;NspireEx v0.1
; (C) 2009 by Brandon Wilson. All rights reserved. 

;v0.1 Changelog
;Initial release

 include "settings.inc"
 NOLIST
 include "ti83plus.inc"
 LIST
 include "equates.inc"
 include "header.asm"

 SEGMENT MAIN
 GLOBALS ON

 EXTERN IPutS

StartApp:
       B_CALL ClrLCDFull
       B_CALL HomeUp
       ld hl,sMainMenu
       call IPutS
mainKeyLoop:
       call IGetKey
       cp kClear
       jr z,ExitApp
       cp kQuit
       jr z,ExitApp
       sub k7
       jr z,ExitApp
       dec a
       jr z,DoAbout
       dec a
       jr z,DoHelp
       dec a
       jr z,disableHook
       dec a
       jr z,enableHook
       dec a
       jr z,DoUninstall
       dec a
       jr nz,mainKeyLoop
;Do install
;Patch sector 70h code (if it exists)
;Redirect BCALLs _ExecuteApp and _ExecutePrgm to routines on page 71h:
;      _ExecuteApp: routine will swap in this page (via app name) and jump to RunApp
;      _ExecutePrgm: routine will swap in this page (via app name) and call RunPrgm
;      RunApp/RunPrgm:
;             Write the following bytes to 3FF0h:
;                    push af
;                    in a,(6)
;                    push af
;                    ld a,<this page>
;                    out (6),a
;                    jp 4083h
;             Change three bytes at 0000h to:
;                    jp 3FF0h
;             Scan the entire page for blocks of "bad" instructions from a table on this page.
;             If a potentially-bad instruction is found, scan both ahead and behind for at least
;               three (customizable) z80 instructions.
;             If a bad instruction is found, log its location and original instruction to page 72h:
;                    bOriginalPage, wOriginalAddress, bInstructionID
;             Depending on the bad instruction, either write rst 00h or rst 00h \ <instruction ID>
;             Terminate the page 72h table with 0FFh.
;             Execute the program or application.
;             Write 0FFh to the start of page 72h (clearing table).
;      4083h code:
;             Determine from the stack the original address/location of "rst 00h".
;             Check the following byte to see if it is a special invalid instruction byte.
;             If so:
;                    Execute the equivalent code for that instruction, increase IP to beyond
;                      the instruction ID, and return.
;             If not:
;                    Get the original page containing "rst 00h" and scan the page 72h table
;                      for the original address.
;                           If found:
;                                  Execute the equivalent code for that instruction, increase IP
;                                         to beyond "rst 00h", and return.
;                           If not found:
;                                  Jump to 0053h.
;NOTE: For common 2+ byte instructions, the instruction ID will be an invalid instruction byte.
       jr StartApp
ExitApp:
       B_CALL ClrLCDFull
       B_CALL HomeUp
       B_JUMP JForceCmdNoChar
DoUninstall:
enableHook:
disableHook:
DoHelp:
DoAbout:
       jr StartApp
sMainMenu:
       DB "NspireEx ",VER_STRING,0
       DB " 1) Install     "
       DB " 2) Uninstall   "
       DB " 3) Run Program "
       DB " 4) Help        "
       DB " 5) About       "
       DB " 6) Quit",0