#pragma once
#include <stdint.h>

namespace Scan {
constexpr uint8_t MIN_ANGLE=30, MAX_ANGLE=150, STEP=4, BINS=31;
constexpr uint32_t TIMEOUT_US=26000, SHOT_GAP_MS=65;
inline bool elapsed(uint32_t now,uint32_t then,uint32_t interval){return uint32_t(now-then)>=interval;}
inline uint16_t cmFromPulse(uint32_t us){
  // Approximate sound speed at room temperature; round to whole centimetres.
  if(us<116 || us>11662)return 0; // 2..200 cm operating window
  return uint16_t((us*343UL+10000UL)/20000UL);
}
struct Filtered {uint16_t cm,spread;uint8_t valid;};
inline Filtered filter(const uint16_t raw[3]){
  uint16_t a[3];uint8_t n=0;
  for(uint8_t i=0;i<3;i++)if(raw[i]>=2&&raw[i]<=200)a[n++]=raw[i];
  for(uint8_t i=0;i<n;i++)for(uint8_t j=i+1;j<n;j++)if(a[j]<a[i]){uint16_t t=a[i];a[i]=a[j];a[j]=t;}
  if(n<2)return {0,0,n};
  return {uint16_t(n==3?a[1]:(a[0]+a[1]+1)/2),uint16_t(a[n-1]-a[0]),n};
}
struct Sweep {
  uint8_t bin=0;int8_t direction=1;uint32_t passes=0;
  uint8_t angle()const{return MIN_ANGLE+bin*STEP;}
  void advance(){
    if((bin==BINS-1&&direction>0)||(bin==0&&direction<0)){direction=-direction;passes++;}
    bin=uint8_t(int16_t(bin)+direction);
  }
};
struct Proximity {
  bool near=false;
  void update(uint16_t cm,uint16_t threshold){
    if(!cm){near=false;return;} // unknown is never displayed as an old near/far result
    if(cm<threshold)near=true;else if(cm>=threshold+5)near=false;
  }
};
struct Button {
  bool raw=false,stable=false;uint32_t changed=0;
  bool update(bool pressed,uint32_t now){
    if(pressed!=raw){raw=pressed;changed=now;}
    if(raw!=stable&&elapsed(now,changed,30)){stable=raw;return stable;}
    return false;
  }
};
}