// syscall.rs
// System calls
// Stephen Marz
// 3 Jan 2020

use crate::{block::process_read, cpu::TrapFrame};
use crate::process::delete_process;

pub fn do_syscall(mepc: usize, frame: *mut TrapFrame) -> usize {
	let syscall_number;
	unsafe {
		// A7 is X17, so it's register number 17.
		syscall_number = (*frame).regs[17];
		// for i in 0..32 {
		//     print!("regs[{:02}] = 0x{:08x}    ", i, (*frame).regs[i]);
		//     if (i+1) % 4 == 0 {
		//         println!();
		//     }
		// }
	}
	// These system call numbers come from libgloss so that we can use newlib
	// for our system calls.
	// Libgloss wants the system call number in A7 and arguments in A0..A6
	// #define SYS_getcwd 17
	// #define SYS_dup 23
	// #define SYS_fcntl 25
	// #define SYS_faccessat 48
	// #define SYS_chdir 49
	// #define SYS_openat 56
	// #define SYS_close 57
	// #define SYS_getdents 61
	// #define SYS_lseek 62
	// #define SYS_read 63
	// #define SYS_write 64
	// #define SYS_writev 66
	// #define SYS_pread 67
	// #define SYS_pwrite 68
	// #define SYS_fstatat 79
	// #define SYS_fstat 80
	// #define SYS_exit 93
	// #define SYS_exit_group 94
	// #define SYS_kill 129
	// #define SYS_rt_sigaction 134
	// #define SYS_times 153
	// #define SYS_uname 160
	// #define SYS_gettimeofday 169
	// #define SYS_getpid 172
	// #define SYS_getuid 174
	// #define SYS_geteuid 175
	// #define SYS_getgid 176
	// #define SYS_getegid 177
	// #define SYS_brk 214
	// #define SYS_munmap 215
	// #define SYS_mremap 216
	// #define SYS_mmap 222
	// #define SYS_open 1024
	// #define SYS_link 1025
	// #define SYS_unlink 1026
	// #define SYS_mkdir 1030
	// #define SYS_access 1033
	// #define SYS_stat 1038
	// #define SYS_lstat 1039
	// #define SYS_time 1062
	// #define SYS_getmainvars 2011
	match syscall_number {
		0 | 93 => unsafe {
			// Exit
			// Currently, we cannot kill a process, it runs forever. We will delete
			// the process later and free the resources, but for now, we want to get
            // used to how processes will be scheduled on the CPU.
            delete_process((*frame).pid as u16);
			0
		},
		1 => {
			println!("Test syscall");
			mepc + 4
		},
		63 => unsafe {
			// Read system call
			// This is an asynchronous call. This will get the process going. We won't hear the answer until
            // we an interrupt back.
            // TODO: The buffer is a virtual memory address that needs to be translated to a physical memory
            // location.
			let _ = process_read(
			                     (*frame).pid as u16,
			                     (*frame).regs[10],
			                     (*frame).regs[11] as *mut u8,
			                     (*frame).regs[12] as u32,
			                     (*frame).regs[13] as u64,
			);
			// If we return 0, the trap handler will schedule another process.
			0
		},
		_ => {
			println!("Unknown syscall number {}", syscall_number);
			mepc + 4
		},
	}
}