// os.c
// Runs on LM4F120/TM4C123/MSP432
// Lab 2 starter file.
// Daniel Valvano
// February 20, 2016

#include <stdint.h>
#include "os.h"
#include "../inc/CortexM.h"
#include "../inc/BSP.h"

// function definitions in osasm.s
void StartOS(void);

periodicType periodic[2];
tcbType tcbs[4];
tcbType *RunPt;
int32_t Stacks[4][STACKSIZE];


// ******** OS_Init ************
// Initialize operating system, disable interrupts
// Initialize OS controlled I/O: systick, bus clock as fast as possible
// Initialize OS global variables
// Inputs:  none
// Outputs: none
void OS_Init(void){
  DisableInterrupts();
  BSP_Clock_InitFastest();// set processor clock to fastest speed
  // initialize any global variables as needed
}

void SetInitialStack(int i){
	tcbs[i].sp = &Stacks[i][STACKSIZE - 16];
	
	Stacks[i][STACKSIZE-1] = 0x01000000; // Thumb bit
	//Stacks[i][STACKSIZE-2] is reserved for PC
	//and is initialized with start address of task
	Stacks[i][STACKSIZE-3] = 0x14141414; // R14 = LR
	Stacks[i][STACKSIZE-4] = 0x12121212; // R12
	Stacks[i][STACKSIZE-5] = 0x03030303; // R3
	Stacks[i][STACKSIZE-6] = 0x02020202; // R2
	Stacks[i][STACKSIZE-7] = 0x01010101; // R1
	Stacks[i][STACKSIZE-8] = 0x00000000; // R0
	Stacks[i][STACKSIZE-9] = 0x11111111; // R11
	Stacks[i][STACKSIZE-10] = 0x10101010; // R10
	Stacks[i][STACKSIZE-11] = 0x09090909; // R9
	Stacks[i][STACKSIZE-12] = 0x08080808; // R8
	Stacks[i][STACKSIZE-13] = 0x07070707; // R7
	Stacks[i][STACKSIZE-14] = 0x06060606; // R6
	Stacks[i][STACKSIZE-15] = 0x05050505; // R5
	Stacks[i][STACKSIZE-16] = 0x04040404; // R4
}

//******** OS_AddThreads ***************
// Add four main threads to the scheduler
// Inputs: function pointers to four void/void main threads
// Outputs: 1 if successful, 0 if this thread can not be added
// This function will only be called once, after OS_Init and before OS_Launch
int OS_AddThreads(void(*thread0)(void),
                  void(*thread1)(void),
                  void(*thread2)(void),
                  void(*thread3)(void)){
// initialize TCB circular list
// initialize RunPt
// initialize four stacks, including initial PC
	uint32_t status = StartCritical();
	tcbs[0].next = &tcbs[1];
	tcbs[1].next = &tcbs[2];
	tcbs[2].next = &tcbs[3];
	tcbs[3].next = &tcbs[0];
	
	SetInitialStack(0); Stacks[0][STACKSIZE-2] = (int32_t)(thread0);
	SetInitialStack(1); Stacks[1][STACKSIZE-2] = (int32_t)(thread1);
	SetInitialStack(2); Stacks[2][STACKSIZE-2] = (int32_t)(thread2);
	SetInitialStack(3); Stacks[3][STACKSIZE-2] = (int32_t)(thread3);
	
	RunPt = &tcbs[0];
	EndCritical(status);
	return 1; // successful
}

//******** OS_AddThreads3 ***************
// add three foregound threads to the scheduler
// This is needed during debugging and not part of final solution
// Inputs: three pointers to a void/void foreground tasks
// Outputs: 1 if successful, 0 if this thread can not be added
int OS_AddThreads3(void(*task0)(void),
                 void(*task1)(void),
                 void(*task2)(void)){ 
// initialize TCB circular list (same as RTOS project)
// initialize RunPt
// initialize four stacks, including initial PC
	uint32_t status = StartCritical();
	tcbs[0].next = &tcbs[1];
	tcbs[1].next = &tcbs[2];
	tcbs[2].next = &tcbs[0];
	
	SetInitialStack(0); Stacks[0][STACKSIZE-2] = (int32_t)(task0);
	SetInitialStack(1); Stacks[1][STACKSIZE-2] = (int32_t)(task1);
	SetInitialStack(2); Stacks[2][STACKSIZE-2] = (int32_t)(task2);
	
	RunPt = &tcbs[0];
	EndCritical(status);
	return 1; // successful
}
                 
//******** OS_AddPeriodicEventThreads ***************
// Add two background periodic event threads
// Typically this function receives the highest priority
// Inputs: pointers to a void/void event thread function2
//         periods given in units of OS_Launch (Lab 2 this will be msec)
// Outputs: 1 if successful, 0 if this thread cannot be added
// It is assumed that the event threads will run to completion and return
// It is assumed the time to run these event threads is short compared to 1 msec
// These threads cannot spin, block, loop, sleep, or kill
// These threads can call OS_Signal
int OS_AddPeriodicEventThreads(void(*thread1)(void), uint32_t period1,
  void(*thread2)(void), uint32_t period2){ //TODO
	int32_t status;
  status = StartCritical();
  periodic[0].period = period1;
  periodic[0].task = thread1;
  periodic[1].period = period2;
  periodic[1].task = thread2;
  EndCritical(status);
	return 1;               // successful
}

//******** OS_Launch ***************
// Start the scheduler, enable interrupts
// Inputs: number of clock cycles for each time slice
// Outputs: none (does not return)
// Errors: theTimeSlice must be less than 16,777,216
void OS_Launch(uint32_t theTimeSlice){
  STCTRL = 0;                  // disable SysTick during setup
  STCURRENT = 0;               // any write to current clears it
  SYSPRI3 =(SYSPRI3&0x00FFFFFF)|0xE0000000; // priority 7
  STRELOAD = theTimeSlice - 1; // reload value
  STCTRL = 0x00000007;         // enable, core clock and interrupt arm
  StartOS();                   // start on the first task
}
static uint32_t timer = 0;
// runs every ms
void Scheduler(void){ // every time slice
  // run any periodic event threads if needed
  // implement round robin scheduler, update RunPt
	
	for (int i = 0; i < 2; ++i) {
		if ((timer % periodic[i].period) == 0) {
			periodic[i].task();
		}
	}
	++timer;
	
	RunPt = RunPt->next;    // Round Robin
}

// ******** OS_InitSemaphore ************
// Initialize counting semaphore
// Inputs:  pointer to a semaphore
//          initial value of semaphore
// Outputs: none
void OS_InitSemaphore(int32_t *semaPt, int32_t value){
	*semaPt = value;
}

// ******** OS_Wait ************
// Decrement semaphore
// Lab2 spinlock (does not suspend while spinning)
// Lab3 block if less than zero
// Inputs:  pointer to a counting semaphore
// Outputs: none
void OS_Wait(int32_t *semaPt){
	uint32_t status = StartCritical();
	while (*semaPt <= 0) {
		EndCritical(status);
		status = StartCritical();
	}
	--(*semaPt);
	EndCritical(status);
	}

// ******** OS_Signal ************
// Increment semaphore
// Lab2 spinlock
// Lab3 wakeup blocked thread if appropriate
// Inputs:  pointer to a counting semaphore
// Outputs: none
void OS_Signal(int32_t *semaPt){
	uint32_t status = StartCritical();
	++(*semaPt);
	EndCritical(status);
}




// ******** OS_MailBox_Init ************
// Initialize communication channel
// Producer is an event thread, consumer is a main thread
// Inputs:  none
// Outputs: none
uint32_t MailBox;
int32_t  MailBox_Send;
int32_t  MailBox_Ack;
void OS_MailBox_Init(void){
  // include data field and semaphore
	MailBox = 0;
	OS_InitSemaphore(&MailBox_Send, 0);
	OS_InitSemaphore(&MailBox_Ack, 0);
}

// ******** OS_MailBox_Send ************
// Enter data into the MailBox, do not spin/block if full
// Use semaphore to synchronize with OS_MailBox_Recv
// Inputs:  data to be sent
// Outputs: none
// Errors: data lost if MailBox already has data
void OS_MailBox_Send(uint32_t data){
    MailBox = data; // Overwrite data (may lose old data)
    OS_Signal(&MailBox_Send); // Signal data availability
}

// ******** OS_MailBox_Recv ************
// retreive mail from the MailBox
// Use semaphore to synchronize with OS_MailBox_Send
// Lab 2 spin on semaphore if mailbox empty
// Lab 3 block on semaphore if mailbox empty
// Inputs:  none
// Outputs: data retreived
// Errors:  none
uint32_t OS_MailBox_Recv(void){
  OS_Wait(&MailBox_Send);
  int32_t data = MailBox; // read mail
  return data;
}