/// SUPER BREAD PAN
// SUPERPANSKATOL'
// Based on Garydos'es Pong example

import nes_joy

segment(chrrom) const array graphics @ $0000 = file("tileset.chr")

// ============================================================================
// STRUCTS
// ============================================================================
// sprite layout in oam
struct Sprite {
	byte y,
	byte tile,
	byte attrs,
	byte x
}

// abstraction for 16x16 animated monstrosities
struct Entity {
	Sprite top0,    // left side, for the record
	Sprite bottom0,
	Sprite top1,    // right side, please kill me
	Sprite bottom1,

	// all this can be crammed into a byte (if merge dircount w frame) `o`
	// note to self: do that
	byte movement,  // 0-3; idle, walk, jump/fall
	byte jump,      // 0/1
	byte direction, // 0/1
	byte dircount,  // counter for time-limited movement; i.e., jumping
	byte frame,      // internal count used for animation; max 5
	byte walkspeed
}

// ============================================================================
// VARIABLES
// ============================================================================
byte i
byte score1
array oam_buffer [256] @$200 // sprite buffer
word framecounter
Entity sam @$204  // player character
Entity baby @$250 // baby character
volatile Gamestate gamestate // the current Gamestate

// ============================================================================
// CONSTANTS
// ============================================================================
const array pallete = [
  $22,$29,$1A,$0F,  $22,$36,$17,$0F,  $22,$30,$21,$0F,  $22,$27,$17,$0F, 
  $22,$1C,$15,$14,
  $0F,$18,$28,$0F,   // sam
  $0F,$28,$29,$0F,  // enemies
  $03,$07,$05,$03  // angry owo
]

const array attribute = [
  %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101,
  %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101,
  %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101, %00000101
]

enum Gamestate {
	STATETITLE, 
	STATEPLAYING, 
	STATEGAMEOVER 
}

const array scorebackground = "P1 Score-	" ascii
const array gameover_msg = "G A M E	O V E R" ascii
const array title_msg = "Press Start" ascii

// -------------------------------------
// LOCATIONS
// -------------------------------------
// vram locations declared as constants for readability/convenience
// *note that these do not correlate to CPU ram locations*
const word ppu_pallete_ram = $3F00
const word ppu_nametable_ram = $2000
const word ppu_nametable_0_attr_ram = $23C0

// -------------------------------------
// LEVEL
// -------------------------------------
const byte RIGHTWALL	= $F4 
const byte TOPWALL	= $18
const byte BOTTOMWALL	= $B0
const byte LEFTWALL	= $04

// -------------------------------------
// ATTRIBUTES
// -------------------------------------
// i don't actually remember if the super crate box guy is named sam or not
// or if he even has a name?
const byte SAM_ATTR		= %00000001
const byte SAM_ATTR_HFLIP 	= %01000001
const byte SAM_ATTR_VFLIP	= %10000001
const byte SAM_ATTR_HVFLIP	= %11000001 

const byte BAD_ATTR		= %00000010
const byte BAD_ATTR_HFLIP 	= %01000010
const byte BAD_ATTR_VFLIP	= %10000010
const byte BAD_ATTR_HVFLIP	= %11000010 

const byte MAD_ATTR		= %00000011
const byte MAD_ATTR_HFLIP 	= %01000011
const byte MAD_ATTR_VFLIP	= %10000011
const byte MAD_ATTR_HVFLIP	= %11000011 

// -------------------------------------
// PHYSICS?
// -------------------------------------
const byte SAM_WALKSPEED	= 2
const byte BABY_WALKSPEED	= SAM_WALKSPEED / 2
const byte FALLSPEED		= 4

// -------------------------------------
// ANIMATIONS
// -------------------------------------
// all Entity (16x16)'s animations are assumed by update_entity() to consist of
// 5 frames. An animation array just contains 20 locations in CHR, four per
// frame, in this totally logical order:
//     top-left, bottom-left, top-right, bottom-right
const array SAM_IDLE = [ $01, $11, $02, $12,
			 $03, $13, $04, $14,
			 $05, $15, $06, $16,
			 $07, $17, $08, $18,
			 $09, $19, $0A, $1A ]

const array SAM_WALK = [ $21, $31, $22, $32,
			 $23, $33, $24, $34,
			 $25, $35, $26, $36,
			 $27, $37, $28, $38,
			 $29, $39, $2A, $3A ]
			 
const array BABY_WALK = [ $00, $C0, $00, $00,
			  $00, $C1, $00, $C2,
			  $00, $C3, $00, $00,
			  $00, $C4, $00, $00,
			  $00, $C5, $00, $00 ]

// ============================================================================
// CORE
// ============================================================================
// quite important uwu

void main() {
	sam.dircount = 0
	gamestate = STATETITLE
	title_init()
	while(true){} // all work is done in nmi
	// thnx nmi <3
}

// run at each non-maskable interrupt
// generated during each vertical blanking interval. cool
void nmi() {
	// push all sprite info to the ppu (picture processing unit)
	// through dma (direct memory access) transfer
	ppu_oam_dma_write( oam_buffer.addr.hi )
	main_game_logic()
}

// run at each interrupt request
// ``an irq temporarily stops a program, running an interupt handler instead''
// thanks wikipedia
// do I know when these are called on the nes? absolutely not
// at reset? maybe?
void irq() {
	
}

// pretty self-explanatory
inline void main_game_logic() {
	// use a return dispatch here
	// to use different logic for each screen/gamestate
	return [gamestate] {
		STATETITLE	@ title_logic
		STATEPLAYING	@ ingame_logic
		STATEGAMEOVER	@ gameover_logic
	}
}

// uwu owo uwu owo uwu owo
inline void init_graphics() {
	init_sprites()
	load_palletes()
}

// loads palletes onto the ppu
macro void load_palletes() {
	byte i
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr( ppu_pallete_ram )

	for i,0,until,$20 {
		ppu_write_data( pallete[i] )
	}
}

// cleans up oam (object attribute memory)
// each sprite gets 4 bytes in oam:
// 1: ypos, 2: tile index, 3: attr table, 4: xpos
void init_sprites() {
	byte i
	for i,0,to,255 {
		if (i & %00000011) == 0 {
			//each sprite takes up 4 bytes, and we want to edit
			//the y position of each sprite (0th byte)
			//so we use the %00000011 mask to write every 4th byte
			//(every 0th sprite byte)
			oam_buffer[i] = $ef // move the sprite off screen
		}
		else {
			oam_buffer[i] = 0
		}
	}
}


// ============================================================================
// TITLE-SCREEN
// ============================================================================
void title_init() {
	byte i
	//for now, turn off the screen and nmi
	ppu_ctrl = 0
	ppu_mask = 0
	
	//initialize the sprites and palletes
	init_graphics()
	
	//write a full screen of background data
	
	load_sky_background()
	
	//write the title screen message
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$018B) // point the PPU to the message's start
	for i,0,until,$0B {
		ppu_write_data(title_msg[i])
	}
	
	//write the border
	//top border
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$0020)
	for i,0,until,$20 {
		ppu_write_data($01)
	}
	//bottom border
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$0380)
	for i,0,until,$20 {
		ppu_write_data($01)
	}
	
	//set ppu address increment to 32 so we can draw the left and right borders
	//(allows us to draw to the nametable in vertical strips rather than horizontal)
	ppu_ctrl = %00000100
	
	//left border
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram)
	for i,0,until,$20 {
		ppu_write_data($01)
	}
	//right border
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$1F)
	for i,0,until,$20 {
		ppu_write_data($01)
	}
	

	framecounter = 0
	ppu_set_scroll(0,0)
	ppu_wait_vblank() //wait for next vblank before re-enabling NMI
			  //so that we don't get messed up scroll registers
	//re-enable the screen and nmi
	ppu_ctrl = %10010000   // enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
	ppu_mask = %00011110   // enable sprites, enable background, no clipping on left side
}

void title_logic() {
	read_joy1()
	if input_start != 0 {
		gamestate = STATEPLAYING
		ingame_init()
		return
	}
	framecounter += 1
}


// ============================================================================
// IN-GAME
// ============================================================================
void ingame_init() {
	//for now, turn off the screen and nmi
	ppu_ctrl = 0
	ppu_mask = 0
	
	//write a full screen of data
	load_sky_background()
	draw_score_text_background()
	draw_boundaries_background()
	load_ingame_attr_table()
	
	ppu_set_scroll(0,0)
	ppu_wait_vblank() //wait for next vblank before re-enabling NMI
			  //so that we don't get messed up scroll registers
	//re-enable the screen and nmi
	ppu_ctrl = %10010000   // enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
	ppu_mask = %00011110   // enable sprites, enable background, no clipping on left side

	sam.top0.y = 40
	sam.top0.x = 50
	sam.walkspeed = SAM_WALKSPEED
	baby.top0.y = 40
	baby.top0.x = 100
	baby.walkspeed = BABY_WALKSPEED
}

void ingame_logic() {
	draw_score()
	//update scroll last because writes to vram also
	//overwrite the scroll register
	ppu_set_scroll(0,0)	// tell the ppu there is no background scrolling
	
	ingame_input()
	update_ingame_sprites()
	if score1 >= 15 {
		//Someone's reached 15 points, the game is over,
		//so set the state to game over and reset the
		//framecounter
		gamestate = STATEGAMEOVER
		
		//move all the sprites off screen
		//in preperation for the gameover screen
		sam.top0.x = $ef
		
		gameover_init()
	}
}

void ingame_input ( ) {
	// Player 1 controls
	read_joy1()
	sam.movement = 0

	// left
	if ( input_dx < 0 ) {
		sam.direction = 0
		sam.movement = 1
	}
	// right
	else if ( input_dx > 0 ) {
		sam.direction = 1
		sam.movement = 1
	}

	// a button
	if ( input_btn == 1 && sam.jump == 0 ) {
			sam.jump = 1
			sam.dircount = 0
	}
}

void update_ingame_sprites ( )
{
	// player. sam is the player.
	update_entity( pointer.Entity( sam.addr ), SAM_IDLE, SAM_WALK )
	update_entity( pointer.Entity( baby.addr ), BABY_WALK, BABY_WALK )
}

macro void load_ingame_attr_table() {
	byte i
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_0_attr_ram) // point the PPU to nametable 0's attribute table
	for i,0,until,$10 {
		ppu_write_data(attribute[i])
	}
}


// ============================================================================
// GAME-OVER
// ============================================================================
void gameover_init() {
	//for now, turn off nmi and sprites
	ppu_ctrl = 0
	ppu_mask = 0
	
	draw_score() //draw the final score
	draw_gameover() //draw the game over message
	
	framecounter = 0
	ppu_set_scroll(0,0)	// tell the ppu there is no background scrolling
	ppu_wait_vblank() //wait for next vblank before re-enabling NMI
			  //so that we don't get messed up scroll registers
	//re-enable the screen and nmi
	ppu_ctrl = %10010000   // enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
	ppu_mask = %00011110   // enable sprites, enable background, no clipping on left side
}

void gameover_logic() {
	if framecounter >= 240{
		//3 seconds have passed,
		//reset the game
		simulate_reset()
	}
	framecounter += 1
}

void draw_gameover() {
	byte i
	
	//draw the static game over message
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$0107) // point the PPU to the message's start
	for i,0,until,$12 {
		ppu_write_data(gameover_msg[i])
	}
	//draw the win message
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$01AC) // point the PPU to the message's start
}


// ============================================================================
// MISC GRAPHICS
// ============================================================================
// -------------------------------------
// BACKGROUND
// -------------------------------------
inline void load_sky_background() {
	word xx
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram) // point the PPU to palette ram
	for xx,0,until,$0060 {
		ppu_write_data($92) // $00 = sky
	}
	for xx,0,until,$0300 {
		ppu_write_data($00) // $00 = sky
	}
}

macro void draw_score_text_background() {
	byte i
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$20) // point the PPU to score text's start
	for i,0,until,$1C {
		ppu_write_data(scorebackground[i])
	}
}

macro void draw_boundaries_background() {
	byte i
	
	//draw top boundary
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$40) // point the PPU to the top boundary's start
	for i,0,until,$20 {
		ppu_write_data($81) //write the top boundary tile
	}
	
	//draw bottom boundary
	read_ppu_status() // read PPU status to reset the high/low latch
	ppu_set_addr(ppu_nametable_ram+$02C0) // point the PPU to the top boundary's start
	for i,0,until,$20 {
		ppu_write_data($80) //write the bottom boundary tile
	}
}

// -------------------------------------
// SPRITES
// -------------------------------------
void update_entity ( pointer.Entity ent, pointer idle, pointer walk ) {
	entity_physics( ent )
	if ( ent[0].bottom0.tile > $39 ) {
		entity_destiny ( ent )
	}
	entity_sprite( ent, ent[0].top0.x, ent[0].top0.y, idle, walk )
}
	
// sets the current frame of ent's animation and determines which animation to use
void entity_sprite ( pointer.Entity ent, byte xx, byte yy, pointer idle, pointer walk ) {
	if ( ent[0].direction == 0 ) {
		if ( ent[0].bottom0.tile < $3A ) {   // if player
			ent[0].top0.attrs    = SAM_ATTR_HFLIP
			ent[0].bottom0.attrs = SAM_ATTR_HFLIP
			ent[0].top1.attrs    = SAM_ATTR_HFLIP
			ent[0].bottom1.attrs = SAM_ATTR_HFLIP
		} else {
			ent[0].top0.attrs    = BAD_ATTR_HFLIP
			ent[0].bottom0.attrs = BAD_ATTR_HFLIP
			ent[0].top1.attrs    = BAD_ATTR_HFLIP
			ent[0].bottom1.attrs = BAD_ATTR_HFLIP
		}
		ent[0].top1.x = xx - 8
		ent[0].bottom1.x = xx - 8
	}
	else {
		if ( ent[0].bottom0.tile < $3A ) {   // if player
			ent[0].top0.attrs    = SAM_ATTR
			ent[0].bottom0.attrs = SAM_ATTR
			ent[0].top1.attrs    = SAM_ATTR
			ent[0].bottom1.attrs = SAM_ATTR
		} else {
			ent[0].top0.attrs    = BAD_ATTR
			ent[0].bottom0.attrs = BAD_ATTR
			ent[0].top1.attrs    = BAD_ATTR
			ent[0].bottom1.attrs = BAD_ATTR
		}
		ent[0].top1.x = xx + 8
		ent[0].bottom1.x = xx + 8
	}

	ent[0].top0.x = xx
	ent[0].bottom0.x = xx

	ent[0].top0.y = yy
	ent[0].bottom0.y = yy + 8
	ent[0].top1.y = yy
	ent[0].bottom1.y = yy + 8
 
	byte ani
	ani = 0
	if ( ent[0].frame < 4 ) {
		ani = 0
	} else if ( ent[0].frame < 8 ) {
		ani = 4
	} else if (ent[0].frame < 12 ) {
		ani = 8
	} else if (ent[0].frame < 16 ) {
		ani = 12
	} else if (ent[0].frame < 20 ) {
		ani = 16
	} else {
		ent[0].frame = 0
		ani = 0
	}

	if ( ent[0].jump == 1 ) {
		ent[0].top0.tile    = idle[0]
		ent[0].bottom0.tile = idle[1]
		ent[0].top1.tile    = idle[2]
		ent[0].bottom1.tile = idle[3]
	} else if ( ent[0].movement == 1 ) {
		ent[0].top0.tile    = walk[ani + 0]
		ent[0].bottom0.tile = walk[ani + 1]
		ent[0].top1.tile    = walk[ani + 2]
		ent[0].bottom1.tile = walk[ani + 3]
	} else {
		ent[0].top0.tile    = idle[ani + 0]
		ent[0].bottom0.tile = idle[ani + 1]
		ent[0].top1.tile    = idle[ani + 2]
		ent[0].bottom1.tile = idle[ani + 3]
	}

	ent[0].frame += 1
}

// -------------------------------------
// "PHYSICS"
// -------------------------------------
void entity_physics ( pointer.Entity ent ) {
	// if player
	if ( ent[0].bottom0.tile < $3A ) {
		entity_jump_physics( ent )
	}

	if ( ent[0].bottom0.y < BOTTOMWALL - 10 && ent[0].jump == 0 ) {
		ent[0].top0.y += FALLSPEED
	}

	if ( ent[0].movement == 1 ) {
		if ( ent[0].direction == 0 ) {
			ent[0].top0.x -= ent[0].walkspeed
		} else if ( ent[0].direction == 1) {
			ent[0].top0.x += ent[0].walkspeed
		}
	}
}

void entity_jump_physics ( pointer.Entity ent ) {
	if ( ent[0].bottom0.y < BOTTOMWALL - 10 && ent[0].jump == 1 && ent[0].dircount == 0 ) {
		// if not on ground, don't start jumping
		ent[0].jump = 0
	} else if ( ent[0].jump == 1 )
	{
		// a meager attempt at replicating scb's jump arc
		// a few deficiencies: 
		// 	* a bit too short
		// 	* "float" is a bit too short
		// it might work out gameplay-wise, though, so idk we'll see
		if ( ent[0].dircount < 3) {
			ent[0].top0.y -= 6
		} else if ( ent[0].dircount == 3 ) {
			ent[0].top0.y -= 2
		} else if ( ent[0].dircount == 4 ) {
			ent[0].top0.y -= 6
		} else if ( ent[0].dircount < 9 ) {
			ent[0].top0.y -= 3
		} else if ( 9 <= ent[0].dircount <= 10 ) {
			ent[0].top0.y -= 1
		} else if ( ent[0].dircount == 13 ) {
			ent[0].top0.y += 2
		} else if ( 13 < ent[0].dircount < 20 ) {
			ent[0].top0.y += 2
		} else if ( 20 < ent[0].dircount ) {
			ent[0].dircount = -1
			ent[0].jump = 0
		}
		ent[0].dircount += 1
	}
}

// enemy pathfinding, blah blah.
// determines an npc's destiny
void entity_destiny ( pointer.Entity ent ) {
	ent[0].movement = 1
}

// -------------------------------------
// ETC
// -------------------------------------
inline void draw_score() {
	byte digit01
	byte digit10
	read_ppu_status() // read PPU status to reset the high/low latch
	
	//display player1's score
	digit01 = score1 %% 10 //get the ones digit
	digit10 = score1 / 10  //get the tens digit
	digit10 %%= 10
	
	ppu_set_addr(ppu_nametable_ram+$29) // point the PPU to player1's score number
	if digit10 > 0 {
		ppu_write_data(digit10 + '0')
	}
	ppu_write_data(digit01 + '0')
}


// ============================================================================
// UTIL
// ============================================================================
inline asm void ppu_wait_vblank() {
	vblankwait:
		BIT $2002
		! BPL vblankwait
	? RTS
}