.section .text
.option norvc
.global _start

# Helper macro to exit with code if condition fails
# Example: ASSERT_EQ a0, 0, 4 (if a0 != 0, exit with code 4)
.macro ASSERT_EQ reg, val, error_code
  li t4, \val
  beq \reg, t4, .L_ok_\@
  li a0, \error_code
  li a7, 93
  ecall
.L_ok_\@:
.endm

# Helper macro to exit with code if registers are not equal
.macro ASSERT_REG_EQ reg1, reg2, error_code
  beq \reg1, \reg2, .L_ok_reg_\@
  li a0, \error_code
  li a7, 93
  ecall
.L_ok_reg_\@:
.endm

# Helper macro to exit with code if a register is negative
.macro ASSERT_GEZ reg, error_code
  bgez \reg, .L_ok_gez_\@
  li a0, \error_code
  li a7, 93
  ecall
.L_ok_gez_\@:
.endm

_start:
  # 1. Write welcome message to stdout
  li a7, 64       # sys_write
  li a0, 1        # stdout
  la a1, msg_welcome
  li a2, 29       # welcome message length
  ecall
  ASSERT_EQ a0, 29, 1

  # 2. Test clock_gettime
  li a7, 113      # sys_clock_gettime
  li a0, 0        # CLOCK_REALTIME
  la a1, timespec_buf
  ecall
  ASSERT_EQ a0, 0, 2
  # verify we wrote something non-zero to seconds
  lw t0, timespec_buf
  ASSERT_GEZ t0, 3

  # 3. Test gettimeofday
  li a7, 169      # sys_gettimeofday
  la a0, timeval_buf
  li a1, 0        # NULL timezone
  ecall
  ASSERT_EQ a0, 0, 4
  lw t0, timeval_buf
  ASSERT_GEZ t0, 5

  # 4. Test openat to create file
  li a7, 56       # sys_openat
  li a0, -100     # AT_FDCWD
  la a1, file_name
  li a2, 577      # O_CREAT | O_WRONLY | O_TRUNC (64 | 1 | 512 = 577)
  li a3, 0644     # permissions
  ecall
  ASSERT_GEZ a0, 6
  mv s2, a0       # save fd in s2

  # 5. Write to the new file
  li a7, 64       # sys_write
  mv a0, s2       # fd
  la a1, msg_to_file
  li a2, 29       # length
  ecall
  ASSERT_EQ a0, 29, 7

  # 6. Close the file
  li a7, 57       # sys_close
  mv a0, s2       # fd
  ecall
  ASSERT_EQ a0, 0, 8

  # 7. Open file O_RDONLY
  li a7, 56       # sys_openat
  li a0, -100     # AT_FDCWD
  la a1, file_name
  li a2, 0        # O_RDONLY
  li a3, 0
  ecall
  ASSERT_GEZ a0, 9
  mv s2, a0       # save fd in s2

  # 7b. Test fstat
  li a7, 80       # sys_fstat
  mv a0, s2       # fd
  la a1, stat_buf
  ecall
  ASSERT_EQ a0, 0, 20
  lw t0, stat_buf + 48
  ASSERT_EQ t0, 29, 21

  # 7c. Test newfstatat
  li a7, 79       # sys_newfstatat
  li a0, -100     # AT_FDCWD
  la a1, file_name
  la a2, stat_buf
  li a3, 0        # flags
  ecall
  ASSERT_EQ a0, 0, 22
  lw t0, stat_buf + 48
  ASSERT_EQ t0, 29, 23


  # 8. Read from the file
  li a7, 63       # sys_read
  mv a0, s2       # fd
  la a1, read_buf
  li a2, 50       # buffer size
  ecall
  ASSERT_EQ a0, 29, 10 # should read 29 bytes

  # verify read content matches
  la t0, msg_to_file
  la t1, read_buf
  li t2, 0        # index
.L_loop:
  add t3, t0, t2
  lb t3, 0(t3)
  add t5, t1, t2
  lb t5, 0(t5)
  ASSERT_REG_EQ t3, t5, 11
  addi t2, t2, 1
  li t6, 29
  blt t2, t6, .L_loop

  # 9. Close the file
  li a7, 57       # sys_close
  mv a0, s2       # fd
  ecall
  ASSERT_EQ a0, 0, 12

  # 9b. Test renameat (rename test_output.txt to test_output_new.txt)
  li a7, 38       # sys_renameat
  li a0, -100     # AT_FDCWD
  la a1, file_name
  li a2, -100     # AT_FDCWD
  la a3, file_name_new
  ecall
  ASSERT_EQ a0, 0, 24

  # 9c. Verify renamed file can be opened O_RDONLY
  li a7, 56       # sys_openat
  li a0, -100     # AT_FDCWD
  la a1, file_name_new
  li a2, 0        # O_RDONLY
  li a3, 0
  ecall
  ASSERT_GEZ a0, 25
  mv s3, a0

  # 9d. Close renamed file
  li a7, 57       # sys_close
  mv a0, s3
  ecall
  ASSERT_EQ a0, 0, 26


  # 10. Test mkdirat
  li a7, 34       # sys_mkdirat
  li a0, -100     # AT_FDCWD
  la a1, dir_name
  li a2, 0755
  ecall
  ASSERT_EQ a0, 0, 13

  # 11. Open directory fd
  li a7, 56       # sys_openat
  li a0, -100     # AT_FDCWD
  la a1, dir_name
  li a2, 0        # O_RDONLY
  li a3, 0
  ecall
  ASSERT_GEZ a0, 14
  mv s2, a0       # save fd in s2

  # 12. Test getdents64
  li a7, 61       # sys_getdents64
  mv a0, s2       # fd
  la a1, dirents_buf
  li a2, 512      # buffer size
  ecall
  ASSERT_GEZ a0, 15

  # 13. Close directory fd
  li a7, 57       # sys_close
  mv a0, s2       # fd
  ecall
  ASSERT_EQ a0, 0, 16

  # 13b. Test readlinkat
  li a7, 78       # sys_readlinkat
  li a0, -100     # AT_FDCWD
  la a1, link_name
  la a2, read_buf
  li a3, 50       # buffer size
  ecall
  ASSERT_EQ a0, 19, 27
  
  # verify symlink target string
  la t0, file_name_new
  la t1, read_buf
  li t2, 0
.L_loop_link:
  add t3, t0, t2
  lb t3, 0(t3)
  add t5, t1, t2
  lb t5, 0(t5)
  ASSERT_REG_EQ t3, t5, 28
  addi t2, t2, 1
  li t6, 19
  blt t2, t6, .L_loop_link

  # 14. Test unlinkat for renamed file
  li a7, 35       # sys_unlinkat
  li a0, -100     # AT_FDCWD
  la a1, file_name_new
  li a2, 0
  ecall
  ASSERT_EQ a0, 0, 17

  # 14b. Test unlinkat for symlink
  li a7, 35       # sys_unlinkat
  li a0, -100     # AT_FDCWD
  la a1, link_name
  li a2, 0
  ecall
  ASSERT_EQ a0, 0, 29

  # 15. Test unlinkat with AT_REMOVEDIR for directory
  li a7, 35       # sys_unlinkat
  li a0, -100     # AT_FDCWD
  la a1, dir_name
  li a2, 512      # AT_REMOVEDIR
  ecall
  ASSERT_EQ a0, 0, 18


  # 15b. Test getrandom
  li a7, 278      # sys_getrandom
  la a0, random_buf
  li a1, 16       # 16 bytes
  li a2, 0        # no flags
  ecall
  ASSERT_EQ a0, 16, 185

  # 16. Write success message
  li a7, 64       # sys_write
  li a0, 1        # stdout
  la a1, msg_success
  li a2, 33       # success message length
  ecall
  ASSERT_EQ a0, 33, 19

  # 17. Exit with 0
  li a7, 93       # sys_exit
  li a0, 0        # status 0
  ecall

.section .rodata
msg_welcome:
  .string "Running Syscall Verification\n"
msg_to_file:
  .string "Hello from RISC-V A-Machine!\n"
msg_success:
  .string "All Extended Syscall Tests PASS!\n"
file_name:
  .string "test_output.txt"
file_name_new:
  .string "test_output_new.txt"
link_name:
  .string "test_link.txt"
dir_name:
  .string "test_dir"

.section .bss
.align 4
timespec_buf:
  .space 16
timeval_buf:
  .space 8
read_buf:
  .space 64
dirents_buf:
  .space 512
random_buf:
  .space 16
stat_buf:
  .space 104