//
//  dolmetschctl
//
//
//  Copyright (C) 2019 Christian Pointner <equinox@spreadspace.org>
//
//  This file is part of dolmetschctl.
//
//  dolmetschctl 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
//  any later version.
//
//  dolmetschctl 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 dolmetschctl. If not, see <http://www.gnu.org/licenses/>.
//

package controller

import (
	"container/list"
	"errors"
	"fmt"
	//	"log"
	"strings"
	"sync"

	"github.com/scgolang/midi"
)

const (
	BUTTON_ON          = byte(0x90)
	BUTTON_OFF         = byte(0x80)
	NOTE_OFFSET_BUTTON = byte(0x00)
	NUM_BUTTONS        = 4

	LED_CC          = byte(0xB0)
	NOTE_OFFSET_LED = byte(0x00)
	NUM_LEDS        = 4
	LED_OFF         = byte(0x00)
	LED_ON          = byte(0x01)
	LED_TOGGLE      = byte(0x02)
	LED_BLINK_MIN   = byte(0x03)
	LED_BLINK_MAX   = byte(0x7f)
)

type EventType int

const (
	ButtonPressed EventType = iota
	ButtonReleased
)

func (e EventType) String() string {
	switch e {
	case ButtonPressed:
		return "button pressed"
	case ButtonReleased:
		return "button released"
	default:
		return "unknown"
	}
}

type Event struct {
	Button byte
	Type   EventType
}

type subscriber struct {
	publish     chan<- Event
	unsubscribe <-chan struct{}
}

type Controller struct {
	Dev             *midi.Device
	subscribersLock sync.Mutex
	subscribers     list.List
}

func openDevice(devices []*midi.Device, prefix string) (d *midi.Device, err error) {
	for _, device := range devices {
		if strings.HasPrefix(device.Name, prefix) {
			d = device
		}
	}
	if d == nil {
		return nil, errors.New("could not find device with prefix: " + prefix)
	}
	return d, d.Open()
}

func NewController(c Config) (*Controller, error) {
	devices, err := midi.Devices()
	if err != nil {
		return nil, err
	}

	ctrl := &Controller{}
	if ctrl.Dev, err = openDevice(devices, c.Dev); err != nil {
		return nil, err
	}
	ctrl.Dev.QueueSize = 100

	return ctrl, nil
}

func (c *Controller) publishEvent(ev Event) {
	c.subscribersLock.Lock()
	defer c.subscribersLock.Unlock()

	var next *list.Element
	for entry := c.subscribers.Front(); entry != nil; entry = next {
		next = entry.Next()

		sub, ok := (entry.Value).(subscriber)
		if !ok {
			panic(fmt.Sprintf("controller: subscriber list element value has wrong type: %T", entry.Value))
		}

		select {
		case <-sub.unsubscribe:
			// log.Printf("controller: removing subscriber '%v', because it has unsubscribed", sub.publish)
			close(sub.publish)
			c.subscribers.Remove(entry)
		default:
			select {
			case sub.publish <- ev:
			default:
				// log.Printf("controller: removing subscriber '%v', because it is not responding", sub.publish)
				close(sub.publish)
				c.subscribers.Remove(entry)
			}
		}
	}
}

func (c *Controller) handleMidiPacket(p midi.Packet) {
	ev := Event{Button: p.Data[1]}
	switch p.Data[0] {
	case BUTTON_ON:
		ev.Type = ButtonPressed
	case BUTTON_OFF:
		ev.Type = ButtonReleased
	default:
		// ignore all other events
		return
	}
	c.publishEvent(ev)
}

func (c *Controller) Init() error {
	ch, err := c.Dev.Packets()
	if err != nil {
		return err
	}

	go func() {
		for {
			ps := <-ch
			for _, p := range ps {
				if p.Err != nil {
					c.Shutdown()
				}
				c.handleMidiPacket(p)
			}
		}
	}()
	return nil
}

func (c *Controller) Shutdown() error {
	if c.Dev != nil {
		c.Dev.Close()
		c.Dev = nil
	}

	c.subscribersLock.Lock()
	defer c.subscribersLock.Unlock()

	for entry := c.subscribers.Front(); entry != nil; entry = entry.Next() {
		sub, ok := (entry.Value).(subscriber)
		if !ok {
			panic(fmt.Sprintf("controller: subscriber list element value has wrong type: %T", entry.Value))
		}
		close(sub.publish)
	}
	c.subscribers.Init()
	return nil
}

func (c *Controller) setLed(num byte, value byte) error {
	if num >= NUM_LEDS {
		return fmt.Errorf("this controller has only %d leds.", NUM_LEDS)
	}

	n, err := c.Dev.Write([]byte{LED_CC, NOTE_OFFSET_LED + num, value})
	if err != nil {
		// reopen device?
		return err
	}
	if n != 3 {
		return errors.New("sending LED command failed.")
	}
	return nil
}

func (c *Controller) LedOff(num byte) error {
	return c.setLed(num, LED_OFF)
}

func (c *Controller) LedOn(num byte) error {
	return c.setLed(num, LED_ON)
}

func (c *Controller) LedToggle(num byte) error {
	return c.setLed(num, LED_TOGGLE)
}

func (c *Controller) LedBlink(num, wait byte) error {
	if (wait + LED_BLINK_MIN) > LED_BLINK_MAX {
		return fmt.Errorf("blink wait must be between 0 and %d.", LED_BLINK_MAX-LED_BLINK_MIN)
	}
	return c.setLed(num, wait+LED_BLINK_MIN)
}

func (c *Controller) Subscribe(out chan<- Event) chan<- struct{} {
	c.subscribersLock.Lock()
	defer c.subscribersLock.Unlock()

	// log.Printf("controller: subscribing '%v' to events", out)
	unsubscribe := make(chan struct{})
	c.subscribers.PushBack(subscriber{publish: out, unsubscribe: unsubscribe})
	return unsubscribe
}