#include "config.h"
#include "history.h"

static Sample s_buf[HISTORY_SIZE];
static int    s_head  = 0;   // next write position
static int    s_count = 0;

void historyBegin() { s_head = 0; s_count = 0; }

void historyAdd(uint32_t epoch, float mslHpa, float tempC) {
  s_buf[s_head] = Sample{ epoch, mslHpa, tempC };
  s_head = (s_head + 1) % HISTORY_SIZE;
  if (s_count < HISTORY_SIZE) s_count++;
}

int historyCount() { return s_count; }

Sample historyGet(int i) {
  int start = (s_head - s_count + HISTORY_SIZE) % HISTORY_SIZE;
  return s_buf[(start + i) % HISTORY_SIZE];
}

Sample historyLatest() { return historyGet(s_count - 1); }

bool historyTrendDelta(float& outDelta) {
  if (s_count < 2) return false;
  Sample latest = historyLatest();
  uint32_t target = latest.epoch - 10800UL;   // 3 h earlier
  int idx = -1;
  for (int i = 0; i < s_count; i++) {
    if (historyGet(i).epoch <= target) idx = i; else break;
  }
  if (idx < 0) return false;
  Sample past = historyGet(idx);
  if (latest.epoch - past.epoch < 9000UL) return false;  // need >= 2.5 h span
  outDelta = latest.mslHpa - past.mslHpa;
  return true;
}