; Beeper engine
; Copyright (C) 2021 by Juan J. Martinez <jjm@usebox.net>
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in
; all copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
; THE SOFTWARE.
;
.globl _beeper_init
.globl _beeper_queue
.globl _beeper_play

_beeper_init::
        di
        ld (sfx_data), hl
        xor a
        ld (sfx_type), a
        ei
        ret

_beeper_queue::
        di
        ld a, l
        call queue_next
        ei
        ret

queue_next:
        ld (sfx_type), a
        or a
        ret z

        dec a

        ld hl, (sfx_data)
        ld c, l
        ld b, h

        ld h, #0
        ld l, a
        ld d, h
        ld e, l
        add hl, hl
        add hl, hl
        add hl, de
        add hl, bc

        ld de, #sfx_type
        ld bc, #5
        ldir
        ret

_beeper_play::
        ld a, (sfx_type)
        or a
        ret z

        dec a
        jr z, tone

        dec a
        ; shouldn't happen!
        ret nz

        ; noise
        ld a, (sfx_freq)
        ld d, a

        ld b, #0

noise_loop:
        call rnd
        and #0x10
        ; FIXME: border ?
        out (0xfe), a

        ld c, d
noise_freq_loop:
        dec b
        jr z, noise_done
        dec c
        jr nz, noise_freq_loop
        jr noise_loop

tone:
        ld a, (sfx_freq)
        ld d, a

        xor a
        ld b, a

tone_loop:
        ; FIXME: border ?
        out (0xfe), a
        xor #0x10

        ld c, d
freq_loop:
        dec b
        jr z, tone_done
        dec c
        jr nz, freq_loop
        jr tone_loop

tone_done:
noise_done:
        ld a, (sfx_next)
        ld hl, #sfx_frames
        dec (hl)
        jr z, queue_next

        ; freq change (slide)
        ld a, (sfx_freq_chg)
        add d
        ld (sfx_freq), a

        ret

rnd:
        ld hl, #0xf3a1
        ld a, h
        rra
        ld a, l
        rra
        xor h
        ld h, a
        ld a, l
        rra
        ld a, h
        rra
        xor l
        ld l, a
        xor h
        ld h, a
        ld (rnd + 1), hl
        ret

sfx_type:       .ds 1
sfx_frames:     .ds 1
sfx_freq:       .ds 1
sfx_freq_chg:   .ds 1
sfx_next:       .ds 1

sfx_data: .ds 2