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/*	$OpenBSD: json.c,v 1.4 2023/06/22 09:08:02 claudio Exp $ */

/*
 * Copyright (c) 2020 Claudio Jeker <claudio@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <ctype.h>
#include <err.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "json.h"

#define JSON_MAX_STACK	16

enum json_type {
	NONE,
	START,
	ARRAY,
	OBJECT
};

static struct json_stack {
	const char	*name;
	unsigned int	count;
	int		compact;
	enum json_type	type;
} stack[JSON_MAX_STACK];

static char indent[JSON_MAX_STACK + 1];
static int level;
static int eb;
static FILE *jsonfh;

static void
do_comma_indent(void)
{
	char sp = '\n';

	if (stack[level].compact)
		sp = ' ';

	if (stack[level].count++ > 0) {
		if (!eb)
			eb = fprintf(jsonfh, ",%c", sp) < 0;
	}

	if (stack[level].compact)
		return;
	if (!eb)
		eb = fprintf(jsonfh, "\t%.*s", level, indent) < 0;
}

static void
do_name(const char *name)
{
	if (stack[level].type == ARRAY)
		return;
	if (!eb)
		eb = fprintf(jsonfh, "\"%s\": ", name) < 0;
}

static int
do_find(enum json_type type, const char *name)
{
	int i;

	for (i = level; i > 0; i--)
		if (type == stack[i].type &&
		    strcmp(name, stack[i].name) == 0)
			return i;

	/* not found */
	return -1;
}

void
json_do_start(FILE *fh)
{
	memset(indent, '\t', JSON_MAX_STACK);
	memset(stack, 0, sizeof(stack));
	level = 0;
	stack[level].type = START;
	jsonfh = fh;
	eb = 0;

	eb = fprintf(jsonfh, "{\n") < 0;
}

int
json_do_finish(void)
{
	while (level > 0)
		json_do_end();
	if (!eb)
		eb = fprintf(jsonfh, "\n}\n") < 0;

	return -eb;
}

void
json_do_array(const char *name)
{
	int i, l;
	char sp = '\n';

	if ((l = do_find(ARRAY, name)) > 0) {
		/* array already in use, close element and move on */
		for (i = level - l; i > 0; i--)
			json_do_end();
		return;
	}
	/* Do not stack arrays, while allowed this is not needed */
	if (stack[level].type == ARRAY)
		json_do_end();

	if (stack[level].compact)
		sp = ' ';
	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "[%c", sp) < 0;

	if (++level >= JSON_MAX_STACK)
		errx(1, "json stack too deep");

	stack[level].name = name;
	stack[level].type = ARRAY;
	stack[level].count = 0;
	/* inherit compact setting from above level */
	stack[level].compact = stack[level - 1].compact;
}

void
json_do_object(const char *name, int compact)
{
	int i, l;
	char sp = '\n';

	if ((l = do_find(OBJECT, name)) > 0) {
		/* roll back to that object and close it */
		for (i = level - l; i >= 0; i--)
			json_do_end();
	}

	if (compact)
		sp = ' ';
	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "{%c", sp) < 0;

	if (++level >= JSON_MAX_STACK)
		errx(1, "json stack too deep");

	stack[level].name = name;
	stack[level].type = OBJECT;
	stack[level].count = 0;
	stack[level].compact = compact;
}

void
json_do_end(void)
{
	char c;

	if (stack[level].type == ARRAY)
		c = ']';
	else if (stack[level].type == OBJECT)
		c = '}';
	else
		errx(1, "json bad stack state");

	if (!stack[level].compact) {
		if (!eb)
			eb = fprintf(jsonfh, "\n%.*s%c", level, indent, c) < 0;
	} else {
		if (!eb)
			eb = fprintf(jsonfh, " %c", c) < 0;
	}

	stack[level].name = NULL;
	stack[level].type = NONE;
	stack[level].count = 0;
	stack[level].compact = 0;

	if (level-- <= 0)
		errx(1, "json stack underflow");

	stack[level].count++;
}

void
json_do_printf(const char *name, const char *fmt, ...)
{
	va_list ap;
	char *str;

	va_start(ap, fmt);
	if (!eb) {
		if (vasprintf(&str, fmt, ap) == -1)
			errx(1, "json printf failed");
		json_do_string(name, str);
		free(str);
	}
	va_end(ap);
}

void
json_do_string(const char *name, const char *v)
{
	unsigned char c;

	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "\"") < 0;
	while ((c = *v++) != '\0' && !eb) {
		/* skip escaping '/' since our use case does not require it */
		switch (c) {
		case '"':
			eb = fprintf(jsonfh, "\\\"") < 0;
			break;
		case '\\':
			eb = fprintf(jsonfh, "\\\\") < 0;
			break;
		case '\b':
			eb = fprintf(jsonfh, "\\b") < 0;
			break;
		case '\f':
			eb = fprintf(jsonfh, "\\f") < 0;
			break;
		case '\n':
			eb = fprintf(jsonfh, "\\n") < 0;
			break;
		case '\r':
			eb = fprintf(jsonfh, "\\r") < 0;
			break;
		case '\t':
			eb = fprintf(jsonfh, "\\t") < 0;
			break;
		default:
			if (iscntrl(c))
				errx(1, "bad control character in string");
			eb = putc(c, jsonfh) == EOF;
			break;
		}
	}
	if (!eb)
		eb = fprintf(jsonfh, "\"") < 0;
}

void
json_do_hexdump(const char *name, void *buf, size_t len)
{
	uint8_t *data = buf;
	size_t i;

	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "\"") < 0;
	for (i = 0; i < len; i++)
		if (!eb)
			eb = fprintf(jsonfh, "%02x", *(data + i)) < 0;
	if (!eb)
		eb = fprintf(jsonfh, "\"") < 0;
}

void
json_do_bool(const char *name, int v)
{
	do_comma_indent();
	do_name(name);
	if (v) {
		if (!eb)
			eb = fprintf(jsonfh, "true") < 0;
	} else {
		if (!eb)
			eb = fprintf(jsonfh, "false") < 0;
	}
}

void
json_do_uint(const char *name, unsigned long long v)
{
	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "%llu", v) < 0;
}

void
json_do_int(const char *name, long long v)
{
	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "%lld", v) < 0;
}

void
json_do_double(const char *name, double v)
{
	do_comma_indent();
	do_name(name);
	if (!eb)
		eb = fprintf(jsonfh, "%f", v) < 0;
}