/*
 * Copyright (C) 2016 Robin Krahl <robin.krahl@ireas.org>
 *
 * dbfp.c
 */

#include "dbfp.h"

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

#define DBFP_BASE_URL "http://open-api.bahn.de/bin/rest.exe"
#define DBFP_URL_FORMAT "%s/%s?authKey=%s&%s"
#define DBFP_URL_LEN 8000

struct parse_data {
	int error;
	void *data;
};

struct location_data {
	size_t n;
	struct dbfp_location *locations;
};

static int dbfp_parse(void *contents, size_t len, size_t n, void *data);
static int dbfp_request(struct dbfp *dbfp, char *service, char *query,
		XML_Parser parser);
static int dbfp_url(struct dbfp *dbfp, char *service, char *query, char **url);

static int check_ele_error(const char *name, const char **atts);
static int read_string(const char **atts, size_t idx, char **str);
static int read_float(const char **atts, size_t idx, float *f);

static int add_location(struct location_data *ld, const char **atts,
		size_t idx_name, size_t idx_id, size_t idx_lon,
		size_t idx_lat);
static void location_start(void *data, const char *name, const char **atts);
static void location_end(void *data, const char *name);

int dbfp_init(struct dbfp *dbfp, char *key)
{
	int err = 0;
	char *keydup = NULL;
	CURL *curl = NULL;

	if (!dbfp || !key)
		return EINVAL;

	keydup = strdup(key);
	if (!keydup) {
		err = ENOMEM;
		goto cleanup;
	}	

	curl_global_init(CURL_GLOBAL_ALL ^ CURL_GLOBAL_SSL);
	curl = curl_easy_init();
	if (!curl) {
		err = DBFP_ERROR_CURL;
		goto cleanup;
	}

	dbfp->key = keydup;
	dbfp->curl = curl;

cleanup:
	if (err) {
		free(keydup);
		if (curl)
			curl_easy_cleanup(curl);
	}

	return err;
}

void dbfp_close(struct dbfp *dbfp)
{
	if (!dbfp)
		return;

	if (dbfp->curl) {
		curl_easy_cleanup(dbfp->curl);
		dbfp->curl = NULL;
	}
	curl_global_cleanup();

	free(dbfp->key);
	dbfp->key = NULL;
}

int dbfp_query_location_name(struct dbfp *dbfp, char *input,
		size_t *n, struct dbfp_location **locations)
{
	int err = 0;
	char *input_enc = NULL;
	char *query = NULL;
	XML_Parser parser = NULL;
	int len;
	struct location_data ld = { .n = 0, .locations = NULL };
	struct parse_data pd = { .error = 0, .data = &ld };

	if (!dbfp || !input || !n || !locations)
		return EINVAL;

	*n = 0;
	*locations = NULL;

	input_enc = curl_easy_escape(dbfp->curl, input, 0);
	if (!input_enc) {
		err = DBFP_ERROR_CURL;
		goto cleanup;
	}
	query = malloc(DBFP_URL_LEN);
	if (!query) {
		err = ENOMEM;
		goto cleanup;
	}
	len = snprintf(query, DBFP_URL_LEN, "input=%s", input_enc);
	if (len < 0 || len >= DBFP_URL_LEN) {
		err = DBFP_ERROR_FORMAT;
		goto cleanup;
	}

	parser = XML_ParserCreateNS(NULL, '\0');
	XML_SetUserData(parser, &pd);
	XML_SetElementHandler(parser, location_start, location_end);

	err = dbfp_request(dbfp, "location.name", query, parser);
	if (pd.error)
		err = pd.error;
	if (err)
		goto cleanup;

	*n = ld.n;
	*locations = ld.locations;

cleanup:
	if (err)
		free(ld.locations);
	if (input_enc)
		curl_free(input_enc);
	XML_ParserFree(parser);
	free(query);

	return err;
}

static int dbfp_parse(void *contents, size_t len, size_t n, void *data)
{
	XML_Parser parser = (XML_Parser)data;
	struct parse_data *pd;
	size_t size = len * n;

	pd = (struct parse_data *)XML_GetUserData(parser);

	if (!pd->error && !XML_Parse(parser, contents, size, 0))
		pd->error = DBFP_ERROR_PARSE;

	return size;
}

static int dbfp_request(struct dbfp *dbfp, char *service, char *query,
		XML_Parser parser)
{
	int err = 0;
	char *url = NULL;

	err = dbfp_url(dbfp, service, query, &url);
	if (err)
		goto cleanup;

	curl_easy_setopt(dbfp->curl, CURLOPT_URL, url);
	curl_easy_setopt(dbfp->curl, CURLOPT_WRITEFUNCTION, dbfp_parse);
	curl_easy_setopt(dbfp->curl, CURLOPT_WRITEDATA, (void *)parser);

	if (curl_easy_perform(dbfp->curl) != CURLE_OK)
		err = DBFP_ERROR_CURL;

cleanup:
	free(url);

	return err;
}

static int dbfp_url(struct dbfp *dbfp, char *service, char *query, char **url)
{
	int len;

	*url = malloc(DBFP_URL_LEN);
	if (!*url)
		return ENOMEM;

	len = snprintf(*url, DBFP_URL_LEN, DBFP_URL_FORMAT, DBFP_BASE_URL,
			service, dbfp->key, query);
	if (len < 0 || len >= DBFP_URL_LEN) {
		free(*url);
		*url = NULL;
		return DBFP_ERROR_FORMAT;
	}

	return 0;
}

static int check_ele_error(const char *name, const char **atts)
{
	if (strcmp(name, "Error") == 0) {
		return DBFP_ERROR_API;
	}

	return 0;
}

static int read_string(const char **atts, size_t idx, char **str)
{
	*str = strdup(atts[idx]);
	if (!*str)
		return ENOMEM;

	return 0;
}

static int read_float(const char **atts, size_t idx, float *f)
{
	char *endptr = NULL;

	errno = 0;
	*f = strtof(atts[idx], &endptr);
	if (atts[idx] == endptr || errno != 0)
		return DBFP_ERROR_STRUCTURE;

	return 0;
}

static int add_location(struct location_data *ld, const char **atts,
		size_t idx_name, size_t idx_id, size_t idx_lon,
		size_t idx_lat)
{
	int err = 0;
	char *name = NULL;
	char *id = NULL;
	float lon;
	float lat;

	err = read_string(atts, idx_name, &name);
	if (err)
		goto cleanup;
	err = read_string(atts, idx_id, &id);
	if (err)
		goto cleanup;
	err = read_float(atts, idx_lon, &lon);
	if (err)
		goto cleanup;
	err = read_float(atts, idx_lat, &lat);
	if (err)
		goto cleanup;

	/* TODO(robin.krahl):  don't give up the old memory if realloc fails */
	ld->locations = realloc(ld->locations,
			(ld->n + 1) * sizeof(*ld->locations));
	if (!ld->locations) {
		err = ENOMEM;
		goto cleanup;
	}

	ld->locations[ld->n].name = name;
	ld->locations[ld->n].id = id;
	ld->locations[ld->n].lon = lon;
	ld->locations[ld->n].lat = lat;
	ld->n++;

cleanup:
	if (err) {
		free(name);
		free(id);
	}

	return err;
}

static void location_start(void *data, const char *name, const char **atts)
{
	int err = 0;
	struct parse_data *pd = (struct parse_data *)data;
	struct location_data *ld = (struct location_data *)pd->data;
	size_t idx_name = 0;
	size_t idx_id = 0;
	size_t idx_lon = 0;
	size_t idx_lat = 0;
	size_t i;

	err = check_ele_error(name, atts);
	if (err)
		goto cleanup;

	if (strcmp(name, "StopLocation") != 0)
		goto cleanup;

	for (i = 0; atts[i]; i += 2) {
		if (strcmp(atts[i], "name") == 0)
			idx_name = i + 1;
		else if (strcmp(atts[i], "id") == 0)
			idx_id = i + 1;
		else if (strcmp(atts[i], "lon") == 0)
			idx_lon = i + 1;
		else if (strcmp(atts[i], "lat") == 0)
			idx_lat = i + 1;
	}

	if (!idx_name || !idx_id || !idx_lon || !idx_lat) {
		err = DBFP_ERROR_STRUCTURE;
		goto cleanup;
	}

	err = add_location(ld, atts, idx_name, idx_id, idx_lon, idx_lat);

cleanup:
	if (err)
		pd->error = err;
}

static void location_end(void *data, const char *name)
{
}