; =============================================================================
; programs.asm - userland program images (text-in-ROM model) + the shell.
;
; Programs are linked to run from the ROMX window ($4000-$7FFF) and live in
; their own ROM banks. exec() maps the bank and jumps in. Programs talk to the
; kernel only via `rst $30`.
; =============================================================================
INCLUDE "include/gbos.inc"

; the shell keeps its line buffer + scratch at the bottom of its RAM bank
DEF SH_LINEBUF EQU $A000        ; up to 32 bytes
DEF SH_PROGID  EQU $A040        ; chosen program id (survives fork via bank copy)
DEF SH_MAXLINE EQU 32

; -----------------------------------------------------------------------------
; PROG_WORKER (bank 2) - print a line, exit(0).
; -----------------------------------------------------------------------------
SECTION "prog_worker", ROMX[$4000], BANK[2]
ProgWorker:
    ld de, .msg
    ld b, .msgend - .msg
    ld c, SYS_WRITE
    rst $30
    ld b, 0
    ld c, SYS_EXIT
    rst $30
.msg
    db "worker!", $0D, $0A
.msgend

; -----------------------------------------------------------------------------
; PROG_HELLO (bank 4) - print a line, exit(0).
; -----------------------------------------------------------------------------
SECTION "prog_hello", ROMX[$4000], BANK[4]
ProgHello:
    ld de, .msg
    ld b, .msgend - .msg
    ld c, SYS_WRITE
    rst $30
    ld b, 0
    ld c, SYS_EXIT
    rst $30
.msg
    db "hello world!", $0D, $0A
.msgend

; -----------------------------------------------------------------------------
; PROG_CHELLO (bank 5) - a program written in C, compiled with SDCC to a
; self-contained ROM-bank image (crt0 + libc + code) and included verbatim.
; Rebuild with: sh c/build.sh c/chello.c c/chello.bin
; -----------------------------------------------------------------------------
SECTION "prog_chello", ROMX[$4000], BANK[5]
ProgChello:
    INCBIN "c/chello.bin"
SECTION "prog_echo",   ROMX[$4000], BANK[6]
ProgEcho:
    INCBIN "c/echo.bin"
SECTION "prog_true",   ROMX[$4000], BANK[7]
ProgTrue:
    INCBIN "c/true.bin"
SECTION "prog_false",  ROMX[$4000], BANK[8]
ProgFalse:
    INCBIN "c/false.bin"
SECTION "prog_uname",  ROMX[$4000], BANK[9]
ProgUname:
    INCBIN "c/uname.bin"
SECTION "prog_pid",    ROMX[$4000], BANK[10]
ProgPid:
    INCBIN "c/pid.bin"
SECTION "prog_cat",    ROMX[$4000], BANK[11]
ProgCat:
    INCBIN "c/cat.bin"
SECTION "prog_wc",     ROMX[$4000], BANK[12]
ProgWc:
    INCBIN "c/wc.bin"
SECTION "prog_head",   ROMX[$4000], BANK[13]
ProgHead:
    INCBIN "c/head.bin"
SECTION "prog_args",   ROMX[$4000], BANK[14]
ProgArgs:
    INCBIN "c/args.bin"
SECTION "prog_ls",     ROMX[$4000], BANK[15]
ProgLs:
    INCBIN "c/ls.bin"
SECTION "prog_save",   ROMX[$4000], BANK[16]
ProgSave:
    INCBIN "c/save.bin"
SECTION "prog_rm",     ROMX[$4000], BANK[17]
ProgRm:
    INCBIN "c/rm.bin"
SECTION "prog_ps",     ROMX[$4000], BANK[18]
ProgPs:
    INCBIN "c/ps.bin"
SECTION "prog_kill",   ROMX[$4000], BANK[19]
ProgKill:
    INCBIN "c/kill.bin"

; -----------------------------------------------------------------------------
; PROG_SH (bank 3) - the shell, now written in C (c/sh.c): parses >/</| and
; drives fork+exec+wait with I/O redirection. Command lookup + StrEqual/SkipName
; live in the kernel now (sys_lookup + NameTable + shell_lib).
; -----------------------------------------------------------------------------
SECTION "prog_sh", ROMX[$4000], BANK[3]
ProgSh:
    INCBIN "c/sh.bin"

; -----------------------------------------------------------------------------
; Shell string helpers (ROM0, always mapped).
; -----------------------------------------------------------------------------
SECTION "shell_lib", ROM0
; StrEqual(HL, DE) - compare NUL-terminated strings. Z set if equal.
; Clobbers A, B; advances HL and DE.
StrEqual::
.l
    ld a, [de]
    ld b, a
    ld a, [hl]
    cp b
    ret nz
    or a
    ret z                       ; both NUL -> equal
    inc hl
    inc de
    jr .l
; SkipName(DE) - advance DE to its NUL terminator.
SkipName::
.l
    ld a, [de]
    or a
    ret z
    inc de
    jr .l

; -----------------------------------------------------------------------------
; Program table (ROM0). Index = program id. Entry: bank (2) + entry addr (2).
; -----------------------------------------------------------------------------
SECTION "progtab", ROM0
ProgramTable::
    db LOW(BANK(ProgWorker)), HIGH(BANK(ProgWorker))
    dw ProgWorker
    db LOW(BANK(ProgSh)), HIGH(BANK(ProgSh))
    dw ProgSh
    db LOW(BANK(ProgHello)), HIGH(BANK(ProgHello))
    dw ProgHello
    db LOW(BANK(ProgChello)), HIGH(BANK(ProgChello))
    dw ProgChello
    db LOW(BANK(ProgEcho)), HIGH(BANK(ProgEcho))
    dw ProgEcho
    db LOW(BANK(ProgTrue)), HIGH(BANK(ProgTrue))
    dw ProgTrue
    db LOW(BANK(ProgFalse)), HIGH(BANK(ProgFalse))
    dw ProgFalse
    db LOW(BANK(ProgUname)), HIGH(BANK(ProgUname))
    dw ProgUname
    db LOW(BANK(ProgPid)), HIGH(BANK(ProgPid))
    dw ProgPid
    db LOW(BANK(ProgCat)), HIGH(BANK(ProgCat))
    dw ProgCat
    db LOW(BANK(ProgWc)), HIGH(BANK(ProgWc))
    dw ProgWc
    db LOW(BANK(ProgHead)), HIGH(BANK(ProgHead))
    dw ProgHead
    db LOW(BANK(ProgArgs)), HIGH(BANK(ProgArgs))
    dw ProgArgs
    db LOW(BANK(ProgLs)), HIGH(BANK(ProgLs))
    dw ProgLs
    db LOW(BANK(ProgSave)), HIGH(BANK(ProgSave))
    dw ProgSave
    db LOW(BANK(ProgRm)), HIGH(BANK(ProgRm))
    dw ProgRm
    db LOW(BANK(ProgPs)), HIGH(BANK(ProgPs))
    dw ProgPs
    db LOW(BANK(ProgKill)), HIGH(BANK(ProgKill))
    dw ProgKill

; -----------------------------------------------------------------------------
; NameTable (ROM0) - command name -> program id, searched by sys_lookup.
; -----------------------------------------------------------------------------
SECTION "nametab", ROM0
NameTable::
    db "worker", 0
    db PROG_WORKER
    db "hello", 0
    db PROG_HELLO
    db "chello", 0
    db PROG_CHELLO
    db "echo", 0
    db PROG_ECHO
    db "true", 0
    db PROG_TRUE
    db "false", 0
    db PROG_FALSE
    db "uname", 0
    db PROG_UNAME
    db "pid", 0
    db PROG_PID
    db "cat", 0
    db PROG_CAT
    db "wc", 0
    db PROG_WC
    db "head", 0
    db PROG_HEAD
    db "args", 0
    db PROG_ARGS
    db "ls", 0
    db PROG_LS
    db "save", 0
    db PROG_SAVE
    db "rm", 0
    db PROG_RM
    db "sh", 0
    db PROG_SH
    db "ps", 0
    db PROG_PS
    db "kill", 0
    db PROG_KILL
    db 0