package synth

import "math"

// LFO is a low-frequency oscillator for modulating synthesis parameters.
// Uses sine waveform. Rate is in Hz (typically 0.01-0.5 Hz for ambient feel).
type LFO struct {
	phase float64
	rate  float64 // Hz
	depth float64 // modulation depth (interpretation depends on usage)
	sr    float64
}

// NewLFO creates an LFO at the given rate (Hz) and depth.
func NewLFO(rate, depth float64, sampleRate int) *LFO {
	return &LFO{
		rate:  rate,
		depth: depth,
		sr:    float64(sampleRate),
	}
}

// Advance returns the current LFO value in [-depth, +depth] and advances the phase.
func (l *LFO) Advance() float64 {
	val := math.Sin(2 * math.Pi * l.phase)
	l.phase += l.rate / l.sr
	if l.phase >= 1.0 {
		l.phase -= math.Floor(l.phase)
	}
	return val * l.depth
}

// PitchLFOFreq returns a pitch-modulated frequency given a base frequency
// and an LFO value in semitones. For example, lfoVal=0.1 shifts pitch up by 0.1 semitones.
func PitchLFOFreq(baseHz, lfoSemitones float64) float64 {
	return baseHz * math.Pow(2.0, lfoSemitones/12.0)
}

// LFOConfig holds LFO parameters for a synthesis layer.
// Each protocol gets unique, incommensurable rates so modulation patterns never repeat.
type LFOConfig struct {
	PitchRate     float64 // Hz, typically 0.02-0.08
	PitchDepth    float64 // semitones, typically 0.05-0.15
	TremoloRate   float64 // Hz, typically 0.05-0.3
	TremoloDepth  float64 // amplitude fraction, typically 0.05-0.2
}

// layerLFOConfigs provides unique incommensurable LFO rates per protocol group.
// Rates chosen as non-integer ratios to avoid periodic sync (Eno technique).
var groupLFOConfigs = map[string]LFOConfig{
	"Infrastructure": {PitchRate: 0.031, PitchDepth: 0.08, TremoloRate: 0.053, TremoloDepth: 0.12},
	"Web":            {PitchRate: 0.043, PitchDepth: 0.10, TremoloRate: 0.071, TremoloDepth: 0.15},
	"Mail":           {PitchRate: 0.037, PitchDepth: 0.07, TremoloRate: 0.059, TremoloDepth: 0.10},
	"Remote Access":  {PitchRate: 0.029, PitchDepth: 0.12, TremoloRate: 0.047, TremoloDepth: 0.18},
	"File Transfer":  {PitchRate: 0.041, PitchDepth: 0.09, TremoloRate: 0.067, TremoloDepth: 0.13},
	"Database":       {PitchRate: 0.023, PitchDepth: 0.06, TremoloRate: 0.083, TremoloDepth: 0.10},
	"VoIP":           {PitchRate: 0.019, PitchDepth: 0.05, TremoloRate: 0.091, TremoloDepth: 0.08},
	"Unknown":        {PitchRate: 0.053, PitchDepth: 0.15, TremoloRate: 0.037, TremoloDepth: 0.20},
}

// DefaultLFOConfig is the fallback for groups not in the map.
var DefaultLFOConfig = LFOConfig{
	PitchRate: 0.033, PitchDepth: 0.10, TremoloRate: 0.057, TremoloDepth: 0.15,
}

// LFOConfigForGroup returns the LFO config for a protocol group.
func LFOConfigForGroup(group string) LFOConfig {
	if cfg, ok := groupLFOConfigs[group]; ok {
		return cfg
	}
	return DefaultLFOConfig
}