// SPDX-License-Identifier: ISC
// database impl
#include "y16t_db.h"
#include "y16t_internal.h"
#include "y16t_idx.h"

#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

typedef struct {
	int fd;
} y16t_db_actx_t;

__attribute__((pure)) static off_t
y16t_db_offstr(const uint32_t offset) { return ((off_t)offset) << 12; }

__attribute__((pure)) static uint32_t
y16t_db_unoffstr(const off_t x)       { return x >> 12; }

__attribute__((nonnull))
static uint32_t y16t_db_palloc(void * context_)
{
	y16t_db_actx_t *context = context_;
	const int fd = context->fd;
	const off_t eoffs_orig = lseek(fd, 0, SEEK_END);
	if(eoffs_orig == -1) return 0;
	const off_t eoffs = (eoffs_orig >= (1 << 18)) ? eoffs_orig : (1 << 18);
	return (-1 == ftruncate(fd, eoffs + (1 << 18)))
		? 0
		: y16t_db_unoffstr(eoffs);
}

__attribute__((nonnull))
static uint32_t y16t_db_palloc2(void * context_)
{
	y16t_db_actx_t *context = context_;
	const int fd = context->fd;
	const off_t eoffs = lseek(fd, 0, SEEK_END);
	if(eoffs == -1) return 0;
	return (-1 == ftruncate(fd, eoffs + y16t_db_offstr(1)))
		? 0
		: y16t_db_unoffstr(eoffs);
}

// @param bufexp must point to 44 valid bytes
__attribute__((nonnull))
static int y16t_db_intern_pgsearch(
	const int fd,
	off_t start_offset,
	uint8_t bufexp[],
	uint32_t *i_
) {
	uint8_t buf[4096] = {0};
	const uint8_t zeros[44] = {0};
	ssize_t tmp = y16t_pread_all(fd, buf, sizeof(buf), start_offset);
	if(tmp < 0) return (int)tmp;

	*i_ = 0;
	uint32_t i;
	for(i = 0; i < sizeof(buf); i += 44) {
		if(memcmp(&buf[i], zeros, 44) == 0)
			break;
		if(memcmp(&buf[i], bufexp, 44) == 0) {
			*i_ = i;
			return 1;
		}
	}
	*i_ = i;
	return 0;
}

// inserts a database entry
// x, y, z should point to arrays of 16 bytes each
int y16t_db_insert(
	y16t_db_t db,
	const uint8_t *x,
	const uint8_t *y,
	const uint8_t *z
) {
	// first table
	uint32_t offset = 0;
	int tmp = 0;
	y16t_db_actx_t actx = { db };
	{
		const y16t_idx_t idx = { db, 0 };
		tmp = y16t_idx_get_or_insert(
			idx, x[0], y[0], &offset,
			y16t_db_palloc, (void*)&actx
		);
		if(tmp < 0) return tmp;
	}

	// second table
	{
		const y16t_idx_t idx = { db, offset };
		tmp = y16t_idx_get_or_insert(
			idx, x[1], y[1], &offset,
			y16t_db_palloc2, (void*)&actx
		);
		if(tmp < 0) return tmp;
	}

	// prepare entry
	uint8_t bufexp[44];
	memcpy(bufexp,      &x[2], 14);
	memcpy(bufexp + 14, &y[2], 14);
	memcpy(bufexp + 28, &z,    16);

	// sequential data, read complete page
	const off_t start_offset = y16t_db_offstr(offset);
	uint32_t i;
	tmp = y16t_db_intern_pgsearch(db, start_offset, bufexp, &i);
	switch(tmp) {
	  case 1:
		return 0;
	  case 0:
		if(i >= 4052) return -ENOMEM;
		return y16t_pwrite_all(db, bufexp, sizeof(bufexp), start_offset + i);
	  default:
		return tmp;
	}
}

// lookup a database entry
// @return 1 means found, 0 means not found, negative is a negated errno value
// x, y, z should point to arrays of 16 bytes each
int y16t_db_lookup(
	y16t_db_t db,
	const uint8_t *x,
	const uint8_t *y,
	const uint8_t *z
) {
	uint32_t offset = 0;
	int tmp = 0;

	// first table
	y16t_idx_t idx = { db, 0 };
	tmp = y16t_idx_lookup(idx, x[0], y[0], &offset);
	if(tmp < 0) return tmp;
	if(!offset) return 0;

	// second table
	idx.offset = offset;
	tmp = y16t_idx_lookup(idx, x[1], y[1], &offset);
	if(tmp < 0) return tmp;
	if(!offset) return 0;

	// prepare entry
	uint8_t bufexp[44];
	memcpy(bufexp,      &x[2], 14);
	memcpy(bufexp + 14, &y[2], 14);
	memcpy(bufexp + 28, &z,    16);

	// sequential data, read complete page
	uint32_t i;
	return y16t_db_intern_pgsearch(db, y16t_db_offstr(offset), bufexp, &i);
}

// iterate over the database
typedef struct {
	y16t_db_t db;
	const uint8_t *xy;
	int (*callback)(const uint8_t*, const uint8_t*, void*);
	void *context;
} y16t_db_fectx_t;

static int y16t_db_foreach_x3(uint32_t offset, void *context_)
{
	if(!offset) return 0;
	const y16t_db_fectx_t *context = context_;

	// sequential data, read complete page
	uint8_t buf[4096] = {0};
	const uint8_t zeros[44] = {0};
	const off_t start_offset = y16t_db_offstr(offset);
	ssize_t tmp = y16t_pread_all(context->db, buf, sizeof(buf), start_offset);
	if(tmp < 0) return (int)tmp;

	uint32_t i;
	const uint8_t *xyrest = &context->xy[2];
	for(i = 0; i < sizeof(buf); i += 44) {
		if(memcmp(&buf[i], zeros, 44) == 0)
			break;
		if(memcmp(&buf[i + 14], xyrest, 14) == 0) {
			const int tmp2 = context->callback(&buf[i], &buf[i + 28], context->context);
			if(tmp2) return tmp2;
		}
	}
	return 0;
}

static int y16t_db_foreach_y3(uint32_t offset, void *context_)
{
	if(!offset) return 0;
	const y16t_db_fectx_t *context = context_;

	// sequential data, read complete page
	uint8_t buf[4096] = {0};
	const uint8_t zeros[44] = {0};
	const off_t start_offset = y16t_db_offstr(offset);
	ssize_t tmp = y16t_pread_all(context->db, buf, sizeof(buf), start_offset);
	if(tmp < 0) return (int)tmp;

	uint32_t i;
	const uint8_t *xyrest = &context->xy[2];
	for(i = 0; i < sizeof(buf); i += 44) {
		if(memcmp(&buf[i], zeros, 44) == 0)
			break;
		if(memcmp(&buf[i], xyrest, 14) == 0) {
			const int tmp2 = context->callback(&buf[i + 14], &buf[i + 28], context->context);
			if(tmp2) return tmp2;
		}
	}
	return 0;
}

static int y16t_db_foreach_x2(uint32_t offset, void *context_) {
	const y16t_db_fectx_t *context = context_;
	if(!offset) return 0;
	const y16t_idx_t idx = { context->db, offset };
	return y16t_idx_foreach_x(idx, context->xy[1],
		y16t_db_foreach_x3, context_);
}

static int y16t_db_foreach_y2(uint32_t offset, void *context_) {
	const y16t_db_fectx_t *context = context_;
	if(!offset) return 0;
	const y16t_idx_t idx = { context->db, offset };
	return y16t_idx_foreach_y(idx, context->xy[1],
		y16t_db_foreach_y3, context_);
}

int y16t_db_foreach_x(
	y16t_db_t db, const uint8_t *y,
	int (*callback)(const uint8_t*, const uint8_t*, void*),
	void *context
) {
	y16t_db_fectx_t fectx = { db, y, callback, context };
	const y16t_idx_t idx = { db, 0 };
	return y16t_idx_foreach_x(idx, y[0], y16t_db_foreach_x2, (void*) &fectx);
}

int y16t_db_foreach_y(
	y16t_db_t db, const uint8_t *x,
	int (*callback)(const uint8_t*, const uint8_t*, void*),
	void *context
) {
	y16t_db_fectx_t fectx = { db, x, callback, context };
	const y16t_idx_t idx = { db, 0 };
	return y16t_idx_foreach_y(idx, x[0], y16t_db_foreach_y2, (void*) &fectx);
}