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

#include "uconfig.h"

struct uconfig_pair_s {
	char *key;
	char *value;
	struct uconfig_pair_s *next;
};

struct uconfig_s {
	struct uconfig_pair_s *head;
	struct uconfig_pair_s *tail;
};

static struct uconfig_pair_s *uconfig_pair_new(char *line, int sep_idx)
{
	assert(line[sep_idx] == '=');
	line[sep_idx] = '\0';
	struct uconfig_pair_s *pair = malloc(sizeof(struct uconfig_pair_s));
	pair->key   = strdup(line);
	pair->value = strdup(line + sep_idx + 1);
	pair->next = NULL;
	return pair;
}

static void uconfig_add_tail(struct uconfig_s *uconfig,
			     struct uconfig_pair_s *pair)
{
	if (!uconfig->head) {
		/* first pair in the config handle */
		uconfig->head = pair;
		uconfig->tail = pair;
	}
	else {
		uconfig->tail->next = pair;
		uconfig->tail = pair;
	}
}

static int uconfig_parse_line(struct uconfig_s *uconfig,
			       const char *file,
			       int line_number,
			       char *line,
			       ssize_t line_len)
{
	/* Remove trailing newline, if any */
	if (line[line_len - 1] == '\n') {
		line[line_len - 1] = '\0';
		line_len--;
	}

	/* Find index of '=' character in the line */
	int sep_idx = 0;
	while ((sep_idx < line_len) && (line[sep_idx] != '=')) {
		sep_idx++;
	}
	if (sep_idx == line_len) {
		fprintf(stderr,
			"%s: %s:%d: no '=' character found\n",
			__func__, file, line_number);
		return -1;
	}

	struct uconfig_pair_s *pair = uconfig_pair_new(line, sep_idx);
	uconfig_add_tail(uconfig, pair);
	return 0;
}

struct uconfig_s *uconfig_new(const char*file)
{
	FILE *input = fopen(file, "r");
	struct uconfig_s *uconfig = NULL;
	ssize_t line_len;
	size_t line_size = 128;
	char *line = NULL;
	int line_number = 1;
	int rc;

	if (input == NULL) {
		fprintf(stderr, "%s: fopen: %s: ", __func__, file);
		perror("");
		goto err;
	}

	uconfig = calloc(1, sizeof(struct uconfig_s));
	line = malloc(line_size);

	while ((line_len = getline(&line, &line_size, input)) != -1) {
		rc = uconfig_parse_line(uconfig, file, line_number, line, line_len);
		if (rc == -1)
			goto err;
		line_number++;
	}

	if (ferror(input)) {
		fprintf(stderr, "%s: getline: %s: ", __func__, file);
		perror("");
		goto err;
	}

	free(line);
	fclose(input);
	return uconfig;

err:
	if (input)
		fclose(input);
	if (line)
		free(line);
	if (uconfig)
		uconfig_destroy(uconfig);
	return NULL;
}

const char *uconfig_get(const struct uconfig_s *uconfig, const char *key)
{
	struct uconfig_pair_s *pair = uconfig->head;
	while (pair) {
		if (strcmp(pair->key, key) == 0)
			return pair->value;
		pair = pair->next;
	}
	return NULL;
}

static void uconfig_destroy_pairs(struct uconfig_pair_s *pair)
{
	if (pair->next)
		uconfig_destroy_pairs(pair->next);
	free(pair->key);
	free(pair->value);
	free(pair);
}

void uconfig_destroy(struct uconfig_s *uconfig)
{
	uconfig_destroy_pairs(uconfig->head);
}