/* A clock program using message passing */ 

/* Simple_OS include */ 
#include <simple_os.h>

/* standard library includes */ 
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

/* fig_begin message_types */ 
#define TIME_MESSAGE 0
#define SET_MESSAGE 1
/* fig_end message_types */ 

/* fig_begin time_struct */ 
/* time data type */ 
typedef struct 
{
    int hours; 
    int minutes; 
    int seconds; 
} time_data_type; 
/* fig_end time_struct */ 

/* fig_begin msg_struct */ 
/* data structure for messages */ 
typedef struct
{
    /* message type */
    int type; 
    /* the time */ 
    time_data_type time; 
} message_data_type; 
/* fig_end msg_struct */ 

/* stack size */ 
#define STACK_SIZE 5000 

/* stack declarations */ 

/* stack for clock_task */ 
stack_item Clock_Stack[STACK_SIZE]; 

/* stack for time_task */ 
stack_item Time_Stack[STACK_SIZE]; 

/* stack for set_task */ 
stack_item Set_Stack[STACK_SIZE]; 

/* task identities, to be set when 
   the tasks are created and then not modified */ 
int Clock_Task_Id; 
int Time_Task_Id; 
int Set_Task_Id; 

/* init_time: initialises a time variable */ 
void init_time(time_data_type *time)
{
    /* set starting time */ 
    time->hours = 23; 
    time->minutes = 59; 
    time->seconds = 30; 
}

/* increment_time: increments time with one second */ 
void increment_time(time_data_type *time)
{
    /* increment time */ 
    time->seconds++; 
    if (time->seconds > 59)
    {
        time->seconds = 0; 
        time->minutes++; 
        if (time->minutes > 59)
        {
            time->minutes = 0; 
            time->hours++; 
            if (time->hours > 23)
            {
                time->hours = 0; 
            }
        }
    }
}

/* set_time: set time to hours, minutes and seconds */ 
void set_time(time_data_type *time, 
              int hours, int minutes, int seconds)
{
    /* assign values */
    time->hours = hours; 
    time->minutes = minutes;
    time->seconds = seconds; 
}

/* get_time: read time */ 
void get_time(time_data_type *time, 
              int *hours, int *minutes, int *seconds)
{
    /* read values */ 
    *hours = time->hours; 
    *minutes = time->minutes; 
    *seconds = time->seconds;
}

/* make_display_message: create string for printout, given a time expressed 
   in hours, minutes and seconds */ 
void make_display_message(char display_message[], int hours, int minutes, int seconds) 
{
    display_message[0] = hours / 10 + '0'; 
    display_message[1] = hours % 10 + '0'; 
    display_message[2] = ':'; 
    display_message[3] = minutes / 10 + '0'; 
    display_message[4] = minutes % 10 + '0'; 
    display_message[5] = ':'; 
    display_message[6] = seconds / 10 + '0'; 
    display_message[7] = seconds % 10 + '0'; 
    display_message[8] = '\0'; 
}

/* time_from_set_message: extract time from set message from user interface */ 
void time_from_set_message(char message[], int *hours, int *minutes, int *seconds)
{
    sscanf(message,"set %d %d %d",hours, minutes, seconds); 
}


/* time_ok: returns nonzero if hours, minutes and seconds represents a valid time */ 
int time_ok(int hours, int minutes, int seconds)
{
    return hours >= 0 && hours <= 23 && minutes >= 0 && minutes <= 59 && 
        seconds >= 0 && seconds <= 59; 
}

/* display_time: displays hours, minutes and seconds by 
   sending them to the user interface */ 
void display_time(time_data_type time)
{
    char display_message[20]; 

    char draw_message[100]; 

    /* convert hours, minutes and seconds to display format */ 
    make_display_message(display_message, time.hours, time.minutes, time.seconds); 

    sprintf(draw_message, "Time: %s", display_message); 

    /* write to user interface */ 
    si_ui_draw_begin(); 
    si_ui_draw_string("send \"set hh mm ss\" to set time", 90, 20); 
    si_ui_draw_string(draw_message, 145, 55);
    si_ui_draw_end(); 
}

/* tasks */ 

/* fig_begin clock_task */ 
/* clock_task: clock task */ 
void clock_task(void) 
{
    /* the current time */ 
    time_data_type time; 

    /* message */
    message_data_type message;

    /* message length */
    int length;

    /* task_id of message sending process */
    int send_task_id;

    /* initialise the time */ 
    set_time(&time, 23, 59, 50); 

    /* infinite loop */
    while (1)
    {
        /* receive message */
        si_message_receive((char *) &message, &length, &send_task_id);

        /* check message type */
        switch(message.type)
        {
            case TIME_MESSAGE:
                /* increment with one second */
                increment_time(&time);
                /* display the time */
                display_time(time); 
                break;
            case SET_MESSAGE:
                /* assign new value to the current time */
                time = message.time;
                /* display the time */
                display_time(time); 
                break;
            default:
                /* an error condition */
                si_ui_show_error("Illegal message type to clock_task");
        }
    }
}
/* fig_end clock_task */ 

/* fig_begin time_task */ 
/* time_task: time task */ 
void time_task(void) 
{
    /* message to be sent to clock task */ 
    message_data_type message; 

    /* infinite loop */ 
    while (1)
    {
        /* it is a move message */ 
        message.type = TIME_MESSAGE; 

        /* send message to clock task */ 
        si_message_send((char *) &message, sizeof(message), Clock_Task_Id); 

        /* wait one second */ 
        si_wait_n_ms(1000); 
    }
}
/* fig_end time_task */ 

/* set_task: reads messages from the user interface, and 
   sets the clock, or exits the program */ 
void set_task(void)
{
    /* fig_begin ui_message */ 
    /* message array */ 
    char ui_message[SI_UI_MAX_MESSAGE_SIZE]; 
    /* fig_end ui_message */ 

    /* time read from user interface */ 
    int hours, minutes, seconds; 

    /* fig_begin clock_task_message */ 
    /* message to be sent to clock task */ 
    message_data_type message; 
    /* fig_end clock_task_message */ 

    /* time variable to use in message */ 
    time_data_type time; 

    /* set GUI size */ 
    si_ui_set_size(400, 200); 

    while(1)
    {
        /* read a message */ 
        si_ui_receive(ui_message); 
        /* fig_begin set_task_mod */ 
        /* check if it is a set message */ 
        if (strncmp(ui_message, "set", 3) == 0)
        {
            time_from_set_message(ui_message, &hours, &minutes, &seconds); 
            if (time_ok(hours, minutes, seconds))
            {
                /* it is a move message */ 
                message.type = SET_MESSAGE; 
                set_time(&time, hours, minutes, seconds); 
                message.time = time; 

                /* send message to clock task */ 
                si_message_send((char *) &message, sizeof(message), Clock_Task_Id); 
            }
            else
            {
                si_ui_show_error("Illegal value for hours, minutes or seconds"); 
            }
        }
        /* fig_end set_task_mod */ 
        /* check if it is an exit message */ 
        else if (strcmp(ui_message, "exit") == 0)
        {
            exit(0); 
        }
        /* not a legal message */ 
        else 
        {
            si_ui_show_error("unexpected message type"); 
        }
    }
}

/* main */ 
int main(void)
{
    /* initialise kernel */ 
    si_kernel_init(); 
    
    /* initialise UI channel */ 
    si_ui_init(); 

    /* initialise message handling */ 
    si_message_init(); 

    /* create tasks */ 

    si_task_create(clock_task, &Clock_Stack[STACK_SIZE-1], 20); 

    Clock_Task_Id = 1; 

    si_task_create(time_task, &Time_Stack[STACK_SIZE-1], 10); 

    Time_Task_Id = 2; 

    si_task_create(set_task, &Set_Stack[STACK_SIZE-1], 15); 

    Set_Task_Id = 3; 

    /* start the kernel */ 
    si_kernel_start(); 

    /* will never be here! */ 
    return 0; 
}