/* SPDX-License-Identifier: MIT */
/*
 * konjson.h
 *
 * Copyright (c) 2026 KonAki
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#ifndef KONJSON_H
#define KONJSON_H

#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

typedef enum kon_jsonType {
	KON_JSON_NULL,
	KON_JSON_BOOL,
	KON_JSON_NUMBER,
	KON_JSON_STRING,
	KON_JSON_ARRAY,
	KON_JSON_OBJECT
} kon_jsonType_t;

/* children of an array or object sit in items, an object's keys sit in the same slots as the values */
typedef struct kon_json {
	kon_jsonType_t type;
	double number;
	char *string;
	char *key;
	struct kon_json *items;
	int count;
} kon_json_t;

/* error gets a short message with the line number when parsing fails, it may be NULL */
kon_json_t *kon_jsonParse(const char *text, size_t length, char *error, int errorSize);
kon_json_t *kon_jsonParseFile(const char *path, char *error, int errorSize);
void kon_jsonFree(kon_json_t *json);

/* all of these accept NULL and give the default (or NULL) when the type is wrong, so lookups can be chained */
const kon_json_t *kon_jsonGet(const kon_json_t *object, const char *key);
const kon_json_t *kon_jsonAt(const kon_json_t *array, int index);
int kon_jsonCount(const kon_json_t *json);
const char *kon_jsonString(const kon_json_t *json, const char *def);
double kon_jsonNumber(const kon_json_t *json, double def);
int kon_jsonInt(const kon_json_t *json, int def);
int kon_jsonBool(const kon_json_t *json, int def);

#ifdef __cplusplus
}
#endif

/*** implementation ***/

#ifdef KONJSON_IMPLEMENTATION

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define KON_JSON_DEPTH 200

typedef struct kon_jsonParser {
	const char *p;
	const char *end;
	const char *begin;
	char *error;
	int errorSize;
	int failed;
} kon_jsonParser_t;

static void kon__jsonClear(kon_json_t *json)
{
	int i;

	for (i = 0; i < json->count; i++) {
		kon__jsonClear(&json->items[i]);
		free(json->items[i].key);
	}
	free(json->items);
	free(json->string);
	json->items = NULL;
	json->string = NULL;
	json->count = 0;
}

static int kon__jsonFail(kon_jsonParser_t *ps, const char *message)
{
	const char *c;
	int line = 1;

	if (!ps->failed && ps->error && ps->errorSize > 0) {
		for (c = ps->begin; c < ps->p && c < ps->end; c++) {
			if (*c == '\n') line++;
		}
		snprintf(ps->error, (size_t)ps->errorSize, "line %d: %s", line, message);
	}
	ps->failed = 1;
	return 0;
}

static void kon__jsonSpace(kon_jsonParser_t *ps)
{
	while (ps->p < ps->end && (*ps->p == ' ' || *ps->p == '\t' || *ps->p == '\n' || *ps->p == '\r')) ps->p++;
}

static int kon__jsonHex4(const char *p, unsigned *out)
{
	unsigned v = 0;
	int i;

	for (i = 0; i < 4; i++) {
		char c = p[i];
		v <<= 4;
		if (c >= '0' && c <= '9') v |= (unsigned)(c - '0');
		else if (c >= 'a' && c <= 'f') v |= (unsigned)(c - 'a' + 10);
		else if (c >= 'A' && c <= 'F') v |= (unsigned)(c - 'A' + 10);
		else return 0;
	}
	*out = v;
	return 1;
}

static int kon__jsonUtf8(char *out, unsigned cp)
{
	if (cp < 0x80) {
		out[0] = (char)cp;
		return 1;
	}
	if (cp < 0x800) {
		out[0] = (char)(0xC0 | (cp >> 6));
		out[1] = (char)(0x80 | (cp & 0x3F));
		return 2;
	}
	if (cp < 0x10000) {
		out[0] = (char)(0xE0 | (cp >> 12));
		out[1] = (char)(0x80 | ((cp >> 6) & 0x3F));
		out[2] = (char)(0x80 | (cp & 0x3F));
		return 3;
	}
	out[0] = (char)(0xF0 | (cp >> 18));
	out[1] = (char)(0x80 | ((cp >> 12) & 0x3F));
	out[2] = (char)(0x80 | ((cp >> 6) & 0x3F));
	out[3] = (char)(0x80 | (cp & 0x3F));
	return 4;
}

static char *kon__jsonString(kon_jsonParser_t *ps)
{
	const char *start, *scan;
	char *out;
	size_t n = 0;

	ps->p++;
	start = ps->p;
	for (scan = start; scan < ps->end && *scan != '"'; scan++) {
		if (*scan == '\\' && scan + 1 < ps->end) scan++;
	}
	out = malloc((size_t)(scan - start) + 1);
	if (!out) {
		kon__jsonFail(ps, "out of memory");
		return NULL;
	}

	while (ps->p < ps->end && *ps->p != '"') {
		unsigned char c = (unsigned char)*ps->p;

		if (c < 0x20) {
			kon__jsonFail(ps, "control character in string");
			free(out);
			return NULL;
		}
		if (c != '\\') {
			out[n++] = (char)c;
			ps->p++;
			continue;
		}

		ps->p++;
		if (ps->p >= ps->end) break;
		switch (*ps->p) {
		case '"': out[n++] = '"'; break;
		case '\\': out[n++] = '\\'; break;
		case '/': out[n++] = '/'; break;
		case 'b': out[n++] = '\b'; break;
		case 'f': out[n++] = '\f'; break;
		case 'n': out[n++] = '\n'; break;
		case 'r': out[n++] = '\r'; break;
		case 't': out[n++] = '\t'; break;
		case 'u': {
			unsigned cp, lo;

			if (ps->end - ps->p < 5 || !kon__jsonHex4(ps->p + 1, &cp)) {
				kon__jsonFail(ps, "bad \\u escape");
				free(out);
				return NULL;
			}
			ps->p += 4;
			if (cp >= 0xD800 && cp < 0xDC00 && ps->end - ps->p >= 7 && ps->p[1] == '\\' && ps->p[2] == 'u' && kon__jsonHex4(ps->p + 3, &lo) && lo >= 0xDC00 && lo < 0xE000) {
				cp = 0x10000 + ((cp - 0xD800) << 10) + (lo - 0xDC00);
				ps->p += 6;
			} else if (cp >= 0xD800 && cp < 0xE000) {
				cp = 0xFFFD;
			}
			n += (size_t)kon__jsonUtf8(out + n, cp);
			break;
		}
		default:
			kon__jsonFail(ps, "bad escape");
			free(out);
			return NULL;
		}
		ps->p++;
	}

	if (ps->p >= ps->end) {
		kon__jsonFail(ps, "unterminated string");
		free(out);
		return NULL;
	}
	ps->p++;
	out[n] = '\0';
	return out;
}

static int kon__jsonValue(kon_jsonParser_t *ps, kon_json_t *out, int depth);

static int kon__jsonPush(kon_jsonParser_t *ps, kon_json_t *parent, int *capacity, const kon_json_t *item)
{
	if (parent->count == *capacity) {
		int grown = *capacity ? *capacity * 2 : 8;
		kon_json_t *items = realloc(parent->items, (size_t)grown * sizeof(kon_json_t));

		if (!items) return kon__jsonFail(ps, "out of memory");
		parent->items = items;
		*capacity = grown;
	}
	parent->items[parent->count++] = *item;
	return 1;
}

static int kon__jsonContainer(kon_jsonParser_t *ps, kon_json_t *out, int depth)
{
	int isObject = *ps->p == '{';
	char close = isObject ? '}' : ']';
	int capacity = 0;

	out->type = isObject ? KON_JSON_OBJECT : KON_JSON_ARRAY;
	ps->p++;
	kon__jsonSpace(ps);
	if (ps->p < ps->end && *ps->p == close) {
		ps->p++;
		return 1;
	}

	for (;;) {
		kon_json_t item;
		char *key = NULL;

		memset(&item, 0, sizeof item);
		kon__jsonSpace(ps);
		if (isObject) {
			if (ps->p >= ps->end || *ps->p != '"') return kon__jsonFail(ps, "expected a key");
			key = kon__jsonString(ps);
			if (!key) return 0;
			kon__jsonSpace(ps);
			if (ps->p >= ps->end || *ps->p != ':') {
				free(key);
				return kon__jsonFail(ps, "expected ':'");
			}
			ps->p++;
		}
		if (!kon__jsonValue(ps, &item, depth + 1)) {
			kon__jsonClear(&item);
			free(key);
			return 0;
		}
		item.key = key;
		if (!kon__jsonPush(ps, out, &capacity, &item)) {
			kon__jsonClear(&item);
			free(key);
			return 0;
		}

		kon__jsonSpace(ps);
		if (ps->p < ps->end && *ps->p == ',') {
			ps->p++;
			continue;
		}
		if (ps->p < ps->end && *ps->p == close) {
			ps->p++;
			return 1;
		}
		return kon__jsonFail(ps, isObject ? "expected ',' or '}'" : "expected ',' or ']'");
	}
}

static int kon__jsonValue(kon_jsonParser_t *ps, kon_json_t *out, int depth)
{
	size_t left;
	char *end;

	if (depth > KON_JSON_DEPTH) return kon__jsonFail(ps, "nested too deep");
	kon__jsonSpace(ps);
	if (ps->p >= ps->end) return kon__jsonFail(ps, "unexpected end");
	left = (size_t)(ps->end - ps->p);

	switch (*ps->p) {
	case '{':
	case '[':
		return kon__jsonContainer(ps, out, depth);
	case '"':
		out->type = KON_JSON_STRING;
		out->string = kon__jsonString(ps);
		return out->string != NULL;
	case 't':
		if (left >= 4 && !memcmp(ps->p, "true", 4)) {
			out->type = KON_JSON_BOOL;
			out->number = 1;
			ps->p += 4;
			return 1;
		}
		break;
	case 'f':
		if (left >= 5 && !memcmp(ps->p, "false", 5)) {
			out->type = KON_JSON_BOOL;
			ps->p += 5;
			return 1;
		}
		break;
	case 'n':
		if (left >= 4 && !memcmp(ps->p, "null", 4)) {
			out->type = KON_JSON_NULL;
			ps->p += 4;
			return 1;
		}
		break;
	default:
		if (*ps->p == '-' || (*ps->p >= '0' && *ps->p <= '9')) {
			char buf[64];
			size_t n = 0;

			while (n < left && n < sizeof buf - 1 && (strchr("+-.eE", ps->p[n]) || (ps->p[n] >= '0' && ps->p[n] <= '9'))) {
				buf[n] = ps->p[n];
				n++;
			}
			buf[n] = '\0';
			out->number = strtod(buf, &end);
			if (end == buf) return kon__jsonFail(ps, "bad number");
			out->type = KON_JSON_NUMBER;
			ps->p += end - buf;
			return 1;
		}
		break;
	}
	return kon__jsonFail(ps, "unexpected character");
}

void kon_jsonFree(kon_json_t *json)
{
	if (!json) return;
	kon__jsonClear(json);
	free(json);
}

kon_json_t *kon_jsonParse(const char *text, size_t length, char *error, int errorSize)
{
	kon_jsonParser_t ps;
	kon_json_t *root;

	if (error && errorSize > 0) error[0] = '\0';
	if (length >= 3 && !memcmp(text, "\xEF\xBB\xBF", 3)) {
		text += 3;
		length -= 3;
	}
	ps.begin = ps.p = text;
	ps.end = text + length;
	ps.error = error;
	ps.errorSize = errorSize;
	ps.failed = 0;

	root = calloc(1, sizeof *root);
	if (!root) return NULL;
	if (!kon__jsonValue(&ps, root, 0)) {
		kon_jsonFree(root);
		return NULL;
	}
	kon__jsonSpace(&ps);
	if (ps.p != ps.end) {
		kon__jsonFail(&ps, "text after the value");
		kon_jsonFree(root);
		return NULL;
	}
	return root;
}

kon_json_t *kon_jsonParseFile(const char *path, char *error, int errorSize)
{
	FILE *f = fopen(path, "rb");
	long size;
	char *text;
	size_t got;
	kon_json_t *json;

	if (error && errorSize > 0) error[0] = '\0';
	if (!f) {
		if (error) snprintf(error, (size_t)errorSize, "cannot open %s", path);
		return NULL;
	}
	if (fseek(f, 0, SEEK_END) != 0 || (size = ftell(f)) < 0 || fseek(f, 0, SEEK_SET) != 0) {
		fclose(f);
		if (error) snprintf(error, (size_t)errorSize, "cannot size %s", path);
		return NULL;
	}
	text = malloc((size_t)size + 1);
	if (!text) {
		fclose(f);
		return NULL;
	}
	got = fread(text, 1, (size_t)size, f);
	fclose(f);

	json = kon_jsonParse(text, got, error, errorSize);
	free(text);
	return json;
}

const kon_json_t *kon_jsonGet(const kon_json_t *object, const char *key)
{
	int i;

	if (!object || object->type != KON_JSON_OBJECT) return NULL;
	for (i = 0; i < object->count; i++) {
		if (object->items[i].key && !strcmp(object->items[i].key, key)) return &object->items[i];
	}
	return NULL;
}

const kon_json_t *kon_jsonAt(const kon_json_t *array, int index)
{
	if (!array || array->type != KON_JSON_ARRAY || index < 0 || index >= array->count) return NULL;
	return &array->items[index];
}

int kon_jsonCount(const kon_json_t *json)
{
	if (!json || (json->type != KON_JSON_ARRAY && json->type != KON_JSON_OBJECT)) return 0;
	return json->count;
}

const char *kon_jsonString(const kon_json_t *json, const char *def)
{
	return json && json->type == KON_JSON_STRING ? json->string : def;
}

double kon_jsonNumber(const kon_json_t *json, double def)
{
	return json && json->type == KON_JSON_NUMBER ? json->number : def;
}

int kon_jsonInt(const kon_json_t *json, int def)
{
	double v;

	if (!json || json->type != KON_JSON_NUMBER) return def;
	v = json->number;
	if (v > 2147483647.0) return 2147483647;
	if (v < -2147483648.0) return -2147483647 - 1;
	return (int)v;
}

int kon_jsonBool(const kon_json_t *json, int def)
{
	return json && json->type == KON_JSON_BOOL ? json->number != 0 : def;
}

#endif /* end of KONJSON_IMPLEMENTATION */
#endif