# Matrix Client Library in C

This is a library implementing parts of the [Matrix](https://matrix.org/) [Client-Server API](https://spec.matrix.org/v1.8/client-server-api/).
It is written in C and supports sending and receiving of messages, including end-to-end encryption.
Device verification is also supported.

## Building

Building requires a C/C++ compiler and make.

To build the dependencies run `make deps`.

To build any of the examples run `make out/examples/<example>`.

To use the library:
- Add `src/matrix.c` to compilation
- Add either `src/matrix_http_mongoose.c` or `src/matrix_http_esp32.c` to compilation
- Add `out/*.o` to compilation
- Add include path `src/`
- Add include path `ext/olm/include/`
- Add include path `ext/mjson/src/`
- Add include path `ext/mongoose/`

## Dependencies
[Mongoose](https://github.com/cesanta/mongoose)

[mjson](https://github.com/cesanta/mjson)

[Olm](https://gitlab.matrix.org/matrix-org/olm)

## Examples

### Sending an encrypted message
```
MatrixMegolmOutSession * megolmOutSession;
MatrixClientNewMegolmOutSession(&client,
    ROOM_ID,
    &megolmOutSession);
printf("megolm session id: %.10s... key: %.10s...\n", megolmOutSession->id, megolmOutSession->key);

MatrixClientShareMegolmOutSession(&client,
    USER_ID,
    "ULZZOKJBYN",
    megolmOutSession);

MatrixClientSendEventEncrypted(&client,
    ROOM_ID,
    "m.room.message",
    "{\"body\":\"Hello\",\"msgtype\":\"m.text\"}");
```

### Verification
```
// Request an encrypted event to enable verification
STATIC char eventBuffer[1024];
MatrixClientGetRoomEvent(client,
    ROOM_ID,
    EVENT_ID,
    eventBuffer, 1024);

#define SYNC_BUFFER_SIZE 1024*10
STATIC char syncBuffer[SYNC_BUFFER_SIZE];
STATIC char nextBatch[1024];

while (! client->verified) {
    MatrixClientSync(client, syncBuffer, SYNC_BUFFER_SIZE, nextBatch, 1024);
}
```