MapEntrances

; (C)2021 Fox Cunning
; This code is licensed under MIT license
; (see https://opensource.org/licenses/MIT for details)
; -----------------------------------------------------------------------------
; Map data table:
; Byte 0 = ROM Bank, Byte 1 = Entrance Y, Byte 2 = Entrance X, Byte 3 = Flags (bits 5-7) / ID (bits 0-4)
;   Flags: bit 7 = dungeon, bit 6 = no guards, bit 5 = continent
;   ID for continents must be $00-$03, towns and castles $04-$1F
;   Dungeons are handled separately and can have any ID even if it's the same as a non-dungeon map

; Map pointers table:
; Bytes 0-1 = Map data pointer, Bytes 2-3 = NPC data pointer

; 48 maps + 8 dungeons
; 8 town entrances + 2 castle entrances + 8 dungeon entrances per continent
; Continent indices: $00, $0B, $14, $1F
TownAndCastleEntrances = $E872
DungeonEntrances = $FB50

; Y = A = Tile ID
*=$C427
EntranceTile:
  cmp #$0D  ; Castle tile ID
  beq _towns
  cmp #$0E  ; Dungeon tile ID
  beq _dungeons

  ; #$0F = Town tile ID

; The town tile ID is used for the alternative grass tile in towns and castles,
; so make sure we are in a continent before trying to use it as an entrance
_towns:
; Make sure this map is a continent
  lda _Map_Flags_ID
  cmp #$04
  bcc $C3FD ; No entrances from this map

; Prepare pointer
  ldy _Map_Flags_ID
  lda TownEntrancePointers,Y
  sta $29   ; Low byte
  lda #$E8  ; High byte always $E8
  sta $2A

  ldy #$00
_entranceLoop:
  lda ($29),Y
  cmp _PartyX
  bne _nextEntrance

  iny
  lda ($29),Y
  cmp _PartyY
  bne _nextEntrance_1

_entranceFound:
; New map index = current map Id + (Y / 2)
  tya
  lsr A
  clc
  adc _CurrentMapId
  sta _CurrentMapId
  asl A
  asl A
  tax
  ldy #$08
  lda MapDataTable+3,X  ; Map flags
  jsr GetContinentFlag
  sty _Map_Flags
  and #$1F
  sta _Map_Flags_ID

  lda _PartyX
  sta $4C       ; Save overworld party location
  lda _PartyY
  sta $4B       ; Will be used when leaving a town/castle

  jmp RequestNewMap_Params

_nextEntrance:
  iny
_nextEntrance_1:
  iny
  cmp #$14
  bcc _townEntranceLoop
  jmp $C3FD ; No entrance found at these coordinates

TownEntrancePointers:
; Low byte only: high byte is always $E8
  .byte $72, $7C, $86, $90

_dungeons:
  ; Backup previous map (needed to set entry point)
  lda _CurrentMapId
  sta $4F
  ; Prepare pointer
  ldy _Map_Flags_ID
  lda DungeonEntrancePointers,Y
  sta $29   ; Low byte
  lda #$FB
  sta $2A   ; High byte is always $FB

  ldy #$00
_dungeonEntranceLoop:
  lda ($29),Y
  cmp _PartyX
  bne _nextDungeonEntrance

  iny
  lda ($29),Y
  cmp _PartyY
  bne _nextDungeonEntrance_1

_dungeonEntranceFound:
; New map index = $28 + (Y / 2)
  tya
  lsr A
  clc
  adc #$28
  sta _CurrentMapId
  asl
  asl
  tax
  ldy #$09
  lda MapDataTable+3,X  ; Map flags
  sty _Map_Flags
  and #$1F
  sta _Map_Flags_ID

; Don't bother saving the previous party location: it won't be used when
; leaving a dungeon map
  jmp RequestNewMap_Params

_nextDungeonEntrance:
  iny
_nextDungeonEntrance_1:
  iny
  cmp #$10
  bcc _dungeonEntranceLoop
  jmp $C3FD ; No entrance found at these coordinates

DungeonEntrancePointers:
; Low byte only: high byte is always $FB
  .byte $50, $60, $70, $80