// Amiga audio HAL: PTPlayer (Frank Wille, public domain) drives Paula
// for both module playback and one-shot SFX overlay.
//
// We build PTPlayer in OSCOMPAT mode so it cooperates with audio.device
// rather than taking Paula away from the OS -- matches our cooperative-
// with-Intuition graphics HAL. mt_install allocates all four Paula
// channels via audio.device; mt_init loads a .MOD; mt_Enable=1 starts
// playback; mt_playfx triggers a SFX on a free channel (or the worst
// channel if all are busy) with priority arbitration.
//
// PTPlayer expects modules and SFX samples to live in Chip RAM. The
// asset pipeline does not yet partition into Chip vs. Fast, so we
// AllocMem(MEMF_CHIP) a copy at PlayMod / PlaySfx time and free it at
// StopMod / StopSfx (or shutdown).

#include <string.h>

#include <exec/types.h>
#include <exec/memory.h>
#include <hardware/custom.h>

#include <proto/exec.h>

#include "ptplayer.h"
#include "hal.h"
#include "joey/audio.h"

extern struct Custom custom;
extern UBYTE         mt_Enable;
extern UBYTE         mt_E8Trigger;

// ----- Constants -----

// Paula's NTSC PAL period for middle-C-ish playback. PTPlayer's SFX
// API takes a hardware period (cycles per sample) rather than a
// frequency. To convert from a sample's authored Hz: period = clock /
// rate, where clock is ~3546895 (PAL) or ~3579545 (NTSC). We default
// PAL since that's what our screen mode requests, and clamp to legal
// Paula period limits.
#define PAULA_CLOCK_PAL    3546895UL
#define PAULA_PERIOD_MIN   124         // Paula HW limit
#define PAULA_PERIOD_MAX   65535

#define SFX_VOLUME_MAX     64

// PTPlayer has no built-in "play once" mode -- songs loop forever
// unless the author placed an `E8FF` effect at song end. mt_E8Trigger
// reflects the most-recently-seen E8 value; mt_init resets it to 0.
// When loop=false on PlayMod, we poll for this sentinel in
// halAudioFrameTick and clear mt_Enable when seen.
#define PTPLAYER_LOOP_END_MARKER 0xFF

// ----- Module state -----

typedef struct {
    UBYTE *samples;     // Chip-RAM copy of one SFX sample
    UWORD  lengthWords; // sample length in 16-bit words
} SfxSlotT;

static UBYTE     *gModuleChip   = NULL; // Chip-RAM copy of the playing module
static ULONG      gModuleLength = 0;    // bytes to FreeMem on swap / shutdown
static SfxSlotT   gSfxSlots[JOEY_AUDIO_SFX_SLOTS];
static bool       gInstalled    = false;
static bool       gModPlaying   = false;
static bool       gWantLoopOnce = false;   // honor loop=false via E8 marker

// ----- Internal helpers -----

static UWORD periodForRate(uint16_t rateHz) {
    unsigned long period;

    if (rateHz == 0) {
        return 428;  // ~middle C, sane default
    }
    period = PAULA_CLOCK_PAL / (unsigned long)rateHz;
    if (period < PAULA_PERIOD_MIN) {
        period = PAULA_PERIOD_MIN;
    }
    if (period > PAULA_PERIOD_MAX) {
        period = PAULA_PERIOD_MAX;
    }
    return (UWORD)period;
}


// ----- HAL API (alphabetical) -----

bool halAudioInit(void) {
    int i;

    if (gInstalled) {
        return true;
    }
    if (mt_install() == 0) {
        return false;
    }
    mt_Enable     = 0;
    gInstalled    = true;
    gModPlaying   = false;
    gWantLoopOnce = false;
    gModuleChip   = NULL;
    gModuleLength = 0;
    for (i = 0; i < JOEY_AUDIO_SFX_SLOTS; i++) {
        gSfxSlots[i].samples     = NULL;
        gSfxSlots[i].lengthWords = 0;
    }
    return true;
}


void halAudioShutdown(void) {
    int i;

    if (!gInstalled) {
        return;
    }
    mt_Enable = 0;
    mt_end((void *)&custom);
    mt_remove();
    gInstalled  = false;
    gModPlaying = false;

    if (gModuleChip != NULL) {
        FreeMem(gModuleChip, gModuleLength);
        gModuleChip   = NULL;
        gModuleLength = 0;
    }
    for (i = 0; i < JOEY_AUDIO_SFX_SLOTS; i++) {
        if (gSfxSlots[i].samples != NULL) {
            FreeMem(gSfxSlots[i].samples, (ULONG)gSfxSlots[i].lengthWords * 2UL);
            gSfxSlots[i].samples     = NULL;
            gSfxSlots[i].lengthWords = 0;
        }
    }
}


bool halAudioIsPlayingMod(void) {
    return gModPlaying && mt_Enable != 0;
}


void halAudioPlayMod(const uint8_t *data, uint32_t length, bool loop) {
    UBYTE *chip;

    if (!gInstalled) {
        return;
    }
    mt_Enable     = 0;
    mt_end((void *)&custom);
    gModPlaying   = false;
    gWantLoopOnce = false;
    if (gModuleChip != NULL) {
        FreeMem(gModuleChip, gModuleLength);
        gModuleChip   = NULL;
        gModuleLength = 0;
    }

    chip = (UBYTE *)AllocMem((ULONG)length, MEMF_CHIP);
    if (chip == NULL) {
        return;
    }
    memcpy(chip, data, length);
    gModuleChip   = chip;
    gModuleLength = (ULONG)length;

    // PTPlayer takes the module pointer in a0, sample-data pointer in
    // a1 (NULL = samples follow the module header), song position in
    // d0. mt_init resets mt_E8Trigger to 0 so subsequent halAudioFrame
    // Tick polling sees a clean state.
    mt_init((void *)&custom, chip, NULL, 0);
    mt_Enable     = 1;
    gWantLoopOnce = !loop;
    gModPlaying   = true;
}


void halAudioPlaySfx(uint8_t slot, const uint8_t *sample, uint32_t length, uint16_t rateHz) {
    SfxStructure  sfx;
    SfxSlotT     *s;
    UBYTE        *chip;
    UWORD         words;

    if (!gInstalled || slot >= JOEY_AUDIO_SFX_SLOTS) {
        return;
    }
    if (length < 2 || length > 0x1FFFEUL) {
        return;  // Paula sample length is 16 bits of words = 128KB max
    }

    s = &gSfxSlots[slot];
    if (s->samples != NULL) {
        FreeMem(s->samples, (ULONG)s->lengthWords * 2UL);
        s->samples     = NULL;
        s->lengthWords = 0;
    }

    chip = (UBYTE *)AllocMem((ULONG)length, MEMF_CHIP);
    if (chip == NULL) {
        return;
    }
    memcpy(chip, sample, length);
    words = (UWORD)(length >> 1);

    s->samples     = chip;
    s->lengthWords = words;

    sfx.sfx_ptr = chip;
    sfx.sfx_len = words;
    sfx.sfx_per = periodForRate(rateHz);
    sfx.sfx_vol = SFX_VOLUME_MAX;
    sfx.sfx_cha = -1;                 // best free channel
    sfx.sfx_pri = (BYTE)(slot + 1);   // priority 1..N from slot index
    mt_playfx((void *)&custom, &sfx);
}


void halAudioStopMod(void) {
    if (!gInstalled) {
        return;
    }
    mt_Enable     = 0;
    mt_end((void *)&custom);
    gModPlaying   = false;
    gWantLoopOnce = false;
}


void halAudioStopSfx(uint8_t slot) {
    UBYTE i;

    if (!gInstalled || slot >= JOEY_AUDIO_SFX_SLOTS) {
        return;
    }
    // PTPlayer addresses SFX by Paula channel (0..3), but mt_playfx
    // picks a channel dynamically and does not return which one. We
    // can't reliably map slot -> channel after the fact, so stop all
    // four channels' SFX state. mt_stopfx is idempotent on idle
    // channels, so stopping a quiet one is harmless.
    for (i = 0; i < 4; i++) {
        mt_stopfx((void *)&custom, i);
    }
}


void halAudioFrameTick(void) {
    // PTPlayer drives itself off CIA-B; the only host-loop work is the
    // play-once watchdog. When the song author placed an `E8FF` at
    // song end, mt_E8Trigger latches to 0xFF -- if the caller passed
    // loop=false to PlayMod, that's our cue to stop the song.
    if (gWantLoopOnce && gModPlaying && mt_E8Trigger == PTPLAYER_LOOP_END_MARKER) {
        mt_Enable     = 0;
        gModPlaying   = false;
        gWantLoopOnce = false;
    }
}