package bridge

// #cgo CFLAGS: -I"${SRCDIR}/../build/"
// #cgo LDFLAGS: "${SRCDIR}/../build/libsointu.a"
// #include <sointu.h>
import "C"
import (
	"errors"
	"fmt"
	"strings"

	"github.com/vsariola/sointu"
	"github.com/vsariola/sointu/compiler"
)

func Synth(patch sointu.Patch) (*C.Synth, error) {
	s := new(C.Synth)
	comPatch, err := compiler.Encode(&patch, compiler.AllFeatures{})
	if err != nil {
		return nil, fmt.Errorf("error compiling patch: %v", err)
	}
	if len(comPatch.Commands) > 2048 { // TODO: 2048 could probably be pulled automatically from cgo
		return nil, errors.New("bridge supports at most 2048 commands; the compiled patch has more")
	}
	if len(comPatch.Values) > 16384 { // TODO: 16384 could probably be pulled automatically from cgo
		return nil, errors.New("bridge supports at most 16384 values; the compiled patch has more")
	}
	for i, v := range comPatch.Commands {
		s.Commands[i] = (C.uchar)(v)
	}
	for i, v := range comPatch.Values {
		s.Values[i] = (C.uchar)(v)
	}
	for i, v := range comPatch.DelayTimes {
		s.DelayTimes[i] = (C.ushort)(v)
	}
	for i, v := range comPatch.SampleOffsets {
		s.SampleOffsets[i].Start = (C.uint)(v.Start)
		s.SampleOffsets[i].LoopStart = (C.ushort)(v.LoopStart)
		s.SampleOffsets[i].LoopLength = (C.ushort)(v.LoopLength)
	}
	s.NumVoices = C.uint(comPatch.NumVoices)
	s.Polyphony = C.uint(comPatch.PolyphonyBitmask)
	s.RandSeed = 1
	return s, nil
}

// Render renders until the buffer is full or the modulated time is reached, whichever
// happens first.
// Parameters:
//   buffer     float32 slice to fill with rendered samples. Stereo signal, so
//              should have even length.
//   maxtime    how long nominal time to render in samples. Speed unit might modulate time
//              so the actual number of samples rendered depends on the modulation and if
//              buffer is full before maxtime is reached.
// Returns a tuple (int, int, error), consisting of:
//   samples    number of samples rendered in the buffer
//   time       how much the time advanced
//   error      potential error
// In practice, if nsamples = len(buffer)/2, then time <= maxtime. If maxtime was reached
// first, then nsamples <= len(buffer)/2 and time >= maxtime. Note that it could happen that
// time > maxtime, as it is modulated and the time could advance by 2 or more, so the loop
// exit condition would fire when the time is already past maxtime.
// Under no conditions, nsamples >= len(buffer)/2 i.e. guaranteed to never overwrite the buffer.
func (synth *C.Synth) Render(buffer []float32, maxtime int) (int, int, error) {
	if len(buffer)%1 == 1 {
		return -1, -1, errors.New("RenderTime writes stereo signals, so buffer should have even length")
	}
	samples := C.int(len(buffer) / 2)
	time := C.int(maxtime)
	errcode := int(C.su_render(synth, (*C.float)(&buffer[0]), &samples, &time))
	if errcode > 0 {
		return int(samples), int(time), &RenderError{errcode: errcode}
	}
	return int(samples), int(time), nil
}

// Trigger is part of C.Synths' implementation of sointu.Synth interface
func (s *C.Synth) Trigger(voice int, note byte) {
	s.SynthWrk.Voices[voice] = C.Voice{}
	s.SynthWrk.Voices[voice].Note = C.int(note)
}

// Release is part of C.Synths' implementation of sointu.Synth interface
func (s *C.Synth) Release(voice int) {
	s.SynthWrk.Voices[voice].Release = 1
}

// Render error stores the exact errorcode, which is actually just the x87 FPU flags,
// with only the critical failure flags masked. Useful if you are interested exactly
// what went wrong with the patch.
type RenderError struct {
	errcode int
}

func (e *RenderError) Error() string {
	var reasons []string
	if e.errcode&0x40 != 0 {
		reasons = append(reasons, "FPU stack over/underflow")
	}
	if e.errcode&0x04 != 0 {
		reasons = append(reasons, "FPU divide by zero")
	}
	if e.errcode&0x01 != 0 {
		reasons = append(reasons, "FPU invalid operation")
	}
	if e.errcode&0x3800 != 0 {
		reasons = append(reasons, "FPU stack push/pops are not balanced")
	}
	return "RenderError: " + strings.Join(reasons, ", ")
}