#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>
#include <gio/gio.h>
#include <json-glib/json-glib.h>
#include "application-service-lru-file.h"

#define ENTRY_CATEGORY   "category"
#define ENTRY_FIRST_TIME "first-time"
#define ENTRY_LAST_TIME  "last-time"
#define ENTRY_VERSION    "version"

#define CONFIG_DIR       ("indicators" G_DIR_SEPARATOR_S "application")
#define CONFIG_FILE      "lru-file.json"

typedef struct _AppLruFilePrivate AppLruFilePrivate;
struct _AppLruFilePrivate {
	GHashTable * apps;
	gboolean dirty;
	guint timer;
	gchar * filename;
};

typedef struct _AppData AppData;
struct _AppData {
	gchar * category;
	GTimeVal last_touched;
	GTimeVal first_touched;
};

#define APP_LRU_FILE_GET_PRIVATE(o) \
		(G_TYPE_INSTANCE_GET_PRIVATE ((o), APP_LRU_FILE_TYPE, AppLruFilePrivate))

static void app_lru_file_class_init (AppLruFileClass *klass);
static void app_lru_file_init       (AppLruFile *self);
static void app_lru_file_dispose    (GObject *object);
static void app_lru_file_finalize   (GObject *object);
static void app_data_free           (gpointer data);
static gboolean load_from_file      (gpointer data);
static void load_file_object_cb (JsonObject * obj, const gchar * key, JsonNode * value, gpointer data);
static void clean_off_hash_cb (gpointer key, gpointer value, gpointer data);
static void clean_off_write_end_cb (GObject * obj, GAsyncResult * res, gpointer data);

G_DEFINE_TYPE (AppLruFile, app_lru_file, G_TYPE_OBJECT);

/* Set up the class variable stuff */
static void
app_lru_file_class_init (AppLruFileClass *klass)
{
	GObjectClass *object_class = G_OBJECT_CLASS (klass);

	g_type_class_add_private (klass, sizeof (AppLruFilePrivate));

	object_class->dispose = app_lru_file_dispose;
	object_class->finalize = app_lru_file_finalize;

	return;
}

/* Set all the data of the per-instance variables */
static void
app_lru_file_init (AppLruFile *self)
{
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(self);

	/* Default values */
	priv->apps = NULL;
	priv->dirty = FALSE;
	priv->timer = 0;
	priv->filename = NULL;

	/* Now let's build some stuff */
	priv->apps = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, app_data_free);
	priv->filename = g_build_filename(g_get_user_config_dir(), CONFIG_DIR, CONFIG_FILE, NULL);

	/* No reason to delay other stuff for this, we'll
	   merge any values that get touched. */
	g_idle_add(load_from_file, self);

	return;
}

/* Get rid of objects and other big things */
static void
app_lru_file_dispose (GObject *object)
{
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(object);

	if (priv->timer != 0) {
		g_source_remove(priv->timer);
		priv->timer = 0;
	}

	if (priv->apps != NULL) {
		/* Cleans up the keys and entries itself */
		g_hash_table_destroy(priv->apps);
		priv->apps = NULL;
	}

	G_OBJECT_CLASS (app_lru_file_parent_class)->dispose (object);
	return;
}

/* Deallocate memory */
static void
app_lru_file_finalize (GObject *object)
{
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(object);
	
	if (priv->filename != NULL) {
		g_free(priv->filename);
		priv->filename = NULL;
	}

	G_OBJECT_CLASS (app_lru_file_parent_class)->finalize (object);
	return;
}

/* Takes an AppData structure and free's the
   memory from it. */
static void
app_data_free (gpointer data)
{
	AppData * appdata = (AppData *)data;

	if (appdata->category != NULL) {
		g_free(appdata->category);
	}

	g_free(appdata);

	return;
}

/* Loads all of the data out of a json file */
static gboolean
load_from_file (gpointer data)
{
	AppLruFile * lrufile = (AppLruFile *)data;
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(lrufile);

	if (!g_file_test(priv->filename, G_FILE_TEST_EXISTS)) {
		return FALSE;
	}

	JsonParser * parser = json_parser_new();

	if (!json_parser_load_from_file(parser, priv->filename, NULL)) {
		g_warning("Unable to parse JSON file '%s'", priv->filename);
		g_object_unref(parser);
		return FALSE;
	}

	JsonNode * root = json_parser_get_root(parser);
	JsonObject * rootobj = json_node_get_object(root);
	if (rootobj == NULL) {
		g_warning("Malformed LRU file.  The root node is not an object.");
		g_object_unref(parser);
		return FALSE;
	}

	json_object_foreach_member(rootobj, load_file_object_cb, priv);

	g_object_unref(parser);
	return FALSE;
}

/* Looks at the various things that we need on a node, makes
   sure that we have them, and then copies them into the
   application hash table of love. */
static void
load_file_object_cb (JsonObject * rootobj, const gchar * key, JsonNode * value, gpointer data)
{
	AppLruFilePrivate * priv = (AppLruFilePrivate *)data;

	/* We're not looking at this today. */
	if (!g_strcmp0(key, ENTRY_VERSION)) {
		return;
	}

	JsonObject * obj = json_node_get_object(value);
	if (obj == NULL) {
		g_warning("Data for node '%s' is not an object.", key);
		return;
	}

	const gchar * obj_category = json_object_get_string_member(obj, ENTRY_CATEGORY);
	const gchar * obj_first    = json_object_get_string_member(obj, ENTRY_FIRST_TIME);
	const gchar * obj_last     = json_object_get_string_member(obj, ENTRY_LAST_TIME);

	if (obj_category == NULL || obj_first == NULL || obj_last == NULL) {
		g_warning("Node '%s' is missing data.  Got: ('%s', '%s', '%s')", key, obj_category, obj_first, obj_last);
		return;
	}

	gpointer datapntr = g_hash_table_lookup(priv->apps, key);
	if (datapntr == NULL) {
		/* Build a new node */
		AppData * appdata = g_new0(AppData, 1);
		appdata->category = g_strdup(obj_category);
		g_time_val_from_iso8601(obj_first, &appdata->first_touched);
		g_time_val_from_iso8601(obj_last, &appdata->last_touched);

		g_hash_table_insert(priv->apps, g_strdup(key), appdata);
	} else {
		/* Merge nodes */
		AppData * appdata = (AppData *)datapntr;
		GTimeVal temptime;
		g_time_val_from_iso8601(obj_first, &temptime);

		if (temptime.tv_sec < appdata->first_touched.tv_sec) {
			g_time_val_from_iso8601(obj_first, &appdata->first_touched);
		}
	}

	return;
}

/* Write out our cache to a file so that we can unmark the dirty
   bit and be happy. */
static gboolean
clean_off (gpointer data)
{
	AppLruFile * lrufile = (AppLruFile *)data;
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(lrufile);
	priv->timer = 0;

	GError * error = NULL;
	
	/* Check to see if our directory exists.  Build it if not. */
	gchar * dirname = g_build_filename(g_get_user_config_dir(), CONFIG_DIR, NULL);
	if (!g_file_test(dirname, G_FILE_TEST_EXISTS | G_FILE_TEST_IS_DIR)) {
		GFile * dirfile = g_file_new_for_path(dirname);
		g_file_make_directory_with_parents(dirfile, NULL, NULL);
		g_object_unref(dirfile);
	}
	g_free(dirname);

	GFile * file = g_file_new_for_path(priv->filename);
	GFileOutputStream * ostream = g_file_replace(file,
	                                             NULL, /* etag */
	                                             TRUE, /* backup */
	                                             G_FILE_CREATE_NONE, /* flags */
	                                             NULL, /* cancelable */
	                                             &error);
	if (error != NULL) {
		g_warning("Unable to open a file to store LRU file: %s", error->message);
		return FALSE;
	}

	/* This is how the file will start */
	GString * filestring = g_string_new("{\n  \"" ENTRY_VERSION "\": 1");

	/* Put the middle in. */
	g_hash_table_foreach (priv->apps, clean_off_hash_cb, filestring);

	/* And then tack on the end. */
	g_string_append(filestring, "\n}\n");
	gchar * filedata = g_string_free(filestring, FALSE);
	g_output_stream_write_async(G_OUTPUT_STREAM(ostream),
	                            filedata,
	                            strlen(filedata),
	                            G_PRIORITY_DEFAULT_IDLE,
	                            NULL,
	                            clean_off_write_end_cb,
	                            filedata);

	return FALSE; /* drop the timer */
}

/* Looks at every value in the applications hash table and
   turns it into a string for writing out. */
static void
clean_off_hash_cb (gpointer key, gpointer value, gpointer data)
{
	/* Mega-cast */
	gchar * id = (gchar *)key;
	AppData * appdata = (AppData *)value;
	GString * string = (GString *)data;

	gchar * firsttime = g_time_val_to_iso8601(&appdata->first_touched);
	gchar * lasttime = g_time_val_to_iso8601(&appdata->last_touched);

	g_string_append_printf(string, ",\n  \"%s\": { \"" ENTRY_FIRST_TIME "\": \"%s\", \"" ENTRY_LAST_TIME "\": \"%s\", \"" ENTRY_CATEGORY "\": \"%s\"}", id, firsttime, lasttime, appdata->category);

	g_free(lasttime);
	g_free(firsttime);

	return;
}

/* Very much like clean_off_write_cb except that it is the
   last actor on this Output Stream so it closes it. */
static void
clean_off_write_end_cb (GObject * obj, GAsyncResult * res, gpointer data)
{
	g_free(data);

	GError * error = NULL;
	g_output_stream_close(G_OUTPUT_STREAM(obj), NULL, &error);

	if (error != NULL) {
		g_warning("Unable to close LRU File: %s", error->message);
		g_error_free(error);
	}

	return;
}

/* Sets the dirty bit if not already set and makes sure that
   we have a timer to fix that at some point. */
static void
get_dirty (AppLruFile * lrufile)
{
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(lrufile);

	priv->dirty = TRUE;

	if (priv->timer == 0) {
		priv->timer = g_timeout_add_seconds(60, clean_off, lrufile);
	}

	return;
}

/* API */

/* Simple helper to create a new object */
AppLruFile *
app_lru_file_new (void)
{
	return APP_LRU_FILE(g_object_new(APP_LRU_FILE_TYPE, NULL));
}

/* This updates the timestamp for a particular
   entry in the database.  It also queues up a 
   write out of the database.  But that'll happen
   later. */
void
app_lru_file_touch (AppLruFile * lrufile, const gchar * id, const gchar * category)
{
	g_return_if_fail(IS_APP_LRU_FILE(lrufile));
	g_return_if_fail(id != NULL && id[0] != '\0');
	g_return_if_fail(category != NULL && category[0] != '\0');

	AppData * appdata = NULL;
	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(lrufile);
	gpointer data = g_hash_table_lookup(priv->apps, id);

	if (data == NULL) {
		/* Oh, we don't have one, let's build it and put it
		   into the hash table ourselves */
		appdata = g_new0(AppData, 1);

		appdata->category = g_strdup(category);
		g_get_current_time(&(appdata->first_touched));
		/* NOTE: last touched set below */

		g_hash_table_insert(priv->apps, g_strdup(id), appdata);
	} else {
		/* Boring, we've got this one already */
		appdata = (AppData *)data;
	}

	/* Touch it and mark the DB as dirty */
	g_get_current_time(&(appdata->last_touched));
	get_dirty(lrufile);
	return;
}

/* Used to sort or compare different applications. */
gint
app_lru_file_sort (AppLruFile * lrufile, const gchar * id_a, const gchar * id_b)
{
	g_return_val_if_fail(IS_APP_LRU_FILE(lrufile), -1);

	/* Let's first look to see if the IDs are the same, this
	   really shouldn't happen, but it'll be confusing if we
	   don't get it out of the way to start. */
	if (g_strcmp0(id_a, id_b) == 0) {
		return 0;
	}

	AppLruFilePrivate * priv = APP_LRU_FILE_GET_PRIVATE(lrufile);

	/* Now make sure we have app data for both of these.  If
	   not we'll assume that the one without is newer? */
	gpointer data_a = g_hash_table_lookup(priv->apps, id_a);
	if (data_a == NULL) {
		return -1;
	}

	gpointer data_b = g_hash_table_lookup(priv->apps, id_b);
	if (data_b == NULL) {
		return 1;
	}

	/* Ugly casting */
	AppData * appdata_a = (AppData *)data_a;
	AppData * appdata_b = (AppData *)data_b;

	/* Look at categories, we'll put the categories in alpha
	   order if they're not the same. */
	gint catcompare = g_strcmp0(appdata_a->category, appdata_b->category);
	if (catcompare != 0) {
		return catcompare;
	}

	/* Now we're looking at the first time that these two were
	   seen in this account.  Only using seconds.  I mean, seriously. */
	if (appdata_a->first_touched.tv_sec < appdata_b->first_touched.tv_sec) {
		return -1;
	}
	if (appdata_b->first_touched.tv_sec < appdata_a->first_touched.tv_sec) {
		return 1;
	}

	/* Eh, this seems roughly impossible.  But if we have to choose,
	   I like A better. */
	return 1;
}