/*
 * Low-level protocol support for the IPC connection to the engine.
 */

#ifndef IPCBASE_H_
#define IPCBASE_H_

#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>

#define IPCBASE_MAPMSG_BYTES 4097

typedef enum {IPC_NOT_CONNECTED, IPC_LISTENING, IPC_CONNECTED} IpcState;

struct _flib_ipcbase;
typedef struct _flib_ipcbase flib_ipcbase;

/**
 * Start an engine connection by listening on a random port. The selected port can
 * be queried with flib_ipcbase_port and has to be passed to the engine.
 *
 * Returns NULL on error. Destroy the created object with flib_ipcbase_destroy.
 *
 * We stop accepting new connections once a connection has been established, so you
 * need to create a new ipcbase in order to start a new connection.
 */
flib_ipcbase *flib_ipcbase_create();

uint16_t flib_ipcbase_port(flib_ipcbase *ipc);

/**
 * Free resources and close sockets.
 */
void flib_ipcbase_destroy(flib_ipcbase *ipc);

/**
 * Determine the current connection state
 */
IpcState flib_ipcbase_state(flib_ipcbase *ipc);

/**
 * Receive a single message (up to 256 bytes) and copy it into the data buffer.
 * Returns the length of the received message, a negative value if no message could
 * be read.
 *
 * The first byte of a message is its content length, which is one less than the returned
 * value.
 *
 * Note: When a connection is closed, you probably want to call this function until
 * no further message is returned, to ensure you see all messages that were sent
 * before the connection closed.
 */
int flib_ipcbase_recv_message(flib_ipcbase *ipc, void *data);

/**
 * Try to receive 4097 bytes. This is the size of the reply the engine sends
 * when successfully queried for map data. The first 4096 bytes are a bit-packed
 * twocolor image of the map (256x128), the last byte is the number of hogs that
 * fit on the map.
 */
int flib_ipcbase_recv_map(flib_ipcbase *ipc, void *data);

int flib_ipcbase_send_raw(flib_ipcbase *ipc, const void *data, size_t len);

/**
 * Write a single message (up to 255 bytes) to the engine. This call blocks until the
 * message is completely written or the connection is closed or an error occurs.
 *
 * Calling this function in a state other than IPC_CONNECTED will fail immediately.
 * Returns a negative value on failure.
 */
int flib_ipcbase_send_message(flib_ipcbase *ipc, void *data, size_t len);

/**
 * Convenience function for sending a 0-delimited string.
 */
int flib_ipcbase_send_messagestr(flib_ipcbase *ipc, char *data);

/**
 * Try to accept a connection. Only has an effect in state IPC_LISTENING.
 */
void flib_ipcbase_accept(flib_ipcbase *ipc);

#endif /* IPCBASE_H_ */