/*
 * CHU - driver for CH375 in disk mode
 * Copyright (C) 2024 Javier S. Pedro
 *
 * 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 <https://www.gnu.org/licenses/>.
 */


#include <stdbool.h>
#include <string.h>

#include "inc/dosapi.h"
#include "inc/dosint.h"
#include "inc/bda.h"

#include "chudisk.h"
#include "ch375.h"
#include "dlog.h"
#include "cio.h"
#include "utils.h"

static int parse_int(const char far * far *s)
{
	int i = 0;
	while (**s >= '0' && **s <= '9') {
		i = (i * 10) + (**s - '0');
		(*s)++;
	}
	if (**s == ' ' || **s == '\r' || **s == '\n') {
		return i;
	} else {
		return -1;
	}
}

static int parse_hex(const char far * far *s)
{
	int i = 0;
	while ((**s >= '0' && **s <= '9') || (**s >= 'A' && **s <= 'F') || (**s >= 'a' && **s <= 'f')) {
		if      (**s >= '0' && **s <= '9') i = (i * 16) + (**s - '0');
		else if (**s >= 'A' && **s <= 'F') i = (i * 16) + (**s - 'A');
		else if (**s >= 'a' && **s <= 'f') i = (i * 16) + (**s - 'a');
		(*s)++;
	}
	if (**s == ' ' || **s == '\r' || **s == '\n') {
		return i;
	} else {
		return -1;
	}
}

static bool parse_cmdline(const char far *cmdline)
{
	// Source command line string
	// E.g. DEVICE.SYS /N3\r\n
	const char far *s = cmdline;

	// Skip filename part (search for first sep)
	while (*s != ' ' && *s != '\r' && *s != '\n') { s++; }
	if (*s == '\r' || *s == '\n') return true; // No arguments
	// Now skip whitespace
	while (*s == ' ') { s++; }

	// Now handle options like /N3 /X4
	while (*s != '\r' && *s != '\n') {
		char c = *s++, opt;
		int num;
		switch (c) {
		case '/':
			opt = *s++;
			switch (opt) {
			case 'N':
			case 'n': // number of units
				num = parse_int(&s);
				if (num > 0 && num <= MAX_UNITS) {
					num_units = num;
				} else {
					c_printf("invalid value '%d' for option '%c'\n", num, opt);
					return false;
				}
				break;
			case 'P':
			case 'p': // IO port
				num = parse_hex(&s);
				if (num > 0) {
					ch375_port = num;
				} else {
					c_printf("invalid value '%d' for option '%c'\n", num, opt);
					return false;
				}
				break;
			case 'R':
			case 'r': // Read only
				read_only = true;
				break;
			case '3': // Show FAT32 partitions
				show_fat32 = true;
				break;
			default:
				c_printf("invalid option '%c'\n", opt);
				return false;
			}
			break;
		case ' ':
			break;
		default:
			c_printf("invalid syntax '%c'\n", c);
			return false;
		}
	}

	dprintf("Configured num drives: %hu\n", num_units);

	return true;
}

static void fill_initial_bpb(DOS_BPB *bpb)
{
	// Dummy, only used during driver init
	// Most likely these values can be anything you want,
	// as long as it remotely looks like a valid FAT16 BPB
	bpb->bytesPerSector = 512;
	bpb->sectorsPerCluster = 1;
	bpb->reservedSectors = 0;
	bpb->numberOfFATs = 2;
	bpb->rootDirEntries = 16;
	bpb->numberOfSectors = 512;
	bpb->mediaType = DOS_BPB_MEDIA_HDD;
	bpb->sectorsPerFAT = 1;
	bpb->sectorsPerTrack = 63;
	bpb->numberOfHeads = 255;
	bpb->hiddenSectors = 0;
	bpb->numberOfSectorsLarge = 0;
	memcpy(bpb->fat16.volumeLabel, "NO NAME    ", 11);
}

void driver_init(DOS_DRS __far *drs)
{
	unsigned i;
	uint16_t dos_version;
	uint8_t dos_major, dos_minor;
	uint8_t hw_version;

	dlog_init();

	// Defaults
	ch375_port = 0x260;
	num_units = 1;
	read_only = false;
	show_fat32 = false;

	// If DOS > 7.1, enable FAT32 by default
	dos_version = dos_get_version();
	dos_major = dos_version & 0xFF;
	dos_minor = (dos_version >> 8) & 0xFF;
	dprintf("DOS version %d.%d\n", dos_major, dos_minor);
	if (dos_major > 7 || (dos_major == 7 && dos_minor >= 10)) {
		show_fat32 = true;
	}

	// Parse command line arguments
	if (!parse_cmdline(drs->cmd.init.in.cmdline)) {
		c_puts("CHUDISK: Syntax error in cmdline arguments");
		goto fail;
	}

	// Try to initialize CH375
	dputs("CH375 reset...");
	ch375_reset();
	bda_wait_ticks(3); // wait 100-150ms
	dputs("CH375 reset wait done");

	if (ch375_check_exists(0xA5) != (uint8_t)~0xA5) {
		c_printf("CHUDISK: CH375 not detected at @%x", ch375_port);
		goto fail;
	}

	hw_version = ch375_get_version();

	// Do not really set up the chip until it is used
	ch375_set_usb_mode(CH375_USB_MODE_HOST_DISABLED);
	ch375_enter_sleep();

	data.ready = false;
	data.sectors = 0;
	data.bytesPerSector = 0;

	// Build the template BPBs
	drs->cmd.init.out.number_units = num_units;
	for (i = 0; i < num_units; i++) {
		fill_initial_bpb(&data.unit[i].bpb);
		data.bpb_ptrs[i] = &data.unit[i].bpb;
	}
	drs->cmd.init.out.bpbs = data.bpb_ptrs;
	drs->cmd.init.out.break_addr = MK_FP(get_cs(), FP_OFF(&resident_end));
	drs->status = DOS_DD_STATUS_DONE;

	c_printf("CHUDISK v.0 (HW v.%x), drives", hw_version);
	for (i = 0; i < num_units; i++) {
		c_printf(" %c:", drive_index_to_letter(drs->cmd.init.in.first_drive_number + i));
	}
	c_putc('\n');

	return;
fail:
	drs->status = DOS_DD_STATUS_DONE | DOS_DD_STATUS_ERROR | DOS_DD_ERR_GENERAL_FAILURE;
	drs->cmd.init.out.number_units = 0;
	drs->cmd.init.out.break_addr = MK_FP(get_cs(), 0); // Deallocate everything
	return;
}