#ifndef MCU_CONTEXT_H
#define MCU_CONTEXT_H

#include <avr/interrupt.h>
#define ret() asm volatile ( "ret" )

/** Default stack size, you may use this definition for declaring tasks. */
#define DEFAULT_STACK_SIZE 256

/** Stack size to be allocated for the idle task. */
#define IDLE_STACK_SIZE 64

/* 
 * The macros save_context(), restore_context() as well as the code contained in 
 * init_stack is adapted from the FreeRTOS kernel (http://www.freertos.org/).
 * Here by copyright, credits attributed to wherever they belong.
 */

/** 
 * Save context to memory location specified by first two chars of
 * a symbol named 'current' (this is why 'sp' has to be the first element of
 * of task control blocks). After executing this macro, the stack pointer will
 * be set to the address contained in 'kstack'.
 */
#define context_save() \
  asm volatile ( \
    "push r0 \n\t" \
    "in r0, __SREG__ \n\t" \
    "cli \n\t" \
    "push r0 \n\t" \
    "push r1 \n\t" \
    "clr r1 \n\t" \
    "push r2 \n\t" \
    "push r3 \n\t" \
    "push r4 \n\t" \
    "push r5 \n\t" \
    "push r6 \n\t" \
    "push r7 \n\t" \
    "push r8 \n\t" \
    "push r9 \n\t" \
    "push r10 \n\t" \
    "push r11 \n\t" \
    "push r12 \n\t" \
    "push r13 \n\t" \
    "push r14 \n\t" \
    "push r15 \n\t" \
    "push r16 \n\t" \
    "push r17 \n\t" \
    "push r18 \n\t" \
    "push r19 \n\t" \
    "push r20 \n\t" \
    "push r21 \n\t" \
    "push r22 \n\t" \
    "push r23 \n\t" \
    "push r24 \n\t" \
    "push r25 \n\t" \
    "push r26 \n\t" \
    "push r27 \n\t" \
    "push r28 \n\t" \
    "push r29 \n\t" \
    "push r30 \n\t" \
    "push r31 \n\t" \
    "lds r26, current \n\t" \
    "lds r27, current +1 \n\t" \
    "in r0, __SP_L__ \n\t" \
    "st x+, r0 	\n\t" \
    "in r0, __SP_H__ \n\t" \
    "st x+, r0 \n\t" \
  )


/** 
 * Restore context to memory location specified by first two chars of
 * a symbol named 'current'.
 */
#define context_restore() \
  asm volatile ( \
    "lds r26, current \n\t" \
    "lds r27, current + 1 \n\t" \
    "ld r28, x+ \n\t" \
    "out __SP_L__, r28 \n\t" \
    "ld r29, x+ \n\t" \
    "out __SP_H__, r29 \n\t" \
    "pop r31 \n\t" \
    "pop r30 \n\t" \
    "pop r29 \n\t" \
    "pop r28 \n\t" \
    "pop r27 \n\t" \
    "pop r26 \n\t" \
    "pop r25 \n\t" \
    "pop r24 \n\t" \
    "pop r23 \n\t" \
    "pop r22 \n\t" \
    "pop r21 \n\t" \
    "pop r20 \n\t" \
    "pop r19 \n\t" \
    "pop r18 \n\t" \
    "pop r17 \n\t" \
    "pop r16 \n\t" \
    "pop r15 \n\t" \
    "pop r14 \n\t" \
    "pop r13 \n\t" \
    "pop r12 \n\t" \
    "pop r11 \n\t" \
    "pop r10 \n\t" \
    "pop r9 \n\t" \
    "pop r8 \n\t" \
    "pop r7 \n\t" \
    "pop r6 \n\t" \
    "pop r5 \n\t" \
    "pop r4 \n\t" \
    "pop r3 \n\t" \
    "pop r2 \n\t" \
    "pop r1 \n\t" \
    "pop r0 \n\t" \
    "out __SREG__, r0 \n\t" \
    "pop r0 \n\t" \
  )

/** Initialize the given memory addresses to contain a valid, initial stackframe. */
char* stack_init(const char* const mem_low, const char* const mem_high, void (*entry)(char), char args);

#endif