/*
Copyright © 2024 filifa

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package cmd

/*
#cgo LDFLAGS: -lprojectM-4
#include "projectM-4/projectM.h"
#include <stdlib.h>
*/
import "C"

import (
	"container/ring"
	"encoding/binary"
	"encoding/json"
	"errors"
	"io"
	"os"
	"unsafe"

	"github.com/veandco/go-sdl2/sdl"
)

const bufSize uint = 2048

type milkDropWindow struct {
	window  *sdl.Window
	context sdl.GLContext
	handle  C.projectm_handle
	preset  *ring.Ring
}

type script struct {
	Presets []string
	Times   []float64
}

func readScript(scriptPath string) (*script, error) {
	if scriptPath == "" {
		return nil, errors.New("no script given")
	}

	f, err := os.Open(scriptPath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	data, err := io.ReadAll(f)
	if err != nil {
		return nil, err
	}

	var s script
	err = json.Unmarshal(data, &s)
	return &s, err
}

func (m *milkDropWindow) nextPreset() {
	m.preset = m.preset.Next()
	m.loadPreset(m.preset.Value.(string))
}

func newMilkDropWindow(width, height int32, scriptPath string) (*milkDropWindow, error) {
	var m milkDropWindow
	var err error

	s, err := readScript(scriptPath)
	if err != nil {
		return nil, err
	}

	m.preset = ring.New(len(s.Presets))
	for _, preset := range s.Presets {
		m.preset.Value = preset
		m.preset = m.preset.Next()
	}

	m.window, err = sdl.CreateWindow("milkbucket", sdl.WINDOWPOS_UNDEFINED, sdl.WINDOWPOS_UNDEFINED, width, height, sdl.WINDOW_OPENGL|sdl.WINDOW_RESIZABLE)
	if err != nil {
		return &m, err
	}

	m.context, err = m.window.GLCreateContext()
	if err != nil {
		return &m, err
	}

	m.handle = C.projectm_create()
	if m.handle == nil {
		return &m, errors.New("error creating projectM instance")
	}

	C.projectm_set_window_size(m.handle, C.ulong(width), C.ulong(height))

	return &m, nil
}

func (m *milkDropWindow) destroy() {
	C.projectm_destroy(m.handle)
	sdl.GLDeleteContext(m.context)
	m.window.Destroy()
}

func (m *milkDropWindow) loadPreset(preset string) {
	cPreset := C.CString(preset)
	defer C.free(unsafe.Pointer(cPreset))
	C.projectm_load_preset_file(m.handle, cPreset, true)
}

func (m *milkDropWindow) render() (bool, error) {
	var audioData [bufSize]int16

	err := binary.Read(os.Stdin, binary.LittleEndian, &audioData)
	if err == io.ErrUnexpectedEOF {
		return false, nil
	} else if err != nil {
		return true, err
	}

	C.projectm_pcm_add_int16(m.handle, (*C.int16_t)(&audioData[0]), C.uint(bufSize), C.PROJECTM_STEREO)

	C.projectm_opengl_render_frame(m.handle)
	m.window.GLSwap()

	return true, nil
}

func (m *milkDropWindow) resize(w, h int32) {
	C.projectm_set_window_size(m.handle, C.ulong(w), C.ulong(h))
}