/*
 * blkio_usb.c — USB Mass Storage (Bulk-Only Transport) blkio_dev backend,
 * see blkio_usb.h. Milestone 2h.
 */

#ifndef __STARKERNEL__
#error "blkio_usb.c is kernel-only"
#endif

#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include "starkernel/blkio_usb.h"
#include "console.h"

typedef struct {
    xhci_dev_t *xdev;
    uint32_t    slot_id;
    uint32_t    scsi_block_size;
    uint32_t    scsi_blocks_per_fblock; /* BLKIO_FORTH_BLOCK_SIZE / scsi_block_size */
    uint32_t    total_forth_blocks;
} BlkioUsbState;

/* Singleton — one USB MSC device (single-outstanding-transaction scope,
 * matching the xHCI driver this backend sits on). */
static BlkioUsbState g_usb_blk;

static int usb_blk_open(blkio_dev_t *dev, const blkio_params_t *p) {
    (void)p;
    if (!dev) return BLKIO_EINVAL;
    dev->state            = &g_usb_blk;
    dev->forth_block_size = BLKIO_FORTH_BLOCK_SIZE;
    dev->total_blocks     = g_usb_blk.total_forth_blocks;
    return BLKIO_OK;
}

static int usb_blk_close(blkio_dev_t *dev) {
    (void)dev;
    return BLKIO_OK;
}

static int usb_blk_read(blkio_dev_t *dev, uint32_t fblock, void *dst) {
    if (!dev || !dst) return BLKIO_EINVAL;
    BlkioUsbState *s = (BlkioUsbState *)dev->state;
    if (fblock >= s->total_forth_blocks) return BLKIO_EINVAL;

    uint32_t lba = fblock * s->scsi_blocks_per_fblock;
    if (xhci_bot_read_block(s->xdev, s->slot_id, lba,
                             (uint16_t)s->scsi_blocks_per_fblock,
                             s->scsi_block_size) != 0) {
        return BLKIO_EIO;
    }
    if (xhci_bot_wait_for_idle(s->xdev, 100000u) != BOT_STATUS_PASS) {
        return BLKIO_EIO;
    }
    memcpy(dst, s->xdev->bot_data_buf, BLKIO_FORTH_BLOCK_SIZE);
    return BLKIO_OK;
}

static int usb_blk_write(blkio_dev_t *dev, uint32_t fblock, const void *src) {
    if (!dev || !src) return BLKIO_EINVAL;
    BlkioUsbState *s = (BlkioUsbState *)dev->state;
    if (fblock >= s->total_forth_blocks) return BLKIO_EINVAL;

    memcpy(s->xdev->bot_data_buf, src, BLKIO_FORTH_BLOCK_SIZE);

    uint32_t lba = fblock * s->scsi_blocks_per_fblock;
    if (xhci_bot_write_block(s->xdev, s->slot_id, lba,
                              (uint16_t)s->scsi_blocks_per_fblock,
                              s->scsi_block_size) != 0) {
        return BLKIO_EIO;
    }
    if (xhci_bot_wait_for_idle(s->xdev, 100000u) != BOT_STATUS_PASS) {
        return BLKIO_EIO;
    }
    return BLKIO_OK;
}

static int usb_blk_flush(blkio_dev_t *dev) {
    (void)dev;
    return BLKIO_OK; /* every write above is already synchronous -- see
                       * usb_blk_write()'s own xhci_bot_wait_for_idle()
                       * call -- nothing buffered here to flush. */
}

static int usb_blk_info(blkio_dev_t *dev, blkio_info_t *out) {
    if (!dev || !out) return BLKIO_EINVAL;
    BlkioUsbState *s = (BlkioUsbState *)dev->state;
    out->forth_block_size = BLKIO_FORTH_BLOCK_SIZE;
    out->total_blocks     = s->total_forth_blocks;
    out->phys_sector_size = s->scsi_block_size;
    out->phys_size_bytes  = (uint64_t)s->total_forth_blocks * BLKIO_FORTH_BLOCK_SIZE;
    out->read_only        = 0; /* WRITE(10) verified live end-to-end on amd64,
                                 * 2026-08-28 (FABRIC-2.md §F.1): BLK-CONFIRM-FORMAT's
                                 * BAM/reloc writes and an explicit content write both
                                 * survived a cold reboot and read back correctly. */
    return BLKIO_OK;
}

static const blkio_vtable_t g_usb_blk_vtable = {
    .open  = usb_blk_open,
    .close = usb_blk_close,
    .read  = usb_blk_read,
    .write = usb_blk_write,
    .flush = usb_blk_flush,
    .info  = usb_blk_info
};

int blkio_usb_open_msc(blkio_dev_t *dev_out, xhci_dev_t *xdev, uint32_t slot_id) {
    if (!dev_out || !xdev) return -1;

    if (xhci_bot_get_capacity(xdev, slot_id) != 0) return -1;
    if (xhci_bot_wait_for_idle(xdev, 100000u) != BOT_STATUS_PASS) return -1;

    uint32_t block_size = xdev->bot_cap_block_size;
    if (block_size == 0 || (BLKIO_FORTH_BLOCK_SIZE % block_size) != 0) {
        console_println("blkio_usb: SCSI block size doesn't divide Forth block size -- refusing");
        return -2;
    }

    uint64_t total_scsi_blocks = (uint64_t)xdev->bot_cap_last_lba + 1u;
    uint32_t blocks_per_fblock = BLKIO_FORTH_BLOCK_SIZE / block_size;
    uint64_t total_forth_blocks = total_scsi_blocks / blocks_per_fblock;

    g_usb_blk.xdev = xdev;
    g_usb_blk.slot_id = slot_id;
    g_usb_blk.scsi_block_size = block_size;
    g_usb_blk.scsi_blocks_per_fblock = blocks_per_fblock;
    g_usb_blk.total_forth_blocks = (total_forth_blocks > 0xFFFFFFFFull)
                                    ? 0xFFFFFFFFu
                                    : (uint32_t)total_forth_blocks;

    console_println("blkio_usb: MSC device ready");

    blkio_params_t params;
    params.forth_block_size = BLKIO_FORTH_BLOCK_SIZE;
    params.total_blocks     = g_usb_blk.total_forth_blocks;
    params.opaque           = NULL;

    return blkio_open(dev_out, &g_usb_blk_vtable, &params);
}