#include "os_port.h"
#include "os_stack.h"
#include "os_macros.h"
#include "os_align.h"
#include "os_compiler.h"
#include "os_systick.h"
#include "os_sched.h"


/* ------------------------------------------------------------------------------------------------------------------ */
/*  */

volatile os_uint_t svc_exc_return;

/* ------------------------------------------------------------------------------------------------------------------ */
/*  */

typedef struct {
#if(OS_CFG_CPU_FPU_PRESENT)
    os_uintptr_t s16;
    os_uintptr_t s17;
    os_uintptr_t s18;
    os_uintptr_t s19;
    os_uintptr_t s20;
    os_uintptr_t s21;
    os_uintptr_t s22;
    os_uintptr_t s23;
    os_uintptr_t s24;
    os_uintptr_t s25;
    os_uintptr_t s26;
    os_uintptr_t s27;
    os_uintptr_t s28;
    os_uintptr_t s29;
    os_uintptr_t s30;
    os_uintptr_t s31;
#endif
/* ==== 以下为手动压栈部分 ==== */
    os_uintptr_t exc_return;    /* r2 - LR */           /* 这是地址最小的位置 */
    os_uintptr_t control;       /* r3 */
    os_uintptr_t r4;
    os_uintptr_t r5;
    os_uintptr_t r6;
    os_uintptr_t r7;
    os_uintptr_t r8;
    os_uintptr_t r9;
    os_uintptr_t r10;
    os_uintptr_t r11;
/* ==== 以下为自动压栈部分 ==== */
    os_uintptr_t r0;
    os_uintptr_t r1;
    os_uintptr_t r2;
    os_uintptr_t r3;
    os_uintptr_t r12;
    os_uintptr_t lr;
    os_uintptr_t pc;
    os_uintptr_t xPSR;
}os_stack_frame_t;

#define STACK_FRAME_SIZE sizeof(os_stack_frame_t)

os_stack_t os_port_cpu_stack_init(os_task_entry_t entry, void* param
        , void* stack_base, os_size_t stack_size, void(*exit_entry)(void)){
    os_uintptr_t stack_max = (os_uintptr_t)((uint8_t *) stack_base + stack_size);
    os_uintptr_t real_max = OS_ALIGN_DOWN(stack_max, OS_ALIGN_SIZE); /* 实际栈顶的位置，对齐后的位置 */
    stack_size -= (stack_max - real_max); /* 实际栈大小 */

    uint8_t flag = 0x01;
    os_stack_frame_t* p_frame = (os_stack_frame_t*)(real_max - STACK_FRAME_SIZE);
    for(os_size_t i=0; i<STACK_FRAME_SIZE/sizeof(os_uintptr_t); i++){
        ((os_uintptr_t*)(p_frame))[i] = ((os_uintptr_t)flag<<24)|((os_uintptr_t)flag<<16)|((os_uintptr_t)flag<<8)|flag;
        flag++;
    }

    p_frame->r0 = (os_uintptr_t)param;          /* 任务参数 */
    p_frame->pc = (os_uintptr_t)entry;          /* 任务入口 */
    p_frame->lr = (os_uintptr_t)exit_entry;     /* 退出地址 */

    p_frame->xPSR = (1u << 24);             /* THUMB */
    p_frame->control = 0x03;                /* 任务使用用户权限，栈使用 PSP */
    p_frame->exc_return = 0xFFFFFFFDul;     /* 任务在中断中切换，这里是退出中断的设置 */

    os_stack_t stack;
    stack.min = (os_uintptr_t)stack_base;
    stack.max = (os_uintptr_t)real_max;
    stack.type = kOsStackType_MaxToMin;
    stack.sp = p_frame;
    return stack;
}

void os_port_init(void){

}

void os_port_startup(void){
    NVIC_SetPriority(PendSV_IRQn, 0xff);
    NVIC_SetPriority(SVCall_IRQn, OS_CFG_SYSCALL_PRIORITY);
    SysTick_Config(SystemCoreClock/OS_CFG_TICKS_PER_SECOND);
}

void os_port_send_context_switch_request(void){
    SCB->ICSR |= SCB_ICSR_PENDSVSET_Msk;
}

void os_port_clear_context_switch_request(void){
    SCB->ICSR &= ~SCB_ICSR_PENDSVSET_Msk;
}

void os_sched(void){
    if(is_cpu_in_privilege()){
        os_sched_in_isr();
    }else{
        cpu_sched_in_svc();
    }
}

void SysTick_Handler(void){
    os_systick_tick();
}

void SVC_Handler_C(os_uintptr_t* svc_args){
    // 读取系统调用号：它存储在原本的 PC 指令前两个字节
    uint8_t svc_number = ((uint8_t *)svc_args[6])[-2];
    switch (svc_number) {
        case CPU_SYSCALL_ID:{
            os_uint_t op = svc_args[0];
            switch (op) {
                case CPU_SYSCALL_OP_SAVE_DISABLE_IRQ:{
                    svc_args[0] = os_port_save_disable_irq_in_isr();
                    break;
                }
                case CPU_SYSCALL_OP_RESTORE_IRQ:{
                    os_port_restore_irq_in_isr(svc_args[1]);
                    break;
                }
                case CPU_SYSCALL_OP_SCHED:{
                    os_sched_in_isr();
                    break;
                }
                default:
                    break;
            }
            break;
        }
        default: break;
    }
}