#ifndef FLOW_H
#define FLOW_H

#include <stdbool.h>

//general error codes that are meant to be communicated to user
#define E_IO -1 //I/O error (port should be closed)
#define E_ACCESS_DENIED -2 //access denied
#define E_BUSY -3 // port is busy
#define E_INVALID_BAUD -4 // baud rate is not valid
#define E_INTERRUPT -5 // not really an error, function call aborted because port is closed

//contains file descriptors used in managing a serial port
struct serial_config {
  
  int port_fd; // file descriptor of serial port
  
  /* a pipe is used to abort a serial read by writing something into the
   * write end of the pipe */
  int pipe_read_fd; // file descriptor, read end of pipe
  int pipe_write_fd; // file descriptor, write end of pipe
  
};

/**Opens a serial port and allocates memory for storing configuration. Note: if this function fails,
 * any internally allocated resources will be freed.
 * @param port_name name of port
 * @param baud baud rate
 * @param serial pointer to memory that will be allocated with a serial structure
 * @return 0 on success
 * @return E_ACCESS_DENIED if permissions are not sufficient to open port
 * @return E_BUSY if port is already in use
 * @return E_INVALID_BAUD if specified baudrate is non-standard
 * @return E_IO on other error */
int serial_open(const char* port_name, int baud, struct serial_config** serial);

/**Closes a previously opened serial port and frees memory containing the configuration. Note: after a call to
 * this function, the 'serial' pointer will become invalid, make sure you only call it once. This function is NOT
 * thread safe, make sure no read or write is in prgress when this function is called (the reason is that per 
 * close manual page, close should not be called on a file descriptor that is in use by another thread). 
 * @param serial pointer to serial configuration that is to be closed (and freed)
 * @return 0 on success
 * @return E_IO on error */
int serial_close(struct serial_config* serial);

/**Starts a blocking read from a previously opened serial port. The read is blocking, however it may be
 * interrupted by calling 'serial_interrupt' on the given serial port.
 * @param serial pointer to serial configuration from which to read
 * @param buffer buffer into which data is read
 * @param size maximum buffer size
 * @return n>0 the number of bytes read into buffer
 * @return E_INTERRUPT if the call to this function was interrupted
 * @return E_IO on IO error */
int serial_read(struct serial_config* serial, unsigned char* buffer, size_t size);

/**Interrupts a blocked read call.
 * @param serial_config the serial port to interrupt
 * @return 0 on success
 * @return E_IO on error */
int serial_interrupt(struct serial_config* serial);

/**Writes data to a previously opened serial port. Non bocking.
 * @param serial pointer to serial configuration to which to write
 * @param data data to write
 * @param size number of bytes to write from data
 * @return n>0 the number of bytes written
 * @return E_IO on IO error */
int serial_write(struct serial_config* serial, unsigned char* data, size_t size);

/**Sets debugging option. If debugging is enabled, detailed error message are printed from method calls. */
void serial_debug(bool value);


#endif /* FLOW_H */