//go:build cgo

package audio

import (
	"errors"
	"fmt"
	"os"
	"strings"
	"sync"
	"sync/atomic"
	"time"
	"unsafe"

	"github.com/jetkvm/kvm/internal/logging"
	"github.com/rs/zerolog"
)

/*
#include "c/audio.c"
*/
import "C"

var (
	errAudioInitFailed   = errors.New("failed to init ALSA/Opus")
	errAudioReadEncode   = errors.New("audio read/encode error")
	errAudioDecodeWrite  = errors.New("audio decode/write error")
	errAudioPlaybackInit = errors.New("failed to init ALSA playback/Opus decoder")
	errEmptyBuffer       = errors.New("empty buffer")
	errNilBuffer         = errors.New("nil buffer")
	errInvalidBufferPtr  = errors.New("invalid buffer pointer")
)

// Error creation functions with enhanced context
func newBufferTooSmallError(actual, required int) error {
	baseErr := fmt.Errorf("buffer too small: got %d bytes, need at least %d bytes", actual, required)
	return WrapWithMetadata(baseErr, "cgo_audio", "buffer_validation", map[string]interface{}{
		"actual_size":   actual,
		"required_size": required,
		"error_type":    "buffer_undersize",
	})
}

func newBufferTooLargeError(actual, max int) error {
	baseErr := fmt.Errorf("buffer too large: got %d bytes, maximum allowed %d bytes", actual, max)
	return WrapWithMetadata(baseErr, "cgo_audio", "buffer_validation", map[string]interface{}{
		"actual_size": actual,
		"max_size":    max,
		"error_type":  "buffer_oversize",
	})
}

func newAudioInitError(cErrorCode int) error {
	baseErr := fmt.Errorf("%w: C error code %d", errAudioInitFailed, cErrorCode)
	return WrapWithMetadata(baseErr, "cgo_audio", "initialization", map[string]interface{}{
		"c_error_code": cErrorCode,
		"error_type":   "init_failure",
		"severity":     "critical",
	})
}

func newAudioPlaybackInitError(cErrorCode int) error {
	baseErr := fmt.Errorf("%w: C error code %d", errAudioPlaybackInit, cErrorCode)
	return WrapWithMetadata(baseErr, "cgo_audio", "playback_init", map[string]interface{}{
		"c_error_code": cErrorCode,
		"error_type":   "playback_init_failure",
		"severity":     "high",
	})
}

func newAudioReadEncodeError(cErrorCode int) error {
	baseErr := fmt.Errorf("%w: C error code %d", errAudioReadEncode, cErrorCode)
	return WrapWithMetadata(baseErr, "cgo_audio", "read_encode", map[string]interface{}{
		"c_error_code": cErrorCode,
		"error_type":   "read_encode_failure",
		"severity":     "medium",
	})
}

func newAudioDecodeWriteError(cErrorCode int) error {
	baseErr := fmt.Errorf("%w: C error code %d", errAudioDecodeWrite, cErrorCode)
	return WrapWithMetadata(baseErr, "cgo_audio", "decode_write", map[string]interface{}{
		"c_error_code": cErrorCode,
		"error_type":   "decode_write_failure",
		"severity":     "medium",
	})
}

func cgoAudioInit() error {
	// Get cached config and ensure it's updated
	cache := GetCachedConfig()
	cache.Update()

	// Enable C trace logging if Go audio scope trace level is active
	audioLogger := logging.GetSubsystemLogger("audio")
	loggerTraceEnabled := audioLogger.GetLevel() <= zerolog.TraceLevel

	// Manual check for audio scope in PION_LOG_TRACE (workaround for logging system bug)
	traceEnabled := loggerTraceEnabled
	if !loggerTraceEnabled {
		pionTrace := os.Getenv("PION_LOG_TRACE")
		if pionTrace != "" {
			scopes := strings.Split(strings.ToLower(pionTrace), ",")
			for _, scope := range scopes {
				if strings.TrimSpace(scope) == "audio" {
					traceEnabled = true
					break
				}
			}
		}
	}

	CGOSetTraceLogging(traceEnabled)

	// Update C constants from cached config (atomic access, no locks)
	C.update_audio_constants(
		C.int(cache.opusBitrate.Load()),
		C.int(cache.opusComplexity.Load()),
		C.int(cache.opusVBR.Load()),
		C.int(cache.opusVBRConstraint.Load()),
		C.int(cache.opusSignalType.Load()),
		C.int(cache.opusBandwidth.Load()),
		C.int(cache.opusDTX.Load()),
		C.int(16), // LSB depth for improved bit allocation
		C.int(cache.sampleRate.Load()),
		C.int(cache.channels.Load()),
		C.int(cache.frameSize.Load()),
		C.int(cache.maxPacketSize.Load()),
		C.int(Config.CGOUsleepMicroseconds),
		C.int(Config.CGOMaxAttempts),
		C.int(Config.CGOMaxBackoffMicroseconds),
	)

	result := C.jetkvm_audio_capture_init()
	if result != 0 {
		return newAudioInitError(int(result))
	}
	return nil
}

func cgoAudioClose() {
	C.jetkvm_audio_capture_close()
}

// AudioConfigCache provides a comprehensive caching system for audio configuration
type AudioConfigCache struct {
	// All duration fields use int32 by storing as milliseconds for optimal ARM NEON performance
	maxMetricsUpdateInterval atomic.Int32 // Store as milliseconds (10s = 10K ms < int32 max)
	restartWindow            atomic.Int32 // Store as milliseconds (5min = 300K ms < int32 max)
	restartDelay             atomic.Int32 // Store as milliseconds
	maxRestartDelay          atomic.Int32 // Store as milliseconds

	// Short-duration fields stored as milliseconds with int32
	minFrameDuration         atomic.Int32 // Store as milliseconds (10ms = 10 ms < int32 max)
	maxFrameDuration         atomic.Int32 // Store as milliseconds (100ms = 100 ms < int32 max)
	maxLatency               atomic.Int32 // Store as milliseconds (500ms = 500 ms < int32 max)
	minMetricsUpdateInterval atomic.Int32 // Store as milliseconds (100ms = 100 ms < int32 max)

	// Atomic int32 fields for lock-free access to frequently used values
	minReadEncodeBuffer  atomic.Int32
	maxDecodeWriteBuffer atomic.Int32
	maxPacketSize        atomic.Int32
	maxPCMBufferSize     atomic.Int32
	opusBitrate          atomic.Int32
	opusComplexity       atomic.Int32
	opusVBR              atomic.Int32
	opusVBRConstraint    atomic.Int32
	opusSignalType       atomic.Int32
	opusBandwidth        atomic.Int32
	opusDTX              atomic.Int32
	sampleRate           atomic.Int32
	channels             atomic.Int32
	frameSize            atomic.Int32

	// Additional cached values for validation functions
	maxAudioFrameSize atomic.Int32
	maxChannels       atomic.Int32
	minOpusBitrate    atomic.Int32
	maxOpusBitrate    atomic.Int32

	// Socket and buffer configuration values
	socketMaxBuffer          atomic.Int32
	socketMinBuffer          atomic.Int32
	inputProcessingTimeoutMS atomic.Int32
	maxRestartAttempts       atomic.Int32

	// Mutex for updating the cache
	mutex       sync.RWMutex
	lastUpdate  time.Time
	cacheExpiry time.Duration
	initialized atomic.Bool

	// Pre-allocated errors to avoid allocations in hot path
	bufferTooSmallReadEncode  error
	bufferTooLargeDecodeWrite error
}

// Global audio config cache instance
var globalAudioConfigCache = &AudioConfigCache{
	cacheExpiry: 30 * time.Second,
}

// GetCachedConfig returns the global audio config cache instance
func GetCachedConfig() *AudioConfigCache {
	return globalAudioConfigCache
}

// Update refreshes the cached config values if needed
func (c *AudioConfigCache) Update() {
	// Fast path: if cache is initialized and not expired, return immediately
	if c.initialized.Load() {
		c.mutex.RLock()
		cacheExpired := time.Since(c.lastUpdate) > c.cacheExpiry
		c.mutex.RUnlock()
		if !cacheExpired {
			return
		}
	}

	// Slow path: update cache
	c.mutex.Lock()
	defer c.mutex.Unlock()

	// Double-check after acquiring lock
	if !c.initialized.Load() || time.Since(c.lastUpdate) > c.cacheExpiry {
		// Update atomic values for lock-free access - CGO values
		c.minReadEncodeBuffer.Store(int32(Config.MinReadEncodeBuffer))
		c.maxDecodeWriteBuffer.Store(int32(Config.MaxDecodeWriteBuffer))
		c.maxPacketSize.Store(int32(Config.CGOMaxPacketSize))
		c.maxPCMBufferSize.Store(int32(Config.MaxPCMBufferSize))
		c.opusBitrate.Store(int32(Config.CGOOpusBitrate))
		c.opusComplexity.Store(int32(Config.CGOOpusComplexity))
		c.opusVBR.Store(int32(Config.CGOOpusVBR))
		c.opusVBRConstraint.Store(int32(Config.CGOOpusVBRConstraint))
		c.opusSignalType.Store(int32(Config.CGOOpusSignalType))
		c.opusBandwidth.Store(int32(Config.CGOOpusBandwidth))
		c.opusDTX.Store(int32(Config.CGOOpusDTX))
		c.sampleRate.Store(int32(Config.CGOSampleRate))
		c.channels.Store(int32(Config.CGOChannels))
		c.frameSize.Store(int32(Config.CGOFrameSize))

		// Update additional validation values
		c.maxAudioFrameSize.Store(int32(Config.MaxAudioFrameSize))
		c.maxChannels.Store(int32(Config.MaxChannels))

		// Store duration fields as milliseconds for int32 optimization
		c.minFrameDuration.Store(int32(Config.MinFrameDuration / time.Millisecond))
		c.maxFrameDuration.Store(int32(Config.MaxFrameDuration / time.Millisecond))
		c.maxLatency.Store(int32(Config.MaxLatency / time.Millisecond))
		c.minMetricsUpdateInterval.Store(int32(Config.MinMetricsUpdateInterval / time.Millisecond))
		c.maxMetricsUpdateInterval.Store(int32(Config.MaxMetricsUpdateInterval / time.Millisecond))
		c.restartWindow.Store(int32(Config.RestartWindow / time.Millisecond))
		c.restartDelay.Store(int32(Config.RestartDelay / time.Millisecond))
		c.maxRestartDelay.Store(int32(Config.MaxRestartDelay / time.Millisecond))
		c.minOpusBitrate.Store(int32(Config.MinOpusBitrate))
		c.maxOpusBitrate.Store(int32(Config.MaxOpusBitrate))

		// Pre-allocate common errors
		c.bufferTooSmallReadEncode = newBufferTooSmallError(0, Config.MinReadEncodeBuffer)
		c.bufferTooLargeDecodeWrite = newBufferTooLargeError(Config.MaxDecodeWriteBuffer+1, Config.MaxDecodeWriteBuffer)

		c.lastUpdate = time.Now()
		c.initialized.Store(true)

		c.lastUpdate = time.Now()
		c.initialized.Store(true)

		// Update the global validation cache as well
		if cachedMaxFrameSize != 0 {
			cachedMaxFrameSize = Config.MaxAudioFrameSize
		}
	}
}

// GetMinReadEncodeBuffer returns the cached MinReadEncodeBuffer value
func (c *AudioConfigCache) GetMinReadEncodeBuffer() int {
	return int(c.minReadEncodeBuffer.Load())
}

// GetMaxDecodeWriteBuffer returns the cached MaxDecodeWriteBuffer value
func (c *AudioConfigCache) GetMaxDecodeWriteBuffer() int {
	return int(c.maxDecodeWriteBuffer.Load())
}

// GetMaxPacketSize returns the cached MaxPacketSize value
func (c *AudioConfigCache) GetMaxPacketSize() int {
	return int(c.maxPacketSize.Load())
}

// GetMaxPCMBufferSize returns the cached MaxPCMBufferSize value
func (c *AudioConfigCache) GetMaxPCMBufferSize() int {
	return int(c.maxPCMBufferSize.Load())
}

// GetBufferTooSmallError returns the pre-allocated buffer too small error
func (c *AudioConfigCache) GetBufferTooSmallError() error {
	return c.bufferTooSmallReadEncode
}

// GetBufferTooLargeError returns the pre-allocated buffer too large error
func (c *AudioConfigCache) GetBufferTooLargeError() error {
	return c.bufferTooLargeDecodeWrite
}

func cgoAudioReadEncode(buf []byte) (int, error) {
	// Minimal buffer validation - assume caller provides correct size
	if len(buf) == 0 {
		return 0, errEmptyBuffer
	}

	// Direct CGO call - hotpath optimization
	n := C.jetkvm_audio_read_encode(unsafe.Pointer(&buf[0]))

	// Fast path for success
	if n > 0 {
		return int(n), nil
	}

	// Error handling with static errors
	if n < 0 {
		if n == -1 {
			return 0, errAudioInitFailed
		}
		return 0, errAudioReadEncode
	}

	return 0, nil
}

// Audio playback functions
func cgoAudioPlaybackInit() error {
	// Get cached config and ensure it's updated
	cache := GetCachedConfig()
	cache.Update()

	// Enable C trace logging if Go audio scope trace level is active
	audioLogger := logging.GetSubsystemLogger("audio")
	CGOSetTraceLogging(audioLogger.GetLevel() <= zerolog.TraceLevel)

	// No need to update C constants here as they're already set in cgoAudioInit

	ret := C.jetkvm_audio_playback_init()
	if ret != 0 {
		return newAudioPlaybackInitError(int(ret))
	}
	return nil
}

func cgoAudioPlaybackClose() {
	C.jetkvm_audio_playback_close()
}

// Audio decode/write metrics for monitoring USB Gadget audio success
var (
	audioDecodeWriteTotal     atomic.Int64
	audioDecodeWriteSuccess   atomic.Int64
	audioDecodeWriteFailures  atomic.Int64
	audioDecodeWriteRecovery  atomic.Int64
	audioDecodeWriteLastError atomic.Value
	audioDecodeWriteLastTime  atomic.Int64
)

// GetAudioDecodeWriteStats returns current audio decode/write statistics
func GetAudioDecodeWriteStats() (total, success, failures, recovery int64, lastError string, lastTime time.Time) {
	total = audioDecodeWriteTotal.Load()
	success = audioDecodeWriteSuccess.Load()
	failures = audioDecodeWriteFailures.Load()
	recovery = audioDecodeWriteRecovery.Load()

	if err := audioDecodeWriteLastError.Load(); err != nil {
		lastError = err.(string)
	}

	lastTimeNano := audioDecodeWriteLastTime.Load()
	if lastTimeNano > 0 {
		lastTime = time.Unix(0, lastTimeNano)
	}

	return
}

func cgoAudioDecodeWrite(buf []byte) (int, error) {
	start := time.Now()
	audioDecodeWriteTotal.Add(1)
	audioDecodeWriteLastTime.Store(start.UnixNano())

	// Minimal validation - assume caller provides correct size
	if len(buf) == 0 {
		audioDecodeWriteFailures.Add(1)
		audioDecodeWriteLastError.Store("empty buffer")
		return 0, errEmptyBuffer
	}

	// Direct CGO call - hotpath optimization
	n := int(C.jetkvm_audio_decode_write(unsafe.Pointer(&buf[0]), C.int(len(buf))))

	// Fast path for success
	if n >= 0 {
		audioDecodeWriteSuccess.Add(1)
		return n, nil
	}

	audioDecodeWriteFailures.Add(1)
	var errMsg string
	var err error

	switch n {
	case -1:
		errMsg = "audio system not initialized"
		err = errAudioInitFailed
	case -2:
		errMsg = "audio device error or recovery failed"
		err = errAudioDecodeWrite
		audioDecodeWriteRecovery.Add(1)
	default:
		errMsg = fmt.Sprintf("unknown error code %d", n)
		err = errAudioDecodeWrite
	}

	audioDecodeWriteLastError.Store(errMsg)

	return 0, err
}

// updateOpusEncoderParams dynamically updates OPUS encoder parameters
func updateOpusEncoderParams(bitrate, complexity, vbr, vbrConstraint, signalType, bandwidth, dtx int) error {
	result := C.update_opus_encoder_params(
		C.int(bitrate),
		C.int(complexity),
		C.int(vbr),
		C.int(vbrConstraint),
		C.int(signalType),
		C.int(bandwidth),
		C.int(dtx),
	)
	if result != 0 {
		return fmt.Errorf("failed to update OPUS encoder parameters: C error code %d", result)
	}
	return nil
}

// Buffer pool for reusing buffers in CGO functions
var (
	// Simple buffer pool for PCM data
	pcmBufferPool = NewAudioBufferPool(Config.MaxPCMBufferSize)

	// Track buffer pool usage
	cgoBufferPoolGets atomic.Int64
	cgoBufferPoolPuts atomic.Int64
	// Batch processing statistics - only enabled in debug builds
	batchProcessingCount atomic.Int64
	batchFrameCount      atomic.Int64
	batchProcessingTime  atomic.Int64
)

// GetBufferFromPool gets a buffer from the pool with at least the specified capacity
func GetBufferFromPool(minCapacity int) []byte {
	cgoBufferPoolGets.Add(1)
	// Use simple fixed-size buffer for PCM data
	return pcmBufferPool.Get()
}

// ReturnBufferToPool returns a buffer to the pool
func ReturnBufferToPool(buf []byte) {
	cgoBufferPoolPuts.Add(1)
	pcmBufferPool.Put(buf)
}

// ReadEncodeWithPooledBuffer reads audio data and encodes it using a buffer from the pool
func ReadEncodeWithPooledBuffer() ([]byte, int, error) {
	cache := GetCachedConfig()
	cache.Update()

	bufferSize := cache.GetMinReadEncodeBuffer()
	if bufferSize == 0 {
		bufferSize = 1500
	}

	buf := GetBufferFromPool(bufferSize)
	n, err := cgoAudioReadEncode(buf)
	if err != nil {
		ReturnBufferToPool(buf)
		return nil, 0, err
	}

	return buf[:n], n, nil
}

// DecodeWriteWithPooledBuffer decodes and writes audio data using a pooled buffer
func DecodeWriteWithPooledBuffer(data []byte) (int, error) {
	if len(data) == 0 {
		return 0, errEmptyBuffer
	}

	cache := GetCachedConfig()
	cache.Update()

	maxPacketSize := cache.GetMaxPacketSize()
	if len(data) > maxPacketSize {
		return 0, newBufferTooLargeError(len(data), maxPacketSize)
	}

	pcmBuffer := GetBufferFromPool(cache.GetMaxPCMBufferSize())
	defer ReturnBufferToPool(pcmBuffer)

	return CGOAudioDecodeWrite(data, pcmBuffer)
}

// GetBatchProcessingStats returns statistics about batch processing
func GetBatchProcessingStats() (count, frames, avgTimeUs int64) {
	count = batchProcessingCount.Load()
	frames = batchFrameCount.Load()
	totalTime := batchProcessingTime.Load()

	// Calculate average time per batch
	if count > 0 {
		avgTimeUs = totalTime / count
	}

	return count, frames, avgTimeUs
}

// cgoAudioDecodeWriteWithBuffers decodes opus data and writes to PCM buffer
// This implementation uses separate buffers for opus data and PCM output
func cgoAudioDecodeWriteWithBuffers(opusData []byte, pcmBuffer []byte) (int, error) {
	start := time.Now()
	audioDecodeWriteTotal.Add(1)
	audioDecodeWriteLastTime.Store(start.UnixNano())

	// Validate input
	if len(opusData) == 0 {
		audioDecodeWriteFailures.Add(1)
		audioDecodeWriteLastError.Store("empty opus data")
		return 0, errEmptyBuffer
	}
	if cap(pcmBuffer) == 0 {
		audioDecodeWriteFailures.Add(1)
		audioDecodeWriteLastError.Store("empty pcm buffer capacity")
		return 0, errEmptyBuffer
	}

	// Get cached config
	cache := GetCachedConfig()
	cache.Update()

	// Ensure data doesn't exceed max packet size
	maxPacketSize := cache.GetMaxPacketSize()
	if len(opusData) > maxPacketSize {
		audioDecodeWriteFailures.Add(1)
		errMsg := fmt.Sprintf("opus packet too large: %d > %d", len(opusData), maxPacketSize)
		audioDecodeWriteLastError.Store(errMsg)
		return 0, newBufferTooLargeError(len(opusData), maxPacketSize)
	}

	// Direct CGO call with minimal overhead - unsafe.Pointer(&slice[0]) is never nil for non-empty slices
	n := int(C.jetkvm_audio_decode_write(unsafe.Pointer(&opusData[0]), C.int(len(opusData))))

	// Fast path for success case
	if n >= 0 {
		audioDecodeWriteSuccess.Add(1)
		return n, nil
	}

	audioDecodeWriteFailures.Add(1)
	var errMsg string
	var err error

	switch n {
	case -1:
		errMsg = "audio system not initialized"
		err = errAudioInitFailed
	case -2:
		errMsg = "audio device error or recovery failed"
		err = errAudioDecodeWrite
		audioDecodeWriteRecovery.Add(1)
	default:
		errMsg = fmt.Sprintf("unknown error code %d", n)
		err = newAudioDecodeWriteError(n)
	}

	audioDecodeWriteLastError.Store(errMsg)

	return 0, err
}

func CGOAudioInit() error                        { return cgoAudioInit() }
func CGOAudioClose()                             { cgoAudioClose() }
func CGOAudioReadEncode(buf []byte) (int, error) { return cgoAudioReadEncode(buf) }
func CGOAudioPlaybackInit() error                { return cgoAudioPlaybackInit() }
func CGOAudioPlaybackClose()                     { cgoAudioPlaybackClose() }

func CGOAudioDecodeWrite(opusData []byte, pcmBuffer []byte) (int, error) {
	return cgoAudioDecodeWriteWithBuffers(opusData, pcmBuffer)
}
func CGOUpdateOpusEncoderParams(bitrate, complexity, vbr, vbrConstraint, signalType, bandwidth, dtx int) error {
	return updateOpusEncoderParams(bitrate, complexity, vbr, vbrConstraint, signalType, bandwidth, dtx)
}

func CGOSetTraceLogging(enabled bool) {
	var cEnabled C.int
	if enabled {
		cEnabled = 1
	} else {
		cEnabled = 0
	}
	C.set_trace_logging(cEnabled)
}