculation() {
        let audio_data = vec![0.0, 0.5, -0.3, 0.8, -0.2, 0.1];
        let dynamic_range = AudioAnalyzer::calculate_dynamic_range(&audio_data);
        assert!(dynamic_range > 0.0);
        assert!(dynamic_range.is_finite());
    }

    #[test]
    fn test_zero_crossing_rate() {
        // Test with alternating positive/negative values
        let audio_data = vec![1.0, -1.0, 1.0, -1.0, 1.0, -1.0];
        let zcr = AudioAnalyzer::zero_crossing_rate(&audio_data);

        // Should have high zero-crossing rate
        assert!(zcr > 0.5);
    }

    #[test]
    fn test_audio_player_creation() {
        let config = AudioConfig::default();
        let result = AudioPlayer::new(config);
        assert!(result.is_ok());
    }
}