#include <LittleFS.h>
#include "config.h"
#include "flog.h"

static FcastEntry s_buf[FORECAST_LOG_SIZE];
static int  s_head  = 0;
static int  s_count = 0;
static char s_lastLetter = 0;   // last logged letter, to detect changes

void flogBegin() { s_head = 0; s_count = 0; s_lastLetter = 0; }

static void push(uint32_t ep, char letter, uint8_t cat) {
  s_buf[s_head] = FcastEntry{ ep, letter, cat };
  s_head = (s_head + 1) % FORECAST_LOG_SIZE;
  if (s_count < FORECAST_LOG_SIZE) s_count++;
}

void flogConsider(uint32_t epoch, const Forecast& f) {
  if (f.letter == s_lastLetter) return;   // no change -> nothing to log
  s_lastLetter = f.letter;
  push(epoch, f.letter, (uint8_t)f.category);
  flogSave();
}

int flogCount() { return s_count; }

FcastEntry flogGet(int i) {
  int start = (s_head - s_count + FORECAST_LOG_SIZE) % FORECAST_LOG_SIZE;
  return s_buf[(start + i) % FORECAST_LOG_SIZE];
}

static const char* FPATH = "/forecasts.dat";

bool flogSave() {
  File f = LittleFS.open(FPATH, "w");
  if (!f) return false;
  int32_t n = s_count;
  f.write((const uint8_t*)&n, sizeof(n));
  for (int i = 0; i < s_count; i++) {
    FcastEntry e = flogGet(i);
    f.write((const uint8_t*)&e, sizeof(e));
  }
  f.close();
  return true;
}

bool flogLoad() {
  File f = LittleFS.open(FPATH, "r");
  if (!f) return false;
  int32_t n = 0;
  if (f.read((uint8_t*)&n, sizeof(n)) != sizeof(n)) { f.close(); return false; }
  if (n < 0 || n > FORECAST_LOG_SIZE) { f.close(); return false; }
  s_head = 0; s_count = 0;
  for (int i = 0; i < n; i++) {
    FcastEntry e;
    if (f.read((uint8_t*)&e, sizeof(e)) != sizeof(e)) break;
    push(e.epoch, e.letter, e.cat);
  }
  f.close();
  if (s_count > 0) s_lastLetter = flogGet(s_count - 1).letter;  // avoid re-logging on boot
  return true;
}