# 2023-10-07

I got distract by hacking last night and forgot to write this, so this
covers my work for the past two days.

## Guru meditations

I spent a while on Friday trying to debug a nagging Guru Meditation
(aka a segfault) in my autoconnection code.  One of the debugging
tricks that really helped with this is to the PlatformIO monitor filter
for decoding ESP stack traces.

Anyways, the problem ended up being trying to use the result of a bool
function when that function wasn't returning anything. I guess the
warning for the was lost in the scrollback.

## Autoconnecting

My first pass at autoconnecting was to scan for SSIDs, looking up each
one in the phonebook. However, I wasn't seeing my home network in the
scan list. I ended up using a Preference (from the ESP Preferences
library) to store the SSID of the last connection, looking that up in
the phonebook, and connecting to that. This worked.

## A question of structure

I want to be able to switch the modem into different modes.  The main
use for the modem is to be able to telnet into a BBS, so I need a way
to say that I/O should be passed between the host machine and the BBS. 
At the same time, there needs to be a way to talk to the modem, to tell
it to connect or disconnect, dial hosts, manage connections, etc.

At first, I thought I would use some kind of an object inheritance
system, so I wrote up a basic skeleton of that.  However, the guiding
constraint is that I'm trying to dynamically allocate as little memory
as possible.  In order to use an abstract base class, though, you need
a pointer, and that got convoluted quickly.  Then I tried putting a
static member in a header, but the fields would be reset to NULL each
time.

What I ended up doing was putting a static variable in a new source
file and added some interaction scaffolding around it.  This works. 
And of course it does when you think about it.  I was thinking of the
extern keyword, and I've spent too much time in Go.

Rather than debug this on the microcontroller, I wrote a quick test
program where I could use gdb and generate coredumps. It was relatively
easy to figure out at that point.

Long story short, this works now:

    MODEM BOOT
    SPIFFS INIT
    DAT FILE 512B
    LOAD PHONEBOOK OK
    dictionary entries: {
    	HomeNet->c00lp4ssw0rd
    	OtherNet->correct horse battery staple
    }
    AUTO ATC
    LAST SSID: HomeNet
    CONNECT HomeNet
    SSID: HomeNet
    IP: 192.168.88.232
    MODEM READY
    > ATW
    802.11 CONNECTED
      SSID: HomeNet
      IP: 192.168.88.232
      RSSI: -53
    > ATWS
    SCAN
      <list of SSIDs>

## File system choices

When I was reading up on storing files on the ESP32, SPIFFS was the
default choice. However, on the ESP8266, it seems like LittleFS is
the default. Do I need to write a compatibility layer? The RC2014 WiFi
module is an ESP8266, but my dev boards are all ESP32. It works now,
but there's the threat of deprecation in the future.

In addition, I could use an SD card. Something to think about. For now,
I'm just using SPIFFS.

I think a generic interface for this would be something like

  // open flags:
  // APPEND
  // CREATE
  // READONLY
  // READWRITE
  // WRITE


  class PersistentStorage {
  public:
          virtual int Open(const char *path, uint8_t mode) = 0;
          virtual int Close() = 0;
          virtual size_t Size() = 0;
          virtual size_t Read(uint8_t *buf, size_t maxlen) = 0;
          virtual size_t Write(uint8_t *buf, size_t length) = 0;
          virtual int Flush() = 0;
  }


## On code organization

Most of this has been a first pass attempt. I'm going to sit down at
some point and work out all the proper organization. I think the
display was helpful for getting off the ground but ultimately it's a
distraction. Also, I need to settle on the hardware. I think I'm going
to make a carrier board with things like an FTDI header, some LEDs,
and the ability to program it.

## On editors

I've switchd over to joe recently. We'll see how long it lasts.