;license:MIT
;(c) 2018 by 4am
;
; generic key/value text parser
;
; Public functions:
; - ParseKeyValueList
;

gAttractModeStore
         !word $FDFD
gFXStore
         !word $FDFD
gDFXStore
         !word $FDFD
gSlideshowStore
         !word $0800

;------------------------------------------------------------------------------
; ParseKeyValueList
; parse buffer with KEY=VALUE lines of a text file into an okvs
; keys and values limited to 127 characters, which should be enough for anyone
; if '=' is missing, key is kept and value is a 0-length string
; blank lines are ignored
; '#' character at beginning of line is a comment, entire line is ignored
; '[' character at beginning of line exits the parser
;
; in:    stack contains 4 bytes of parameters:
;          +1 [word] handle to storage space for okvs
;          +3 [word] handle to buffer containing contents of text file
;          +5 [byte] max length for okvs records (or 0)
; out:   all registers and flags clobbered
;        $1F00..$1FFF clobbered
;        $00/$01 clobbered
;        $02/$03 clobbered
;        $04/$05 has the address of the next available byte after the okvs
;        $FE/$FF clobbered
;------------------------------------------------------------------------------
ParseKeyValueList
         +PARAMS_ON_STACK 5

         +LDPARAM 1
         +STAY @store1
         +STAY @store2

         +LDPARAM 3
         +STAY $FE

         ldy   #5
         lda   (PARAM),y
         sta   @maxLength

         ldy   #0
         lda   ($FE),y
         pha
         iny
         lda   ($FE),y
         tay
         pla
         sec
         sbc   #$01
         sta   $FE
         bcs   +
         dey
+        sty   $FF
         jsr   okvs_init             ; reset key/value store
@store1  !word $FDFD                 ; SMC

         ldy   #$00                  ; index into ($FE) pointing to current character
@newkey  ldx   #$00                  ; X = index into current key
         stx   gValLen               ; initialize value length (in case this line has no value)
         jsr   IncAndGetChar
         cmp   #$0D                  ; CR in first position (blank line) -> no key
         beq   @newkey
         cmp   #$23                  ; '#' starts a comment -> no key, skip to CR
         beq   @skipLine
         cmp   #$5B                  ; '[' ends the parsing
         beq   .parseKeyValueDone
         bne   @appendToKey
@gatherKey
         jsr   IncAndGetChar
         cmp   #$0D                  ; CR -> finalize key, no value
         beq   @finalizeKey
         cmp   #$3D                  ; '=' -> finalize key, start gathering value
         beq   @finalizeKey
@appendToKey
         sta   gKey,x
         inx
         bpl   @gatherKey
@finalizeKey
         stx   gKeyLen
         cmp   #$0D
         beq   @storeInOKVS
         ldx   #$00                  ; now X = index into the current value
@gatherValue
         jsr   IncAndGetChar
         cmp   #$0D                  ; CR -> finalize value
         beq   @finalizeValue
         sta   gVal,x
         inx
         bpl   @gatherValue
@finalizeValue
         stx   gValLen
@storeInOKVS
         tya
         pha                         ; okvs functions clobber everything but we need Y
         jsr   okvs_append
@store2  !word $FDFD                 ; SMC
         !word gKeyLen
         !word gValLen
@maxLength
         !byte $FD                   ; SMC
         pla
         tay
         clc
         bcc   @newkey               ; always branches

@skipLine                            ; skip to CR
         jsr   IncAndGetChar
         cmp   #$0D                  ; CR
         bne   @skipLine
         beq   @newkey               ; always branches

;------------------------------------------------------------------------------
; IncAndGetChar
;
; in:    Y = index into ($FE)
;        ($FE) -> buffer
; out:   A contains next byte from buffer
;        Y incremented
;        $FF possibly incremented
;------------------------------------------------------------------------------
IncAndGetChar
         iny
         bne   +
         inc   $FF
+        lda   ($FE),y
.parseKeyValueDone
         rts