/*
 * abcdisk.c
 *
 * Emulate an ABC80/800 disk controller
 */

#include <string.h>
#include <stdio.h>

#include "fw.h"
#include "io.h"
#include "abcio.h"
#include "console.h"
#include "ff.h"

/* Option flags, mostly for debugging */
#define NOTTHERE	0
#define READONLY	0
#define INTERLEAVE	0
#define FORMAT_SUPPORT	0

enum drive_flags {
    DF_MOUNTED,			/* Host file open, drive exported */
    DF_READONLY,		/* Drive is readonly */
    DF_DISABLED			/* Drive is disabled */
};

enum pending {
    PEND_IO    = 1,
    PEND_RESET = 2
};

/* Per-drive state */
struct drive_state {
    FIL file;			/* Host file */
    char name[4];               /* Drive name */
    uint16_t sectors;		/* Total size in 256-byte sectors */
#if INTERLEAVE
    uint8_t ilmsk, ilfac;       /* Software interleaving parameters */
#endif
    enum drive_flags flags;
    enum drive_flags force;	/* Option to force flags */
};

/* Fixed parameters for each controller */
struct ctl_params {
    uint8_t clustshift;		/* log2(clustersize/256) */
    uint8_t devsel;		/* I/O device select */
    uint16_t maxsectors;	/* Maximum sectors for this controller */
    uint8_t c, h, s;		/* Disk geometry */
    bool newaddr;		/* "New addressing" */
    const char name[4];		/* Name of controller (disk type) */
#if INTERLEAVE
    uint8_t ilmsk, ilfac;	/* Software interleaving parea */
#endif
#if FORMAT_SUPPORT
    bool fmtdata_i_buf;	/* Use user-provided formatting data */
#endif
} __attribute__((aligned(4)));

/* Per-controller state */
struct ctl_state {
    struct abc_dev iodev;
    const struct ctl_params *params;
    uint8_t k[4];		/* Command bytes */
    uint8_t drives;		/* Total drives present */
    bool initialized;	        /* Controller initialized */
    volatile enum pending pending;	/* Need to do I/O */
    struct drive_state drv[8];	/* Per-drive state */
    uint8_t buf[4][256];	/* 4 host buffers @ 256 bytes */
};

/*
 * DOSGEN depends on this value... and different DOSGEN
 * expect different values. If this value is wrong, DOSGEN
 * will spin forever on "testing sector..."
 */
#define OUT_OF_RANGE 0x21	/* Status code for an invalid sector */

#define DISK_NOT_READY 0x80
#define WRITE_PROTECT  0x40
#define WRITE_FAULT    0x20
#define CRC_ERROR      0x08

enum controller_types {
    MOx,
    MFx,
    SFx,
    HDx,
    CONTROLLER_TYPES
};

#if INTERLEAVE
# define IL(mask, fac) .ilmsk = (mask), .ilfac = (fac),
#else
# define IL(mask, fac)
#endif

static const struct ctl_params parameters[CONTROLLER_TYPES] = {
    /*
     * MOx: covers all of these formats:
     * SSSD = 40×8×1 (80K, FD2/DD80),
     * SSDD = 40×16×1 (160K, FD2D/DD82/ABC830) and
     * DSDD = 40×16×2 (320K, FD4D/DD84/DD52)
     */
    [MOx] = {
	.devsel = 45,
	.clustshift = 0,
	.maxsectors = 40 * 2 * 16,
	.c = 40, .h = 2, .s = 16,
	.name = "mo",
#if FORMAT_SUPPORT
	.fmtdata_in_buf = true,
#endif
	IL(15, 7)
    },

    /* MFx: DSQD = 80×16x2 (640K, ABC832/834) */
    [MFx] = {
	.devsel = 44,
	.clustshift = 2,
	.maxsectors = 80 * 2 * 16,
	.c = 80, .h = 2, .s = 16,
	.name = "mf"
    },

    /* SFx: 8" floppy (DD88, ABC838) */
    [SFx] = {
	.devsel = 46,
	.clustshift = 2,
	.maxsectors = (77 * 2 - 1) * 26, /* Track 0, side 0 not used */
	.c = 77, .h = 2, .s = 26,
	.name = "sf"
    },

    [HDx] = {
	.devsel = 36,
	.clustshift = 5,
	.newaddr = true,            /* Actually irrelevant for clustshift = 5 */
	.maxsectors = (239 * 8 - 1) * 32,     /* Maximum supported by UFD-DOS */
	.c = 238, .h = 16, .s = 64,
	.name = "hd"
    }
};

static struct ctl_state __dram_bss controllers[CONTROLLER_TYPES];

static inline bool mounted(const struct drive_state *drv)
{
    return !!(drv->flags & DF_MOUNTED);
}

static inline struct drive_state *cur_drv_mutable(struct ctl_state *state)
{
    return &state->drv[state->k[1] & 7];
}

static inline const struct drive_state *cur_drv(const struct ctl_state *state)
{
    return &state->drv[state->k[1] & 7];
}

static inline unsigned int cur_sector(const struct ctl_state *state)
{
    uint8_t k2 = state->k[2], k3 = state->k[3];

    if (state->params->newaddr)
        return (k2 << 8) + k3;
    else
        return (((k2 << 3) + (k3 >> 5)) << state->params->clustshift)
	    + (k3 & 31);
}

/* Get physical sector number, after interleaving */
static inline unsigned int
virt2phys(const struct drive_state *drv, unsigned int sector)
{
#if INTERLEAVE
    unsigned int ilmsk = drv->ilmsk;
    unsigned int ilfac = drv->ilfac;

    sector = (sector & ~ilmsk) | ((sector * ilfac) & ilmsk);
#endif
    return sector;
}

static inline unsigned int phys_sector(const struct ctl_state *state)
{
    return virt2phys(cur_drv(state), cur_sector(state));
}

static inline unsigned int file_pos(const struct ctl_state *state)
{
    return phys_sector(state) << 8;
}

static inline bool file_pos_valid(const struct ctl_state *state)
{
    return phys_sector(state) < cur_drv(state)->sectors;
}

static inline bool cur_sector_valid(const struct ctl_state *state)
{
    uint8_t k3 = state->k[3];

    if (!state->params->newaddr && ((k3 & 31) >> state->params->clustshift))
	return false;

    return phys_sector(state) < state->params->maxsectors;
}

static inline uint8_t *cur_buf(struct ctl_state *state)
{
    return state->buf[state->k[1] >> 6];
}

static void disk_start_command(struct ctl_state *state)
{
    abc_setup_out_queue(&state->iodev, state->k, 4, 0x81);
}

static void sync_drives(struct ctl_state *state)
{
    for (int i = 0; i < 8; i++)
	if (state->drv[i].flags & DF_MOUNTED)
	    f_sync(&state->drv[i].file);
}

static void disk_set_error(struct ctl_state *state, unsigned int error)
{
    abc_set_inp_default(&state->iodev, error);
}

static void disk_reset_state(struct ctl_state *state)
{
    abc_set_inp_status(&state->iodev, 0);
    disk_set_error(state, 0);

    sync_drives(state);

    disk_start_command(state);
}

static struct drive_state *
name_to_drive(const char *drive)
{
    struct ctl_state *state;
    unsigned int ndrive;

    /* All drive names are three letters long */
    if (strlen(drive) != 3)
	return NULL;

    ndrive = drive[2] - '0';
    if (ndrive > 7)
	return NULL;

    if (!memcmp("dr", drive, 2)) {
	/* DRx alias for MOx (matches "old DOS") */
	return &controllers[MOx].drv[ndrive];
    }

    for (int i = 0; i < CONTROLLER_TYPES; i++) {
	struct ctl_state *state = &controllers[i];

	if (!memcmp(state->params->name, drive, 2))
	    return &state->drv[ndrive];
    }

    return NULL;		/* No such disk */
}

bool valid_drive_name(const char *drive)
{
    return name_to_drive(drive) != NULL;
}

static int mount_drive(struct drive_state *drv, struct ctl_state *state,
		       const char *filename)
{
    if (mounted(drv)) {
	f_close(&drv->file);
	drv->flags &= ~DF_MOUNTED;
    }

    if (drv->force & DF_DISABLED)
	return -1;

    drv->flags = drv->force & ~DF_MOUNTED;

    if (!filename) {
	return 0;		/* Explicit unmount */
    } else {
	while (1) {
	    BYTE mode = FA_OPEN_EXISTING | FA_READ;

	    if (!(drv->flags & DF_READONLY))
		mode |= FA_WRITE;

	    FRESULT rv = f_open(&drv->file, filename, mode);

	    if (rv == FR_WRITE_PROTECTED && (mode & FA_WRITE)) {
		drv->flags |= DF_READONLY;
		continue;
	    }

	    if (rv != FR_OK)
		drv->flags |= DF_DISABLED;
	    else
		drv->flags |= DF_MOUNTED;

	    break;
	}

	if (!(drv->flags & DF_MOUNTED))
	    return -1;

	con_printf("abcdisk: %-3s = %s\n", drv->name, filename);
    }

    /*
     * Smaller than the standard disk size?  Treat the sectors
     * beyond the end as bad.
     */
    unsigned int filesec = f_size(&drv->file) >> 8;
    drv->sectors = min(filesec, state->params->maxsectors);

    /* Interleaving parameters */
#if INTERLEAVE
	drv->ilfac = state->params->ilfac;
	drv->ilmsk = state->params->ilmsk;
#endif

	return 0;
}

#define IDLE_CALLBACK_MASK	(1 << 4)

static void abcdisk_callback_out(struct abc_dev *dev, uint8_t data)
{
    struct ctl_state *state = container_of(dev, struct ctl_state, iodev);

    dev->callback_mask = IDLE_CALLBACK_MASK;
    ABC_INP1_DATA = dev->inp_data[1] = 0;
    state->pending |= PEND_IO;
}

static void abcdisk_callback_inp(struct abc_dev *dev)
{
    struct ctl_state *state = container_of(dev, struct ctl_state, iodev);

    dev->callback_mask = IDLE_CALLBACK_MASK;
    ABC_INP1_DATA = dev->inp_data[1] = 0;
    state->pending |= PEND_IO;
}

static void abcdisk_callback_cmd(struct abc_dev *dev, uint8_t data, uint8_t addr)
{
    struct ctl_state *state = container_of(dev, struct ctl_state, iodev);
    if (addr == 4)
	state->pending |= PEND_RESET;
}

static char * const disk_pfx[] = {
    "/abcdisk.800/", "/abcdisk/", "/abcdisk.", "/", NULL
};

static void init_drives(struct ctl_state *state)
{
    static bool disk_initialized;
    static int disk_init_status;
    uint32_t abc_status = ABC_STATUS;
    const char * const *pfx_list;
    int i;

    if (!disk_initialized) {
	disk_init_status = disk_init();
	disk_initialized = true;
    }

    /* .80/ or .800/ for the first entry */
    strcpy(disk_pfx[0] + 10 + !!(abc_status & ABC_STATUS_800), "0/");

    /* If any of these don't exist we simply report device not ready */
    state->drives = 0;

    if (!disk_init_status) {
	for (i = 0; i < 8; i++) {
	    struct drive_state *drv = &state->drv[i];
	    unsigned int filesec;
	    char * const *pfx;

	    snprintf(drv->name, sizeof drv->name, "%-.2s%c",
		     state->params->name, i + '0');

	    for (pfx = disk_pfx; *pfx; pfx++) {
		char filename_buf[64];
		snprintf(filename_buf, sizeof filename_buf,
			 "%s%s", *pfx, drv->name);

		if (!mount_drive(drv, state, filename_buf)) {
		    state->drives++;
		    break;
		}
	    }
	}
    }
}

static void do_next_command(struct ctl_state *state)
{
    struct drive_state *drv = cur_drv_mutable(state);
    uint8_t *buf = cur_buf(state);

    if (state->k[0] & 0x01) {
        /* READ SECTOR */
	if (!(drv->flags & DF_MOUNTED)) {
	    disk_set_error(state, DISK_NOT_READY);
	} else if (!cur_sector_valid(state)) {
	    disk_set_error(state, OUT_OF_RANGE);
	} else if (!file_pos_valid(state)) {
	    disk_set_error(state, CRC_ERROR);
	} else {
	    UINT rlen = 0;
	    FRESULT rv;

	    rv = f_lseek(&drv->file, file_pos(state));
	    if (rv == FR_OK)
		rv = f_read(&drv->file, buf, 256, &rlen);
	    if (rv != FR_OK || rlen != 256) {
		disk_set_error(state, CRC_ERROR);
	    }
	}
        state->k[0] &= ~0x01;   /* Command done */
    }
    if (state->k[0] & 0x02) {
        /* SECTOR TO HOST */
        state->k[0] &= ~0x02;   /* Command done */
	abc_setup_inp_queue(&state->iodev, buf, 256, 0x01);
        return;
    }
    if (state->k[0] & 0x04) {
        /* SECTOR FROM HOST */
        state->k[0] &= ~0x04;   /* Command done */
	abc_setup_out_queue(&state->iodev, buf, 256, 0x01);
        return;
    }
    if (state->k[0] & 0x08) {
        /* WRITE SECTOR */
	if (!(drv->flags & DF_MOUNTED)) {
	    disk_set_error(state, DISK_NOT_READY);
	} else if (drv->flags & DF_READONLY) {
	    disk_set_error(state, WRITE_PROTECT);
	} else if (!cur_sector_valid(state)) {
	    disk_set_error(state, OUT_OF_RANGE);
	} else if (!file_pos_valid(state)) {
	    disk_set_error(state, CRC_ERROR);
	} else {
	    UINT wlen = 0;
	    FRESULT rv;

	    rv = f_lseek(&drv->file, file_pos(state));
	    if (rv == FR_OK)
		rv = f_write(&drv->file, buf, 256, &wlen);
	    if (rv != FR_OK || wlen != 256)
		disk_set_error(state, WRITE_FAULT);
        }
	state->k[0] &= ~0x08;   /* Command done */
    }

#if FORMAT_SUPPORT
    /* This code needs additional work */

    if (state->k[0] & 0x10 && state->k[1] & 0x08) {
	state->out_ptr = 0;
	/* FORMAT */
	if (!drv->hf) {
	    state->error = 0x80;	/* Not ready */
	} else if (!file_wrok(hf)) {
            state->error = 0x40;	/* Write protect */
	} else {
	    unsigned int s, c0, c1, s0, s1;
	    unsigned int cylsec = state->s * state->h;
	    uint8_t data[256];
	    unsigned int fmtsec, filesec;

	    /* Sector count produced by format */
	    fmtsec = state->params->maxsectors;

	    /* For non-MO-drives, this seems to be internally generated */
	    memset(data, 0x40, 256);

	    if (state->fmtdata_in_buf) {
		/*
		 * MO drives put the sector image in the buffers, for
		 * backwards compatibility and to support single density.
		 *
		 * Right before the F7 header CRC opcode is a density byte;
		 * 00 for single, and 01 for double.  The data begins after
		 * a byte of FB.
		 */
		bool single = false;
		const uint8_t *p, *ep;

		ep = state->buf[1];
		for (p = state->buf[0]+1; p < ep; p++) {
		    if (*p == 0xf7)
			single = (p[-1] == 0);
		    if (*p == 0xfb)
			break;
		}

		fmtsec >>= single;

		if (*p++ == 0xfb) { /* Data block found */
		    if (single) {
			/* Really two 128-byte sectors! */
			memcpy(data, p, 128);
			memcpy(data+128, p, 128);
		    } else {
			memcpy(data, p, 256);
		    }
		}
	    }

	    /*
	     * Adjust the size of the accessible device to the smallest
	     * of the physical file and the formatted size
	     */
	    filesec = drv->hf->filesize >> 8;
	    drv->sectors = (filesec && filesec < fmtsec) ? filesec : fmtsec;

	    /*
	     * k2 and k3 contain the first and last cylinder numbers to
	     * format, inclusively.  The last cylinder may be partial due
	     * to virtual remapping, e.g. for sf floppies.
	     */

	    c0 = state->k[2];
	    s0 = c0 * cylsec;
	    c1 = state->k[3] + 1;
	    s1 = c1 * cylsec;

	    if (tracing(TRACE_DISK)) {
		fprintf(tracef, "%s: formatting cyl %u..%u, sectors %u..%u\n",
			drv->name, c0, c1-1, s0, s1-1);
	    }

	    clearerr(hf->f);
	    state->error = 0;

	    for (s = s0; s < s1; s++) {
		unsigned int ps = virt2phys(drv, s);
		if (ps >= drv->sectors) {
		    state->error |= 0x02; /* Track 0/Lost data? */
		    break;
		} else if (hf->map) {
		    memcpy(hf->map + (ps << 8), data, 256);
		} else {
		    fseek(hf->f, ps << 8, SEEK_SET);
		    fwrite(data, 1, 256, hf->f);
		}
	    }
	    if (ferror(hf->f))
		state->error |= 0x20; /* Write fault */
	}
	state->k[1] &= ~0x08;
    }
#endif	/* FORMAT support */

    if (!(state->k[1] & 0x38))
	state->k[0] &= ~0x10;

    disk_start_command(state);
}

#define SYNC_TIME (2*CPU_HZ)

/* Called from the main loop */
void abcdisk_io_poll(void)
{
    static uint32_t last_sync;
    uint32_t now = rdtime();
    bool need_sync = (now - last_sync) >= SYNC_TIME;
    last_sync = now;

    for (int i = 0; i < CONTROLLER_TYPES; i++) {
	struct ctl_state *state = &controllers[i];
	enum pending pending;

	mask_irq(ABC_IRQ);
	pending = state->pending;
	state->pending = 0;
	unmask_irq(ABC_IRQ);

	if (!pending)
	    continue;

	if (pending & PEND_RESET) {
	    if (state->initialized)
		disk_reset_state(state);
	}

	if (pending & PEND_IO) {
	    if (!state->initialized)
		init_drives(state);

	    do_next_command(state);
	}

	if (need_sync)
	    sync_drives(state);
    }
}

/*
 * Called during initialization. Don't initialize the SD card here;
 * it will take too long and ABC will time out claiming no drives present.
 */
void abcdisk_init(void)
{
    static const struct abc_dev iodev_template = {
	.callback_mask = IDLE_CALLBACK_MASK,
	.status_first_out_mask = (uint8_t)~0x80,
	.status_first_inp_mask = (uint8_t)~0x80,
	.callback_out = abcdisk_callback_out,
	.callback_inp = abcdisk_callback_inp,
	.callback_cmd = abcdisk_callback_cmd
    };

    for (int i = 0; i < CONTROLLER_TYPES; i++) {
	struct ctl_state *state = &controllers[i];

	state->params = &parameters[i];
	state->iodev  = iodev_template;

	disk_reset_state(state);
	abc_register(&state->iodev, state->params->devsel);
    }
}