-- Picotron PCM driver
--
--
-- 8-bit 44.1 kHz stereo PCM for Picotron
--
-- Entrypoint is pcm_init(), call it in update to set up.
--
-- You can pass {n_bufs = 4} to pcm_init for lower latency, but this will probably result in audio breakups in the web
-- player.
--
-- Uses these resources:
-- * memory from 0xe00000-0xe08000 (or more, if you want more than 8 buffers)
-- * instruments 56-63 (or more instruments, going lower as you add more buffers)
-- * sfx 63
-- * output channel 15
--
--
-- EXAMPLE
-- =======
--[[
include 'pcm.lua'

function gen_sine(n_samples)
    local sound_left = userdata('f64', n_samples)
    local sound_right = userdata('f64', n_samples)
    for i = 0, n_samples - 1 do
        sound_left[i] = sin(sine_phase_left)
        sound_right[i] = sin(sine_phase_right)
        sine_phase_left += 0.01
        sine_phase_right += 0.015
    end

    -- output range is -128 to 127
    return sound_left * 32, sound_right * 32
 end

function _init()
    sine_phase_left = 0
    sine_phase_right = 0
    pcm_callback, pcm_start, pcm_stop = pcm_init()
    pcm_start()
end

function _update()
    -- call pcm_callback() every frame until you call pcm_stop()
    pcm_callback(gen_sine)
end
--]]
--
-- LICENSE
-- =======
--
-- Copyright (C) 2024 by luchak <[email protected]>
--
-- Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby
-- granted.
--
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
-- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
-- AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
-- PERFORMANCE OF THIS SOFTWARE.

function pcm_init(options)
    options = options or {}
    local n_bufs = options.n_bufs or 8
    local base_addr = options.base_addr or 0xe00000
    local sfx_id = 63
    local channel_id = 15

    local sfx_spd = 2
    local buf_size = 10
    local buf_len = 2<<buf_size

    local first_instrument=64-n_bufs

    local play_queue={}

    local buf_addrs_left={}
    local buf_addrs_right={}
    for i=0,n_bufs-1 do
        local buf_addr_left = base_addr + 2*i*buf_len
        local buf_addr_right = buf_addr_left + buf_len

        add(buf_addrs_left, buf_addr_left)
        add(buf_addrs_right, buf_addr_right)

        -- fill output buffer with enough 0s to avoid startup glitches
        add(play_queue, userdata('f64',buf_len))
        add(play_queue, userdata('f64',buf_len))

        _pcm_make_stream_instrument(first_instrument+i, buf_addr_left, buf_addr_right, buf_size)
    end

    _pcm_setup_sfx(sfx_id, sfx_spd, first_instrument, n_bufs)

    local next_row=0

    local function pcm_callback(gen_chunk)
        local row = stat(400+channel_id, 9)
        local tick_len = stat(400+channel_id, 21)
        if #play_queue<n_bufs*2 then
            local chunk_left, chunk_right = gen_chunk(sfx_spd*tick_len)
            add(play_queue, chunk_left)
            add(play_queue, chunk_right or chunk_left)
        end
        while next_row ~= row and #play_queue>0 do
            local chunk_left = deli(play_queue, 1)
            local chunk_right = deli(play_queue, 1)
            local prev_idx = (next_row + n_bufs - 1) % n_bufs + 1
            local this_idx = next_row + 1
            local prev_base_left = buf_addrs_left[prev_idx]
            local prev_base_right = buf_addrs_right[prev_idx]
            local base_left = buf_addrs_left[this_idx]
            local base_right = buf_addrs_right[this_idx]
            local chunk_size = #chunk_left

            poke(prev_base_left + chunk_size, chunk_left:get(0, chunk_size))
            poke(prev_base_right + chunk_size, chunk_right:get(0, chunk_size))
            poke(base_left, chunk_left:get(0, chunk_size))
            poke(base_right, chunk_right:get(0, chunk_size))
            next_row = (next_row + 1) % n_bufs
        end
    end

    local function pcm_start()
        sfx(sfx_id, channel_id)
    end

    local function pcm_stop(channel)
        sfx(-1, channel_id)
    end

    return pcm_callback, pcm_start, pcm_stop
end

function _pcm_make_stream_instrument(instrument_id, wave_addr_left, wave_addr_right, wave_size)
    -- instr comments here mostly copied from sfx.p64/data.lua
    poke(0x40000 + (instrument_id * 512) + 0x1df, 2) -- wide

    -- node 0: root
    poke(0x40000 + (instrument_id * 512) + (0 * 32), -- instrument 63, node 0
        0,    -- parent (0x7)  op (0xf0)
        1,    -- kind (0x0f): 1 root  kind_p (0xf0): 0  -- wavetable_index
        0,    -- flags
        0,    -- unused extra

        -- MVALs:  kind/flags,  val0, val1, envelope_index

        0x0,0x40,0,0,  -- volume: mult. 0x40 is max (-0x40 to invert, 0x7f to overamp)
        0x1,0,0,0,     -- pan:   add. center
        0x1,0,0,0,     -- tune: +0 -- 0,48,0,0 absolute for middle c (c4) 261.6 Hz
        0x1,0,0,0,     -- bend: none
        -- following shouldn't be in root
        0x0,0,0,0,     -- wave: use wave 0
        0x0,0,0,0      -- phase
    )

    -- node 1: custom wt (left)
    poke(0x40000 + (instrument_id * 512) + (1 * 32), -- instrument 63, node 1
        0,    -- parent (0x7)  op (0xf0)
        0x20|2,    -- kind (0x0f): 2 osc  kind_p (0xf0): 2  -- wavetable_index
        0x0,    -- flags
        0,    -- unused extra

        -- MVALs:  kind/flags,  val0, val1, envelope_index

        0x0,0x40,0,0,  -- volume: mult. 0x40 is max (-0x40 to invert, 0x7f to overamp)
        0x0,-128,0,0,     -- pan:   left
        0x0,77,0,0x20|0x80,    -- tune: +0 -- 0,5,0,0 absolute for f0
                       -- tune is quantized to semitones with 0x20
        0x0,0,0,0x20|0x80,   -- can fine-tune here but unsure of exact setting
        0x0,0,0,0,     -- wave: 0
        0x0,-128,0,0      -- phase
    )

    -- node 2: custom wt (right)
    poke(0x40000 + (instrument_id * 512) + (2 * 32), -- instrument 63, node 2
        0,    -- parent (0x7)  op (0xf0)
        0x30|2,    -- kind (0x0f): 2 osc  kind_p (0xf0): 3  -- wavetable_index
        0x0,    -- flags
        0,    -- unused extra

        -- MVALs:  kind/flags,  val0, val1, envelope_index

        0x0,0x40,0,0,  -- volume: mult. 0x40 is max (-0x40 to invert, 0x7f to overamp)
        0x0,127,0,0,     -- pan:   right
        0x0,77,0,0x20|0x80,    -- tune: +0 -- 0,5,0,0 absolute for f0
                       -- tune is quantized to semitones with 0x20
        0x0,0,0,0x20|0x80,   -- can fine-tune here but unsure of exact setting
        0x0,0,0,0,     -- wave: 0
        0x0,-128,0,0      -- phase
    )

    -- wavetable 2 (node 1)
    poke(0x40000 + 0x200*instrument_id + 0x1e0 + 4*2,
        (wave_addr_left >> 8) & 255, -- address (low)  in 256 byte increments
        (wave_addr_left >> 16) & 255, -- address (high) in 64k increments
        wave_size, -- samples (1 << n)
        0x1   -- wt_height 256(0); wave mval points at one of the entries
    )

    -- wavetable 3 (node 2)
    poke(0x40000 + 0x200*instrument_id + 0x1e0 + 4*3,
        (wave_addr_right >> 8) & 255, -- address (low)  in 256 byte increments
        (wave_addr_right >> 16) & 255, -- address (high) in 64k increments
        wave_size, -- samples (1 << n)
        0x1   -- wt_height 256(0); wave mval points at one of the entries
    )

    memset(wave_addr_left, 2 << wave_size, 0)
    memset(wave_addr_right, 2 << wave_size, 0)
end

function _pcm_setup_sfx(sfx_id, sfx_spd, first_instrument, n_bufs)
    local base = 0x50000 + 328*sfx_id
    poke2(base, 64)                              -- track length
    poke(base + 2, sfx_spd)                      -- spd
    poke(base + 3, 0)                            -- loop to 0
    poke(base + 4, n_bufs)                       -- loop len n_bufs
    poke(base + 5, 0)
    poke(base + 6, 0)
    for i=0,n_bufs-1 do
        poke(base + 8 + i,0)                      -- note
        poke(base + 8 + 64 + i, first_instrument + i)  -- instrument
        poke(base + 8 + 128 + i, 64)                 -- volume
    end
end