.word   0xDEADBEEF
whatever: ; debugging stuff
    .word   0

.include "common.asm"

hash:
tunic_color:
    .word   0xFFFFFFFF

old_exit:
    .half   0
new_exit:
    .half   0
.align

rng_seed:
    .word   0

.include "entrances.asm"
.include "crc32.asm"

dma_hook:
    push    4, 1, ra
    call    setup_hook
    pop     4, 1, ra
    addiu   sp, 0xFF58 ; original code
    j       0x8016A2D0 ; return to scene setup function
    sw      s1, 0x30(sp) ; original code

set_scene_flag:
    ; a0: scene number
    ; a1: scene word (0-4)
    ; a2: bit to set (0-31)
    ; v0: new scene flag word
    li      t0, @link_save
    addiu   t1, t0, @scene_flags_ingame
    li      t2, @scene_record_size
    multu   a0, t2
    mflo    t2
    addu    t3, t1, t2
    sll     t4, a1, 2 ; t4 = a1*sizeof(word)
    addu    t3, t4
    lw      v0, (t3) ; load scene flag word
    li      t6, 1
    sllv    t6, a2
    or      v0, t6 ; set flag
    jr
    sw      v0, (t3) ; write it back

get_event_flag:
    ; a0: event flag offset
    ; a1: byte offset
    ; a2: bit to set (0-7)
    ; v0: 1 if set, else 0
    li      t0, @link_save
    addu    t1, t0, a0
    addu    t2, t1, a1
    lb      v0, (t2)
    li      t6, 1
    sllv    t6, a2
    and     v0, t6
    beqz    v0, +
    cl      v0
    li      v0, 1
+:
    jr
    nop

set_event_flag:
    ; a0: event flag offset
    ; a1: byte offset
    ; a2: bit to set (0-7)
    ; v0: new event flag value
    li      t0, @link_save
    addu    t1, t0, a0
    addu    t2, t1, a1
    lb      v0, (t2)
    li      t6, 1
    sllv    t6, a2
    or      v0, t6
    jr
    sb      v0, (t2)

tunic_color_hook:
    ; copypasta from CloudMax's old hack
    ; registers available for use without blowing up: at, t3, t4, a0
    lw      t3, @link_object_ptr
    lui     t4, 0x0001
    sub     t3, t3, t4 ; t3 -= 0x10000
    lw      t4, tunic_color
    sw      t4, 0xF184(t3)
    sw      t4, 0xEFFC(t3)
    sw      t4, 0xECB4(t3)
    sw      t4, 0xEB2C(t3)
    sw      t4, 0xE8F4(t3)
    sw      t4, 0xE47C(t3)
    sw      t4, 0xDE74(t3)
    sw      t4, 0xDDB4(t3)
    sw      t4, 0xDBDC(t3)
    sw      t4, 0xD6D4(t3)
    sw      t4, 0xD1AC(t3)
    j       0x801261D8
    lhu     v0, 0xF6DC(v0) ; original code

load_hook:
    push    4, s0, s1, ra, 1
    li      s0, @link_save
    lb      t0, @has_completed_intro(s0)
    bnez    t0, +
    li      t0, 1
    ; first time setup
    sb      t0, @has_completed_intro(s0)
    sb      t0, @have_tatl(s0)

    ; deku intro area
    ; "Hey, you! C'mon! Press Z and talk to me!"
    call    set_scene_flag, 0x001A, 2, 2

    ; inside clock tower
    ; second word
    ; first bit ("You've met with a terrible fate")
    call    set_scene_flag, 0x0063, 1, 0

    ; Tatl reminding you about the four directions
    call    set_event_flag, @week_event_reg, 31, 2

    ; woken turtle once (shortens cutscene)
    call    set_event_flag, @week_event_reg, 93, 3

    ; taken turtle once (skips pirates getting wrekt)
    call    set_event_flag, @week_event_reg, 53, 6

+:
    addi    a0, s0, @player_name
    call    crc32, a0, 8, 0xFFFFFFFF

    not     v0, v0
    sw      v0, hash
    sw      v0, rng_seed
    call    shuffle_all
    ret     4, s0, s1, ra, 1

prng:
    ; just a reimplementation of the PRNG the game uses.
    ; it's from Numerical Recipes in C, by the way.
    ; random = random*0x19660D + 0x3C6EF35F;
    lw      t0, rng_seed
    li      t1, 0x19660D
    multu   t0, t1
    li      t2, 0x3C6EF35F
    mflo    t3
    addu    v0, t3, t2
    sw      v0, rng_seed
    jr
    nop

randint:
    ; v0 = random integer from 0 to a0; a0 >= 0
    push    4, s0, ra
    jal     prng
    addi    s0, a0, 1
    divu    v0, s0
    mfhi    v0
    ret     4, s0, ra

shuffle_all:
    push    4, s0, s1, s2, ra
    ; https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_.22inside-out.22_algorithm
    li      s0, 0
    li      s1, @entries
    la      s2, shuffles
-:
    call    randint, s0
    ; s0 is i, v0 is j
    sll     t0, s0, 2 ; 1<<2 == 2*sizeof(half)
    sll     t1, v0, 2 ; likewise
    addu    t0, s2, t0 ; [i]
    addu    t1, s2, t1 ; [j]
    ; a[i] = a[j]
    lhu     t3, 2(t1)
    sh      t3, 2(t0)
    ; a[j] = source[i]
    lhu     t4, 0(t0)
    sh      t4, 2(t1)
    ; iterate
    addi    s0, 1
    bne     s0, s1, -
    nop
+:
    ret     4, s0, s1, s2, ra

shuffle_get:
    ; a0: exit value
    ; v0: shuffled exit value
    push    4, ra, 1
    mov     v0, a0
    li      t0, @entries
    li      t1, 0
    la      t3, shuffles
    mov     t4, t3
-:
    lhu     t5, (t4)
    beq     a0, t5, +
    nop
    addi    t1, t1, 1
    beq     t1, t0, +return
    nop
    b       -
    addi    t4, t4, 4 ; 2*sizeof(halfword)
+:
    lhu     v0, 2(t4)
+return:
    ret     4, ra, 1

unset_alt_scene:
    andi    t9, a0, 0x01FF
    andi    t0, a0, 0xFE00
    ; use poisoned swamp
    li      at, 0x0C00
    bne     t0, at, +
    li      at, 0x8400
    addu    a0, t9, at
+:
    ; use frozen mountain
    li      at, 0x8A00
    bne     t0, at, +
    li      at, 0x9400
    addu    s0, t9, at
+:
    li      at, 0xAE00
    bne     t0, at, +
    li      at, 0x9A00
    addu    s0, t9, at
+:
    li      at, 0xB600
    bne     t0, at, +
    li      at, 0xB400
    addu    s0, t9, at
+:
    jr
    mov     v0, a0

set_alt_scene:
    push    4, s0, ra
    mov     s0, a0
    ; use clean swamp when odolwa is beaten
    call    get_event_flag, @week_event_reg, 20, 1
    beqz    v0, +
    nop
    andi    t9, s0, 0x01FF
    andi    t0, s0, 0xFE00
    ; can't actually use bnei here because unsignedness, oops
    li      at, 0x8400
    bne     t0, at, +
    li      at, 0x0C00
    addu    s0, t9, at
+:
    ; use unfrozen mountain when goht is beaten
    call    get_event_flag, @week_event_reg, 33, 7
    beqz    v0, +return
    nop
    andi    t9, s0, 0x01FF
    andi    t0, s0, 0xFE00
    li      at, 0x9400
    bne     t0, at, +
    li      at, 0x8A00
    addu    s0, t9, at
+:
    li      at, 0x9A00
    bne     t0, at, +
    li      at, 0xAE00
    addu    s0, t9, at
+:
    li      at, 0xB400
    bne     t0, at, +
    li      at, 0xB600
    addu    s0, t9, at
+:
+return:
    mov     v0, s0
    ret     4, s0, ra

shuffle_exit:
    push    4, s0, ra
    sh      a0, old_exit
    li      t0, @link_save
    lw      t1, @voidout_type(t0)
    ; if this was a death warp, don't use coordinates for respawning
    li      at, -6
    bne     t1, at, +
    nop
    cl      t1
    sw      t1, @voidout_type(t0)
+:
    ; same for walking between areas in ikana castle
    li      at, -2
    bne     t1, at, +
    nop
    cl      t1
    sw      t1, @voidout_type(t0)
+:
    ; if this was a void out, don't shuffle
    bnez    t1, +
    mov     s0, a0
    ; if this is a cutscene, don't shuffle
    lh      t2, @exit_mod_setter(t0)
    bnei    t2, 0xFFEF, +
    nop
    call    unset_alt_scene, a0
    call    shuffle_get, v0
    call    set_alt_scene, v0
    mov     s0, v0
    sh      v0, new_exit
    ; set woodfall temple as raised after beating odolwa
    ; otherwise the swamp won't be cleansed
    li      at, 0x8601
    bne     s0, at, +
    call    set_event_flag, @week_event_reg, 20, 0
+:
    mov     v0, s0
    ret     4, s0, ra

setup_hook:
    push    4, a0, ra
    lw      a0, @link_save
    jal     shuffle_exit
    andi    a0, 0xFFFF
    sw      v0, @link_save
    ret     4, a0, ra

.word 0xDEADBEEF