package audio

import (
	"bytes"
	"encoding/binary"
	"math"
)

const sampleRate = 48000 // PipeWire native rate

// seg is one tone segment: linear frequency sweep with pluck envelope
type seg struct {
	f0, f1 float64 // Hz
	dur    float64 // seconds
	amp    float64 // 0..1
	square bool
}

// effectSegs defines each effect's tone sequence — the tuning surface
var effectSegs = [EffectCount][]seg{
	EffectPickup:      {{988, 988, 0.055, 0.5, false}, {1319, 1319, 0.11, 0.5, false}},   // B5→E6 coin
	EffectMagnet:      {{523, 1319, 0.10, 0.45, false}, {784, 1976, 0.16, 0.4, false}},   // rising double sweep — reads as a suction, distinct from the coin
	EffectShield:      {{659, 988, 0.07, 0.45, false}, {1319, 1319, 0.16, 0.40, false}},  // chime up into a held tone — armor
	EffectShieldBreak: {{1200, 300, 0.06, 0.50, true}, {700, 180, 0.14, 0.45, true}},     // square shatter; brighter and shorter than the death crunch
	EffectBoost:       {{392, 1568, 0.16, 0.50, false}, {1568, 1568, 0.10, 0.35, false}}, // fast sweep up — tempo kick
	EffectDeflect:     {{1200, 1600, 0.025, 0.20, true}, {1600, 900, 0.035, 0.15, true}}, // fires once per walled chord traversed under a Boost — short, dry, low
	EffectMoveRow:     {{300, 620, 0.07, 0.35, false}},                                   // whoosh up
	EffectMoveLane:    {{440, 470, 0.04, 0.28, false}},                                   // tick
	EffectHitWall:     {{140, 50, 0.30, 0.6, true}},                                      // crunch drop
	EffectLevelClear: { // C-major arpeggio
		{523, 523, 0.09, 0.45, false},
		{659, 659, 0.09, 0.45, false},
		{784, 784, 0.09, 0.45, false},
		{1047, 1047, 0.18, 0.45, false},
	},
}

// synth renders segments to 16-bit mono PCM
func synth(segs []seg) []int16 {
	var out []int16
	for _, s := range segs {
		n := int(s.dur * sampleRate)
		phase := 0.0
		for i := range n {
			t := float64(i) / float64(n)
			f := s.f0 + (s.f1-s.f0)*t
			phase += 2 * math.Pi * f / sampleRate
			v := math.Sin(phase)
			if s.square {
				if v >= 0 {
					v = 1
				} else {
					v = -1
				}
			}
			env := math.Min(t*24, 1) * math.Exp(-4.2*t) // fast attack, pluck decay
			out = append(out, int16(v*env*s.amp*32767))
		}
	}
	return out
}

// wavBytes wraps PCM in a minimal RIFF/WAVE container (PCM16 mono)
func wavBytes(samples []int16) []byte {
	var b bytes.Buffer
	dataLen := uint32(len(samples) * 2)
	b.WriteString("RIFF")
	binary.Write(&b, binary.LittleEndian, 36+dataLen)
	b.WriteString("WAVEfmt ")
	binary.Write(&b, binary.LittleEndian, uint32(16))
	binary.Write(&b, binary.LittleEndian, uint16(1)) // PCM
	binary.Write(&b, binary.LittleEndian, uint16(1)) // mono
	binary.Write(&b, binary.LittleEndian, uint32(sampleRate))
	binary.Write(&b, binary.LittleEndian, uint32(sampleRate*2)) // byte rate
	binary.Write(&b, binary.LittleEndian, uint16(2))            // block align
	binary.Write(&b, binary.LittleEndian, uint16(16))           // bits/sample
	b.WriteString("data")
	binary.Write(&b, binary.LittleEndian, dataLen)
	binary.Write(&b, binary.LittleEndian, samples)
	return b.Bytes()
}