model_breadcrumbs.h

#pragma once   // Please format this file with clang before check-in to GitHub
/*
  File:     model_breadcrumbs.h

            Contains everything about the breadcrumb history trail.
            This is a circular buffer in memory, which periodically written to a CSV file.
            Buffer is never full; we can always add more records and overwrite the oldest.

  Breadcrumb trail strategy:
            This is a "model" of the Model-View-Controller design pattern.
            As such, it contains the data for holding all the breadcrumbs  and is a
            low-level component with minimal side effects and few dependencies.

            This "Breadcrumbs" object will just only manage itself.
            It does not schedule events or request actions from other objects.
            The caller is responsible for asking us to write to a file, output to console,
            produce a formatted KML file, and etc when it's needed.
            We don't reach into the "model" from here and tell it what to do.
            If the controller tells us to save to file, don't tell the "model" to do anything.

            When should the controller should remember a new breadcrumb?
            1. Every ten minutes
            2. When we drive a visible distance on the screen
            3. When we drive into a new 6-digit grid square (todo)
            4. When we turn a sharp corner (todo)

  Todo:     1. refactor "class Location" into this file
            2. refactor "makeLocation()" into ctor (or public member) of "class Location"
            3. add rememberPDN(), rememberTOD()

  API Design:
      Initialization:
            We need to initialize the circular buffer container with a buffer and size
            We need to reset the circular buffer container
      State tracking:
            We need to know whether the buffer is full or empty
            We need to know the current number of elements in the buffer
            We need to know the max capacity of the buffer
      Add/read records:
            We need to be able to add data to the buffer
            We need to be able to read values by iterating through the buffer
            We don't need to remove elements from the buffer
            We don't need thread safety
      I/O:
            We need to send various neatly-formatted reports to the console
            We need to save and restore the buffer to/from a file
            We want to hide implementation details from other modules

  Full and Empty:
            The "full" and "empty" cases look the same: head and tail pointer are equal.
            There are two approaches to differentiating between full and empty:
            1. Waste a slot in the buffer:
                  Full state is head + 1 == tail
                  Empty state is head == tail
            2. Use a bool flag and additional logic:    <-- Griduino chooses this approach
                  Full state has "bool full"
                  Empty state is (head == tail) && !full
            Griduino wants efficient memory usage and doesn't need thread safety.

  Size of GPS breadcrumb trail:
            Our goal is to keep track of at least one long day's travel, 500 miles or more.
            If 180 pixels horiz = 100 miles, then we need (500*180/100) = 900 entries.
            If 160 pixels vert = 70 miles, then we need (500*160/70) = 1,140 entries.
            For example, if I drive a drunken-sailor route around the Olympic Peninsula,
            we need at least 800 entries to capture the whole out-and-back 500-mile loop.

            array  bytes        total          2023-04-08
            size   per entry    memory         comment
            2500     48 bytes  120,000 bytes   ok
            2950     48 bytes  141,600 bytes   ok
            2980     48 bytes  143,040 bytes   ok
            3000     48 bytes  144,000 bytes   crash on "list files" command

  Inspiration:
            https://embeddedartistry.com/blog/2017/05/17/creating-a-circular-buffer-in-c-and-c/

  Software: Barry Hansen, K7BWH, barry@k7bwh.com, Seattle, WA
  Hardware: John Vanderbeck, KM7O, Seattle, WA

*/

#include "logger.h"         // conditional printing to Serial port
#include "grid_helper.h"    // lat/long conversion routines
#include "date_helper.h"    // date/time conversions
#include "save_restore.h"   // Configuration data in nonvolatile RAM

// ========== extern ===========================================
extern Logger logger;   // Griduino.ino
extern Grids grid;      // grid_helper.h
extern Dates date;      // date_helper.h

// ========== class History ======================
class Breadcrumbs {
public:
  // Class member variables
  const int totalSize  = sizeof(history);          // bytes
  const int recordSize = sizeof(Location);         // bytes
  const int capacity   = totalSize / recordSize;   // max number of records
  int saveInterval     = 2;

private:
  Location history[2500];   // remember a list of GPS coordinates and stuff
  bool full   = false;      //
  int head    = 0;          // index of next item to write = nextHistoryItem
  int tail    = 0;          // index of oldest item
  int current = 0;          // index used for iterators begin(), next()

  const PointGPS noLocation{-1.0, -1.0};   // eye-catching value, and nonzero for "isEmpty()"
  const float noSpeed        = -1.0;       // mph
  const float noDirection    = -1.0;       // degrees from N
  const float noAltitude     = -1.0;       // meters above MSL
  const uint8_t noSatellites = 0;

public:
  // ----- Initialization -----
  Breadcrumbs() {}   // Constructor - create and initialize member variables

  void clearHistory() {   // wipe clean the in-memory trail of breadcrumbs
    head = tail = 0;
    full        = false;
    for (uint ii = 0; ii < capacity; ii++) {
      history[ii].reset();
    }
    logger.info("Breadcrumb trail history[%d] has been erased", capacity);
  }

  // ----- State tracking
  const int getCurrent() {
    return current;
  }
  const int getHistoryCount() {   // how many history slots currently contain breadcrumb data
    int count;
    if (full) {
      count = capacity;
    } else {
      if (head >= tail) {
        count = head - tail;
      } else {
        count = capacity + head - tail;
      }
    }
    return count;
  }

  const int isEmpty() {   // indicate empty
    return (head == tail);
  }

  const bool isFull() {   // buffer is never full; we can always add more records
    return false;
  }

  // ----- Add or read records
  void rememberPUP() {   // save "power-up" event in the history buffer
    Location pup{rPOWERUP, noLocation, now(), noSatellites, noSpeed, noDirection, noAltitude};
    remember(pup);
  }

  void rememberAOS(Location vLoc) {   // save "acquisition of signal" in history buffer
    strncpy(vLoc.recordType, rACQUISITIONOFSIGNAL, sizeof(vLoc.recordType));
    remember(vLoc);
  }

  void rememberLOS(Location vLoc) {   // save "loss of signal" in history buffer
    strncpy(vLoc.recordType, rLOSSOFSIGNAL, sizeof(vLoc.recordType));
    remember(vLoc);
  }

  void rememberFirstValidTime(time_t vTime, uint8_t vSats) {   // save "first valid time received from GPS"
    // "first valid time" can happen _without_ a satellite fix,
    // so the only data stored is the GMT timestamp
    Location fvt{rFIRSTVALIDTIME, noLocation, vTime, vSats, noSpeed, noDirection, noAltitude};
    remember(fvt);
  }

  const TimeElements GRIDUINO_FIRST_RELEASE{0, 0, 0, 0, FIRST_RELEASE_DAY, FIRST_RELEASE_MONTH, FIRST_RELEASE_YEAR - 1970};

  void rememberGPS(Location vLoc) {
    // our GPS receiver can generate bogus locations in case of buffer overrun
    // identifiable by a timestamp in the year 2000 and latitude==longitude
    // so ignore readings that occurred before Griduino was built
    time_t cutoff = makeTime(GRIDUINO_FIRST_RELEASE);
    if (vLoc.timestamp > cutoff) {
      strncpy(vLoc.recordType, rGPS, sizeof(vLoc.recordType));
      remember(vLoc);
    } else {
      vLoc.printLocation("Bogus GPS date ");
    }
  }

  void rememberGPS(PointGPS vLoc, time_t vTime, uint8_t vSats, float vSpeedMPH, float vDirection, float vAltitudeMeters) {
    time_t cutoff = makeTime(GRIDUINO_FIRST_RELEASE);
    Location gps{rGPS, vLoc, vTime, vSats, vSpeedMPH, vDirection, vAltitudeMeters};
    if (vTime > cutoff) {
      remember(gps);
    } else {
      gps.printLocation("Bogus GPS date ");
    }
  }

protected:
  void remember(Location vLoc) {   // save GPS location and timestamp in history buffer
    // so that we can display it as a breadcrumb trail
    history[head] = vLoc;
    advance_pointer();
  }

public:
  void advance_pointer() {
    if (full) {
      tail = (tail + 1) % capacity;   // if buffer full, advance tail pointer
    }
    head = (head + 1) % capacity;   // always advance head pointer
    full = (head == tail);          // check if adding a record triggers the full condition
  }

  Location *begin() {   // returns pointer to tail of buffer, or null if buffer is empty
    // todo: test if buffer empty and return null
    current = tail;
    return &history[current];
  }

  Location *next() {   // returns pointer to next element, or null if buffer is empty
    Location *ptr = nullptr;
    current       = (current + 1) % capacity;
    if (current == head) {
      // nothing returned - end of data
    } else {
      ptr = &history[current];
    }
    return ptr;
  }

  // ----- I/O
  // our breadcrumb trail file is CSV format -- you can open this Arduino file directly in a spreadsheet
  int saveGPSBreadcrumbTrail();   // save trail to file, returns 1=success, 0=failure

  int restoreGPSBreadcrumbTrail();   // restore trail from file, returns 1=success, 0=failure

  void deleteFile();   // remove breadcrumb trail file

  void dumpHistoryGPS(int limit = 0);   // print neatly formatted breadcrumb trail to console

  void dumpHistoryKML();   // print Keyhole Markup Language trail to console

  // ----- Internal helpers
private:
  bool isValidBreadcrumb(const char *original_line) {
    // input: entire line from CSV file
    // examine a line from saved history file to see if it's a plausible record
    // the goal is to ignore comment lines
    if (strlen(original_line) < 5) {
      return false;
    }

    char rec[4];
    memcpy(rec, original_line, sizeof(rec));
    rec[3] = 0;   // because memcpy doesn't add null terminator
    if (!Location::isValidRecordType(rec)) {
      return false;
    }

    return true;
  }

};   // end class Breadcrumbs