#pragma once
#ifndef DSY_ADSR_H
#define DSY_ADSR_H

#include <stdint.h>
#ifdef __cplusplus

namespace daisysp
{
/** Distinct stages that the phase of the envelope can be located in.
- IDLE   = located at phase location 0, and not currently running
- ATTACK  = First segment of envelope where phase moves from 0 to 1
- DECAY   = Second segment of envelope where phase moves from 1 to SUSTAIN value
- SUSTAIN = Third segment of envelope, stays at SUSTAIN level until GATE is released
- RELEASE =     Fourth segment of envelop where phase moves from SUSTAIN to 0
- LAST    =  Last segment, aka release
*/
enum
{
    ADSR_SEG_IDLE,
    ADSR_SEG_ATTACK,
    ADSR_SEG_DECAY,
    ADSR_SEG_SUSTAIN,
    ADSR_SEG_RELEASE,
    ADSR_SEG_LAST,
};


/** adsr envelope module

Original author(s) : Paul Batchelor

Ported from Soundpipe by Ben Sergentanis, May 2020
*/
class Adsr
{
  public:
    Adsr() {}
    ~Adsr() {}
    /** Initializes the Adsr module.
        \param sample_rate - The sample rate of the audio engine being run. 
    */
    void Init(float sample_rate);


    /** Processes one sample through the filter and returns one sample.
        \param gate - trigger the envelope, hold it to sustain 
    */
    float Process(bool gate);

    /** Sets time
        Set time per segment in seconds
    */
    inline void SetTime(int seg, float time) { seg_time_[seg] = time; }
    /** Sustain level
        \param sus_level - sets sustain level
    */
    inline void SetSustainLevel(float sus_level) { sus_ = sus_level; }
    /** get the current envelope segment
        \return the segment of the envelope that the phase is currently located in.
    */
    inline uint8_t GetCurrentSegment() { return mode_; }
    /** Tells whether envelope is active
        \return true if the envelope is currently in any stage apart from idle.
    */
    inline bool IsRunning() const { return mode_ != ADSR_SEG_IDLE; }

  private:
    float   sus_, seg_time_[ADSR_SEG_LAST], a_, b_, y_, x_, prev_, atk_time_;
    int     sample_rate_;
    uint8_t mode_;
    float   Tau2Pole(float tau);
    float   AdsrFilter();
};
} // namespace daisysp
#endif
#endif