#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
#include <errno.h>
#include <sys/mman.h>
#include "flash.h"
#include "linuxbios_tables.h"
#include "debug.h"

char *lb_part=NULL, *lb_vendor=NULL;

static unsigned long compute_checksum(void *addr, unsigned long length)
{
	uint8_t *ptr;
	volatile union {
		uint8_t  byte[2];
		uint16_t word;
	} value;
	unsigned long sum;
	unsigned long i;
	/* In the most straight forward way possible,
	 * compute an ip style checksum.
	 */
	sum = 0;
	ptr = addr;
	for(i = 0; i < length; i++) {
		unsigned long value;
		value = ptr[i];
		if (i & 1) {
			value <<= 8;
		}
		/* Add the new value */
		sum += value;
		/* Wrap around the carry */
		if (sum > 0xFFFF) {
			sum = (sum + (sum >> 16)) & 0xFFFF;
		}
	}
	value.byte[0] = sum & 0xff;
	value.byte[1] = (sum >> 8) & 0xff;
	return (~value.word) & 0xFFFF;
}

#define for_each_lbrec(head, rec) \
	for(rec = (struct lb_record *)(((char *)head) + sizeof(*head)); \
		(((char *)rec) < (((char *)head) + sizeof(*head) + head->table_bytes))  && \
		(rec->size >= 1) && \
		((((char *)rec) + rec->size) <= (((char *)head) + sizeof(*head) + head->table_bytes)); \
		rec = (struct lb_record *)(((char *)rec) + rec->size)) 
		

static int  count_lb_records(struct lb_header *head)
{
	struct lb_record *rec;
	int count;
	count = 0;
	for_each_lbrec(head, rec) {
		count++;
	}
	return count;
}


static struct lb_header *find_lb_table(void *base, unsigned long start, unsigned long end)
{
	unsigned long addr;
	/* For now be stupid.... */
	for(addr = start; addr < end; addr += 16) {
		struct lb_header *head = (struct lb_header *)(((char*)base) + addr);
		struct lb_record *recs = (struct lb_record *)(((char*)base) + addr + sizeof(*head));
		if (memcmp(head->signature, "LBIO", 4) != 0)
			continue;
		printf_debug( "Found canidate at: %08lx-%08lx\n", 
			addr, addr + head->table_bytes);
		if (head->header_bytes != sizeof(*head)) {
			fprintf(stderr, "Header bytes of %d are incorrect\n",
				head->header_bytes);
			continue;
		}
		if (count_lb_records(head) != head->table_entries) {
			fprintf(stderr, "bad record count: %d\n",
				head->table_entries);
			continue;
		}
		if (compute_checksum((uint8_t *)head, sizeof(*head)) != 0) {
			fprintf(stderr, "bad header checksum\n");
			continue;
		}
		if (compute_checksum(recs, head->table_bytes)
			!= head->table_checksum) {
			fprintf(stderr, "bad table checksum: %04x\n",
				head->table_checksum);
			continue;
		}
		fprintf(stdout, "Found LinuxBIOS table at: %08lx\n", addr);
		return head;

	};
	return 0;
}

static void find_mainboard(struct lb_record *ptr, unsigned long addr)
{
	struct lb_mainboard *rec;
	int max_size;
	char vendor[256], part[256];
	rec = (struct lb_mainboard *)ptr;
	max_size = rec->size - sizeof(*rec);
	printf("vendor id: %.*s part id: %.*s\n",
		max_size - rec->vendor_idx, 
		rec->strings + rec->vendor_idx, 
		max_size - rec->part_number_idx, 
		rec->strings + rec->part_number_idx);
	snprintf(vendor, 255, "%.*s", max_size - rec->vendor_idx, 
			rec->strings + rec->vendor_idx);
	snprintf(part, 255, "%.*s", max_size - rec->part_number_idx,
			rec->strings + rec->part_number_idx);

	if(lb_part) {
		printf("overwritten by command line, vendor id: %s part id: %s\n",
				lb_vendor, lb_part);
	} else {
		lb_part=strdup(part);
		lb_vendor=strdup(vendor);
	}
}

static struct lb_record *next_record(struct lb_record *rec)
{
	return (struct lb_record *)(((char *)rec) + rec->size);
}

static void search_lb_records(struct lb_record *rec, struct lb_record *last, 
	unsigned long addr)
{
	struct lb_record *next;
	int count;
	count = 0;

	for(next = next_record(rec); (rec < last) && (next <= last); 
		rec = next, addr += rec->size) { 
		next = next_record(rec);
		count++;
		if(rec->tag == LB_TAG_MAINBOARD) {
			find_mainboard(rec,addr);
			break;
		}
	}
}

int linuxbios_init(void) 
{
	uint8_t *low_1MB;
	struct lb_header *lb_table;
	struct lb_record *rec, *last;
	
	int fd;
	fd = open(MEM_DEV, O_RDONLY);
	if (fd < 0) {
		fprintf(stderr, "Can not access memory using " MEM_DEV "\n");
		exit(-1);
	}
	low_1MB = mmap(0, 1024*1024, PROT_READ, MAP_SHARED, fd, 0x00000000);
	if (low_1MB == ((void *) -1)) {
		fprintf(stderr, "Can not mmap " MEM_DEV " at %08lx errno(%d):%s\n",
			0x00000000UL, errno, strerror(errno));
		exit(-2);
	}
	lb_table = 0;
	if (!lb_table)
		lb_table = find_lb_table(low_1MB, 0x00000, 0x1000);
	if (!lb_table)
		lb_table = find_lb_table(low_1MB, 0xf0000, 1024*1024);
	if (lb_table) {
		unsigned long addr;
		addr = ((char *)lb_table) - ((char *)low_1MB);
		printf_debug("lb_table found at address %p\n", lb_table);
		rec  = (struct lb_record *)(((char *)lb_table) + lb_table->header_bytes);
		last = (struct lb_record *)(((char *)rec) + lb_table->table_bytes);
		printf_debug("LinuxBIOS header(%d) checksum: %04x table(%d) checksum: %04x entries: %d\n",
		lb_table->header_bytes, lb_table->header_checksum,
		lb_table->table_bytes, lb_table->table_checksum, lb_table->table_entries);
		search_lb_records(rec, last, addr + lb_table->header_bytes);
	}
	else {
		printf("No LinuxBIOS table found.\n");
		return -1;
	}
	return 0;
}