#include <dcfg.h>

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

typedef enum {
	T_FIELD,
	T_INDEX,
} TokenType;

typedef struct {
	TokenType type;
	union {
		dcfg_StringView field;
		size_t index;
	} v;
} Token;

#define MAX_TOKENS 256

static size_t tokenize(char const *query, Token *out)
{
	size_t count = 0;
	size_t i = 0;
	if (query[i] == '.')
		i++;
	while (query[i] && count < MAX_TOKENS) {
		if (query[i] == '.') {
			i++;
			size_t start = i;
			while (query[i] && query[i] != '.' && query[i] != '[')
				i++;
			out[count].type = T_FIELD;
			out[count].v.field.data = query + start;
			out[count].v.field.size = i - start;
			count++;
		} else if (query[i] == '[') {
			i++;
			char *end;
			size_t idx = strtoul(query + i, &end, 10);
			if (*end != ']') {
				fprintf(stderr, "invalid index\n");
				exit(1);
			}
			i = (size_t)(end - query) + 1;
			out[count].type = T_INDEX;
			out[count].v.index = idx;
			count++;
		} else {
			size_t start = i;
			while (query[i] && query[i] != '.' && query[i] != '[')
				i++;
			out[count].type = T_FIELD;
			out[count].v.field.data = query + start;
			out[count].v.field.size = i - start;
			count++;
		}
	}
	return count;
}

static void print_value(dcfg_Value *v)
{
	dcfg_StringView sv;
	if (dcfg_serialize_value(v, &sv)) {
		fwrite(sv.data, 1, sv.size, stdout);
		free((void *)sv.data);
		putchar('\n');
	} else {
		puts("null");
	}
}

int main(int argc, char **argv)
{
	if (argc < 3) {
		fprintf(stderr, "usage: %s <query> <file>\n", argv[0]);
		return 1;
	}
	char const *query = argv[1];
	char const *file = argv[2];

	dcfg_Instance *inst = dcfg_make_instance(&(dcfg_InstanceCreateInfo) { 0 });
	if (!inst) {
		fprintf(stderr, "failed to create instance\n");
		return 1;
	}
	dcfg_Value *root = dcfg_parse(inst, dcfg_SV(file));
	if (!root) {
		fprintf(stderr, "parse error: %s\n", dcfg_last_error(inst));
		dcfg_destroy_instance(inst);
		return 1;
	}

	Token toks[MAX_TOKENS];
	size_t n = tokenize(query, toks);

	dcfg_Value *evaled;
	if (!dcfg_Value_evaluate_toplevel(root, &evaled, NULL, NULL, 0)) {
		fprintf(stderr, "evaluation error: %s\n", dcfg_last_error(inst));
		dcfg_destroy(root);
		dcfg_destroy_instance(inst);
		return 1;
	}

	dcfg_Value *cur = evaled;
	for (size_t i = 0; i < n; i++) {
		Token *t = &toks[i];
		dcfg_Value *next = NULL;

		if (t->type == T_FIELD) {
			if (!dcfg_Value_get_object_field_ex(cur, t->v.field, &next, true)) {
				fprintf(stderr, "no such field\n");
				dcfg_destroy(evaled);
				dcfg_destroy(root);
				dcfg_destroy_instance(inst);
				return 1;
			}
		} else {
			if (!dcfg_Value_get_array_item_ex(cur, t->v.index, &next, true)) {
				fprintf(stderr, "index out of bounds\n");
				dcfg_destroy(evaled);
				dcfg_destroy(root);
				dcfg_destroy_instance(inst);
				return 1;
			}
		}

		if (cur != evaled)
			dcfg_destroy(cur);

		cur = next;
	}
	print_value(cur);
	if (cur != evaled)
		dcfg_destroy(cur);

	dcfg_destroy(evaled);
	dcfg_destroy(root);
	dcfg_destroy_instance(inst);
	return 0;
}