mainloop:
la ra,uidrawend # Will call a function to draw the current page, but it will return to the end instead of here
la t0,uipage
lbu t0,0(t0)

beqz t0,uidrawidle # Page 0: Idle screen

li t1,1
beq t0,t1,uidrawmainmenu # Page 1: Main menu

li t1,2
beq t0,t1,uidrawcountryselect # Page 2: Country selection

li t1,3
beq t0,t1,uidrawadjusttiming # Page 3: Timing adjustments

li t1,4
beq t0,t1,uidrawgatedropdelay # Page 4: Gate drop delay adjustment

li t1,5
beq t0,t1,uidrawinitialtime # Page 5: Initial active time adjustment

li t1,6
beq t0,t1,uidrawextensiontime # Page 6: Extension time adjustment

li t1,7
beq t0,t1,uidrawinvalidinput # Page 7: Invalid (time) input

j uidrawunknown

uidrawend:
wfi # Program is entirely interrupt-driven, so wait for something to happen
j mainloop

handler_console:
li t0,262144 # 2^18, value of MCIP bit
csrc mip,t0
la ra,uihandlingend # Will call a function to handle input for the current page, but it will return to the end instead of here
la t0,uipage
lbu t0,0(t0)

beqz t0,uihandleidle # Page 0: Idle screen

li t1,1
beq t0,t1,uihandlemainmenu # Page 1: Main menu

li t1,2
beq t0,t1,uihandlecountryselect # Page 2: Country selection

li t1,3
beq t0,t1,uihandleadjusttiming # Page 3: Timing adjustments

li t1,4
beq t0,t1,uihandlegatedropdelay # Page 4: Gate drop delay adjustment

li t1,5
beq t0,t1,uihandleinitialtime # Page 5: Initial active time adjustment

li t1,6
beq t0,t1,uihandleextensiontime # Page 6: Extension time adjustment

li t1,7
beq t0,t1,uihandleinvalidinput # Page 7: Invalid (time) input

uihandlingend:
li a7,131
ecall # Drop anything else the user may have typed
j handler_epilogue

copystring:
# Destination pointer in a0, source pointer in a1, copies until null is reached (but doesn't copy the null), not very optimized
lb t0,0(a1)
beqz t0,1f
sb t0,0(a0)
addi a0,a0,1
addi a1,a1,1
j copystring
1: ret

uidrawidle:
cm.push {ra},-16
la a0,uiidle+44
la a3,uiidle
la t0,currstate # Check if currently running or not
lbu t0,0(t0)
andi t0,t0,0xf
beqz t0,1f
la a0,uiactive+44 # If so, then show the active message instead
la a3,uiactive
1: la a1,uide
la t0,country
lb t0,0(t0)
li t1,1
bne t0,t1,1f
la a1,uiuk
1: li t1,2
bne t0,t1,1f
la a1,uius
1: call copystring
mv a0,a3
li a7,4
ecall
cm.popret {ra},16

uihandleidle:
cm.push {ra},-16
li a7,132
ecall # Read one character of input
li t0,'m'
bne a0,t0,1f # If it was 'm'...
la t0,uipage
li t1,1
sb t1,0(t0) # ...go to the main menu (page 1)
1: li t0,'a'
bne a0,t0,1f # If it was 'a', then start the sequence now
la t0,currstate
lbu t0,0(t0)
andi t0,t0,0xf
bnez t0,1f # Unless it's already running, that is
la t1,country
lb t1,0(t1) # Read current country setting
slli t1,t1,4 # Multiply by 16 to get the offset into the state table
addi t1,t1,1 # And add 1 to get to the first non-idle state
la t0,currstate
sb t1,0(t0) # Update state in RAM to the first state in the current country
la t0,states
sh2add t0,t1,t0 # Calculate the proper offset in the list of pointers (state number * 4 + base address)
lw t0,0(t0) # Load the pointer
jalr ra,t0,0 # And call that function
1: cm.popret {ra},16
ret

uidrawmainmenu:
la a0,uimainmenu
li a7,4
ecall
ret

uihandlemainmenu:
li a7,132
ecall # Read one character of input
li t0,'1'
bne a0,t0,1f
la t1,uipage
li t2,2
sb t2,0(t1) # User entered '1', go to country selection (page 2)
1: li t0,'2'
bne a0,t0,1f
la t1,uipage
li t2,3
sb t2,0(t1) # User entered '2', go to timing adjustment (page 3)
1: li t0,'0'
bne a0,t0,1f
la t1,uipage
sb x0,0(t1) # User entered '0', go to idle screen (page 0)
1: ret

uidrawcountryselect:
la a0,uicountryselect
li a7,4
ecall
ret

uihandlecountryselect:
li a7,132
ecall # Read one character of input
li t0,'1'
bne a0,t0,1f
la t1,country
sb x0,0(t1) # User entered '1', change country to DE (0)
la t1,uipage
li t2,1
sb t2,0(t1) # Return to main menu (page 1)
1: li t0,'2'
bne a0,t0,1f
la t1,country
li t2,1
sb t2,0(t1) # User entered '2', change country to UK (1)
la t1,uipage
li t2,1
sb t2,0(t1) # Return to main menu (page 1)
1: li t0,'3'
bne a0,t0,1f
la t1,country
li t2,2
sb t2,0(t1) # User entered '3', change country to US (2)
la t1,uipage
li t2,1
sb t2,0(t1) # Return to main menu (page 1)
1: li t0,'0'
bne a0,t0,1f
la t1,uipage
li t2,1
sb t2,0(t1) # User entered '0', return to main menu (page 1) without changing anything
1: ret

uidrawadjusttiming:
la a0,uiadjusttiming
li a7,4
ecall
ret

uihandleadjusttiming:
li a7,132
ecall # Read one character of input
li t0,'1'
bne a0,t0,1f
la t1,uipage
li t2,4
sb t2,0(t1) # User entered '1', go to gate drop time setting (page 4)
1: li t0,'2'
bne a0,t0,1f
la t1,uipage
li t2,5
sb t2,0(t1) # User entered '2', go to initial active time setting (page 5)
1: li t0,'3'
bne a0,t0,1f
la t1,uipage
li t2,6
sb t2,0(t1) # User entered '3', go to extension time setting (page 6)
1: li t0,'0'
bne a0,t0,1f
la t1,uipage
li t2,1
sb t2,0(t1) # User entered '0', go to main menu (page 1)
1: ret
ret

uidrawgatedropdelay:
la a0,uigatedropdelay
la t0,gatedroptime
lbu t0,0(t0) # Load the current setting
li t1,10
div t2,t0,t1 # Split it into tens and ones places
rem t3,t0,t1
addi t2,t2,0x30 # Convert to ASCII
addi t3,t3,0x30
sb t2,27(a0) # Insert the digits into the string
sb t3,28(a0)
li a7,4
ecall # And print it
ret

uihandlegatedropdelay:
# Read first digit
li a7,132
ecall

# Check if the user wanted to cancel
li t0,'c'
bne a0,t0,1f
la t0,uipage
li t1,3 # User chose to cancel, go back to timing adjustment (page 3)
sb t1,0(t0)
ret
1:

# Validate and process first digit
addi s0,a0,-0x30 # Convert the first digit to ASCII
li t0,10
bltu s0,t0,1f # Inputs less than 0x30 become negative in the addi above, this branch is unsigned so those become large positive numbers
la t0,uipage # ^ Thank the RISC-V manual for that trick
li t1,7
sb t1,0(t0) # First digit was not valid, go to invalid input error (page 7)
ret
1: mul s0,s0,t0 # Multiply the first digit by 10

# Read second digit
li a7,132
ecall
bnez a0,1f
div s0,s0,t0 # Second digit was null, so the first digit was really the ones place
li a0,0x30 # Pretend this digit was 0 so validation still passes but the addition doesn't change anything
1: addi a0,a0,-0x30
bltu a0,t0,1f # Inputs less than 0x30 become negative in the addi above
la t0,uipage
li t1,7
sb t1,0(t0) # Second digit was not valid, go to invalid input error (page 7)
ret
1: add s0,s0,a0 # Sum the two digits together
bnez s0,1f
la t0,uipage
li t1,7
sb t1,0(t0) # Input was 0, go to invalid input error (page 7)
ret
1: la t0,gatedroptime
sb s0,0(t0) # Write out the new setting
la t0,uipage
li t1,3 # Go back to timing adjustment (page 3)
sb t1,0(t0)
ret

uidrawinitialtime:
la a0,uiinitialtime
la t0,activetime
lbu t0,0(t0) # Load the current setting
li t1,10
div t2,t0,t1 # Split it into tens and ones places
rem t3,t0,t1
addi t2,t2,0x30 # Convert to ASCII
addi t3,t3,0x30
sb t2,29(a0) # Insert the digits into the string
sb t3,30(a0)
li a7,4
ecall # And print it
ret

uihandleinitialtime:
# Read first digit
li a7,132
ecall

# Check if the user wanted to cancel
li t0,'c'
bne a0,t0,1f
la t0,uipage
li t1,3 # User chose to cancel, go back to timing adjustment (page 3)
sb t1,0(t0)
ret
1:

# Validate and process first digit
addi s0,a0,-0x30 # Convert the first digit to ASCII
li t0,10
bltu s0,t0,1f # Inputs less than 0x30 become negative in the addi above, this branch is unsigned so those become large positive numbers
la t0,uipage # ^ Thank the RISC-V manual for that trick
li t1,7
sb t1,0(t0) # First digit was not valid, go to invalid input error (page 7)
ret
1: mul s0,s0,t0 # Multiply the first digit by 10

# Read second digit
li a7,132
ecall
bnez a0,1f
div s0,s0,t0 # Second digit was null, so the first digit was really the ones place
li a0,0x30 # Pretend this digit was 0 so validation still passes but the addition doesn't change anything
1: addi a0,a0,-0x30
bltu a0,t0,1f # Inputs less than 0x30 become negative in the addi above
la t0,uipage
li t1,7
sb t1,0(t0) # Second digit was not valid, go to invalid input error (page 7)
ret
1: add s0,s0,a0 # Sum the two digits together
bnez s0,1f
la t0,uipage
li t1,7
sb t1,0(t0) # Input was 0, go to invalid input error (page 7)
ret
1: la t0,activetime
sb s0,0(t0) # Write out the new setting
la t0,uipage
li t1,3 # Go back to timing adjustment (page 3)
sb t1,0(t0)
ret

uidrawextensiontime:
la a0,uiextensiontime
la t0,extensiontime
lbu t0,0(t0) # Load the current setting
li t1,10
div t2,t0,t1 # Split it into tens and ones places
rem t3,t0,t1
addi t2,t2,0x30 # Convert to ASCII
addi t3,t3,0x30
sb t2,26(a0) # Insert the digits into the string
sb t3,27(a0)
li a7,4
ecall # And print it
ret

uihandleextensiontime:
# Read first digit
li a7,132
ecall

# Check if the user wanted to cancel
li t0,'c'
bne a0,t0,1f
la t0,uipage
li t1,3 # User chose to cancel, go back to timing adjustment (page 3)
sb t1,0(t0)
ret
1:

# Validate and process first digit
addi s0,a0,-0x30 # Convert the first digit to ASCII
li t0,10
bltu s0,t0,1f # Inputs less than 0x30 become negative in the addi above, this branch is unsigned so those become large positive numbers
la t0,uipage # ^ Thank the RISC-V manual for that trick
li t1,7
sb t1,0(t0) # First digit was not valid, go to invalid input error (page 7)
ret
1: mul s0,s0,t0 # Multiply the first digit by 10

# Read second digit
li a7,132
ecall
bnez a0,1f
div s0,s0,t0 # Second digit was null, so the first digit was really the ones place
li a0,0x30 # Pretend this digit was 0 so validation still passes but the addition doesn't change anything
1: addi a0,a0,-0x30
bltu a0,t0,1f # Inputs less than 0x30 become negative in the addi above
la t0,uipage
li t1,7
sb t1,0(t0) # Second digit was not valid, go to invalid input error (page 7)
ret
1: add s0,s0,a0 # Sum the two digits together
bnez s0,1f
la t0,uipage
li t1,7
sb t1,0(t0) # Input was 0, go to invalid input error (page 7)
ret
1: la t0,extensiontime
sb s0,0(t0) # Write out the new setting
la t0,uipage
li t1,3 # Go back to timing adjustment (page 3)
sb t1,0(t0)
ret

uidrawinvalidinput:
la a0,uiinvalidinput
li a7,4
ecall
ret

uihandleinvalidinput:
la t0,uipage
li t1,3 # Go back to timing adjustment (page 3)
sb t1,0(t0)
ret

uidrawunknown:
la a0,uiunknown
li a7,4
ecall
ret

uipage: .byte 0
uiidle: .asciz "\nRailroad Crossing 2\nfor RVController\nMode: ??\n\nPress 'm' for menu\n'a' to activate now"
uiactive: .asciz "\nRailroad Crossing 2\nfor RVController\nMode: ??\nCrossing is active\n\nPress 'm' for menu"
uimainmenu: .asciz "\nMAIN MENU\n1: Change Country\n2: Adjust Timing\n\n\n0: Exit"
uiunknown: .asciz "\nInternal error\n\nUnknown UI page\n\n\n"
uicountryselect: .asciz "\nCHANGE COUNTRY\n1: Germany\n2: United Kingdom\n3: United States\n\n0: Cancel"
uiadjusttiming: .asciz "\nADJUST TIMING\n1: Gate Drop Delay\n2: Init. Active Time\n3: Extension Time\n\n0: Cancel"
uigatedropdelay: .asciz "\nGATE DROP DELAY\n\nCurrent: XX sec\n\nEnter new time or\n'c' to cancel:"
uiinitialtime: .asciz "\nINIT. ACTIVE TIME\n\nCurrent: XX sec\n\nEnter new time or\n'c' to cancel:"
uiextensiontime: .asciz "\nEXTENSION TIME\n\nCurrent: XX sec\n\nEnter new time or\n'c' to cancel:"
uiinvalidinput: .asciz "\nInvalid entry\n\nPress any key\n\n\n"
uide: .asciz "DE"
uiuk: .asciz "UK"
uius: .asciz "US"