/*
 * JR-IDE Project
 * - (c) 2017 Alan Hightower
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "pimount.h"

#pragma data_seg("_TEXT", "CODE");
#pragma code_seg("_TEXT", "CODE");

extern uint16_t get_ds (void);
#pragma aux get_ds = \
    "mov ax,ds" \
    value [ax];

typedef int (*_handler)(void);

ctx_t ctx;  // Operational context block - resident

static union INTPACK far *r;    // saved register file from 2Fh entry


// Resident helper functions

static void _fmemcpy_local (void far *dst, const void far *src, size_t num)
{
	// fastest implementation so far using rep movsw
	
	__asm
	{
		push es;
		push ds;
		push si;
		push di;

		mov cx, num;
		les di, dst;
		lds si, src;

		shr cx,1;
		rep movsw;

		adc cx,cx;
		rep movsb;

		pop di;
		pop si;
		pop ds;
		pop es;
	}

	return;
}


static int _success (void)
{
	r->w.ax     = DOS_SUCCESS;
	r->w.flags &= ~INTR_CF;

	return 0;
}


// ***** Function 00h *****
static int _installation_check (void)
{
	r->w.ax = 0x00ff;  // installed - generic redirector (PC Tools v8 DRIVEMAP)
	r->w.flags &= ~INTR_CF;

	return 0;
}


// ***** Function 05h *****
static int _chdir (void)
{
	redir_stat_t *arg = (redir_stat_t *) ctx.scratch;

	_fmemcpy_local (MK_FP(get_ds(), arg->filename_a), ctx.filename1, 128);

	arg->filename_a_nul = '\0';
	arg->statop  = REDIR_STAT_ATTR;
	arg->driveno = ctx.sdb->driveno;

	_redir_push (REDIR_FEAT_STAT_PUSH);
	_redir_pull (REDIR_FEAT_STAT_PULL);

	if (arg->found && (arg->attrib & 0x10))
		return _success();

	r->w.ax = DOS_PATHNOTFND;

	return 0;
}


// ***** Function 0Ch *****
static int _get_diskinfo (void)
{
	redir_info_t *info = (redir_info_t *) ctx.scratch;
	dlist_t far *drive = (dlist_t far *) MK_FP(r->w.es, r->w.di);

	if (drive->magic != PIMOUNT_MAGIC)
		return -1;

	if (_redir_pull (REDIR_FEAT_GET_STATUS))
		return -1;

	r->w.ax = info->sector_per_cluster;
	r->w.cx = info->bytes_per_sector;
	r->w.bx = info->total_clusters;
	r->w.dx = info->avail_clusters;
	r->w.flags &= ~INTR_CF;

	return 0;
}


// ***** Function 1Ch *****
static int _find_next (void)
{
	redir_nextdir_t *next = (redir_nextdir_t *) ctx.scratch;
	redir_dentry_t *entry;

	int i;

	if ((ctx.sdb->driveno & 0x40) == 0x00)
		return 0;

	do
	{
		// Check cache(scratch) validity
		if (ctx.prev_pull != REDIR_FEAT_DIR_NEXT)
			break;

		if (next->index == NEXT_DENTRIES)
			_redir_pull (REDIR_FEAT_DIR_NEXT);

		entry = &next->entry[next->index];

		if (entry->filename[0] == '\0')
			break; // end of list

		ctx.sdb->entryno = next->start + next->index;

		ctx.fdb->attr  = entry->attrib;
		ctx.fdb->mtime = entry->dos_time;
		ctx.fdb->mdate = entry->dos_date;
		ctx.fdb->size  = entry->size;

		for (i = 0; i < 11; i++)
			ctx.fdb->name[i] = entry->filename[i];

		next->index++;

		return _success();

	} while (0);

	// error

	r->w.ax = DOS_NFILES;

	return 0;
}


// ***** Function 1Bh *****
static int _find_first (void)
{
	uint8_t attrmask = ctx.sda[0x24d];

	redir_opendir_t *arg = (redir_opendir_t *) ctx.scratch;

	if (attrmask == _A_VOLID) // Volume Label
	{
		ctx.sdb->driveno = ctx.driveno | 0x80;
		ctx.sdb->entryno = 0;
		_fmemcpy_local (ctx.sdb->search_mask, ctx.fcbname1, 11);
		
		ctx.fdb->attr  = _A_VOLID;
		ctx.fdb->mtime = 0;
		ctx.fdb->mdate = 0;
		ctx.fdb->size  = 0;

		ctx.fdb->name[0]  = 'J';
		ctx.fdb->name[1]  = 'R';
		ctx.fdb->name[2]  = '-';
		ctx.fdb->name[3]  = 'I';
		ctx.fdb->name[4]  = 'D';
		ctx.fdb->name[5]  = 'E';
		ctx.fdb->name[6]  = '_';
		ctx.fdb->name[7]  = 'R';
		ctx.fdb->name[8]  = 'P';
		ctx.fdb->name[9]  = 'I';
		ctx.fdb->name[10] = 'Z';

		return _success ();
	}

	_fmemcpy_local (MK_FP(get_ds(), arg->filename), ctx.filename1, 128);
	_fmemcpy_local (MK_FP(get_ds(), arg->mask), ctx.sdb->search_mask, 11);

	arg->filename_nul = '\0';
	arg->mask_nul = '\0';

	arg->driveno  = ctx.sdb->driveno;
	arg->attrib_a = attrmask;
	arg->attrib_b = ctx.sdb->attr_mask;

	_redir_push (REDIR_FEAT_DIR_FIRST);

	_fmemcpy_local (ctx.sdb->search_mask, ctx.fcbname1, 11);
	ctx.sdb->driveno   = ctx.driveno | 0xc0;
	ctx.sdb->attr_mask = attrmask;
	ctx.sdb->entryno   = 0;

	_redir_pull (REDIR_FEAT_DIR_NEXT);

	return _find_next ();
}


// Local (resident) clone of _chain_intr() from
//   ./owc/src/bld/clib/intel/a/chint086.asm
void _chain_prev (void (__interrupt __far *)(void));
#pragma aux _chain_prev = \
	"mov    cx, ax" \
	"mov    ax, dx" \
	"mov    sp, bp" \
	"xchg   cx, 20[bp]" \
	"xchg   ax, 22[bp]" \
	"pop    dx" \
	"pop    dx" \
	"pop    es" \
	"pop    ds" \
	"pop    di" \
	"pop    si" \
	"pop    bp" \
	"pop    bx" \
	"pop    bx" \
	"pop    dx" \
	"retf" \
	parm [dx ax] \
	modify [];


// From Ralf's List
static const _handler dispatchTable[] = {
	_installation_check,       // 00 : Installation Check
	NULL,                      // 01 : Remove Directory
	NULL,                      // 02 :
	NULL,                      // 03 : Make Directory
	NULL,                      // 04 :
	_chdir,                    // 05 : Change Directory
	NULL,                      // 06 : Close File
	_success,                  // 07 : Commit File
	NULL,                      // 08 : Read from File
	NULL,                      // 09 : Write to File
	_success,                  // 0a : Lock Region
	_success,                  // 0b : Unlock Region
	_get_diskinfo,             // 0c : Get Disk Information
	NULL,                      // 0d :
	_success,                  // 0e : Set File Attributes
	NULL,//_get_file_attrib,          // 0f : Get File Attributes and Size
	NULL,                      // 10 :
	NULL,                      // 11 : Rename File
	NULL,                      // 12 :
	NULL,                      // 13 : Delete File
	NULL,                      // 14 :
	NULL,                      // 15 :
	NULL,                      // 16 : Open Existing File
	NULL,                      // 17 : Create/Truncate File
	NULL,                      // 18 :    Create/Truncate File w/o CDS
	NULL,                      // 19 :    Find First File w/o CDS
	NULL,                      // 1a :
	_find_first,               // 1b : Find First File
	_find_next,                // 1c : Find Next File
	NULL,                      // 1d :    Close all Files for Process
	NULL,                      // 1e :    Do Redirection
	NULL,                      // 1f :    Printer Setup
	NULL,                      // 20 : Flush All Disk Buffers
	NULL,                      // 21 : Seek from end of File
	NULL,                      // 22 :    Process Termination Hook
	NULL,                      // 23 :    Qualify Remote File Name
	NULL,                      // 24 :    Turn Off Printer
	NULL,                      // 25 :    Redirected Printer Mode
	NULL,                      // 26 :    Remote Printer Echo On/Off
	NULL,                      // 27 :
	NULL,                      // 28 :
	NULL,                      // 29 :
	NULL,                      // 2a :
	NULL,                      // 2b :
	NULL,                      // 2c :    Update CB
	NULL,                      // 2d :
	NULL                       // 2e : Extended Open/Create File
};

#define MAX_FUNCTION (int) (sizeof (dispatchTable) / sizeof (dispatchTable[0]))


static int _redirect_chain (uint8_t function)
{
//	dlist_t far *sda_drive;

	if (function == 0)
		return 0;
#if 0
	sda_drive = (dlist_t far *) FPDRF(ctx.sda + 0x282);

	if (sda_drive->magic != PIMOUNT_MAGIC)
		return 1;

	if ((ctx.sdb->driveno & 0x1f) != ctx.driveno)
		return 1;

#endif

	return 0;
}


void __interrupt redirector (union INTPACK regset)
{
	_asm
	{
		push cs
		pop ds
	}

	do
	{
		static _handler dispatch;

		if ((regset.h.ah != 0x11) || (regset.h.al >= MAX_FUNCTION))
			break;

		if (!(dispatch = dispatchTable[regset.h.al]))
			break;

		if (_redirect_chain(regset.h.al))
			break;

		r = &regset;

		// assume failure

		regset.w.ax = DOS_INVALID_FUNC;
		regset.w.flags |= INTR_CF;

		if (dispatch ())
			break;

		return;

	} while (0);

	_chain_prev (ctx.prev_handler);

	return;
}


// ***** End of RESIDENT segment *****

uint16_t _get_resident_psize (void)
{
	uint16_t bytes;

	bytes  = (uint16_t) _get_resident_psize;
	bytes += 15;        // round up to paragraph (16 bytes) size

	return bytes >> 4;
}